CN106486639B - Lithium battery pole piece and manufacturing method thereof - Google Patents

Abstract

The invention discloses a lithium battery pole piece and a manufacturing method thereof. The ion battery pole piece includes a positive inner pole piece and a positive outer pole piece, the positive inner pole piece includes a positive inner layer active material, and the positive outer pole piece Including the positive outer layer active material, the stability of the positive inner active material is better than that of the positive outer active material; wherein, the positive inner active material includes lithium iron phosphate, lithium cobaltate, nickel-cobalt-manganese ternary material, nickel One or more of cobalt-aluminum high-nickel materials and lithium titanate, the positive outer layer active materials include lithium iron phosphate, lithium cobaltate, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum high-nickel materials and lithium titanate one or more. The pole piece of the lithium battery proposed by the present invention adopts a double-layer electrode structure, which can obtain higher safety performance.

Description

Lithium battery pole piece and manufacturing method thereof

technical field

The invention relates to a lithium battery pole piece and a manufacturing method thereof.

Background technique

Lithium-ion batteries have outstanding advantages such as high energy density, long cycle life, and high energy conversion efficiency. They occupy a dominant position in mobile device power supplies and are also one of the most promising energy storage methods in applications such as electric vehicles and smart grids. These application areas have increasingly higher requirements on the energy density and individual battery capacity of lithium-ion batteries. The lithium-ion battery used in notebook computers has increased from a single capacity of about 2Ah to the current 3-4Ah; while the capacity of a single cell in car batteries and energy storage batteries has reached the level of tens of Ah or even two to three hundred Ah. Because lithium-ion batteries use flammable organic solvents as electrolyte solvents, there are potential safety hazards. When the battery encounters safety problems such as acupuncture, if the positive electrode falls off and the exposed aluminum foil contacts the fully charged negative electrode, the internal resistance of the short circuit is equivalent to the internal resistance of the battery cell, and the most heat will be generated. See the attached picture 1 is the change curve of battery heat production over time; if the heat dissipation rate of the battery is lower than the heat production of the battery, it will directly lead to thermal runaway of the battery, and the direct contact between the aluminum foil and the fully charged negative electrode will generate the most heat, which is very easy to cause battery damage. thermal runaway and cause further safety incidents.

Professor Ai Xinping of Wuhan University once proposed the use of redox couples to improve the safety performance of batteries, but the anti-oxidation potential of redox couples is low, and oxidation of redox couples will generally occur at around 3.6V. 4V grade materials such as lithium cobalt oxide, lithium manganese oxide, and nickel-cobalt-manganese ternary with higher voltage are difficult to apply. At the same time, the redox couple has low solubility and low clamping capacity in the currently used carbonate electrolyte, and is generally suitable for charging currents < 0.5C; Professor Ai also proposed to use active materials such as PTC-coated lithium cobaltate to improve The safety performance of the battery, but the electrical conductivity of the coated material drops sharply, and more conductive agents need to be used to reduce the polarization of the battery, which will severely limit the energy density of the battery.

In the domestic patent "An electrode and production method of a double-layer composite lithium-ion battery" (application number CN201210212137.4), it is disclosed that a double-layer lithium iron phosphate material is coated on an aluminum foil to improve the stability of the battery. However, in this solution, the lithium iron phosphate material A of the inner layer is less stable than the lithium iron phosphate material B of the outer layer, which will still bring certain hidden dangers to the safety of the battery.

Contents of the invention

The purpose of the present invention is to propose a lithium battery pole piece and a manufacturing method thereof, so as to solve the technical problem of low safety of a large-capacity lithium battery existing in the above-mentioned prior art.

