Electrode sheet and preparation method therefor, and lithium-ion battery

Abstract

An electrode sheet and a preparation method therefor, and a lithium-ion battery. The electrode sheet comprises a first electrode sheet, which comprises a first current collector and a first active material coating layer coated on one surface of the first current collector, wherein the first active material coating layer comprises a first active substance, a first binder and a first conductive agent. The mass content of the first conductive agent is D1, the mass content of the first binder is P1, and the total mass of the first active material coating layer is CW1; the electrode efficiency of the first electrode sheet is Q1; and Q1, CW1, D1 and P1 satisfy the relational expression: Q1=CW1*(1-D1-P1), and 1≤P1 / D1≤8. By reducing the content of a conductive agent, the source of lithium ions is limited, thereby reducing the precipitation ability of lithium ions. Moreover, the content of a binder is increased so as to improve the bonding capability between an electrode sheet and a separator, which reduces lithium precipitation of the electrode sheet. In addition, the warping phenomenon of a single-sided sheet is reduced by controlling the mass of the active material coating.

Description

An electrode sheet, a preparation method thereof and a lithium ion battery TECHNICAL FIELD

[0001] The present application relates to the field of secondary batteries, in particular to an electrode sheet, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] Lithium ion batteries are widely used in the fields of electronic digital, electric vehicles, energy storage and aerospace due to their high working voltage, long cycle life, high energy density, environmental friendliness. With the increasing demand for high-rate charging, more and more wound multi-tab batteries and stacked batteries are used. Compared with wound multi-tab batteries, the stacked batteries have the advantage of avoiding the phenomenon of corner lithium precipitation during cycling, which leads to cycle failure. Therefore, the stacked batteries are more popular.

[0003] However, the conventional stacked battery has a cathode single-sided sheet structure. During the manufacturing process, the single-sided sheet needs to be treated with NMP solvent to reduce the warping problem of the single-sided sheet. On the other hand, during the cycling process of the stacked battery, the stress on both sides of the single-sided sheet is uneven, and the edge of the single-sided sheet is easy to separate from the main body, leading to cycle purple stain and even lithium precipitation failure, which greatly deteriorates the use of the stacked battery.

[0004] Therefore, it is urgent to develop an electrode sheet and a lithium ion battery that can improve the lithium precipitation of the electrode sheet while considering the cycle performance.

[0005] SUMMARY

[0006] The present application aims to: in view of the shortcomings of the prior art, provide an electrode sheet that can improve the lithium precipitation of the electrode sheet while considering the cycle performance and electrochemical performance.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] An electrode sheet, comprising a first electrode sheet, the first electrode sheet comprising a first current collector and a first active material coating layer coated on one surface of the first current collector, the first active material coating layer comprising a first active material, a first binder and a first conductive agent;

[0009] The mass content of the first conductive agent in the first active material coating layer is D1, the mass content of the first binder is P1, and the total mass of the first active material coating layer is CW1; the electrode utility amount of the first electrode sheet is Q1;

[0010] Wherein, Q1, CW1, D1 and P1 satisfy the following relationship: Q1=CW1*(1-D1-P1); 1≤P1 / D1≤8.

[0011] By limiting the content of the conductive substance in the first pole piece active material coating, the transmission rate of electrons is reduced to inhibit the speed of lithium ion release. By limiting the content of the binder in the first pole piece active material coating, the adhesion of the pole piece is ensured, while the resistance of lithium ion transmission is increased to reduce the speed of lithium ion release, thereby improving the lithium precipitation of the single-sided sheet.

[0012] Preferably, it further comprises a second pole piece, which comprises a second current collector and a second active material coating coated on both sides of the second current collector, the second active material coating comprising a second active material, a second binder and a second conductive agent; the mass content of the second conductive agent in the second active material coating is D2, the mass content of the second binder is P2, and the total mass of the second active material coating is CW2; the electrode utility amount of the second pole piece is Q2.

[0013] Preferably, Q1 and Q2 satisfy the following relationship: 0.7 < Q1 / Q2 < 0.92; Q2 = CW2*(1-D2-P2).

