Title of the invention: Composite particles for negative electrode active material and negative electrode for all-solid battery comprising the same
Technical field
[One]
This application claims priority based on Korean Patent Application No. 10-2018-0059800 filed on May 25, 2018. It relates to a composite particle for an anode active material and an electrochemical device including the same. The electrochemical device according to the present invention is particularly an all-solid battery using a solid electrolyte.
[2]
Background
[3]
A lithium ion battery using a liquid electrolyte has a structure in which the negative electrode and the positive electrode are partitioned by a separator, so if the separator is damaged by deformation or external impact, a short circuit may occur, which may lead to a risk of overheating or explosion. In order to solve the above-described problems, development of a solid electrolyte material using an ion conductive polymer or inorganic material and an all-solid battery using the same has been made. A lithium secondary battery using a solid electrolyte has advantages in that the safety of the battery is increased, leakage of an electrolyte solution can be prevented, so that the reliability of the battery is improved, and it is easy to manufacture a thin battery. These solid electrolytes can be largely classified into polymer electrolyte materials and inorganic solid electrolyte materials according to the properties of the material. The use of a solid electrolyte is known to be advantageous in terms of battery performance, such as safety, high energy density, high output, and long life, and is also known to be advantageous in terms of simplification of manufacturing processes, large-sized/compact, and low-cost of the battery. . Although the lithium ion conductivity of the solid electrolyte is still lower than that of the liquid electrolyte, it is theoretically reported that the ionic conductivity of the solid is higher than that of the liquid. There is a need.
[4]
In the case of using a solid electrolyte, the active material and the electrolyte must be in close contact to secure ionic conductivity. In the case of using spheroidized graphite, which is a carbon material, as the negative active material of an all-solid battery, in the case of using a liquid electrolyte, the voids inside the graphite particles may be filled with an electrolyte. The area where the active material particles contact, that is, the sites where electrochemical reactions can occur, decreases, resulting in problems of capacity reduction and output reduction.
[5]
Accordingly, there is a need to develop a new negative electrode material that does not cause problems of capacity reduction and output reduction even when used in all-solid-state batteries.
[6]
Detailed description of the invention
Technical challenge
[7]
An object of the present invention is to provide a carbonaceous negative electrode active material that does not cause problems of capacity reduction and output reduction by sufficiently securing an electrochemical reaction site between a solid electrolyte and an electrode active material even when applied to an all-solid battery using a solid electrolyte. In addition, another object of the present invention is to provide a method of manufacturing such a carbon material negative electrode active material. Other objects and advantages of the present invention will be understood by the following description. On the other hand, it will be easily understood that the objects and advantages of the present invention can be realized by means or methods described in the claims, and combinations thereof.
[8]
Means of solving the task
[9]
The present invention relates to composite particles for an all-solid battery negative active material. The first aspect of the present invention relates to the composite particle, wherein the composite particle includes graphite particles in which graphite materials are granulated, the graphite material is derived from any one of natural graphite and artificial graphite, and The gap between the graphite materials is filled with a mixture containing a solid electrolyte and a conductive material, and all or at least part of the outer surface of the graphite particles is covered with the mixture.
[10]
In the second aspect of the present invention, in the first aspect, the particle diameter of the composite particles is 5 μm to 50 μm.
[11]
The third aspect of the present invention is, in any one of the first to second aspects, the natural graphite is a high crystalline natural material selected from among plate-like, scale-like, crushed, oval-like and whisker-like natural graphite. It is graphite.
[12]
A fourth aspect of the present invention is that in any one of the first to third aspects, the content of the solid electrolyte is 3% to 50% by weight relative to 100% by weight of the composite particles.
[13]
In any one of the first to fourth aspects of the fifth aspect of the present invention, the solid electrolyte includes a sulfide-based solid electrolyte.
[14]
In any one of the first to fifth aspects of the present invention, the conductive material is selected from graphite, carbon black, conductive fiber, metal powder, potassium titanate, conductive whiskey, conductive metal oxide, and polyphenylene derivative. It includes one kind or a mixture of two or more kinds.
[15]
In addition, the present invention relates to a method of manufacturing composite particles for an anode active material. The seventh aspect of the present invention relates to the manufacturing method, wherein the method comprises preparing a mixture including a graphite material, a conductive material, and a solid electrolyte, and performing a granulation process of spheroidizing the mixture with a mechanical external force. It is characterized in that a composite particle in which a material, a conductive material and a solid electrolyte are composited is obtained.
[16]
In the eighth aspect of the present invention, in the seventh aspect, the granulation process is selected from among a counter jet mill (Hosokawa Micron, JP), an ACM palletizer (Hosokawa Micron, JP), and a current jet (Nissin, JP). Device; Assembly equipment selected from SARARA (Kawasaki Heavy Industries, Ltd, JP), GRANUREX (Freund Corporation, JP), New Gramasin (Seichin, JP), and Acromasta (Hosakawa Micron, JP); A kneading device selected from a dispersion kneader and a double roll; And a compression shear processing device selected from a mechano micro device, an extruder, a ball mill, a planetary mill, a mechano fusion device, a nobilta, hybridization, and a rotary ball mill.
[17]
The ninth aspect of the present invention is according to any one of the seventh to eighth aspects, wherein the mixture is 49% to 95% by weight of a graphite material, 3% to 50% by weight of a solid electrolyte, and 1% by weight to a conductive material. It is 10% by weight.
[18]
A tenth aspect of the present invention includes a negative electrode, a positive electrode, and a solid electrolyte membrane interposed between the negative electrode and the positive electrode according to any one of the seventh to ninth aspects, wherein the negative electrode is a negative electrode active material and the composite particles according to the present invention It includes.