For this reason, a kind of lithium battery pole piece that the present invention proposes, comprises positive electrode inner layer pole piece and positive electrode outer layer pole piece, described positive electrode inner layer pole piece comprises positive electrode inner layer active material, and described positive electrode outer layer pole piece comprises positive electrode The outer layer active material, the stability of the positive inner layer active material is better than the stability of the positive outer layer active material; wherein, the positive inner layer active material includes lithium iron phosphate, lithium cobaltate, nickel cobalt manganese One or more of element materials, nickel-cobalt-aluminum high-nickel materials and lithium titanate, the positive outer layer active materials include lithium iron phosphate, lithium cobaltate, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum high-nickel materials and one or more of lithium titanate.

Preferably, the positive inner layer pole piece further includes a conductive agent and a binder, and the positive electrode outer layer pole piece further includes a conductive agent and a binder.

Preferably, it also includes a negative inner layer pole piece and a negative electrode outer layer pole piece, the negative electrode inner layer pole piece includes the negative electrode inner layer active material, the negative electrode outer layer pole piece includes the negative electrode outer layer active material, the negative electrode inner layer The stability of the active material is better than that of the negative electrode outer layer active material; wherein, the negative electrode inner layer active material includes natural graphite, artificial graphite, a composite material of natural graphite and artificial graphite, soft carbon, hard carbon, titanium One or more of Lithium Oxide, the negative electrode outer layer active material includes one or more of natural graphite, artificial graphite, composite material of natural graphite and artificial graphite, soft carbon, hard carbon, lithium titanate.

Preferably, the negative inner layer pole piece further includes a conductive agent and a binder, and the negative electrode outer layer pole piece further includes a conductive agent and a binder.

Preferably, the mass percentages of the components of the inner layer of the positive electrode are: 85% to 99% of the active material in the inner layer of the positive electrode, 0.5% to 6% of the conductive agent, and 0.5% to 9% of the binder; The mass percentages of each component of the layered electrode sheet are: 85% to 99% of the active material in the outer layer of the positive electrode, 0.5% to 6% of the conductive agent, and 0.5% to 9% of the binder; The mass percentages are: 85% to 99% of the active material in the inner layer of the negative electrode, 0.5% to 6% of the conductive agent, and 0.5% to 9% of the binder; the mass percentage of each component of the negative electrode outer layer pole piece is: the negative electrode outer layer The active material is 85%-99%, the conductive agent is 0.5%-6%, and the binder is 0.5%-9%.

Preferably, the conductive agent includes one or more of acetylene black, carbon black conductive agent, conductive graphite, carbon nanotubes, graphene and other materials; the binder includes epoxy resin, polytetrafluoroethylene, One or more of polyvinylidene fluoride and polyacrylate, or, the binder includes one or more of sodium carboxymethyl cellulose, sodium alginate and styrene-butadiene rubber.

Preferably, the positive inner pole piece, the positive outer pole piece, the negative inner pole piece and the negative outer pole piece are coated at one time by a coating machine.

The present invention also proposes a method for making a lithium battery pole piece, comprising the steps of:

S1. Prepare the positive electrode inner layer slurry and the positive electrode outer layer slurry, the positive electrode inner layer slurry includes the positive electrode inner layer active material, the positive electrode outer layer slurry includes the positive electrode outer layer active material, and the positive electrode inner layer active material The stability of the positive electrode outer layer active material is better than that of the positive electrode outer layer active material; wherein, the positive electrode inner layer active material includes lithium iron phosphate, lithium cobalt oxide, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum high-nickel material and titanic acid One or more of lithium, the positive outer layer active material includes one or more of lithium iron phosphate, lithium cobaltate, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum high-nickel material and lithium titanate;

S2. Coating the positive electrode inner layer slurry and the positive electrode outer layer slurry on the positive electrode of the battery to obtain a lithium battery positive electrode sheet.