[0014] When Q1 and Q2 satisfy the above relationship, the amount of lithium ions can be reduced while the speed of lithium ion release is inhibited, the adhesion of the pole piece is increased, the problem of lithium precipitation caused by too fast lithium release of the single-sided sheet is effectively overcome, and the charge and discharge safety performance of the battery is improved. The lower the ratio of the electrode utility amount, the more obvious the effect, and when the ratio is lower than the value, the cathode has weak lithium release ability and the anode cannot be fully charged, and when the ratio is higher than the value, lithium precipitation problem is prone to occur.

[0015] Preferably, CW1 is 0.20g / 15 40.250mm 2 -0.23g / 15 40.250mm 2 Reducing the mass of the active material coating reduces the warping phenomenon of the single-sided sheet, thereby improving the quality and production efficiency of the single-sided sheet.

[0016] Preferably, D1 is 0.5-1.5%.

[0017] Preferably, P1 is 2.0-3.5%.

[0018] Preferably, CW2 is 0.25g / 15 40.250mm 2 -0.28g / 15 40.250mm 2 .

[0019] Preferably, D2 is 2.0-4.0%.

[0020] Preferably, P2 is 0.5-1.5%.

[0021] In addition, the application also provides a preparation method of the electrode sheet, comprising the following steps:

[0022] Step S1, uniformly mixing the first active material, the first conductive agent and the first binder to prepare an electrode slurry A;

[0023] Step S2, uniformly mixing the second active material, the second conductive agent and the second binder to prepare an electrode slurry B;

[0024] Step S3, coating the electrode slurry A prepared in step S1 on one surface of the first current collector, drying to prepare a first electrode tab;

[0025] Step S4, coating the electrode slurry B prepared in step S2 on both surfaces of the second current collector, drying to prepare a second electrode tab.

[0026] In addition, the present application also provides a lithium ion battery, comprising an electric core prepared by stacking a negative electrode tab, a positive electrode tab and a separator, and an electrolyte, and a shell packaging the electric core and the electrolyte, wherein the positive electrode tab is the electrode tab described above.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] (1) The present application precisely controls the ratio of the conductive agent to the binder within the range of 1≤P1 / D1≤8, and this ratio adjustment significantly improves the kinetic performance of the electrode tab. By reducing the amount of conductive agent used, the present application not only reduces the source of lithium ions, thereby reducing the internal resistance of the battery, but also effectively reduces the precipitation of lithium ions on the surface of the electrode tab, thereby inhibiting the lithium precipitation phenomenon. In addition, increasing the content of the binder strengthens the adhesion between the electrode tab and the separator, further reducing the lithium precipitation problem caused by physical separation, improving the overall stability of the electrode tab and the reliability of the battery. In addition, the warping phenomenon of the single-sided tab is also reduced by controlling the mass of the active material coating, thereby improving the quality and production efficiency of the single-sided tab.

[0029] (2) The present application optimizes the lithium ion distribution and kinetic characteristics of the electrode tab by controlling the electrode utility ratio between the first electrode tab and the second electrode tab within the range of 0.7 DETAILED DESCRIPTION

[0030] In order to make the technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0031] According to a first aspect of the present application, the present application aims to provide an electrode sheet, comprising a first electrode sheet, the first electrode sheet comprising a first current collector and a first active material coating coated on a surface of the first current collector, the first active material coating comprising a first active material, a first binder and a first conductive agent; the mass content of the first conductive agent in the first active material coating is D1, the mass content of the first binder is P1, and the total mass of the first active material coating is CW1; the electrode utility amount of the first electrode sheet is Q1; wherein Q1, CW1, D1 and P1 satisfy the following relationship: Q1=CW1*(1-D1-P1); 1≤P1 / D1≤8.

[0032] When P1 / D1>8, the content of the binder is too much and the content of the conductive agent is too little, the lithium ions in the cathode cannot be removed, resulting in insufficient lithium intercalation in the anode; when P1 / D1<1, the content of the conductive agent is too little, the speed of lithium removal in the cathode is too fast, and the speed of lithium intercalation in the anode is not matched, thereby causing lithium precipitation.

