[1]Mutual citations and related applications
[2]This application claims the benefit of priority based on Patent Application No. 10-2016-0156826 Korea dated 23 November 2016 and May, all information disclosed in the literature of the Korea patent application are included as part of the specification.
[3]Art
[4]The present invention relates to a lithium secondary battery comprising a positive electrode, and this secondary battery.
BACKGROUND
[5]
There is demand for secondary batteries as an energy source is rapidly increasing as the development of technology and the demand for mobile devices increases. The secondary battery has a high energy density and voltage, long cycle life, self-discharge rate are commercially available and widely used low-lithium secondary battery.
[6]
As a cathode active material of a lithium secondary battery has been used the lithium transition metal complex oxide, among the operation voltage it is high and capacitance characteristics superior LiCoO 2 is mainly used for the lithium-cobalt composite metal oxide. However, LiCoO 2 has the thermal properties since the extremely poor in destabilization of the crystal structure of the de-lithium, and also high mass limit to use as a power source in fields such as electric cars.
[7]
LiCoO 2 as a material to replace, the lithium manganese-metal composite oxide (LiMnO 2 or LiMn 2 O 4 and the like), a lithium iron phosphate compound (LiFePO 4 , etc.) or lithium nickel-metal composite oxide (LiNiO 2 , etc., etc.) have been developed. Among them get a high reversible capacity of about 200mAh / g has been actively studied than the research and development for a high-capacity lithium-nickel composite metal oxide which is easily implemented in the cell. However, LiNiO 2 has LiCoO 2 has a problem that as compared to the poor thermal stability happens, an internal short circuit due to pressure from the outside in the charge is at a positive electrode active material itself is decomposed resulting in a rupture or ignition of the battery.
[8]
Accordingly, LiNiO 2 superior reversible capacity is maintained, while as a method for improving the low thermal stability, a method for substituting part of nickel (Ni), cobalt (Co) or manganese (Mn) has been proposed. However, a LiNi substituting a part of Ni with Co 1 - α Co α O 2 In the case of (α = 0.1 ~ 0.3) look excellent charge and discharge characteristics and life characteristics, a low thermal stability problems. In the case of substituting a part of Ni with excellent thermal stability Mn nickel manganese-based lithium-metal composite oxide, and nickel-cobalt-manganese-based lithium-metal composite oxide substituted by Mn, and Co (hereinafter simply referred to as "NCM-based lithium oxide") but the advantage of a relatively good cycle characteristics and thermal stability, does not lower the resistance is not a metal body penetrate when an internal short circuit, such as nail bars, can lead to serious problems in the safety aspects such as fire or explosion due to instantaneous overcurrent .
Detailed Description of the Invention
SUMMARY
[9]
The present invention can suppress the over-current by high capacity, high output performance, increasing the resistance of the excellent cycle characteristics and while maintaining thermal stability, in the case of passing through the metal body electrode as not from the outside electrode upper layer and the metal element due to over-current the reliability that can prevent ignition or explosion of a battery improved secondary battery positive electrode and intended to provide a secondary battery including the same.
Problem solving means
[10]
Throughout the present invention the cathode current collector; The positive electrode collector is laminated on the whole, the first positive electrode active material and the first positive electrode material mixture layer containing a first conductive material; And it is stacked on the first positive electrode material mixture layer and the second positive electrode active material and a second conductive material, the second positive electrode material mixture layer comprising; average particle size of the second cathode active material, includes (D 50 ) is the first the positive electrode active material average particle diameter (D 50 is from 5 to 80%), the ratio of the specific surface area of the second conductive material to the specific surface area of the second positive electrode active material provides not more than 9, a secondary battery positive electrode.
[11]
[12]
Further, the present invention provides a rechargeable lithium battery including the positive electrode.
Effects of the Invention
[13]
Secondary battery positive electrode according to the invention are high-capacity, while maintaining the high output performance, and excellent cycle characteristics and thermal stability, when passing through the metal body electrode, such as nail from outside the resistance of the electrode upper layer and the metal body is increased to an over-current can be suppressed, it is possible to prevent the ignition or explosion of the battery due to over-current.
Brief Description of the Drawings
[14]
1 is a schematic cross-sectional view of a secondary battery positive electrode according to an embodiment of the present invention.
Mode for the Invention
[15]
Hereinafter, the present invention will be described to assist understanding of the present invention in more detail. In this case, the specification and are should not be construed as limited to the term general and dictionary meanings used in the claims, the inventor has properly define terms to describe his own invention in the best way on the basis of the principle that can be interpreted based on the meanings and concepts corresponding to technical aspects of the present invention.
[16]
The accompanying drawings are intended to clarify the invention, but is not limited to the embodiment of the figure. The shapes of the elements in the figures and the size and the like than can be exaggerated for the sake of clarity, the description and the related portion is not omitted, and the same components, functions in the scope of the same idea will be described with the same reference numerals.