Preferably, after step S2, the following steps are also included:

S3. Prepare the negative electrode inner layer slurry and the negative electrode outer layer slurry, the negative electrode inner layer slurry includes the negative electrode inner layer active material, the negative electrode outer layer slurry includes the negative electrode outer layer active material, the negative electrode inner layer active material The stability of the negative electrode outer layer active material is better than that of the negative electrode outer layer active material; wherein, the negative electrode inner layer active material includes natural graphite, artificial graphite, a composite material of natural graphite and artificial graphite, soft carbon, hard carbon, lithium titanate One or more of them, the negative electrode outer layer active material includes one or more of natural graphite, artificial graphite, composite material of natural graphite and artificial graphite, soft carbon, hard carbon, lithium titanate;

S4. Applying the negative electrode inner layer slurry and the negative electrode outer layer slurry to the battery negative electrode to obtain a lithium battery negative electrode sheet.

Preferably, the preparation of the positive electrode inner layer slurry comprises the following steps:

S11, mixing the binder and the solvent to obtain the positive electrode glue;

S12. Mix the positive inner layer active material and the conductive agent evenly, then add the positive electrode glue, adjust the solid content to 70%-75%, and obtain the positive electrode inner layer slurry;

The preparation of the positive electrode outer layer slurry comprises the steps:

S11', the binding agent is mixed with a solvent to obtain the positive electrode glue;

S12', mix the active material of the positive outer layer and the conductive agent evenly, add the positive electrode glue, adjust to a solid content of 70% to 75%, and obtain the positive electrode outer layer slurry;

The preparation of the negative electrode inner layer slurry comprises:

S31, mixing the binder and the solvent to form a negative electrode glue;

S32. Mix the negative electrode inner layer active material and the conductive agent evenly, and then add the negative electrode glue to obtain negative electrode slurry;

S33. Add the styrene-butadiene rubber emulsion into the negative electrode slurry, stir evenly, and adjust the solid content to 50%-55% with water to obtain the negative electrode inner layer slurry;

The preparation of the negative electrode outer layer slurry comprises:

S31', binding agent and solvent are mixed into negative electrode glue;

S32', mixing the negative electrode outer layer active material and conductive agent evenly, then adding the negative electrode glue to obtain negative electrode slurry;

S33', adding the styrene-butadiene rubber emulsion into the negative electrode slurry, stirring evenly, and adjusting the solid content to 50%-55% with water to obtain the negative electrode outer layer slurry.

Further, the present invention also proposes a lithium battery, including the positive electrode sheet of the above-mentioned lithium battery (the aluminum foil is the positive electrode substrate, and the positive electrode substrate has a positive electrode active material), the negative electrode sheet of the lithium battery (the copper foil is the negative electrode substrate, There are negative electrode active material), polyolefin diaphragm and non-aqueous organic electrolyte on the negative plate substrate. Carry out conventional drying, rolling, cutting, spot welding of tabs on the above-mentioned coated pole piece, and process such as winding with the corresponding negative pole piece, entering the shell, injecting liquid, and performing battery sealing, etc., to prepare a 18650-2.5Ah battery.

The lithium battery pole piece proposed by the present invention is a slurry that is uniformly stirred with the active material, the conductive agent, the binder, and the solvent according to a certain ratio, and the coating of the inner and outer pole pieces can use a double-layer coating machine, such as a slot die coater , to achieve one-time coating, or it can be divided into two times by using a common transfer coater. Since the components of the inner and outer pole pieces are similar and the preparation method is the same, the coating process is simple and easy, and it is more conducive to mass production.

Description of drawings

Accompanying drawing 1 is the change curve of battery heat production with time; Wherein, 1 represents the change curve of battery heat production with time when aluminum foil and negative electrode are in direct contact; 2 shows the change of battery heat production with time when aluminum foil and copper foil are in direct contact Curve; 3 represents the change curve of battery heat generation with time when the negative electrode and positive electrode are in direct contact; 4 represents the change curve of battery heat generation with time when the positive electrode and copper foil are in direct contact.

Detailed ways

The present invention will be described in detail below through preferred embodiments.