[0033] In some embodiments, a second electrode sheet is further included, the second electrode sheet comprising a second current collector and a second active material coating coated on both surfaces of the second current collector, the second active material coating comprising a second active material, a second binder and a second conductive agent;

[0034] The mass content of the second conductive agent in the second active material coating is D2, the mass content of the second binder is P2, and the total mass of the second active material coating is CW2; the electrode utility amount of the second electrode sheet is Q2;

[0035] Wherein Q1 and Q2 satisfy the following relationship: 0.7Q1 / Q2<0.92; Q2=CW2*(1-D2-P2).

[0036] When Q1 / Q2<0.7, interface purple will occur, i.e. insufficient lithium intercalation in the anode, thereby affecting the appearance of the electrode sheet; when Q1 / Q2>0.92, lithium precipitation will occur in the electrode sheet.

[0037] In some embodiments, the electrode sheet is a positive electrode sheet, and the first active material and the second active material are both positive active materials, which can be, but are not limited to, positive active materials with chemical formula such as Li a Ni x Co y Mz O 2-b N b (where 0.95≤a≤1.2, x>0, y≥0, z≥0, and x+y+z=1, 0≤b≤1, M is selected from one or more combinations of Mn and Al, and N is selected from one or more combinations of F, P, and S) The positive electrode active material may also be, but is not limited to, LiCoO2, LiNiO2, LiVO2, LiCrO2, LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5 The positive electrode active material can be one or more combinations thereof, including O4, LiCoPO4, LiMnPO4, LiFePO4, LiNiPO4, LiCoFSO4, CuS2, FeS2, MoS2, NiS, and TiS2. The positive electrode active material can also be modified. Methods for modifying the positive electrode active material are known to those skilled in the art. For example, coating, doping, and other methods can be used to modify the positive electrode active material. The materials used for modification can be one or more combinations thereof, including but not limited to Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, and W. The positive electrode current collector is typically a structure or component that collects current. The positive electrode current collector can be any material suitable for use as a positive electrode current collector in lithium-ion batteries. For example, the positive electrode current collector can be, but is not limited to, metal foil, and more specifically, aluminum foil.

[0038] In some embodiments, the first adhesive and the second adhesive may be one or more of the following: polyvinylidene fluoride (PVDF), sodium alginate (SA), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), hydrogenated nitrile butadiene rubber (HNBR), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), styrene-butadiene rubber latex (SBR).

[0039] In some embodiments, the first conductive agent and the second conductive agent may be one or more of the following: acetylene black (AB), superconducting carbon black, graphite emulsion, carbon nanotubes (CNT), graphene, Ketjen black (KB), vapor-grown carbon fiber (VGCF), etc.

[0040] In some embodiments, CW1 is 0.18g / 1540.250mm. 2 -0.23g / 1540.250mm 2 For example, it could be 0.18g / 1540.250mm 2 0.19g / 1540.250mm 20.20g / 15 40.250mm 2 0.21g / 15 40.250mm 2 0.22g / 15 40.250mm 2 0.23g / 15 40.250mm 2 .

[0041] In some embodiments, D1 is 0.5-1.5%, for example, can be 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.5%.

[0042] In some embodiments, P1 is 2.0-3.5%, for example, can be 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, 3.2%, 3.4%, 3.5%.

[0043] CW2 is 0.25g / 15 40.250mm 2 -0.30g / 15 40.250mm 2 for example, can be 0.25g / 15 40.250mm 2 0.26g / 15 40.250mm 2 0.27g / 15 40.250mm 2 0.28g / 15 40.250mm 2 0.29g / 15 40.250mm 2 0.30g / 15 40.250mm 2 .

[0044] D2 is 2.0-4.0%, for example, can be 2.0%, 2.5%, 3.0%, 3.5%, 4.0%.

[0045] P2 is 0.5-1.5%, for example, can be 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.5%.