[17]
[18]
1 is a schematic cross-sectional view of a secondary battery positive electrode according to an embodiment of the present invention.
[19]
1, a secondary battery, the positive electrode 100 according to an embodiment of the present invention includes a positive electrode collector 10, the cathode current collector 10, a first positive electrode material mixture layer 21 and the second stacked on the 1 includes a positive electrode material mixture layer of the second positive electrode material mixture layer 22 is laminated on the (21). The first positive electrode material mixture, and layer 21 includes the first material is a cathode active material and the first challenge, it said second positive electrode material mixture layer 22 includes a second material is a cathode active material and the second conductive.
[20]
The first and second positive electrode mixture layer (21, 22) is the additive of a filler, etc. to the slurry according to the positive electrode active material, then applying a slurry by mixing a conductive material and a binder, it may be made by drying and rolling, need the may further include.
[21]
[22]
The first positive electrode active material and / or the second cathode active material may include a lithium transition metal oxide represented by the following general formula (1).
[23]
Formula 1
[24]
Li and Ni 1 eral y Co x Mn y M z O 2
[25]
Wherein, M is any one or more elements selected from the group consisting of Al, Zr, Ti, Mg, Ta, Nb, Mo and Cr, 0.9≤a≤1.5, 0≤x≤0.5, 0≤y≤0.5, 0≤z≤0.1, a 0≤x + y≤0.7.
[26]
However, the first positive electrode active material and / or the not necessarily be two positive electrode active material is a lithium transition necessarily limited to a metal oxide represented by the general formula (1), wherein the first cathode active material and / or the second cathode active material is lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ) substituted with a compound or layered compound, one or more transition metals, and the like; Formula Li 1 + x1 Mn 2-x1 O 4 (here, x 1 is 0 to 0.33), LiMnO 3 , LiMn 2 O 3 , LiMnO 2 Li-Mn oxide and the like; Lithium copper oxide (Li 2 CuO 2 ); LiV 3 O 8 , LiV 3 O 4 , V 2O 5 , Cu 2 V 2 O 7 of vanadium oxide and the like; Formula LiNi 1 - x2 M 1 x2 O 2 (where, M 1 = Co, and Mn, Al, Cu, Fe, Mg, B or Ga, x 2 = 0.01 ~ 0.3 Im) Ni site type lithium nickel oxide which is represented by .; Formula LiMn 2-x3 M 2 x3 O 2 (where, M 2 = a Co, Ni, Fe, Cr, Zn or Ta, x 3 = 0.01 ~ 0.1 Im) or Li 2 Mn 3 M 3 O 8(Wherein, M 3 lithium-manganese composite oxide represented by = Fe, Co, Ni, Cu or Zn); LiNi x4 Mn 2 - x4 O 4 (here, x 4 = 1 0.01 ~ Im), lithium-manganese composite oxide of a spinel structure represented by; A portion of Li is substituted with alkaline earth metal ions formula LiMn 2 O 4 ; Disulfide compounds; Fe 2 (MoO 4 ) 3 and the like.
[27]
On the other hand, the first and second positive electrode active material may comprise lithium transition metal oxide having the same composition, may comprise a lithium transition metal oxide of a different composition.
[28]
[29]
Wherein the mean particle size of the first cathode active material (D of the present invention 50 ) has an average particle diameter (D of the second positive electrode active material 50 is larger than), specifically, the mean particle size of the second cathode active material (D 50 of) the first positive electrode active material the average particle diameter (D 50 meets the 5-80% of).
[30]
In the present invention, the average particle diameter (D 50 ) is defined as a particle diameter corresponding to 50% of the cumulative volume in the particle size distribution curve. The average particle diameter (D 50 ), for example, can be measured using a laser diffraction method (laser diffraction method). For example, the average particle diameter (D in the positive electrode active material 50 by introducing a method for measuring a) is then dispersed in a dispersion medium, the particles of the positive electrode active material, a commercially available laser diffraction particle size measuring apparatus (for example, Microtrac MT 3000) of about after examining the ultrasound output of 28kHz to 60W, the average particle diameter (D equal to 50% of the volume of the accumulation in the measurement device 50 can be calculated).
[31]
That is, the positive electrode collector 10 and the adjacent first positive electrode material mixture layer 21 includes a first cathode active material of a relatively large particle diameter as, the relatively small second positive electrode material mixture layer 22 located in the electrode upper It includes a second positive electrode active material particle.
[32]
Accordingly, the first surface area of ​​the first positive electrode active material contained in the first positive electrode material mixture layer 21 is relatively small, the specific surface area of ​​the second positive electrode active material included in the second positive electrode material mixture layer 22 is large relatively, the first and second if containing a conductive material in the same amount in the positive electrode material mixture layer first positive electrode material mixture layer 21 represents a relatively high electrical conductivity, and the second positive electrode material mixture layer 22 represents a relatively low electrical conductivity. If the electrical conductivity of the electrode of the upper second positive electrode material mixture layer 22 is less the greater the resistance of the positive electrode and the metallic body of the case to pass through the metal body is the electrode from the outside.