[19]
Effects of the Invention
[20]
The composite particle according to the present invention is filled with a conductive material including a solid electrolyte and a conductive material, so that the contact area between the active material and the solid electrolyte is increased. And the path of ion conduction and electron conduction to the inside of the active material particle is extended and maintained. Therefore, in the case of manufacturing a battery using such composite particles, unlike the conventional graphite negative electrode active material, even if a solid electrolyte is used, the problem of lowering the capacity or output of the battery does not occur. In addition, since the composite particles are filled with a solid electrolyte and a conductive material in the carbon particles, a high-density electrode having a low porosity can be manufactured without pressing under severe conditions in order to lower the porosity of the electrode during electrode manufacturing.
[21]
Brief description of the drawing
[22]
The drawings appended to the present specification illustrate preferred embodiments of the present invention, and serve to better understand the technical spirit of the present invention together with the content of the present invention, so the present invention is limited to the matters described in such drawings. Is not interpreted. Meanwhile, the shape, size, scale, or ratio of elements in the drawings included in the present specification may be exaggerated to emphasize a clearer description.
[23]
FIG. 1 is a schematic diagram of a cross-sectional shape of spheroidized graphite particles used as a conventional negative electrode active material and an electrode including the same.
[24]
2 is a schematic diagram of a cross-sectional shape of a composite particle and an electrode including the composite particle according to an embodiment of the present invention.
[25]
3 is an SEM image of composite particles according to Example 1. FIG.
[26]
Mode for carrying out the invention
[27]
Hereinafter, embodiments of the present invention will be described in detail. Prior to this, terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventors appropriately explain the concept of terms in order to explain their own invention in the best way. Based on the principle that it can be defined, it should be interpreted as a meaning and concept consistent with the technical idea of ​​the present invention. Therefore, the configuration described in the embodiments described in the present specification is only the most preferred embodiment of the present invention, and does not represent all the technical spirit of the present invention, and various equivalents that can replace them at the time of application It should be understood that there may be variations.
[28]
[29]
In the entire specification of the present application, when a certain part "includes" a certain constituent element, it means that other constituent elements may be further included rather than excluding other constituent elements unless otherwise stated.
[30]
[31]
In addition, the terms "about" and "substantially" used throughout the specification of the present application are used as a meaning at or close to the numerical value when a manufacturing and material tolerance specific to the stated meaning is presented to aid understanding of the present application. In order to prevent unreasonable use by unscrupulous infringers of the stated disclosures, exact or absolute figures are used.
[32]
[33]
In the entire specification of the present application, description of "A and/or B" means "A or B or both".
[34]
[35]
Throughout this specification, the ratio of each component is based on weight unless otherwise specified.
[36]
[37]
Certain terms used in the detailed description that follow are for convenience and are not limiting. The words'right','left','top surface' and'bottom' indicate directions in the drawings to which reference is made. The words'inwardly' and'outwardly' refer to a direction towards or away from the geometric center of the specified device, system and members, respectively. “Forward”, “rear”, “upward”, “downward” and related words and phrases represent positions and orientations in the drawings to which reference is made and should not be limited. These terms include the words listed above, their derivatives, and words of similar meaning.
[38]
[39]
The present invention relates to a composite particle that can be used as a negative active material for an electrochemical device, a negative electrode including the composite particle, and an electrochemical device including the same. In addition, the present invention provides a method of manufacturing the composite particles. In the present invention, the electrochemical device may be a lithium ion secondary battery, and in particular, may be an all-solid battery using a solid electrolyte as an electrolyte.
[40]
[41]
Composite particles
[42]
The present invention relates to a negative active material for an all-solid-state battery capable of high density of a negative electrode and excellent in high capacity characteristics and cycle characteristics.
[43]
In one embodiment of the present invention, the negative active material is a composite particle including a graphite material, a solid electrolyte, and a conductive material. The composite particle according to the present invention may have the form of secondary particles formed by granulating graphite materials in the form of primary particles, wherein the gap between the granulated graphite materials is a mixture containing a solid electrolyte and a conductive material. Is filled with. Further, all or at least part of the surface of the composite particle may be coated with the mixture.
[44]
In a specific embodiment of the present invention, the composite particles include graphite particles formed by shape adjustment treatment such as spheronization treatment of graphite materials such as scale and/or plate graphite, and the interior thereof is a mixture of a solid electrolyte and a conductive material. Is filled with. In addition, all or at least part of the surface of the graphite particles may be coated with the mixture. In one embodiment of the present invention, the composite particles are obtained through a process of shaping and granulating a mixture comprising a graphite material such as flaky graphite and/or plate-like graphite, a solid electrolyte, and a conductive material with a mechanical external force. Can be.
[45]
2 is a schematic diagram showing a cross section of the composite particle 110 of the present invention and a cross section of an electrode 100 including the same. As shown in FIG. 2, the composite particle 100 according to the present invention includes a graphite particle 113, a solid electrolyte 112, and a conductive material 111 that have been subjected to spherical shape adjustment. In one embodiment of the present invention, the composite particle may have a particle diameter of about 5 μm to 50 μm based on the longest diameter. In one embodiment of the present invention, the particle diameter may be adjusted to 45 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less, or 7 μm or more, 15 μm or more, It can be adjusted to 20㎛ or more, 25㎛ or more, 35㎛ or more, or 45㎛ or more. For example, the particle diameter may have a range of 5 μm to 25 μm or 10 μm to 20 μm.