[0046] According to a second aspect of the present application, the present application aims to provide a method for preparing an electrode sheet, comprising the following steps:

[0047] Step S1, uniformly mixing the first active material, the first conductive agent and the first binder to prepare an electrode slurry A;

[0048] Step S2, uniformly mixing the second active material, the second conductive agent and the second binder to prepare an electrode slurry B;

[0049] Step S3, coating the electrode slurry A prepared in step S1 on one surface of the first current collector, drying to prepare a first electrode sheet;

[0050] Step S4, coating the electrode slurry B prepared in step S2 on the two side surfaces of the second current collector, drying, to prepare a second electrode tab.

[0051] According to a third aspect of the present application, the present application provides a lithium ion battery, comprising a battery cell formed by stacking a negative electrode tab, a positive electrode tab and a separator, and an electrolyte, and a shell encapsulating the battery cell and the electrolyte, wherein the positive electrode tab is the electrode tab described above.

[0052] In some embodiments, the negative electrode tab comprises a negative current collector and a negative active material layer coated on at least one surface of the negative current collector. The negative active material layer can be one or more of, but not limited to, graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based material, tin-based material, lithium titanate or other metals capable of forming alloys with lithium.

[0053] wherein the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon alloy; and the tin-based material can be selected from one or more of elemental tin, tin oxide compound, tin alloy. The negative current collector is generally a structure or part that collects current, and the negative current collector can be any material suitable for use as a negative current collector in a lithium ion battery in the art, for example, the negative current collector can be, but not limited to, a metal foil, and more specifically can be, but not limited to, a copper foil.

[0054] The separator can be any material suitable for use as a separator in a lithium ion battery in the art, for example, can be a combination of one or more of, but not limited to, polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.

[0055] The lithium ion battery further comprises an electrolyte, which comprises an organic solvent, an electrolyte lithium salt and an additive. The electrolyte lithium salt can be LiPF6 and / or LiBOB used in high-temperature electrolyte; can be at least one of LiBF4, LiBOB, LiPF6 used in low-temperature electrolyte; can be at least one of LiBF4, LiBOB, LiPF6, LiTFSI used in overcharge-preventing electrolyte; can be at least one of LiClO4, LiAsF6, LiCF3SO3, LiN(CF3SO2)2. The organic solvent can be a cyclic carbonate, including PC, EC; can be a chain carbonate, including DFC, DMC, or EMC; can be a carboxylic acid ester, including MF, MA, EA, MP, etc. The additive includes, but not limited to, at least one of a film-forming additive, a conductive additive, a flame-retardant additive, an overcharge-preventing additive, an additive for controlling the content of H2O and HF in the electrolyte, an additive for improving low-temperature performance, a multifunctional additive.

[0056] In order to make the technical solutions and advantages of the present application clearer, the present application and its beneficial effects will be further described in detail below with specific embodiments, but the embodiments of the present application are not limited thereto.

[0057] Example 1

[0058] (1) Preparation of positive electrode tab

[0059] Step S1, the first active material lithium cobaltate, the first conductive agent acetylene black and the first binder polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 97:1:2 in an N-methyl pyrrolidone solvent system to prepare electrode slurry A;

[0060] Step S2, the second active material lithium cobaltate, the second conductive agent acetylene black and the second binder polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 96.5:2:1.5 in an N-methyl pyrrolidone solvent system to prepare electrode slurry B;

[0061] Step S3, the electrode slurry A is coated on one side of the Al foil, and after drying, rolling, and slitting, the first tab is prepared;

[0062] Step S4, the electrode slurry B is coated on both sides of the Al foil, and after drying, rolling, and slitting, the second tab is prepared.

[0063] The total mass CW1 of the first active material coating corresponding to the first tab is 0.230 g / 1540.25 mm 2 , the mass content P1 of the first binder is 2.0%, and the mass content D1 of the first conductive agent is 1.0%; the total mass CW2 of the second active material coating corresponding to the second tab is 0.257 g / 1540.25 mm 2 , the mass content P2 of the second binder is 1.5%, and the mass content D2 of the second conductive agent is 2.0%.