[33]
However, only by forming a multi-layer structure, unlike the particle diameter of the positive electrode active material had when passing through the metal body is the electrode from the exterior of the improved stability requirements there is a limit to increase the resistance of the anode and a metal body.
[34]
[35]
The purpose of this invention is the average particle diameter (D of the positive electrode active material 50 anode if the first and second through the metal body electrode by controlling the conductive material in the specific surface area ratio of the specific surface area of the positive electrode active material in the positive electrode material mixture layer, unlike a) and stylized significantly increase the resistance of the metal body, thereby suppressing the over-current, and improved the stability to avoid the possibility of ignition or explosion of the battery due to overcurrent along.
[36]
[37]
Specifically, the second positive electrode material mixture layer 22 located in the upper part of the electrode is such that the second conductive material in the specific surface area ratio is 9 or less to the specific surface area of ​​the second cathode active material.
[38]
In this manner the can further reduce the electrical conductivity of the second positive electrode material mixture layer 22 by ensuring that the specific surface area of ​​the non-member second conductive 9 or less to the specific surface area of ​​the second positive electrode active material, whereby the penetrating body is a metal from the outside If the second positive electrode material mixture layer 22 is greatly increased, and a resistance between the metal body may have an effect on the voltage drop through the initial significantly improve stability.
[39]
[40]
In addition, the first positive electrode material mixture layer 21 adjacent to the positive electrode collector 10 may be such that the first conductive material in the specific surface area ratio is 11 or more to the specific surface area of ​​the first positive electrode active material.
[41]
In this manner the can further increase the electrical conductivity of the first positive electrode material mixture layer 21 by ensuring that at least 11 of the specific surface area ratio material first conductivity to the specific surface area of the first positive electrode active material, the electrical conductivity of the positive electrode thus It is maintained at a constant level, yet it is possible to increase the resistance between the anode and a metal body when the body is through the metal from the outside.
[42]
[43]
That is, one embodiment of the present invention, the average particle diameter (D of the positive electrode active material 50 by controlling the conductive material in the specific surface area ratio of the specific surface area of the positive electrode active material according to the first and second positive electrode material mixture layer, unlike a) the upper layer of the electrode positioned in the second anode further reduce the electrical conductivity and the first electrically conductive is a certain level of electrical conductivity of the positive electrode by increasing the positive electrode material mixture layer 21 located in the lower part of the electrode material mixture layer 22 that is passing through the initial It was maintained by significantly increasing the resistance between the anode and a metal body when the body is through the metal from the outside even without reducing the output characteristics and the like.
[44]
[45]
Wherein the mean particle size of the first cathode active material (D 50 ) is from 10 to be 100㎛ and, wherein the mean particle size of the second cathode active material (D 50 ) may be 1 to 15㎛.
[46]
The average particle diameter (D 50 average particle size (D of the second positive electrode active material in the) range of 50 a) the first positive electrode active material average particle diameter (D in 50 can be such that 5-80% of).
[47]
Wherein the average particle diameter (D 2 positive electrode active material 50 ) is a first positive electrode active material average particle diameter (D 50 , and may cause a lot due to the extremely large specific surface area of a side reaction, if smaller than 5% of), the dispersibility over electrode fabrication process there can be difficulties, there is a conductive electrode and the resistance difference between the lower layer electrode can be insufficient if it exceeds 80%.
[48]
[49]
Wherein the specific surface area of the first cathode active material is in the range of 0.1 to 0.8 m 2 may be / g. The first is 0.1m specific surface area of the positive electrode active material 2 , if / g and less than might be a problem, such as a cell output characteristic deterioration, 0.8 m 2, there is a problem such as the adhesion of the positive electrode current collecting body and falling if it exceeds / g can.
[50]
[51]
The specific surface area of the second cathode active material is 0.5 to 1.5 m 2 may be / g. The second is the specific surface area of the positive electrode active material 0.5m 2 can be difficult to improve, if / g less than the stability, 1.5m 2 / g exceeds because of the extremely large specific surface area may result in a portion of the reactivity with the electrolyte solution increases cell performance have.
[52]
[53]
Wherein the weight ratio of the first and the second positive electrode active material contained in the first and second positive electrode mixture layer (21, 22) is from 1: 1 to 1: may be 8 days.
[54]
By the first and second positive electrode active material to satisfy the above weight ratio range it is possible to ensure the properties such as improved cell output characteristics and long life.
[55]
[56]
On the other hand, the first and second positive electrode material mixture layer 21, the first and second conductive total weight of material contained in can be a 0.2 to 20% by weight relative to the total weight of the first and second positive electrode active material.