Embodiment one:

This embodiment proposes a manufacturing method of a lithium battery pole piece, comprising steps:

S1. Prepare positive electrode inner layer slurry, positive electrode outer layer slurry, negative electrode inner layer slurry and negative electrode outer layer slurry;

S2. Add the positive electrode inner layer slurry, the positive electrode outer layer slurry, the negative electrode inner layer slurry and the negative electrode outer layer slurry into different slurry tanks of the Slot Die coater for coating to obtain a double-layer coating structure. Lithium battery pole piece.

Wherein, the preparation of positive electrode inner layer slurry comprises:

S11a, mixing 5.5 g of polyvinylidene fluoride with 30 g of NMP solvent, and stirring for 1 to 3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 15.5%;

S11b. Mix 97.5g of lithium iron phosphate and 1.0g of VGCF dry powder evenly, add the above-mentioned glue solution and mix evenly, and use NMP solvent to adjust the solid content of the slurry to 70%-75% to obtain positive electrode inner layer slurry.

The preparation of positive electrode outer layer slurry includes:

S12a. Mix 1.5 g of polyvinylidene fluoride with 30 g of NMP solvent, and stir for 1 to 3 hours to prepare a glue that is uniformly mixed and has a solid content of 15.5%;

S12b. Mix 92g of lithium cobaltate and 2.5g of acetylene black dry powder evenly, add the above glue and mix evenly, and use NMP solvent to adjust the solid content of the slurry to 70%-75%, to obtain the positive electrode outer layer slurry.

The preparation of negative electrode inner layer slurry includes:

S13a. Mix 2.5 g of sodium carboxymethyl cellulose and 75 g of water solvent, and stir for 1 to 3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 3.2%;

S13b, 92g of natural graphite A, 2.5g of acetylene black dry powder are mixed uniformly, then add above-mentioned glue and mix uniformly;

S13c. Add 6g (50% solid content) of styrene-butadiene rubber emulsion into the above slurry, stir evenly, and adjust the solid content of the slurry to 50%-55% with water to obtain negative electrode inner layer slurry.

The preparation of negative electrode outer layer slurry includes:

S14a. Mix 1.5 g of sodium alginate and 75 g of water solvent, and stir for 1 to 3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 3.2%;

S14b, mix the natural graphite B of 96.5g, 1.0g SP (carbon black conductive agent) dry powder, then add above-mentioned glue and mix;

S14c. Add 2 g (50% solid content) of styrene-butadiene rubber emulsion into the above slurry, stir evenly, and adjust the solid content of the slurry to 50%-55% with water to obtain negative electrode inner layer slurry.

Embodiment two:

This example proposes a method for manufacturing a lithium battery pole piece. The difference from Example 1 lies in the preparation of the positive electrode inner layer slurry, the positive electrode outer layer slurry, the negative electrode inner layer slurry, and the negative electrode outer layer slurry. in,

Preparation of positive electrode inner layer slurry:

S11a. Mix 6.5g of polyvinylidene fluoride with 30g of NMP solvent, and stir for 1-3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 17.8%;

S11b. Mix 98g of nickel-cobalt-manganese ternary material and 1.0g of VGCF dry powder evenly, then add the above glue and mix evenly, and use NMP to adjust the solid content of the slurry to 70%-75%.

Preparation of positive electrode outer layer slurry:

S12a. Mix 1.05g of polyvinylidene fluoride with 30g of NMP solvent, and stir for 1-3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 17.8%;

S12b. Mix 90g of lithium cobaltate and 3.5g of acetylene black dry powder evenly, then add the above glue and mix evenly, and use NMP to adjust the solid content of the slurry to 70%-75%.

Preparation of negative electrode inner layer slurry:

S13a. Mix 1.5 g of sodium carboxymethyl cellulose and 75 g of water solvent, and stir for 1 to 3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 2.0%;

S13b, mixing 93g of natural graphite A and 3.5g of carbon nanotube dry powder, then adding the above glue and mixing;

S13c. Add 4 g (50% solid content) of styrene-butadiene rubber emulsion into the above slurry, stir evenly, and adjust the solid content of the slurry to 50%-55% with water.