[0064] (2) Preparation of negative electrode tab

[0065] The negative electrode active material, sodium carboxymethyl cellulose, and SBR emulsion are mixed in a weight ratio of 97.4:1.3:1.3 to prepare a negative electrode active material slurry, and the negative electrode active material can be a silicon-carbon material; the active material slurry is coated on a copper current collector to obtain an active material layer, and then cold-pressed and slitted to obtain a negative electrode tab.

[0066] (3) Preparation of separator

[0067] A porous polyethylene (PE) polymer film is used as the isolation film.

[0068] (4) Preparation of electrolyte

[0069] A solution of lithium salt LiPF6and non-aqueous organic solvent (vinyl carbonate (EC) : diethyl carbonate (DEC) : propylene carbonate (PC) : propyl propionate (PP) : vinylene carbonate (VC)) = 25:25:15:31:4, mass ratio) formulated at a mass ratio of 8:92 was used as the electrolyte.

[0070] (5) Preparation of battery

[0071] The above-mentioned first electrode sheet, second electrode sheet, separator, and negative electrode sheet were laminated to produce a bare battery cell, which was then packaged and injected with electrolyte to produce a finished lithium ion battery.

[0072] Example 2

[0073] Unlike Example 1, in this example, the total mass CW1 of the first active material coating corresponding to the first electrode sheet was 0.220 g / 1540.25 mm 2 , and the mass content P1 of the first binder was 3.0%. The rest was the same as Example 1, which will not be repeated here.

[0074] Example 3

[0075] Unlike Example 1, in this example, the total mass CW1 of the first active material coating corresponding to the first electrode sheet was 0.200 g / 1540.25 mm 2 , the mass content P1 of the first binder was 3.5%, and the mass content D1 of the first conductive agent was 0.5%.

[0076] The rest was the same as Example 1, which will not be repeated here.

[0077] Example 4

[0078] Unlike Example 1, in this example, the total mass CW1 of the first active material coating corresponding to the first electrode sheet was 0.180 g / 1540.25 mm 2 , the mass content P1 of the first binder was 2.5%; the total mass CW2 of the second active material coating corresponding to the second electrode sheet was 0.250 g / 1540.25 mm 2 , the mass content D2 of the second conductive agent was 2.5%, and the mass content P2 of the second binder was 0.5%.

[0079] The rest was the same as Example 1, which will not be repeated here.

[0080] Example 5

[0081] Unlike Example 1, in this example, the total mass CW1 of the first active material coating corresponding to the first electrode sheet was 0.190 g / 1540.25 mm2 , the mass content D1 of the first conductive agent is 1.5%, and the mass content P1 of the first binder is 2.5%; the total mass CW2 of the second active material coating corresponding to the second electrode plate is 0.260 g / 15 40.25 mm 2 , the mass content D2 of the second conductive agent is 3.0%, and the mass content P2 of the second binder is 1.0%.

[0082] The rest is the same as that in Example 1, which will not be repeated here.

[0083] Example 6

[0084] Different from Example 1, the total mass CW1 of the first active material coating corresponding to the first electrode plate in this example is 0.210 g / 15 40.25 mm 2 , the mass content D1 of the first conductive agent is 0.5%; the total mass CW2 of the second active material coating corresponding to the second electrode plate is 0.270 g / 15 40.25 mm 2 , the mass content D2 of the second conductive agent is 3.5%, and the mass content P2 of the second binder is 1.0%.

[0085] The rest is the same as that in Example 1, which will not be repeated here.

[0086] Example 7

[0087] Different from Example 1, the total mass CW2 of the second active material coating corresponding to the second electrode plate in this example is 0.280 g / 15 40.25 mm 2 , the mass content D2 of the second conductive agent is 4.0%, and the mass content P2 of the second binder is 0.5%.

[0088] The rest is the same as that in Example 1, which will not be repeated here.