[57]
[58]
The first and so long as it has suitable conductivity without causing chemical changes up to the second cell conductive material is not particularly limited, for example, graphite such as natural graphite or artificial graphite; Carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fibers; Copper, nickel, aluminum, silver metal powder or metal fiber and the like; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or it may be a conductive polymer such as polyphenylene derivative.
[59]
The first and may be used the same conductive material, second conductive material, it is also possible to use a conductive material of different materials. However, when considering the ease of the process and cost reduction may be desirable to use the same conductive material.
[60]
[61]
First and second conductive material in a weight ratio comprised in the first and second positive electrode mixture layer (21, 22) is from 1: 0.1 to 1: may be one day, more preferably from 1: 0.1 to 1: 0.8 days have.
[62]
Thus, the first and second positive electrode material mixture layer 21, the first and second conductive for the content material conductive to a specific surface area of ​​the positive electrode active material in the first and second positive electrode material mixture layer by within the range material contained in it is possible to adjust the specific surface area ratio. However, it is not necessarily limited to varying the content of the conductive material in the method for adjusting the specific surface area ratio.
[63]
[64]
The first and second conductivity-average particle diameter (D material 50 ) may be from 5 to 150nm.
[65]
The average particle diameter (D in the range of 50 using the first and second conductive material having a) can be adjusted to the conductive material surface area ratio of the specific surface area of the positive electrode active material in the first and second positive electrode material mixture layer. In this case, the first and second conductive material is the same average particle diameter (D 50 may use a conductive material), different average particle size (D 50 may use a conductive material).
[66]
[67]
Secondary battery, the positive electrode 100 in accordance with one embodiment of the present invention may be a surface resistance of the electrode showing the electrical conductivity of the first positive electrode material mixture layer 21 is 0.010 to 1,000Ωcm, the second positive electrode material mixture layer 22 the surface resistance of the electrode showing the electrical conductivity of the may be 20 to 50,000Ωcm.
[68]
The first and the can 2, significantly increasing the resistance between the anode and a metal body to have an electrical conductivity of the positive electrode mixture layer (21, 22) when the through-body metal even from the outside without lowering the light output characteristic by satisfying the above-mentioned range .
[69]
[70]
On the other hand, the positive electrode current collector 10 so long as it has suitable conductivity without causing chemical changes in the battery is not particularly limited, for example in stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface carbon, nickel, titanium, can be used as such as to a surface treatment or the like. In addition, the cathode current collector 10, typically may have a thickness of from 3 to 500㎛, the positive electrode collector 10 may be processed to form fine irregularities on the surface to increase the adhesion of the positive electrode active material. For example, films, sheets, foils, nets, porous structures, foams and non-woven fabrics or the like can be used in various forms.
[71]
[72]
The thickness ratio of the first and second positive electrode mixture layer (21, 22) is from 1: may be 8: 1 to 1. Specifically, the thickness of the first thickness may be from 15 to 100㎛ of the positive electrode material mixture layer 21 and the second positive electrode material mixture layer 22 may be 30 to 150㎛.
[73]
[74]
On the other hand, the binder contained in the first and second positive electrode mixture layer (21, 22) serves to improve the adhesion of the entire positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode collector. Specific examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile (polyacrylonitrile), woods (CMC as carboxymethylcellulose ), starch, hydroxypropylcellulose with a Woods, reproduced cellulose cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated -EPDM, styrene-butadiene rubber (SBR), and a fluorine rubber, or the like of these various copolymers, a singly or in combination of two or more thereof may be used of these. The binder may comprise from 1% by weight to 30% by weight based on the total weight of the positive electrode active material layer.
[75]
[76]
The positive electrode may be produced according to the conventional method of manufacturing a positive electrode. Specifically, there can be prepared the positive electrode active material, conductive material, binder, and after coating the composition for forming a positive electrode material mixture layer containing a solvent on the positive electrode collector and dried and rolled. In this case the same as the positive electrode active material, binder, conductive material type and content discussed above.
[77]
The solvent may be a day for one commonly used in the art, and dimethyl cell width side (dimethyl sulfoxide, DMSO), isopropyl alcohol (isopropyl alcohol), N- methylpyrrolidone (NMP), acetone (acetone) or water, etc., and there is a singly or as mixtures of two or more thereof may be used of these. The amount of the solvent is in about in consideration of the coating thickness of the slurry, the production yield by dissolving or dispersing the positive electrode active material, conductive material and a binder, so as to have a subsequent viscosity that can indicate the excellent thickness uniformity upon coating for the positive electrode produced sufficient Do.
[78]
[79]
Further, as another method, the positive electrode may be manufactured by laminating a film obtained by peeling the support from the casting for forming a positive electrode material mixture layer composition on a separate support, and then on the positive electrode collector.
[80]
[81]
Further, one embodiment of the present invention provides an electrochemical device comprising the cathode. The electrochemical device is specifically battery, capacitor and the like, may be more particularly to a lithium secondary battery.
