This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0151259 on November 29, 2018, and all contents disclosed in the documents of the Korean patent application are incorporated as a part of this specification.
[2]
The present invention relates to an electrode assembly, and more particularly, two or more positive electrodes are stacked, and each positive electrode has a structure in which a positive electrode active material having a different composition ratio is applied to a positive electrode current collector, thereby increasing charge/discharge capacity and thermal stability at the same time. It relates to an electrode assembly that can be used.
[3]
background
[4]
A battery for storing electrical energy may be generally divided into a primary battery and a secondary battery. A primary battery is a disposable consumable battery, whereas a secondary battery is a rechargeable battery manufactured using a material in which oxidation and reduction processes between an electric current and a substance are repeatable. That is, when the reduction reaction of the material is performed by the electric current, the power is charged, and when the oxidation reaction is performed on the material, the power is discharged. Such charge-discharge can be repeatedly performed.
[5]
Among various types of secondary batteries, lithium secondary batteries are generally manufactured by mounting an electrode assembly in which a positive electrode, a separator, and an anode are stacked in a case, and lithium ions are produced from the lithium metal oxide of the positive electrode to the negative electrode. As the process of intercalation and deintercalation is repeated, charging and discharging of the lithium secondary battery proceeds.
[6]
The electrode assembly is manufactured such that the positive electrode 1 / separator 3 / negative electrode 2 are repeatedly stacked, and the electrode assembly is accommodated in a case such as a cylindrical can or a square pouch. As shown in Fig. 1a showing a side view of the electrode assembly, the positive electrode 1 of the electrode assembly is a positive electrode current collector 1a on both sides of the positive electrode active material 1b, and the negative electrode 2 is a negative electrode collector ( 2a) has a structure in which a negative electrode active material 2b is coated on both sides, and in the negative electrode 2 and the positive electrode 1, respectively, in the negative electrode current collector 2a and the positive electrode current collector 1a (active material is not applied) The negative electrode tab 2c and the positive electrode tab 1c respectively protrude, and current flows through the negative electrode tab 2c and the positive electrode tab 1c.
[7]
Meanwhile, as the demand for secondary batteries increases in fields such as ESS (Energy Storage System) and electric vehicles, research and development to increase the capacity of secondary batteries is being conducted.
[8]
As a part of this, secondary batteries using NCM (nickel (Ni), cobalt (Co), manganese (Mn))-based cathode materials have been developed. However, the NCM-based secondary battery has a problem in that when the nickel content is relatively high, the capacity is increased, but the thermal stability is lowered and the ignition possibility is also increased. 1b is a graph showing the change in thermal stability according to the nickel content is shown. In FIG. 1B, (A) is a thermal stability test result of an electrode assembly coated with a cathode active material having a composition ratio of nickel (Ni), cobalt (Co), and manganese (Mn) of 6:2:2, (B) is nickel ( Ni), cobalt (Co), and manganese (Mn) composition ratio of 8:1:1 is the thermal stability test result of the electrode assembly coated with the positive electrode active material. As for the experimental conditions, temperature change (vertical axis) versus time (horizontal axis) was measured while heating from 80°C to 200°C at a rate of 2K/min. Both electrode assemblies were ignited and damaged (the point at which the cell voltage [Cell V] reached 0: 460 minutes when the cell voltage became 0 in A, 280 minutes when the cell voltage became 0 in B), but the composition ratio was 8 It can be seen that the electrode assembly coated with the positive electrode active material having a ratio of 1:1:1 ignites faster than the electrode assembly coated with the positive electrode active material having a composition ratio of 6:2:2. That is, it can be confirmed that the thermal stability is lowered as the nickel content is increased.
[9]
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[10]
Accordingly, the main object of the present invention is to provide a secondary battery capable of using a positive electrode active material having a large nickel content to improve capacity while also having improved thermal stability.
[11]
means of solving the problem
[12]
The present invention for achieving the object as described above, in an electrode assembly in which a positive electrode, a separator, and a negative electrode are repeatedly stacked, at least two or more are stacked in the electrode assembly, and a positive electrode active material is applied to the surface of the positive electrode current collector. a positive electrode having a structure; including, wherein the positive electrode active material contains nickel, cobalt, and manganese, and the composition ratio of nickel, cobalt, and manganese of the positive electrode active material applied to any one positive electrode is that of the positive electrode active material applied to the other positive electrode. It is characterized in that it is different from the composition ratio of nickel, cobalt, and manganese.