[46]
In one embodiment of the present invention, the graphite material may be included in the range of 49% to 95% by weight of 100% by weight of the composite particles. Within the above range, the graphite material may be included in an amount of 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In addition, in 100% by weight of the composite particles, the solid electrolyte may be included in a ratio of 3% to 50% by weight, and within the above range, 40% by weight or less, 30% by weight or less, 20% by weight or less, or 10% by weight or less It can be included in the range of. When the content of the graphite material is less than 50% by weight, the ionic conductivity of lithium may be high in the electrode including the composite particles, but the battery energy density decreases. On the other hand, when the content of the graphite material in the composite particles is more than 95% by weight, the conductivity of lithium ions is lowered, so that battery capacity cannot be realized by charging and discharging, and output characteristics are deteriorated. In addition, the content of the conductive material in 100% by weight of the composite particle may be 1 to 10%, and may be appropriately adjusted within the above range according to the content and volume of the solid electrolyte constituting the composite particle. If the content of the conductive material is small compared to the solid electrolyte, the conductivity between the graphite material particles may be lowered.
[47]
In one embodiment of the present invention, the graphite material may be at least one selected from natural graphite and artificial graphite. The natural graphite is a high crystalline natural graphite, which is at least one selected from among plate, scale, crushed, oval and whisker natural graphite. In addition, the artificial graphite may include at least one selected from the group consisting of Mosaic coke-based artificial graphite and needle coke-based artificial graphite.
[48]
In a specific embodiment of the present invention, the graphite material may be a highly crystalline graphite having a surface spacing (d 002 ) of less than 0.337 nm, for example, 0.3340 nm to 0.3360 nm according to the X-ray diffraction measurement device. have. As such graphite material, for example, plate-like and scale-like natural graphite are typical. The higher the crystallinity graphite, the more the crystallinity grows regularly and has a scale shape.
[49]
As for the plate-like graphite or flaky graphite, it is preferable to use a commercial item or to pulverize the graphite of various shapes such as coarse-grained natural graphite or artificial graphite using a pulverizing device to form a plate or scale. In one embodiment of the present invention, the plate-like and/or flaky graphite may have an average particle diameter (D 50 ) of 2 μm to 30 μm.
[50]
As such a grinding device, a counter jet mill (Hosokawa Micron Co., Ltd.) and a current jet (Nisshin Engineering Co., Ltd.) can be used. The plate-like and/or flaky graphite obtained by pulverization or the like has an acute angled portion on the surface, but when assembling into a spherical shape by applying an external mechanical force, the surface is smoothed.
[51]
[52]
The solid electrolyte includes an ion conductive solid electrolyte material and may include a polymer solid electrolyte, an inorganic solid electrolyte, or a mixture of both. The solid electrolyte preferably has an ionic conductivity of 10 -7 s/cm or more.
[53]
In an embodiment of the present invention, the polymer solid electrolyte is a solid polymer electrolyte formed by adding a polymer resin to a solvated lithium salt, or a polymer gel electrolyte containing an organic electrolyte containing an organic solvent and a lithium salt in the polymer resin. I can.
[54]
[55]
The solid polymer electrolyte may be, for example, a polyether polymer, a polycarbonate polymer, an acrylate polymer, a polysiloxane polymer, a phosphazene polymer, a polyethylene derivative, an alkylene oxide derivative, a phosphate ester polymer, a polyeditated lysine ( agitation lysine), polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and a mixture of two or more selected from the group consisting of a polymer containing an ionic dissociation group, but is not limited thereto.
[56]
[57]
In a specific embodiment of the present invention, the solid polymer electrolyte is a polymer resin in which an amorphous polymer such as PMMA, polycarbonate, polysiloxane (pdms) and/or phosphazene is copolymerized with a comonomer in a PEO (polyethylene oxide) main chain. It may include one or a mixture of two or more selected from the group consisting of a branched copolymer, a comb-like polymer, and a crosslinked polymer resin.
[58]
In addition, in a specific embodiment of the present invention, the polymer gel electrolyte includes an organic electrolyte containing a lithium salt and a polymer resin, and the organic electrolyte may include 60 to 400 parts by weight based on the weight of the polymer resin. The polymer resin applied to the gel electrolyte is not limited to a specific component, but, for example, PVC (Polyvinyl chloride)-based, PMMA (Poly (methyl methacrylate))-based, polyacrylonitrile (PAN), polyvinyl fluoride It may be one or a mixture of two or more selected from the group consisting of leadene (PVdF) and polyvinylidene fluoride-hexafluoropropylene (poly(vinylidene fluoride-hexafluoropropylene)), but is not limited thereto.
[59]
[60]
In the electrolyte of the present invention, the lithium salt described above is an ionizable lithium salt , which can be expressed as Li + X − . In this lithium salt anion (X) is not particularly limited, F - , Cl - , Br - , I - , NO 3 - , N (CN) 2 - , BF 4 - , ClO 4 - , PF 6 - , ( CF 3 ) 2 PF 4 - , (CF 3 ) 3 PF 3 - , (CF 3 ) 4 PF 2 - , (CF 3 ) 5 PF - , (CF 3 ) 6 P - , CF 3 SO 3 - , CF 3 CF 2 SO 3 - , (CF 3 SO 2 ) 2 N - , (FSO 2 ) 2 N - , CF 3 CF 2 (CF 3 ) 2 CO - , (CF 3 SO 2 ) 2 CH - , (SF 5 ) 3 C - , (CF 3 SO 2 ) 3 C - , CF 3 (CF 2 ) 7 SO 3 - , CF 3 CO 2 - , CH 3 CO 2 -, SCN - , (CF 3 CF 2 SO 2 ) 2 N - and the like can be given.