[82]
[83]
The lithium secondary battery is specifically positive electrode, a negative electrode for the anode and for facing position, comprising a separator and an electrolyte interposed between the positive electrode and the negative electrode, the positive electrode is the same as the above. Further, the lithium secondary battery may optionally further include a sealing member for sealing the cell case, and the battery case for housing the electrode assembly of the cathode, an anode, a separator.
[84]
[85]
In the above lithium secondary battery, the negative electrode comprises a negative electrode material mixture layer on the negative electrode current collector and the anode current collector.
[86]
On the surface of the negative electrode current collector without causing chemical changes in the battery if it has suitable conductivity not particularly limited, for example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel surface-treated with carbon, nickel, titanium or silver, and aluminum-cadmium alloys. In addition, the anode current collector is typically may have a thickness of 3㎛ to 500㎛, may be Similar to the cathode current collector, enhance the bonding strength between the negative electrode active material to form fine irregularities on the whole surface of the anode current collector. For example, films, sheets, foils, nets, porous structures, foams and non-woven fabrics or the like can be used in various forms.
[87]
[88]
The negative electrode material mixture layer includes a binder and a conductive material with the negative electrode active material. Layer and the negative electrode material mixture is a negative electrode active material on a negative electrode current collector by way of example, and, optionally, a binder, and coating the negative electrode material mixture layer-forming composition comprising a conductive material, and dried, or the negative electrode material mixture layer-forming composition to a separate phase support for casting the following may be made and removed from the support by laminating a film obtained on the negative electrode collector.
[89]
[90]
The cathode active material has a reversible intercalation and de-intercalation of lithium can be used a compound. Carbonaceous material such as concrete examples of artificial graphite, natural graphite, graphitized carbon fibers, amorphous carbon; Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn-alloy, or Al alloy, a lithium alloy and a metal compound to be; SiO β (0 <β <2), SnO 2And vanadium oxide, which can dope and de-dope a lithium metal oxide such as lithium vanadium oxide; Or as Si-C composite or a Sn-C bokhapchegwa may be made of composites such as containing a metallic compound and a carbonaceous material, there is any one or a mixture of two or more of them may be used. It is also a lithium metal thin film used as the cathode active material. The carbon material may be used including all of the low-crystalline carbon and high crystalline carbon. A low-crystalline carbon is soft carbon (soft carbon) and curing carbon (hard carbon) is representative, and the high crystalline carbon include amorphous, plate, scaly, spherical or fibrous natural graphite or artificial graphite, Kish graphite (Kish graphite), pyrolytic carbon (pyrolytic carbon), liquid crystal pitch based carbon fibers (mesophase pitch based carbon fiber), carbon microspheres (meso-carbon microbeads), a liquid crystal pitch of (mesophase pitches), and the oil and coal cokes (petroleum or coal tar pitch the high temperature firing carbon such as derived cokes) are typical.
[91]
The may be the same as described above in the positive electrode material and the binder and conductive.
[92]
[93]
On the other hand, in the lithium secondary battery, a separator can be used without that separate the anode and cathode and provides the moving path of the lithium ions, so long as it is used as a separator in ordinary lithium secondary battery, no particular limitation and, in particular, ion mobility of the electrolyte while a low resistance against the electrolyte is preferably excellent humidification ability. Specifically, the porous polymer film, such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymers and ethylene / methacrylate, the porous polymer made of a polyolefin-based polymer such as copolymer film thereof the two or more layers of the multilayer structure may be used. In addition there is a porous non-woven fabric in a conventional, such as high melting point glass of the fiber, polyethylene terephthalate fiber, such as non-woven fabric may be used. Further, the separator may have a coating containing a ceramic component or a high molecular material used for the heat resistance or mechanical strength secured, may optionally be used in a single layer or multi-layer structure.
[94]
[95]
The electrolyte used in the present invention may be made of a lithium secondary battery produced when free organic liquid electrolyte, an inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, molten-type inorganic electrolyte, such as, limited to it is not.
[96]
[97]
Specifically, the electrolyte may comprise an organic solvent and a lithium salt.