[13]
In the present invention, the positive electrode disposed relatively outside in the stacking direction of the electrode assembly is coated with a positive electrode active material containing a relatively small amount of manganese and a relatively large amount of nickel, and is relatively inside in the stacking direction of the electrode assembly. The disposed positive electrode is coated with a positive electrode active material containing a relatively large amount of manganese and a relatively low amount of nickel.
[14]
In Example 1 of the present invention, the positive electrode disposed relatively outside in the stacking direction of the electrode assembly is coated with a positive electrode active material containing nickel, cobalt, and manganese in an 8:1:1 ratio, and the electrode assembly is stacked in the stacking direction. In the positive electrode disposed on the inside relatively in the positive electrode active material containing nickel, cobalt, and manganese in a 1:1:1 ratio is applied.
[15]
In Example 2 of the present invention, a positive electrode active material containing nickel, cobalt, and manganese in a ratio of 6:2:2 is applied to the positive electrode disposed relatively outside in the stacking direction of the electrode assembly, and the electrode assembly is stacked in the stacking direction In the positive electrode disposed on the inside, nickel, cobalt, and manganese are coated with a positive electrode active material in a 1:1:1 ratio.
[16]
In Example 3 of the present invention, the positive electrode disposed relatively outside in the stacking direction of the electrode assembly is coated with a positive electrode active material containing nickel, cobalt, and manganese in an 8:1:1 ratio, and the electrode assembly is stacked in the stacking direction. In the cathode disposed on the inside, a cathode active material containing nickel, cobalt, and manganese in a ratio of 6:2:2 is applied.
[17]
In addition, the electrode assembly includes: a positive electrode in which three or more positive electrodes are stacked, a positive electrode active material containing nickel, cobalt, and manganese in a 1:1:1 ratio is applied; a positive electrode coated with a positive electrode active material containing nickel, cobalt, and manganese in a ratio of 6:2:2; a positive electrode coated with a positive electrode active material containing nickel, cobalt, and manganese in a ratio of 8:1:1; Each may include one or more.
[18]
In addition, the positive electrode tab of the positive electrode coated with the positive electrode active material containing relatively little manganese and relatively high nickel and the positive electrode tab of the positive electrode coated with the positive electrode active material containing relatively large amount of manganese and relatively little nickel are arranged to be separated from each other.
[19]
At this time, in the electrode assembly, the negative electrode tab formed on the negative electrode is disposed on one side, the positive electrode tab is disposed on the opposite side, and the positive electrode is coated with a positive electrode active material containing relatively little manganese and relatively much nickel. of the positive electrode tab and the positive electrode tab of the positive electrode coated with a positive electrode active material containing a relatively large amount of manganese and containing relatively little nickel are spaced apart from each other at a predetermined distance.
[20]
The electrode assembly having such technical characteristics may be embedded in a case to provide a secondary battery, and a plurality of secondary batteries may be electrically connected to provide a secondary battery module.
[21]
Effects of the Invention
[22]
According to the present invention having the above technical characteristics, since positive electrodes having different composition ratios of nickel, cobalt, and manganese of the positive electrode active material are stacked, thermal stability and capacity can be appropriately improved.
[23]
More specifically, the positive electrode disposed on the outside has a positive electrode active material containing a lot of nickel to realize high capacity, and the positive electrode disposed on the inside (which can be accelerated due to heat dissipation because it is relatively difficult to dissipate heat) is designed to increase thermal stability. A positive electrode active material containing less nickel is disposed, and both thermal stability and capacity can be improved than when any type of positive electrode is used.
[24]
In addition, the positive electrode tab of the positive electrode coated with the positive electrode active material containing a lot of nickel and the positive electrode tab of the positive electrode coated with the positive electrode active material containing a small amount of nickel are arranged to be separated from each other to further lower the electrical resistance (according to the current divided and flowing). can
[25]
Brief description of the drawing
[26]
1a is a side view showing a side view of a conventional electrode assembly;
[27]
Figure 1b is a graph showing a state that the thermal stability varies according to the nickel content.
[28]
Figure 2a is a side view showing a side view of the electrode assembly according to the first embodiment of the present invention.
[29]
Figure 2b is a side view showing a side view of the electrode assembly according to the second embodiment of the present invention.