[0089] Example 8

[0090] Different from Example 1, the total mass CW2 of the second active material coating corresponding to the second electrode plate in this example is 0.290 g / 15 40.25 mm 2 , the mass content D2 of the second conductive agent is 2.0%, and the mass content P2 of the second binder is 1.5%.

[0091] The rest is the same as that in Example 1, which will not be repeated here.

[0092] Example 9

[0093] Different from Example 1, the total mass CW2 of the second active material coating corresponding to the second electrode plate in this example is 0.300 g / 15 40.25 mm 2, the mass content D2 of the second conductive agent is 3.0%, and the mass content P2 of the second binder is 0.5%.

[0094] The rest is the same as Example 1, which will not be repeated here.

[0095] Comparative Example 1

[0096] Different from Example 1, in the present comparative example, the total mass CW1 of the first active material coating corresponding to the first pole piece is 0.257g / 1540.25mm 2 , the mass content D1 of the first conductive agent is 2.0%, and the mass content P1 of the first binder is 1.5%.

[0097] The rest is the same as Example 1, which will not be repeated here.

[0098] Comparative Example 2

[0099] Different from Example 1, in the present comparative example, the total mass CW1 of the first active material coating corresponding to the first pole piece is 0.250g / 1540.25mm 2 , the mass content D1 of the first conductive agent is 1.0%, and the mass content P1 of the first binder is 3.0%.

[0100] The rest is the same as Example 1, which will not be repeated here.

[0101] Comparative Example 3

[0102] Different from Example 1, in the present comparative example, the total mass CW1 of the first active material coating corresponding to the first pole piece is 0.160g / 1540.25mm 2 , the mass content D1 of the first conductive agent is 0.5%, and the mass content P1 of the first binder is 5.0%.

[0103] The rest is the same as Example 1, which will not be repeated here.

[0104] Comparative Example 4

[0105] Different from Example 1, in the present comparative example, the total mass CW1 of the first active material coating corresponding to the first pole piece is 0.150g / 1540.25mm 2 , the mass content D1 of the first conductive agent is 1.0%, and the mass content P1 of the first binder is 3.0%.

[0106] The rest is the same as Example 1, which will not be repeated here.

[0107] Comparative Example 5

[0108] Different from example 1, the total mass CW1 of the first active material coating corresponding to the first tab in the present comparative example is 0.240 g / 1540.25 mm 2 , the mass content D1 of the first conductive agent is 0.5%, and the mass content P1 of the first binder is 5.0%.

[0109] The rest is the same as example 1, which will not be repeated here.

[0110] Among them, the specific parameters of examples 1-9 and comparative examples 1-5 are shown in Table 1 below.

[0111] Table 1

[0112] The lithium ion batteries prepared in the examples and comparative examples were respectively subjected to the following performance tests:

[0113] 1. The finished battery cell was discharged at 1C constant current to 3V, and rested for 5 min,

[0114] 2. Different battery cells were respectively charged at a current I = 0.7C, 1C, 1.2C, 1.5C, 1.8C, 2C, 2.3C, 2.5C constant current constant voltage to 4.35V, cutoff rate 0.5C, and then 0.5C constant current constant voltage to 4.5V, cutoff rate 0.05C, and rested for 5 min,

[0115] 3. Repeat steps 1 and 2 for 20 times, and finally fully charge the disassembled battery cell, record the appearance of the anode tab corresponding to the second tab, and record the maximum charging current Imax when the appearance of the anode tab corresponding to the second tab does not lithiumize (this step is to explore the charging capacity of the battery cell, i.e. the maximum charging current that the battery cell can withstand).

[0116] 4. Take Imax obtained in step 3, repeat steps 1 and 2 for 1000 cls, record the capacity retention rate, expansion rate of the battery cell after cycling, and the appearance of the anode corresponding to the first tab after full charging.

[0117] The results of the above performance tests are shown in Table 2 below.