[98]
As the organic solvent so long as it can be a medium that can serve to move the ions involved in the electrochemical reaction of the cell, it may be used without any particular limitation. Specifically, the organic solvent is methyl acetate (methyl acetate), ethyl acetate (ethyl acetate), γ- -butyrolactone (γ-butyrolactone), ε- caprolactone (ε-caprolactone) ester based solvents such as; Dibutyl ether (dibutyl ether) or tetrahydrofuran (tetrahydrofuran) solvent include ether solvents such as; Cyclohexanone (cyclohexanone) ketone-based solvents, and the like; Benzene (benzene), benzene (fluorobenzene) an aromatic hydrocarbon-based solvents such as fluoro; Dimethyl carbonate (dimethylcarbonate, DMC), diethyl carbonate (diethylcarbonate, DEC), methyl ethyl carbonate (methylethylcarbonate, MEC), ethylmethyl carbonate (ethylmethylcarbonate, EMC), ethylene carbonate (ethylene carbonate, EC), propylene carbonates (propylene carbonate, carbonate-based solvent such as PC); Alcohol-based solvents such as ethyl alcohol, isopropyl alcohol; Nitriles such as R-CN (R may include a straight chain, branched, and branched or cyclic structure, a group of the hydrocarbon group, double bond, an aromatic ring or an ether bond in the C2 to C20); Amides such as dimethylformamide; Dioxolane acids such as 1,3-dioxolane; Or it can be used, such as sulfolane (sulfolane) flow. Among these, the carbonate-based solvents are preferred, and cyclic carbonates having a high ionic conductivity and a high dielectric constant to increase the charge-discharge performance of the battery (for example, Ethylene carbonate or propylene carbonate, and the like), a linear carbonate-based compound of a low viscosity mixture (e.g., ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate, and the like) is more preferable. In this case, cyclic carbonate and chain carbonate is about 1: there may be used a mixture in a volume ratio of 1 to 9, the superior performance of the electrolyte.
[99]
[100]
The lithium salt is a compound capable of providing lithium ions used in the lithium secondary battery may be used without any particular limitation. Specifically, the lithium salt, LiPF 6 , LiClO 4 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAl0 4 , LiAlCl 4 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiN (C 2 F 5 SO 3 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiN (CF 3 SO 2 ) 2 . LiCl, LiI, or LiB (C 2 O 4 ) 2 and the like can be used. The concentration of the lithium salt is preferably used within the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, since the electrolyte have an appropriate conductivity and viscosity, and can exhibit excellent performance, the electrolyte, the lithium ions can move efficiently.
[101]
[102]
The electrolyte, halo alkylene carbonate compound such as the electrolyte component as well as for improving the life characteristics of the battery, the battery capacity is decreased inhibition, for the purpose of improving the discharge capacity of the battery, for example, difluoromethyl ethylene carbonate; Or pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n- glyme (glyme), hexamethyl phosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N- substituted oxazolidinone, N, N - it may be substituted imidazole further include Jolly Dean, ethylene glycol dialkyl ether, an additive of ammonium salts, pyrrole, 2-methoxy ethanol, aluminum trichloride or at least one. In this case, the additive may comprise from 0.1% to 5% by weight relative to the total weight of electrolyte.
[103]
[104]
Because a lithium secondary battery comprising a positive electrode active material according to the invention as described above find stable indicated by the excellent discharge capacity and output characteristics and capacity retention rate, portable devices such as cellular phones, notebook computers, digital cameras, and hybrid electric vehicles ( it is useful, for example, an electric vehicle sector, such as hybrid electric vehicle, HEV).
[105]
[106]
Thus, according to another embodiment of the invention, the battery pack including the battery module, and it comprises a unit cell, the lithium secondary battery is provided.
[107]
The battery module or battery pack, the power tool (Power Tool); Electric Vehicles (Electric Vehicle, EV), hybrid electric vehicles, electric vehicles and plug-in hybrid electric vehicle comprising a (Plug-in Hybrid Electric Vehicle, PHEV); Or the power storage may be used as any one or more of the middle- or large-sized devices for the power supply of the system.
[108]
[109]
[110]
Will be described in detail below, embodiments of the present to the invention can easily be made self-of ordinary skill in the art to practice invention belongs. However, the invention is not to be implemented in many different forms and limited to the embodiments set forth herein.
[111]
[112]
Example 1
[113]
The average particle diameter of the positive electrode active material 1 (D 50 ) of 13㎛ LiNi 0 . 6 Mn 0 . 2 Co 0 . 2 O 2 , the carbon black as a conductive agent 1 (average particle size (D 50 ): 60nm), and a PVdF binder N- methylpyrrolidone in a weight ratio in a solvent money 91: 4: 5 in a ratio of the first positive electrode material mixture layer composition (positive electrode active material specific surface area of 0.2m for forming two a / g, a specific surface area of the conductive material / anode active material, the specific surface area = 15) was prepared.
[114]
Further, the average particle size of 2 to the positive electrode active material (D 50 ) of 7㎛ LiNi 0 . 6 Mn 0 . 2 Co 0 . 2 O 2 , the second carbon black as a conductive material (average particle diameter (D 50 ): 60nm), and a PVdF binder N- methylpyrrolidone in a weight ratio in a solvent money 93: 3: a mixture in a ratio of 4 second positive electrode material mixture layer composition (positive electrode active material specific surface area of 0.6m for forming two a / g, a specific surface area of the conductive material / anode active material, the specific surface area = 9) was prepared.
[115]
After applying the first positive electrode material mixture layer-forming composition to the total aluminum current collector, and wherein the re-applying the composition for forming the second positive electrode material mixture layer thereon, and then dried at 130 ℃, a positive electrode was prepared by rolling. The first was the thickness of the positive electrode material mixture layer is 30㎛, and the thickness of the second positive electrode material mixture layer is 30㎛.