[30]
Figure 2c is a side view showing a side view of the electrode assembly according to the third embodiment of the present invention.
[31]
3 is a plan view of an electrode assembly according to the present invention.
[32]
Modes for carrying out the invention
[33]
Hereinafter, based on the accompanying drawings, the present invention will be described in detail so that those of ordinary skill in the art can easily implement it. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.
[34]
In order to clearly explain the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar elements throughout the specification.
[35]
In addition, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor appropriately defines the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of ​​the present invention based on the principle that it can be done.
[36]
The present invention relates to an electrode assembly in which anode (10: 10', 10'', 10''), a separator 30, and a cathode 20 are repeatedly stacked, wherein at least two or more anodes 10 are It is characterized in that the composition ratio of the stacked positive electrode active material 10b applied to the positive electrodes 10 is different from each other.
[37]
In more detail, in the present invention, the positive electrode 10 is coated with a positive electrode active material 10b containing nickel, cobalt, and manganese, and the composition ratio of nickel, cobalt, and manganese of the positive electrode active material 10b applied to any one positive electrode is configured differently from the composition ratio of nickel, cobalt, and manganese of the positive electrode active material 10b applied to the other positive electrode.
[38]
In addition, in the present invention, the anodes 10' and 10''' disposed on the outside in the stacking direction of the electrode assembly relatively contain relatively little manganese so as to increase thermal stability in the middle part, where heat dissipation is relatively difficult. and a positive electrode active material (High Ni-based active material) containing a relatively large amount of nickel is applied, and the positive electrode 10'' disposed on the inside relatively in the stacking direction of the electrode assembly contains a relatively large amount of manganese and relatively nickel A cathode active material (Low Ni-based active material) containing a small amount of is coated. At this time, the amount of nickel is relatively determined.
[39]
Hereinafter, embodiments according to the present invention will be described in more detail with reference to the accompanying drawings.
[40]
[41]
first embodiment
[42]
[43]
Referring to FIG. 2A showing a side view of the electrode assembly according to the first embodiment (for reference, in FIGS. 2A to 2C , three or more positive electrodes are stacked, although it is illustrated as having a stacked structure. ), in this embodiment from top to bottom separator 30 / positive electrode 10 ' / separator 30 / negative electrode 20 / separator 30 / positive electrode (10 '') / separator 30 / negative electrode ( 20)/separator 30/anode 10''' have a stacked structure.
[44]
The negative electrode 20 has a structure in which a negative electrode active material 20b is applied on both sides of a negative electrode current collector 20a, and the positive electrode 10: 10', 10'', 10''' and a positive electrode current collector 10a has a structure in which the positive electrode active material 10b is coated on both surfaces of the The positive electrode active material 10b is prepared to contain lithium, cobalt, and manganese. At this time, the positive electrodes disposed relatively outside in the stacking direction of the electrode assembly, that is, the first positive electrode 10 ′ and the third positive electrode from top to bottom. The cathode active material 10b of (10''') has a structure in which nickel, cobalt, and manganese are contained in a ratio of 8:1:1. On the other hand, the positive electrode active material 10b of the positive electrode 10 ″ disposed relatively inside in the stacking direction of the electrode assembly has a structure in which nickel, cobalt, and manganese are contained in a 1:1:1 ratio.
[45]
[46]
second embodiment
[47]
[48]
Referring to FIG. 2B showing a side view of the electrode assembly according to the second embodiment, in this embodiment as well, from top to bottom, separator 30 / positive electrode 10 ′ / separator 30 / negative electrode 20 / separator (30)/anode (10'')/separator (30)/cathode (20)/separator (30)/anode (10''').
[49]
Similarly, the positive electrode active material 10b is prepared to contain lithium, cobalt, and manganese, at this time, the positive electrodes disposed relatively outside in the stacking direction of the electrode assembly, that is, the first positive electrode 10 ′ from top to bottom and The positive electrode active material 10b of the third positive electrode 10''' has a structure in which nickel, cobalt, and manganese are contained in a ratio of 8:1:1. On the other hand, the positive electrode active material 10b of the positive electrode 10 ″ disposed relatively inside in the stacking direction of the electrode assembly has a structure in which nickel, cobalt, and manganese are contained in a 6:2:2 ratio.