[61]
[62]
Meanwhile, in a specific embodiment of the present invention, the polymer-based solid electrolyte may further include an additional polymer gel electrolyte. The polymer gel electrolyte has excellent ionic conductivity (or 10 -4 s/m or more) and has a binding property, providing a function as an electrolyte, as well as providing a binding force between an electrode active material and a binding force between an electrode layer and a current collector. The function of the electrode binder resin to be provided can be provided.
[63]
[64]
Meanwhile, in the present invention, the inorganic solid electrolyte may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or both.
[65]
[66]
In a specific embodiment of the present invention, the sulfide-based solid electrolyte includes a sulfur atom among the electrolyte components, and is not particularly limited to a specific component, and a crystalline solid electrolyte, an amorphous solid electrolyte (glass solid electrolyte), and glass ceramic It may contain one or more of the solid electrolytes. Specific examples of the sulfide-based solid electrolyte include LPS-type sulfide containing sulfur and phosphorus (for example, Li 2 S-P 2 S 5 ), Li 4-x Ge1 -x P x S 4 (x is 0.1 to 2, specifically As x is 3/4, 2/3), Li 10 ± 1 MP 2 X 12 (M=Ge, Si, Sn, Al, X=S, Se), Li 3 . 833 Sn 0 . 833 As 0 . 166 S 4 , Li 4 SnS 4 , Li 3 . 25 Ge 0 .25 P 0. 75 S 4 , Li 2 S-P 2 S 5 , B 2 S 3 -Li 2 S, xLi 2 S-(100-x)P 2 S 5 (x is 70 to 80), Li 2 S-SiS 2 -Li 3 N, Li 2 S-P 2 S 5 -LiI , Li 2 S-SiS 2 -LiI, Li 2 S-B 2 S 3 -LiI, Li 10 SnP 2 S 12 , Li 3 . 25 Ge 0 .25 P 0. 75 S 4 , and the like Thio-LISICON compounds such as, but not limited to this.
[67]
[68]
In a specific embodiment of the present invention, the oxide-based solid electrolyte is an LLTO-based compound ((La,Li)TiO 3 ), Li 6 La 2 CaTa 6 O 12 , Li 6 La 2 ANb 2 O 12 (A is Ca And/or Sr), Li 2 Nd 3 TeSbO 12 , Li 3 BO 2 . 5 N 0 .5 , Li 9 SiAlO 8 , compound LAGP (Li 1 + x Al x Ge 2 -x (PO 4 ) 3 , where 0≤x≤1, 0≤y≤1), a LATP-based compound such as Li 2 O-Al 2 O 3 -TiO 2 -P 2 O 5 (Li 1 + x Al x Ti 2 -x (PO 4 ) 3 , where 0≤x≤1, 0≤y≤1), Li 1 + x Ti 2 - x Al x Si y (PO 4 ) 3 -y (here, 0≤x≤1,0≤y≤1), LiAl x Zr 2-x (PO 4 ) 3 (here , 0≤x≤1, 0≤y≤1 ), LiTi x Zr 2 -x (PO 4 ) 3 (here, 0≤x≤1, 0≤y≤1 ), LPS-based compounds such as Li 2 S-P 2 S 5 , Li 3 . 833 Sn 0 . 833 As 0 . 166 S 4 , Li 4 SnS 4 , Li 3.25 Ge 0.25 P 0.75 S 4 , B 2 S 3 -Li 2 S, xLi 2 S-(100-x)P 2 S 5 (x is 70 ~ 80), Li 2 S-SiS 2 -Li 3 N, Li 2 S-P 2 S 5 -LiI, Li 2 S-SiS 2 -LiI, Li 2 S-B 2 S 3 -LiI, Li 3 N, LISICON, LIPON-based compounds (Li 3+y PO 4-x N x , where 0≤x≤1, 0≤y≤1 ), Li 3 . 25 Ge 0 .25 P 0. 75 S 4 Thio-LISICON compounds such as, perop Sky teugye compound ((La, Li) TiO 3 ), LiTi 2 (PO 4 ) 3 lithium pear kongye compound, components such as , LLZO-based compounds containing lanthanum, zirconium, and oxygen, and the like, and may include one or more of them. However, it is not particularly limited thereto.
[69]
The conductive material is not particularly limited as long as it has conductivity without causing chemical changes to the battery, and examples thereof include graphite such as natural graphite or artificial graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fibers or metal fibers such as VGCF (Vapor grown carbon fiber); Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; It may include one or a mixture of two or more selected from conductive materials such as polyphenylene derivatives.
[70]
[71]
Method for producing composite particles
[72]
The present invention provides a method for producing the composite particles. The composite particles are prepared by preparing a mixture including a graphite material, a conductive material, and a solid electrolyte as described above, and performing a granulation process in which the mixture is spheronized with a mechanical external force, so that the graphite material, the conductive material, and the solid electrolyte are integrated. Complexed particles can be obtained.
[73]
The mixing may be performed using a known mixing device such as a planetary mixer. For example, a graphite material, a conductive material, and a solid electrolyte may be added to the mixing device and stirred at a speed of about 20 rpm to 100 rpm to obtain a mixture thereof. The mixing may be performed in the range of about 1 hour to 3 hours, and the temperature during the mixing process may be performed under conditions of about 30°C to 100°C. However, the conditions such as the stirring speed, stirring time, and stirring temperature are not particularly limited to the above-described range, and may be appropriately controlled so as to obtain a mixed phase in which the introduced materials are uniformly mixed.