[0118] Table 2

[0119] From the data of examples 1-9 and comparative examples 1-5 in table 2, it can be seen that when the ratio of conductive agent and binder in the single-sided sheet does not match, the performance of the battery cell will also be affected. When P1 / D1>8, the content of the binder is too high and the content of the conductive agent is too low, the lithium ions in the cathode cannot be removed, resulting in insufficient lithium insertion in the anode; when P1 / D1<1, the content of the conductive agent is too low, the speed of lithium removal in the cathode is too fast, and the speed of lithium ion acceptance in the anode does not match, thereby causing lithium precipitation. When Q1 and Q2 satisfy the relationship: 0.7Q1 / Q2<0.92, the amount of lithium ions can be reduced while the speed of lithium ion removal is inhibited, the adhesion of the sheet is increased, the problem of lithium precipitation caused by too fast lithium removal in the single-sided sheet is effectively overcome, and the charge and discharge safety performance of the battery is improved. The lower the ratio of the electrode effective amount, the more obvious the effect, and when the value is lower than this, the cathode lithium removal capacity is weak and the anode cannot be fully charged, and when the value is higher than this, lithium precipitation problem is prone to occur.

[0120] Therefore, when the ratio of the electrode effective amount, the content of the conductive agent and the content of the binder in the single-sided sheet satisfy the above relationship, the amount of lithium removal in the cathode single-sided sheet is appropriate, and the speed of lithium removal can match the speed of lithium ion acceptance in the anode, thereby improving the corresponding electrical performance of the battery.

[0121] According to the disclosure and teaching of the above description, those skilled in the art of the present application can also make changes and modifications to the above embodiments. Therefore, the present application is not limited to the above specific embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art on the basis of the present application all belong to the protection scope of the present application. In addition, although some specific terms are used in the present specification, these terms are only for convenience of explanation and do not constitute any limitation on the present application.

Claims

1. An electrode sheet, characterized by, The first electrode tab comprises a first current collector and a first active material coating coated on one surface of the first current collector, the first active material coating comprising a first active material, a first binder and a first conductive agent; The mass content of the first conductive agent is D1, the mass content of the first binder is P1, and the total mass of the first active material coating is CW1; the electrode effective amount of the first electrode tab is Q1; Wherein Q1, CW1, D1 and P1 satisfy the following relationship: Q1=CW1*(1-D1-P1); 1≤P1 / D1≤8.

2. The electrode pad of claim 1, wherein The second electrode tab comprises a second current collector and a second active material coating coated on both surfaces of the second current collector, the second active material coating comprising a second active material, a second binder and a second conductive agent; The mass content of the second conductive agent is D2, the mass content of the second binder is P2, and the total mass of the second active material coating is CW2; the electrode effective amount of the second electrode tab is Q2; Wherein Q1 and Q2 satisfy the following relationship: 0.7 3. The electrode pad of claim 1, wherein CW1 is 0.18 g / 15 40.250 mm 2 -0.23 g / 15 40.250 mm 2 .

4. The electrode pad of claim 1, wherein The D1 is 0.5-1.5%.

5. The electrode pad of claim 1, wherein The P1 is 2.0-3.5%.

6. The electrode pad of claim 2, wherein CW2 is 0.25 g / 15 40.250 mm 2 -0.30 g / 15 40.250 mm 2 .

7. The electrode pad of claim 2, wherein The D2 is 2.0-4.0%.

8. The electrode pad of claim 2, wherein The P2 is 0.5-1.5%.

9. A method of producing the electrode sheet according to any one of claims 1 to 8, characterized by, The method comprises the following steps: Step S1, uniformly mixing a first active material, a first conductive agent and a first binder to prepare an electrode slurry A; Step S2, uniformly mixing a second active material, a second conductive agent and a second binder to prepare an electrode slurry B; Step S3, coating the electrode slurry A prepared in step S1 on one surface of a first current collector, and drying to prepare a first electrode tab; Step S4, coating the electrode slurry B prepared in step S2 on both surfaces of a second current collector, and drying to prepare a second electrode tab. The electrode tab according to any one of claims 1-8.

10. A lithium-ion battery, characterized by, ​

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