Preparation of negative electrode outer layer slurry:

S14a, mixing 1.5 g of sodium alginate with 75 g of water solvent, and stirring for 1 to 3 hours, to prepare a glue solution that is uniformly mixed and has a solid content of 2.0%;

S14b, mix the composite graphite of 96g core-shell structure, 1.5g SP dry powder evenly, then add above-mentioned glue solution and mix evenly;

S14c. Add 2 g (50% solid content) of styrene-butadiene rubber emulsion into the above slurry, stir evenly, and adjust the solid content of the slurry to 50%-55% with water.

Embodiment three:

This example proposes a method for manufacturing a lithium battery pole piece. The difference from Example 1 lies in the preparation of the positive electrode inner layer slurry, the positive electrode outer layer slurry, the negative electrode inner layer slurry, and the negative electrode outer layer slurry. in,

Preparation of positive electrode inner layer slurry:

S11a. Mix 4.5g of polyvinylidene fluoride with 30g of NMP solvent, and stir for 1-3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 13.0%;

S12b. Mix 97.5g of nickel-cobalt-manganese ternary material LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and 1.2g of SP dry powder evenly, then add the above glue and mix evenly, and use NMP to adjust the slurry The solid content is 70% to 75%.

Preparation of positive electrode outer layer slurry:

S12a. Mix 1.3g of polyvinylidene fluoride with 30g of NMP solvent, and stir for 1-3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 13.0%;

S13b. Mix 93g of nickel-cobalt-manganese ternary material LiNi _0.5 Co _0.2 Mn _0.3 O ₂ and 2.5g of VGCF dry powder evenly, then add the above glue and mix evenly, and use NMP to adjust the solid content of the slurry to 70%-75% %.

Preparation of negative electrode inner layer slurry:

S13a. Mix 2 g of sodium carboxymethyl cellulose with 75 g of water solvent, and stir for 1 to 3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 2.6%;

S13b, mix the natural graphite A of 94g, 1.5g SFG-6 (conductive graphite) dry powder, then add above-mentioned glue and mix;

S13c. Add 4 g (50% solid content) of styrene-butadiene rubber emulsion into the above slurry, stir evenly, and adjust the solid content of the slurry to 50%-55% with water.

Preparation of negative electrode outer layer slurry:

S14a. Mix 1.5 g of sodium alginate with 75 g of water solvent, and stir for 1 to 3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 2.6%;

S14b. Mix 96g of lithium titanate and 1.5g of SP dry powder evenly, then add the above glue and mix evenly;

S14c. Add 2 g (50% solid content) of styrene-butadiene rubber emulsion into the above slurry, stir evenly, and adjust the solid content of the slurry to 50%-55% with water.

Due to the different stability of the active material of the positive inner pole piece and the positive outer pole piece, the degree of deformation of the positive inner pole piece and the positive outer pole piece is also different under the condition of collision or low temperature, such as being subjected to external pressure or at low temperature In the environment, the material with better stability of the inner layer of the positive electrode has a smaller degree of deformation, so the volume change of the internal electrolyte is reduced, and the impact on the conductivity of the battery can be minimized. Negative inner layer pole piece and negative pole outer layer pole piece are also the same reason.

Due to the better stability of the active material of the inner layer of the positive electrode, it reduces the occurrence of material drop caused by the unstable structure and poor adhesion of the battery electrode, thus better avoiding the leakage of bare aluminum foil and A large amount of heat is released by the direct contact of the fully charged negative plate, which improves the safety of the battery.

When charging, the active material with better stability in the inner layer has a larger temperature sensitivity coefficient than the active material with poorer stability in the outer layer. At high temperature, the battery impedance increases, making it easier to be in an open circuit state, which plays a role in the battery overshoot. The role of charging protection.