[74]
The mixture obtained in the mixing step is subjected to a granulation step in which a mechanical external force such as shear compressive stress is applied to spheroidize. In a specific embodiment of the present invention, the assembling step may be performed using a mechanofusion device or the like. In one embodiment of the present invention, the process may be performed at a speed of about 2,000 rpm to 5,000 rpm. In addition, the process may be performed for about 0.2 hours to 2 hours. In addition, the granulation step may be performed under the conditions of about 30 ℃ to 70 ℃. However, the conditions such as the stirring speed, stirring time and stirring temperature are not particularly limited to the above-described range, and may be appropriately controlled so that the mixture can be obtained as composite particles having an appropriate particle diameter.
[75]
In one embodiment of the present invention, in the assembling process, granurex (Granurex, Furointo Industries, Ltd.), New Daramashin (Seishin Corporation), and Aglaromastar (Hosokawa Micron) are assembled. Shear stress devices with shear compression processing capability such as firearms, hybridization systems (Nara Machinery Co., Ltd.), Mekano Iclos (Nara Machinery Co., Ltd.), and Mechanofusion devices (eg, Hosokawa Micron Co., Ltd.) can be used. .
[76]
In addition, in addition to this, a crushing device selected from among counter jet mills (Hosokawa Micron, JP), ACM palletizers (Hosokawa Micron, JP), and current jets (Nissin, JP); Assembly equipment selected from SARARA (Kawasaki Heavy Industries, Ltd, JP), GRANUREX (Freund Corporation, JP), New Gramasin (Seichin, JP), and Acromasta (Hosakawa Micron, JP); And using a pressure kneader (dispersion kneader), a kneading device selected from two rolls, it is possible to appropriately control the particle size of the graphite material.
[77]
Flaky and/or flat graphite materials introduced as raw materials are subjected to this spheronization treatment, so that the particles are bent or folded, or when other particles are bent or folded, they are introduced into the inside thereof, or attached to the surface of another particle. do. As a result of this, the composite particles may exhibit a granulated shape by overlapping a plurality of scale-like and/or plate-like graphite particles, such as spheroidized graphite particles, and the gap in which the scale-like and/or plate-like particles are overlapped is It is filled with a mixture containing a solid electrolyte (see Fig. 2).
[78]
As described above, since the composite particles according to the present invention are filled with a solid electrolyte and a conductive material, electrochemical performance such as ionic conductivity is remarkably improved compared to the conventional negative electrode active material particles. 1 is a view showing a negative active material particle 11 and an electrode 10 including the same according to the prior art, wherein the gap inside the negative active material particle 11c is left as an empty space, and the conductive material 11a and the solid electrolyte (11b) As this active material is only distributed on the surface of the active material particles, the rate of participating in the electrochemical reaction to the inside of the active material particles was low, and thus, the electrochemical performance such as ionic conductivity and output characteristics is sufficiently exhibited compared to the amount of the input active material. There was a problem that couldn't be done.
[79]
[80]
Hereinafter, a negative electrode of a lithium ion secondary battery using the composite particles of the present invention, and an all-solid-state battery including the negative electrode will be described.
[81]
[82]
cathode
[83]
The present invention relates to a negative electrode for an electrochemical device, and the electrochemical device is preferably an all-solid battery using a solid electrolyte.
[84]
[85]
In one embodiment of the present invention, the negative electrode may include a current collector and a negative active material layer formed on at least one surface of the current collector, and the negative active material layer includes a negative active material, a solid electrolyte, and a conductive material, The negative active material includes the composite particles according to the present invention.
[86]
[87]
Conventional spheronized graphite particles have been particularly difficult to use as a negative electrode for an all-solid battery. For example, spheroidized graphite particles obtained by assembling a flaky graphite material by mechanical external force have a gap, which is an empty space, between the graphite scales. When these spheronized graphite particles are applied to a battery using a liquid electrolyte, the electrolytic solution penetrates into the particles to fill the gap, so that the contact area between the electrode active material and the electrolytic solution does not decrease. However, when the spheroidized graphite particles are applied to an all-solid battery using a solid electrolyte, the gaps in the spheroidized graphite particles are not filled with the electrolyte but remain empty spaces, so contact between the electrolyte and the particles is limited to the surface of the particles. Accordingly, the electrochemical reaction site was reduced, and there was a problem of capacity reduction. In order to increase the discharge capacity per volume by removing such gaps and densifying the active material layer, rolling must be performed at high pressure. In this case, since the particles are flattened and oriented in one direction, there is a problem in that the diffusion of ions is lowered.
[88]
However, on the contrary, in the composite particle according to the present invention, the inside of the particle is filled with a mixture of a solid electrolyte and a conductive material, so that the porosity in the particle is very low.
[89]
In addition, in a specific embodiment of the present invention, the negative active material layer may further include a binder material. The addition of the binder material may increase the bonding strength between the negative electrode active material layer and the current collector and/or the solid electrolyte membrane, and independently or at the same time, it is helpful to improve the bonding strength between the constituent components included in the negative electrode active material.
[90]
The method of manufacturing the negative electrode is not particularly limited, and may, for example, be manufactured according to the following procedure. First, an electrode mixture comprising composite particles, a solid electrolyte, and a conductive material is prepared, and the mixture is coated on the surface of a current collector to form an electrode active material layer. At this time, by applying an appropriate pressure to the coated electrode active material layer, the porosity in the electrode can be controlled to a desired level.