[116]
[117]
Example 2
[118]
The average particle diameter (D 50 ) 6㎛ the second positive electrode active material using the second positive electrode material mixture layer-forming composition (positive electrode active material specific surface area of 0.7m 2 to prepare a / g, a specific surface area of the conductive material / anode active material, the specific surface area = 8) It is a positive electrode was prepared in the same manner as in example 1 except that.
[119]
[120]
Example 3
[121]
The average particle diameter (D 50 ) 13㎛ the first positive electrode active material and the carbon black as a conductive agent 1 (average particle size (D 50 ): 80nm) the use, wherein the first cathode active material and the first conductive material 91: 3.5: 4.5 the first positive electrode material mixture layer-forming composition are mixed in a weight ratio of (positive electrode active material specific surface area of 0.2m 2 / g, a specific surface area of the conductive material / anode active material, the specific surface area = 12) were prepared, and the average particle diameter (D 50 a) of claim 7㎛ 2, the positive electrode active material and the second conductive material (average particle diameter (D 50 ): 60nm) 93: 2.5: the second positive electrode material mixture layer-forming composition are mixed in a weight ratio of 4.5 (the positive electrode active material specific surface area of 0.6m 2 / g, the conductive material except that manufactured the surface area / the positive electrode active material surface area = 8.5) to prepare a positive electrode in the same manner as in example 1.
[122]
[123]
Comparative Example 1
[124]
The average particle diameter (D 50 ) 13㎛ the first positive electrode active material and the carbon black as a conductive agent 1 (average particle size (D 50 ): 80nm) the use, wherein the first cathode active material and the first conductive material 91: 3.5: 4.5 the first positive electrode material mixture layer-forming composition are mixed in a weight ratio of (positive electrode active material specific surface area of 0.2m 2 / g, a specific surface area of the conductive material / anode active material, the specific surface area = 12) were prepared, and the average particle diameter (D 50 a) of claim 7㎛ 2, the positive electrode active material and a second carbon black as a conductive material (average particle diameter (D 50 : using a) 50nm), a second positive electrode active material and the second conductive material 93: 3: 4 the second positive electrode material mixture layer were mixed at a weight ratio of forming composition (positive electrode active material specific surface area of 0.6m 2 a / g, a specific surface area of the conductive material / anode active material, the specific surface area = 9.5) and the positive electrode is conducted in the same manner as in example 1 except that the Preparation was prepared.
[125]
[126]
Comparative Example 2
[127]
The average particle diameter (D 50 ) 13㎛ the first positive electrode active material and a first conductive material (average particle diameter (D 50 ): 60nm) 93: 2: 5 were mixed in a weight ratio of the composition for the positive electrode material mixture layer 1 is formed (the positive electrode active material non- surface area 0.35m 2 / g, a specific surface area of the conductive material / anode active material was prepared in the specific surface area = 10.5), average particle size (D 50 ) 8㎛ the second positive electrode active material and the second conductive material (average particle diameter (D 50 ): 60nm ) 93: 2: 5 mixture by weight ratio to the second positive electrode material mixture layer-forming composition (positive electrode active material specific surface area of 0.5m 2 and is conducted except that the production / g, a specific surface area of the conductive material / anode active material, the specific surface area = 9.5). of example 1, to thereby prepare a positive electrode in the same manner.
[128]
[129]
[ Preparation Example : Manufacture of a lithium secondary battery;
[130]
Example 1-3 and Comparative Example 1, to prepare a lithium secondary battery by using the positive electrode prepared in each 2.
[131]
[132]
First, natural graphite, carbon black conductive agent, and PVdF binder as the negative electrode active material in a weight ratio from 85 N- methylpyrrolidone money solvent: 10: a ratio of 5 to prepare a composition for forming a negative electrode, and applying it onto the copper collector a negative electrode was prepared.
[133]
And the Examples 1-3 and Comparative Example 1, and after interposing a porous polyethylene separator between the positive electrode and the negative electrode is manufactured from 2 to prepare an electrode assembly, and position the electrode assembly inside the case, an electrolyte solution into the case injection to manufacture a lithium secondary battery. At this time, the electrolytic solution is phosphate (LiPF lithium hexafluoro a 1.0M concentration in an organic solvent consisting of ethylene carbonate / dimethyl carbonate / ethylmethyl carbonate (EC / DMC / EMC volume ratio of the mixture = 3/4/3) 6 was dissolved in a) Preparation It was.
[134]
[135]
[ Experimental Example ] Electrical conductivity and reliability evaluation
[136]
The above Examples 1-3 and Comparative Example 1, using 4-point probe device for the positive electrode prepared in the second surface resistance (sheet resistance) of the electrode was determined by measuring the electrical conductivity of the electrode.