Nickel-cobalt-manganese ternary materials are considered to be anode materials with great development potential due to their advantages such as high energy density. The ratio of the three elements in the ternary material is different, and its electrochemical performance is also different. The increase of nickel content can obtain higher capacitance, but it will reduce the safety, and the increase of manganese content can improve the stability of the matrix, but it will reduce the safety. destroy the layered structure. Therefore, when using ternary materials as battery active materials in the prior art, it is difficult to achieve both high specific energy and safety of the battery, which seriously affects the application of ternary materials in the field of battery production. However, the above-mentioned problems are well solved by adopting the manufacturing method of the lithium battery pole piece proposed by the present invention.

The safety of the lithium battery of the present invention is verified by comparative examples below.

Comparative example one:

Lithium iron phosphate material is used as the active material of the positive electrode, and natural graphite is used as the active material of the negative electrode. The preparation method of the slurry is as follows:

Preparation of positive electrode slurry:

S1. Mix 5.5 g of polyvinylidene fluoride and 30 g of NMP solvent, and stir for 1 to 3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 6.4%;

S2. Mix 92g of lithium iron phosphate and 2.5g of acetylene black dry powder evenly, then add the above-mentioned uniformly mixed glue solution and stir until uniformly mixed, and use NMP to adjust the solid content of the slurry to 75%.

S3. After the preparation of the above-mentioned slurry is completed, the slurry is put into the trough of the coating machine for coating so as to obtain a pole piece with a single-layer coating structure.

Negative electrode slurry preparation:

S1. Mix 1.5 g of sodium carboxymethyl cellulose with 80 g of water, and stir for 1 to 3 hours to prepare a glue solution that is uniformly mixed and has a solid content of 1.84%;

S1. Mix 95g of natural graphite and 2.5g of SP dry powder evenly, then add the above-mentioned uniformly mixed glue solution and stir until evenly mixed, and use water to adjust the solid content of the slurry to 50%-55%.

After the preparation of the above-mentioned slurry is completed, the slurry is put into a feed tank of a coating machine for coating to obtain a pole piece with a single-layer coating structure. The coated electrode piece is subjected to conventional drying, rolling, cutting, and spot welding of tabs, and is wound with the corresponding negative electrode piece, put into the shell, injected liquid, and sealed the battery to prepare 18650 -2.5Ah battery.

Comparative example two:

This comparative example is compared with comparative example 1, except that the active material lithium iron phosphate of the positive electrode is replaced by a nickel-cobalt-manganese ternary material, the slurry formula, the pole piece manufacturing process, etc. are the same, and 15% triphosphate triphosphate is added to the electrolyte. Phenyl ester, the electrolyte solution is injected into the prepared battery cell to prepare a 18650-2.5Ah battery.

Comparative example three:

This comparative example adopts the same formula as that of Example 2, but the order of coating the inner and outer layer slurry is replaced. That is to say, the stability of the inner layer material is slightly worse, and the coating order of the outer layer material is better, and the cell production and related performance tests are completed.

Safety performance comparison of batteries with double-layer electrode structure, single-layer electrode structure, and flame-retardant additives:

battery capacity acupuncture side extrusion heavy impact Embodiment one 2.52Ah 10/10 pass 10/10 pass 10/10 pass Embodiment two 2.50Ah 10/10 pass 10/10 pass 8/10 pass Embodiment Three 2.53Ah 9/10 pass 10/10 pass 10/10 pass Comparative example one 2.52Ah 2/10 passed 3/10 passed 2/10 passed Comparative example two 2.32Ah 5/10 pass 2/10 passed 4/10 pass Comparative example three 2.50Ah 6/10 pass 4/10 pass 5/10 pass

For comparative example 1, the aluminum foil is in contact with the fully charged negative electrode, and the heat generated by the battery is relatively large, and due to the problem of the cylindrical structure, the heat generated is too late to dissipate, and the proportion of thermal runaway increases significantly; A large amount of flame retardant, but due to the compatibility between the flame retardant and the negative electrode, the capacity of the battery cannot be fully utilized and the energy density of the battery is reduced; for Comparative Example 3, although the double-layer pole piece is also used. However, due to the poor stability of the inner layer material, there are still structural instability, poor adhesion, etc., and material drop occurs, resulting in the direct contact between the exposed aluminum foil and the fully charged negative electrode sheet to release a large amount of heat, while Since the heat cannot be dissipated in time, the risk of thermal failure of the battery cell is still high and the purpose of improving the safety performance of the battery cell is not achieved.