[50]
The electrode assembly according to this embodiment has a relatively smaller nickel content than the first embodiment, so it is a configuration focusing on capacity increase rather than thermal stability.
[51]
[52]
3rd embodiment
[53]
[54]
Referring to FIG. 2C showing a side view of the electrode assembly according to the third embodiment, in this embodiment as well, from top to bottom, separator 30 / positive electrode 10 ′ / separator 30 / negative electrode 20 / separator (30)/anode (10'')/separator (30)/cathode (20)/separator (30)/anode (10''').
[55]
Similarly, the positive electrode active material 10b is prepared to contain lithium, cobalt, and manganese, at this time, the positive electrodes disposed relatively outside in the stacking direction of the electrode assembly, that is, the first positive electrode 10 ′ from top to bottom and The positive electrode active material 10b of the third positive electrode 10''' has a structure in which nickel, cobalt, and manganese are contained in a 6:2:2 ratio. On the other hand, the positive electrode active material 10b of the positive electrode 10 ″ disposed relatively inside in the stacking direction of the electrode assembly has a structure in which nickel, cobalt, and manganese are contained in a 1:1:1 ratio.
[56]
Since the electrode assembly according to this embodiment has a relatively smaller nickel content than the first and second embodiments above, it is a configuration focusing on thermal stability rather than capacity increase.
[57]
[58]
For reference, in the present invention, three or more electrode assemblies may be stacked as described above. Accordingly, three types of positive electrodes having different composition ratios of nickel, cobalt, and manganese may be stacked.
[59]
Also at this time, it is preferable that a positive electrode coated with a positive electrode active material having a low nickel content is disposed on the inner side, which is relatively difficult to dissipate heat, and a positive electrode coated with a positive electrode active material having a large nickel content is disposed on the outer side, which is relatively easy to dissipate heat. For example, assuming that five positive electrodes are stacked from top to bottom, a positive electrode coated with a positive electrode active material containing nickel, cobalt, and manganese in an 8:1:1 ratio is disposed on the first and fifth outermost layers. , a positive electrode coated with a positive electrode active material containing nickel, cobalt, and manganese in a ratio of 6:2:2 is arranged in the second and fourth, and nickel, cobalt, and manganese (which has the smallest nickel content) are arranged in the third one, 1:1 A positive electrode coated with a positive electrode active material contained in a 1:1 ratio may be disposed.
[60]
On the other hand, in the electrode assembly configured as described above, the anode 10 is preferably electrically connected to each other having the same composition ratio. That is, since the electrical conductivity of the positive electrode active material 10b also varies as the composition ratio is changed, it is preferable that the positive electrode tabs of the positive electrodes having different composition ratios are separated from each other. When the positive electrode tab is separated according to the composition ratio as described above, the current is divided and moved, so that cell damage can be minimized and battery life can be increased. In addition, at this time, a positive electrode having relatively high thermal stability may be charged by applying a high current, and a positive electrode having relatively low thermal stability may be charged by applying a low current.
[61]
Referring to FIG. 3 showing a plan view of an electrode assembly according to the present invention, the positive electrode tab 10c' of the first positive electrode 10' and the positive electrode tab of the third positive electrode 10''' having the same composition ratio are bonded to each other. While connected, the positive electrode tab 10c'' of the second positive electrode 10'' having a different composition ratio is spaced apart from the positive electrode tab 10c' of the first positive electrode 10'. In this case, since the negative electrode tab 20c formed on the negative electrode 20 in the electrode assembly is disposed on one side, the positive electrode tabs are disposed at intervals on the same side opposite to the negative electrode tab 20c.
[62]
In the present invention having the above technical characteristics, since positive electrodes having different composition ratios of nickel, cobalt, and manganese of the positive electrode active material 10b are stacked, thermal stability and capacity can be appropriately improved.
[63]
More specifically, the positive electrode disposed on the outside has a positive electrode active material containing a lot of nickel to realize high capacity, and the positive electrode disposed on the inside (which can be accelerated due to heat dissipation because it is relatively difficult to dissipate heat) is designed to increase thermal stability. A positive electrode active material containing less nickel is disposed, and both thermal stability and capacity can be improved than when any type of positive electrode is used.