[91]
In addition, in a specific embodiment of the present invention, the electrode preferably has a porosity as low as 0 to 10 vol%. The porosity can be measured using BEL JAPAN's BELSORP (BET equipment) using an adsorption gas such as nitrogen or by a method such as a mercury intrusion porosimetry. Alternatively, in one embodiment of the present invention, the true density of the electrode active material layer is determined from the density (apparent density) of the obtained electrode (electrode active material layer) and the composition ratio of the materials included in the electrode (electrode active material layer) and the density of each component. Then, the porosity of the electrode active material layer can be calculated from the difference between the apparent density and the net density.
[92]
Meanwhile, the solid electrolyte and the conductive material used when manufacturing the negative electrode may be used without limitation as long as it is used for manufacturing the composite particle.
[93]
[94]
All solid battery
[95]
The present invention relates to an all-solid-state battery, wherein the all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane interposed between the positive electrode and the negative electrode, and the negative electrode is according to the present invention and has the above-described structural features.
[96]
[97]
The positive electrode includes a current collector and a positive electrode active material layer formed on at least one side of the current collector, and the upper electrode active material layer includes a positive electrode active material, a solid electrolyte, and a conductive material. In addition, in a specific embodiment of the present invention, the positive active material layer may further include a binder material. The addition of the binder material may increase the bonding strength between the positive electrode active material layer and the current collector and/or the solid electrolyte membrane, and independently or in addition to this, it is helpful to improve the bonding strength between the constituents included in the positive electrode active material.
[98]
[99]
The positive electrode active material may be used without limitation as long as it can be used as a positive electrode active material for a lithium ion secondary battery. For example, the positive electrode active material may include a layered compound such as lithium cobalt oxide (LiCoO 2 ) or lithium nickel oxide (LiNiO 2 ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as the formula Li 1 + x Mn 2 - x O 4 (wherein x is 0 to 0.33), LiMnO 3 , LiMn 2 O 3 , LiMnO 2, etc.; Lithium copper oxide (Li 2 CuO 2 ); LiV 3 O 8 , LiFe 3 O 4 , V 2Vanadium oxides such as O 5 and Cu 2 V 2 O 7 ; Ni site type lithium nickel oxide represented by the formula LiNi 1 - x M x O 2 (here, M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn 2 - x M x O 2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 ~ 0.1) or Li 2 Mn 3 MO 8 (where M = Fe, Co, A lithium manganese composite oxide represented by Ni, Cu or Zn); LiNi x Mn 2 - xSpinel structure lithium manganese composite oxide represented by O 4 ; LiMn 2 O 4 in which part of Li in the formula is substituted with alkaline earth metal ions ; Disulfide compounds; Fe 2 (MoO 4 ) 3 and the like. However, it is not limited only to these.
[100]
[101]
The conductive material and the solid electrolyte can be used without limitation as long as it can be used for the composite particles.
[102]
[103]
In the present invention, the solid electrolyte membrane is made of a polymer material and/or an inorganic material exhibiting ionic conduction characteristics, and may be applied as an ion conductive electrolyte to an all-solid-state battery that does not use a liquid electrolyte. The ion conductive polymer material and inorganic material included in the solid electrolyte membrane can be used without limitation as long as it can be used in the manufacture of the composite particles of the present invention. You can refer to it.
[104]
[105]
In one embodiment of the present invention, the negative electrode and/or the positive electrode may further include various additives for the purpose of supplementing or improving physicochemical properties. The additive is not particularly limited, but may include one or more additives such as an oxidation stabilizer additive, a reduction stabilizer additive, a flame retardant, a heat stabilizer, an antifogging agent, and the like.
[106]
[107]
On the other hand, the binder material used for the negative electrode and/or positive electrode is not particularly limited as long as it is a component that aids in bonding of an active material and a conductive material and bonding to a current collector, and for example, polyvinylidene fluoride polyvinyl alcohol, carboxymethyl Cellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM , Styrene butadiene rubber, fluorine rubber, and various copolymers. The binder resin may be included in a range of 1 to 30% by weight, or 1 to 10% by weight, based on 100% by weight of the electrode layer.
[108]
[109]
In addition, in one embodiment of the present invention, the negative electrode and/or positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes to the battery, for example, stainless steel, aluminum Nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver or the like may be used. Among them, it may be appropriately selected and used according to the polarities of the anode and the cathode. In one embodiment of the present invention, the current collector may have a thickness of about 6 μm to 500 μm.
[110]
[111]
In addition, the present invention provides a battery module including the secondary battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source.
[112]
[113]
In this case, a specific example of the device may include a power tool that is driven by an electric motor; Electric vehicles including electric vehicles (EV), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; Electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); Electric golf cart; Power storage systems, etc., but are not limited thereto.
[114]
[115]
Hereinafter, the present invention will be further described through examples, but the following examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.
[116]
[117]
1) Preparation Example 1 Preparation of composite particles
[118]
Example 1
[119]
Plate-shaped natural graphite (BTR four UP10, the average particle diameter (D 50 ) = 9㎛), Li 7 La 3 Zr 2 O 12 15:: 84, and the carbon black in a weight ratio flag four planetary mixer of 500ml capacity at the rate of 1 (pri -mix, 2P-03), and stirred at room temperature for 60 minutes at a speed of 50 rpm to prepare a mixture. The temperature of the planetary mixer was maintained at 40°C. The obtained mixture was introduced into a mechano fusion device (NOB-130-VC manufactured by Hosokawa micron), and a shear compressive stress was applied at 3,000 rpm for 30 minutes to prepare composite particles. At this time, the temperature of the mechanofusion device was maintained at 40°C. The particle diameter of the obtained composite particles was about 15 μm. The particle size and particle size distribution were measured using a Malvern mastersizer 3000 by diluting the composite particles 1,000 times in xylene.