Those skilled in the art will recognize that many variations on the above description are possible, so the examples are merely intended to describe one or more particular implementations.

Although there have been described and described what are considered to be exemplary embodiments of the present invention, it will be apparent to those skilled in the art that various changes and substitutions may be made therein without departing from the spirit of the invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the invention without departing from the inventive central concept described herein. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but the present invention may also include all embodiments and their equivalents falling within the scope of the present invention.

Claims (5)

1. A lithium battery pole piece, characterized in that it comprises a positive inner pole piece, a positive outer pole piece, a negative inner pole piece and a negative outer pole piece, and said positive inner pole piece comprises a positive inner layer active material, the positive outer layer pole piece includes a positive outer layer active material, and the stability of the positive inner layer active material is better than that of the positive outer layer active material; wherein, the positive inner layer active material includes phosphoric acid One or more of iron lithium, lithium cobaltate, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum high-nickel material, and lithium titanate, and the positive outer layer active material includes lithium iron phosphate, lithium cobaltate, nickel-cobalt One or more of manganese ternary materials, nickel-cobalt-aluminum high-nickel materials, and lithium titanate; the mass percentage of each component of the positive inner layer pole sheet is: 85% to 99% of the positive inner layer active material, conductive 0.5% to 6% of the binder, 0.5% to 9% of the binder; the mass percentages of the components of the outer layer of the positive electrode are: 85% to 99% of the active material of the outer layer of the positive electrode, 0.5% to 6% of the conductive agent, Binder 0.5% ~ 9%; The negative inner layer pole piece includes the negative electrode inner layer active material, the negative electrode outer layer pole piece includes the negative electrode outer layer active material, and the stability of the negative electrode inner layer active material is better than the stability of the negative electrode outer layer active material ; Wherein, the negative electrode inner layer active material includes one or more of natural graphite, artificial graphite, composite material of natural graphite and artificial graphite, soft carbon, hard carbon, lithium titanate, and the negative electrode inner layer pole piece The mass percent of each component is: 85% to 99% of the active material in the inner layer of the negative electrode, 0.5% to 6% of the conductive agent, and 0.5% to 9% of the binder. The active material in the outer layer of the negative electrode includes natural graphite, artificial graphite, One or more of composite materials of natural graphite and artificial graphite, soft carbon, hard carbon, lithium titanate, the mass percentage of each component of the negative electrode outer layer pole piece is: negative electrode outer layer active material 85% ~ 99% %, conductive agent 0.5%~6%, binder 0.5%~9%; When subjected to external pressure or in a low temperature environment, the material with better stability in the inner layer of the positive electrode deforms less; when charging, the active material with better stability in the inner layer of the positive electrode is more stable than the active material with poorer stability in the outer layer of the positive electrode With a larger temperature sensitivity coefficient, the battery impedance increases at high temperatures, making it easier to be in a disconnected state; When subjected to external pressure or in a low temperature environment, the material with better stability in the inner layer of the negative electrode deforms less; when charging, the active material with better stability in the inner layer of the negative electrode is more stable than the active material with poorer stability in the outer layer of the negative electrode With a greater temperature sensitivity coefficient, the battery impedance increases at high temperatures, making it easier to be in a disconnected state. 2. lithium battery pole piece as claimed in claim 1, is characterized in that, described conductive agent comprises one or more in carbon black conductive agent, conductive graphite, carbon nanotube, graphene material; The agent includes one or more of epoxy resin, polytetrafluoroethylene, polyvinylidene fluoride, and polyacrylate, or, the binder includes sodium carboxymethyl cellulose, sodium alginate, and styrene-butadiene rubber. one or more of . 