[64]
In addition, the positive electrode tab of the positive electrode coated with the positive electrode active material containing a lot of nickel and the positive electrode tab of the positive electrode coated with the positive electrode active material containing a small amount of nickel are arranged to be separated from each other to further lower the electrical resistance (according to the current divided and flowing). can
[65]
The electrode assembly having such technical characteristics may be embedded in a case to provide a secondary battery, and a plurality of secondary batteries may be electrically connected to provide a secondary battery module.
[66]
In the above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is described below with the technical idea of ​​the present invention by those of ordinary skill in the art to which the present invention pertains. Various implementations are possible within the scope of equivalents of the claims to be made.
Claims
[Claim 1]
In an electrode assembly in which a positive electrode, a separator, and a negative electrode are repeatedly stacked, at least two or more are stacked in the electrode assembly and a positive electrode having a structure in which a positive electrode active material is applied to a surface of a positive electrode current collector; It contains nickel, cobalt, and manganese, wherein the composition ratio of nickel, cobalt, and manganese of the positive electrode active material applied to one positive electrode is different from the composition ratio of nickel, cobalt, and manganese of the positive electrode active material applied to the other positive electrode electrode assembly.
[Claim 2]
The positive electrode of claim 1, wherein the positive electrode disposed on the outside in the stacking direction of the electrode assembly is coated with a positive electrode active material containing relatively little manganese and relatively high nickel, and relatively in the stacking direction of the electrode assembly. The positive electrode disposed inside the electrode assembly, characterized in that the positive electrode active material containing a relatively large amount of manganese and a relatively small amount of nickel is applied.
[Claim 3]
The positive electrode of claim 2, wherein the positive electrode disposed on the outside in the stacking direction of the electrode assembly is coated with a positive electrode active material containing nickel, cobalt, and manganese in an 8:1:1 ratio, and is relatively in the stacking direction of the electrode assembly. The positive electrode disposed inside the electrode assembly, characterized in that nickel, cobalt, and a positive electrode active material containing manganese in a 1:1:1 ratio is coated.
[Claim 4]
The positive electrode of claim 2, wherein the positive electrode disposed on the outside in the stacking direction of the electrode assembly is coated with a positive electrode active material containing nickel, cobalt, and manganese in an 8:1:1 ratio, and is relatively in the stacking direction of the electrode assembly. The positive electrode disposed inside the electrode assembly, characterized in that nickel, cobalt, and a positive electrode active material containing manganese in a ratio of 6:2:2 is coated.
[Claim 5]
The positive electrode of claim 2, wherein the positive electrode disposed on the outside in the stacking direction of the electrode assembly is coated with a positive electrode active material containing nickel, cobalt, and manganese in a ratio of 6:2:2, and is relatively in the stacking direction of the electrode assembly. The positive electrode disposed inside the electrode assembly, characterized in that nickel, cobalt, and a positive electrode active material containing manganese in a 1:1:1 ratio is coated.
[Claim 6]
The electrode assembly of claim 2, wherein the electrode assembly comprises: a positive electrode in which three or more positive electrodes are stacked, and a positive electrode active material containing nickel, cobalt, and manganese in a 1:1:1 ratio is applied; a positive electrode coated with a positive electrode active material containing nickel, cobalt, and manganese in a ratio of 6:2:2; a positive electrode coated with a positive electrode active material containing nickel, cobalt, and manganese in a ratio of 8:1:1; An electrode assembly comprising one or more of each.
[Claim 7]
The positive electrode according to claim 2, wherein the positive electrode tab of the positive electrode is coated with a positive electrode active material containing relatively little manganese and a relatively large amount of nickel and a positive electrode coated with a positive electrode active material containing relatively large amount of manganese and relatively little nickel. The positive electrode tabs of the electrode assembly, characterized in that arranged to be separated from each other.
[Claim 8]
The positive electrode active material of claim 7, wherein the negative electrode tab formed on the negative electrode in the electrode assembly is disposed on one side, and the positive electrode tab is disposed on the opposite side thereof, and contains relatively little manganese and relatively high nickel. An electrode assembly, characterized in that the positive electrode tab of the coated positive electrode and the positive electrode tab of the positive electrode coated with the positive electrode active material containing a relatively large amount of manganese and relatively little nickel are spaced apart from each other at a predetermined distance.
[Claim 9]
A secondary battery in which the electrode assembly of any one of claims 1 to 8 is built in a case.
[Claim 10]
A secondary battery module in which a plurality of the secondary batteries of claim 9 are electrically connected.