[120]
[121]
Examples 2 to 4
[122]
Plate-shaped natural graphite (BTR company UP10, average particle diameter (D 50 ) = 9㎛ ), Li 2 S-P 2 S 5 and carbon black in the ratio of [Table 1] 500 ml capacity planetary mixer (pri-mix company, 2P -03) and stirred at room temperature for 60 minutes at a speed of 50 rpm to prepare a mixture. The temperature of the planetary mixer was maintained at 40°C. The obtained mixture was introduced into a mechano fusion device (NOB-130-VC manufactured by Hosokawa micron), and a shear compressive stress was applied at 3,000 rpm for 30 minutes to prepare composite particles. At this time, the temperature of the mechanofusion device was maintained at 40°C. The particle diameter of the obtained composite particles was about 15 μm. The particle size and particle size distribution were measured using a Malvern mastersizer 3000 by diluting the composite particles 1,000 times in xylene. 3 shows a SEM image of the composite particle of Example 2. According to this, it was confirmed that as the plate-shaped particles were spheroidized and granulated, the gaps between the particles were filled with a mixture of a solid electrolyte and a conductive material, and the surface of the composite particles was covered with the mixture. The mixing ratio (% by weight) of each material is shown in Table 1 below.
[123]
[124]
Example 5
[125]
Plate-shaped natural graphite (BTR company UP10, average particle diameter (D 50 ) = 9㎛ ), Li 2 S-P 2 S 5 and carbon black in a weight ratio of 84:15 : 1 500 ml capacity planetary mixer (pri-mix) Inc., 2P-03), and stirred at room temperature for 60 minutes at a speed of 50 rpm to prepare a mixture. The temperature of the planetary mixer was maintained at 40°C. The obtained mixture was introduced into a mechano fusion device (NOB-130-VC manufactured by Hosokawa micron), and a shear compressive stress was applied at 4,000 rpm for 15 minutes to prepare composite particles. At this time, the temperature of the mechanofusion device was maintained at 40°C. The particle diameter of the obtained composite particles was about 11 μm. The particle size and particle size distribution were measured using a Malvern mastersizer 3000 by diluting the composite particles 1,000 times in xylene.
[126]
[127]
Example 6
[128]
Composite particles were prepared in the same manner as in Example 5, except that the mechano fusion device was subjected to shear compressive stress at 2,000 rpm for 60 minutes to obtain composite particles having a particle diameter of about 19 μm.
[129]
[130]
Example 7
[131]
Plate-shaped natural graphite (BTR company UP5, average particle diameter (D 50 ) = 5㎛), Li 2 S-P 2 S 5 and carbon black in a weight ratio of 84:15 : 1 500 ml capacity planetary mixer (pri-mix Inc., 2P-03), and stirred at room temperature for 60 minutes at a speed of 50 rpm to prepare a mixture. The temperature of the planetary mixer was maintained at 40°C. The obtained mixture was introduced into a mechano fusion device (NOB-130-VC manufactured by Hosokawa micron), and a shear compressive stress was applied at 3,000 rpm for 30 minutes to prepare composite particles. At this time, the temperature of the mechanofusion device was maintained at 40°C. The particle diameter of the obtained composite particles was about 13.8 µm. The particle size and particle size distribution were measured using a Malvern mastersizer 3000 by diluting the composite particles 1,000 times in xylene.
[132]
[133]
Comparative Example 1
[134]
Active material particles were prepared in the same manner as in Example 1, except that only plate graphite was used without adding a conductive material and a solid electrolyte.
[135]
[136]
[Table 1]
Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7
Graphite material (planar natural graphite) (% by weight) 100 85 94 89 84 84 84 84
Solid electrolyte (Li 2 S-P 2 S 5 ) (% by weight) - 15 5 10 15 15 15 15
Conductive material (carbon black) (% by weight) - One 10 11 One One One One
[137]
[138]
2) Preparation Example 2 Preparation of negative electrode
[139]
A negative electrode was prepared by using the composite particles obtained in each of the Examples and Comparative Examples as a negative active material. The negative electrode composition was prepared as shown in Table 2 below. In Comparative Example 1-1 and Comparative Example 1-2, the composite particles of Comparative Example 1 were used, and as shown in Table 2, a solid electrolyte material was differently prepared. The negative active material obtained in each of the Examples and Comparative Examples exhibited an electric capacity of about 355mAh/g. An electrode mixture was prepared by mixing an active material, a solid electrolyte, a conductive material, and a binder as shown in Table 2, and the electrode mixture was coated on a copper thin plate (20 μm in thickness) and rolled at room temperature to prepare a negative electrode. In the obtained negative electrode, the loading amount of the negative active material was 9.2 mg/cm 2 based on the electrode area, and its electric capacity was 3.27 mAh/cm 2 based on the electrode area, and the porosity was 22%. For the porosity, the true density of the electrode active material layer was calculated from the composition ratio of electrode materials and the density of each component, and then the porosity of the electrode active material layer was calculated from the difference between the apparent density and the net density.
[140]
[141]
3) Manufacture of all solid battery
[142]
Lithium metal was used as the counter electrode, and a battery (coin type half cell) was manufactured using each electrode prepared in Preparation Example 2. A solid electrolyte membrane (70㎛, 2.8x10 -3 S/cm, Li 10 SnP 2 S 12 ) was interposed between the used electrodes .