3. The lithium battery pole piece according to claim 1, wherein the positive inner pole piece and the positive outer pole piece or the negative inner pole piece and the negative outer pole piece are coated once by a coating machine. coating. 4. A method for making the lithium battery pole piece according to any one of claims 1-3, characterized in that, comprising the steps of: S1. Prepare the positive electrode inner layer slurry and the positive electrode outer layer slurry, the positive electrode inner layer slurry includes the positive electrode inner layer active material, the positive electrode outer layer slurry includes the positive electrode outer layer active material, and the positive electrode inner layer active material The stability of the positive electrode outer layer active material is better than that of the positive electrode outer layer active material; wherein, the positive electrode inner layer active material includes lithium iron phosphate, lithium cobalt oxide, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum high-nickel material and titanic acid One or more of lithium, the positive outer layer active material includes one or more of lithium iron phosphate, lithium cobaltate, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum high-nickel material and lithium titanate; S2. Apply the positive electrode inner layer slurry and the positive electrode outer layer slurry to the positive electrode carrier of the battery to obtain the positive electrode sheet of the lithium battery; S3. Prepare the negative electrode inner layer slurry and the negative electrode outer layer slurry, the negative electrode inner layer slurry includes the negative electrode inner layer active material, the negative electrode outer layer slurry includes the negative electrode outer layer active material, the negative electrode inner layer active material The stability of the negative electrode outer layer active material is better than that of the negative electrode outer layer active material; wherein, the negative electrode inner layer active material includes natural graphite, artificial graphite, a composite material of natural graphite and artificial graphite, soft carbon, hard carbon, lithium titanate One or more of them, the negative electrode outer layer active material includes one or more of natural graphite, artificial graphite, composite material of natural graphite and artificial graphite, soft carbon, hard carbon, lithium titanate; S4. Applying the negative electrode inner layer slurry and the negative electrode outer layer slurry to a battery negative electrode carrier to obtain a lithium battery negative electrode sheet. 5. The manufacturing method of lithium battery pole piece as claimed in claim 4, is characterized in that, the preparation of described positive electrode inner layer slurry comprises the steps: S11, mixing the binder and the solvent to obtain the positive electrode inner layer glue; S12. After uniformly mixing the positive inner layer active material and conductive agent, adding the positive inner layer glue, adjusting the solid content to 70% to 75%, to obtain the positive inner layer slurry; The preparation of the positive electrode outer layer slurry comprises the steps: S11', binding agent and solvent are mixed to obtain positive electrode outer glue; S12', mix the positive outer layer active material and the conductive agent evenly, add the positive electrode outer layer glue, adjust to a solid content of 70% to 75%, and obtain the positive electrode outer layer slurry; The preparation of the negative electrode inner layer slurry comprises: S31, mixing the binder and the solvent to form a negative electrode inner layer glue; S32. After uniformly mixing the negative electrode inner layer active material and conductive agent, adding the negative electrode inner layer glue to obtain negative electrode pre-slurry; S33, adding the styrene-butadiene rubber emulsion into the negative electrode pre-slurry, stirring evenly, and adjusting the solid content to 50%-55% with water to obtain the negative electrode inner layer slurry; The preparation of the negative electrode outer layer slurry comprises: S31', binding agent and solvent are mixed into negative electrode outer glue; S32', mixing the negative electrode outer layer active material and conductive agent evenly, then adding the negative electrode outer layer glue to obtain negative electrode slurry; S33', adding the styrene-butadiene rubber emulsion into the negative electrode slurry, stirring evenly, and adjusting the solid content to 50%-55% with water to obtain the negative electrode outer layer slurry.