[137]
In addition, the Examples 1-3 and Comparative Example 1, for a lithium secondary battery each produced by using the positive electrode prepared in 2 Chinese GB / T ± the same diameter 5-8mm metal body and the authentication condition 25 5mm / sec the drop rate was measured by the penetration resistance with a resistance change after that penetrate the cells, and evaluated whether or explosion.
[138]
The results are shown in Table 1.
[139]
[140]
TABLE 1
전기전도도(Ωcm)(sheet resistance) Puncture resistance (Ω) Whether explosion
Example 1 2,500 4.0 US explosion
Example 2 3,000 5.1 US explosion
Example 3 2,500 4.5 US explosion
Comparative Example 1 1,500 3.0 explosion
Comparative Example 2 2,000 3.5 explosion

[141]
[142]
As can be seen from Table 1, the present embodiment to satisfy the ratio of the conductive material surface area to the specific surface area of ​​the cathode active material according to the invention examples 1 to 3 is the total electrical conductivity of the positive electrode as compared to Comparative Examples 1 and 2 do not satisfy this requirement this was somewhat excellent, the through resistance was significantly increased, and thus was able to suppress the overcurrent to prevent the explosion of the battery due to over-current.
[143]
[144]
[145]

Claims

[Claim 1]The anode current collector; The positive electrode collector is laminated on the whole, the first positive electrode active material and the first positive electrode material mixture layer containing a first conductive material; And it is stacked on the first positive electrode material mixture layer and the second positive electrode active material and a second conductive material, the second positive electrode material mixture layer comprising; average particle size of the second cathode active material, includes (D 50 ) is the first the positive electrode active material average particle diameter (D 50 is from 5 to 80%), the second non-conductive surface area of the material is less than or equal to 9, a secondary battery positive electrode to the specific surface area of the second cathode active material.
[Claim 2]
According to claim 1, wherein the first non-conductive surface area of ​​the material is 11 or secondary battery, the positive electrode to the specific surface area of ​​the first positive electrode active material on.
[Claim 3]
The method of claim 1, wherein the average particle size of the first cathode active material (D 50 ) is from 10 to 100㎛ a secondary battery positive electrode.
[Claim 4]
The method of claim 1, wherein the average particle size of the second cathode active material (D 50 ) is from 1 to 15㎛ a secondary battery positive electrode.
[Claim 5]
The method of claim 1, wherein the specific surface area of the first cathode active material is 0.1 to 0.8m 2 / g of secondary battery positive electrode.
[Claim 6]
The method of claim 1, wherein the specific surface area of the second cathode active material is 0.5 to 1.5m 2 / g of secondary battery positive electrode.
[Claim 7]
The method of claim 1, wherein the first and the weight ratio of the first and second positive electrode active material included in the second positive electrode material mixture layer is from 1: 1 to 1: 8, the secondary battery positive electrode.
[Claim 8]
The method of claim 1, wherein the first and second conductive material in the total weight of the first and the second secondary battery, the positive electrode from 0.2 to 20% by weight relative to the total weight of the positive electrode active material.
[Claim 9]
The method of claim 1, wherein the first and second first and second conductive material in a weight ratio contained in the positive electrode material mixture layer is from 1: 0.1 to 1: 1, a secondary battery positive electrode.
[Claim 10]
The method of claim 1 wherein said first and said second conductive material average particle diameter (D 50 ) is from 5 to 150nm a secondary battery positive electrode.
[Claim 11]
According to claim 1, wherein the first anode and the surface resistance of the electrode material mixture layer is 0.010 to 1,000Ωcm, the positive electrode for a secondary battery, the surface resistance of the second positive electrode material mixture layer 20 to the 50,000Ωcm.
[Claim 12]
The method of claim 1 wherein the first cathode active material and second cathode active material to at least one of a secondary battery positive electrode of the lithium-transition metal oxide include represented by the general formula (1). [Chemical Formula 1] Li a Ni 1 -x- y Co x Mn y M z O 2 (wherein, M is at least one selected from the group consisting of Al, Zr, Ti, Mg, Ta, Nb, Mo and Cr element, and is 0.9≤a≤1.5, 0≤x≤0.5, 0≤y≤0.5, 0≤z≤0.1, 0≤x + y≤0.7.)
[Claim 13]
The method of claim 1, wherein the first conductive material and second conductive material is natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fibers, copper, nickel , aluminum, silver, zinc oxide, potassium titanate, titanium oxide and at least one or more poly-secondary battery positive electrode selected from the group consisting of phenylene derivative.
[Claim 14]
The method of claim 1, wherein the first and second thickness ratio of the positive electrode material mixture layer is from 1: 1 to 1: 8, the secondary battery positive electrode.
[Claim 15]
Positive electrode, a negative electrode and an electrode assembly including a separator interposed between the positive electrode and the negative electrode; A battery case which incorporates the electrode assembly; And the cells implanted in a case the non-aqueous electrolyte; wherein a, the positive electrode of claim 1 to claim 14, wherein the positive electrode of lithium secondary battery according to any one of Items.