[143]
[144]
[145]
[Table 2]
Comparative Example 1-1 Comparative Example 1-2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7
Active material (composite particles) (% by weight) 75 75 89.28 79.79 84.27 89.28 89.28 89.28 89.28
Solid electrolyte (Li 2 S-P 2 S 5 ) (% by weight) 20 20 6.61 16.01 11.57 6.61 6.61 6.61 6.61
Conductive material (carbon black) (% by weight) 3 3 2.11 2.2 2.16 2.11 2.11 2.11 2.11
Binder (NBR) (% by weight) 2 2 2 2 2 2 2 2 2
[146]
[147]
4) Battery performance evaluation
[148]
For the batteries prepared in each of the Examples and Comparative Examples, initial use and cycle characteristics were confirmed. The first 3 cycles were charged to 0.05V in 0.05C CC mode and then charged in CV mode to a current density of 0.05C, and discharge was discharged to 1.5V in 0.05C CC mode. From the 4th time, it was charged to 0.05V in 0.3C CC mode and then charged in CV mode to a current density of 0.05C, and the discharge was discharged 30 times in 0.3C CC mode to 1.5V to compare capacity retention. In the experiment, the capacity retention rate was calculated based on the following .
[149]
[150]

[151]
Capacity retention rate (%)=[30th cycle discharge capacity/2nd cycle discharge capacity] X 100
[152]
[153]
Table 3 below summarizes the initial capacity and capacity retention results of 30 cycles of the batteries prepared in each Example and Comparative Example. Accordingly, it was confirmed that the batteries according to the examples exhibited superior performance compared to the batteries of the comparative examples in terms of initial capacity and capacity retention rate.
[154]
[155]
[Table 3]
Comparative Example 1-1 Comparative Example 1-2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7
Initial capacity (0.05C-rate)(mAh/g) 278 262 294 315 336 342 331 326 307
0.3C capacity retention 30 cycle 40 32 61 74 82 79 68 72 64
[156]
[157]
As described above, it was confirmed that the higher the electrolyte ratio inside the composite particles, the better the ion mobility into the composite particles, resulting in excellent low-rate capacity characteristics and excellent capacity retention.
[158]
On the other hand, when the composite particles were prepared using the oxide-based solid electrolyte as in Example 1, the performance improvement effect was confirmed compared to the case where it was not (Comparative Example 2), but when a sulfide-based solid electrolyte such as Example 4 was used. Compared to that, the ductility of the material was low, and the performance improvement effect was not high.
[159]
On the other hand, looking at Examples 4, 5 and 6, when the particle diameter of the composite particle is small, the electrolyte component between the composites is insufficient, and when the particle diameter of the composite particle is large, the electrolyte component contained in the particle is insufficient. It was confirmed that the performance was somewhat lower than in Example 4.
[160]
In addition, in the case of Example 7 to which small particle plate-like graphite was applied, composite particles could be obtained, but the ionic conductivity of the solid electrolyte was lowered due to the increase in the surface area of ​​the graphite particles, and the battery performance was slightly lowered.
Claims
[Claim 1]
Graphite materials include granulated graphite particles, the graphite material is derived from any one of natural graphite and artificial graphite, and the gap between the graphite materials of the graphite particles is a mixture containing a solid electrolyte and a conductive material. The composite particle for negative electrode active material is filled and all or at least part of the outer surface of the graphite particle is covered with the mixture.
[Claim 2]
The composite particle of claim 1, wherein the composite particle has a particle diameter of 5 μm to 50 μm.
[Claim 3]
The composite particle of claim 1, wherein the natural graphite is a highly crystalline natural graphite selected from among plate-like, scale-like, crushed, oval-like and whisker-like natural graphite.
[Claim 4]
The composite particle for negative active material according to claim 1, wherein the content of the solid electrolyte is 3% to 50% by weight relative to 100% by weight of the composite particle.
[Claim 5]
The composite particle for negative active material according to claim 1, wherein the solid electrolyte contains a sulfide-based solid electrolyte.
[Claim 6]
The composite of claim 1, wherein the conductive material comprises one or a mixture of two or more selected from graphite, carbon black, conductive fiber, metal powder, potassium titanate, conductive whiskey, conductive metal oxide, and polyphenylene derivative. particle.
[Claim 7]
A method for manufacturing composite particles for negative electrode active materials, comprising preparing a mixture including a graphite material, a conductive material, and a solid electrolyte, and performing a granulation process of spheroidizing the mixture with a mechanical external force to form a graphite material, a conductive material. And a solid electrolyte to obtain a composite particle composite, wherein the composite particle is according to claim 1, wherein the composite particle is produced.
[Claim 8]
The method of claim 7, wherein the granulation process comprises: a crushing device selected from a counter jet mill (Hosokawa Micron, JP), an ACM palliator (Hosokawa Micron, JP), and a current jet (Nissin, JP); Assembly equipment selected from SARARA (Kawasaki Heavy Industries, Ltd, JP), GRANUREX (Freund Corporation, JP), New Gramasin (Seichin, JP), and Acromasta (Hosakawa Micron, JP); A kneading device selected from a dispersion kneader and a double roll; And Mechano micro device, extruder, ball mill, planetary mill, mechano fusion device, nobilta, hybridization, and a compression shear type processing device selected from a rotary ball mill that is performed by combining one or two or more devices selected from , A method of manufacturing composite particles.
[Claim 9]
The method of claim 7, wherein the mixture is 49% to 95% by weight of a graphite material, 3% to 50% by weight of a solid electrolyte, and 1% to 10% by weight of a conductive material.
[Claim 10]
An all-solid-state battery comprising a negative electrode, a positive electrode, and a solid electrolyte membrane interposed between the negative electrode and the positive electrode, wherein the negative electrode includes the composite particles according to claim 1 as a negative electrode active material.