CN115832207A

CN115832207A - Pole piece slurry, pole piece, preparation method of pole piece, lithium ion secondary battery, battery module, battery pack and electric device

Info

Publication number: CN115832207A
Application number: CN202210005144.0A
Authority: CN
Inventors: 王亚龙; 陆雷; 李世松
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-01-05
Filing date: 2022-01-05
Publication date: 2023-03-21

Abstract

The disclosure relates to a lithium ion secondary battery pole piece slurry, a pole piece, a preparation method of the pole piece, a lithium ion secondary battery, a battery module, a battery pack and an electric device. The lithium ion secondary battery pole piece slurry comprises an electrode material and a solvent, wherein the electrode material comprises an electrode active substance and a polymer additive, and the polymer additive has an aspect ratio of 500. The polymeric additive is selected from Polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polypyrrole (PPY) and polythiophene (PTh). The pole piece slurry can be used for preparing a thick pole piece with high compaction density, the pole piece has improved toughness, and does not crack in the hot pressing process, and the prepared battery cell has excellent electrical properties.

Description

Pole piece slurry, pole piece, preparation method of pole piece, lithium ion secondary battery, battery module, battery pack and electric device

Technical Field

The disclosure belongs to the field of lithium ion secondary batteries, and particularly relates to a lithium ion secondary battery pole piece slurry and a preparation method thereof, a lithium ion secondary battery pole piece prepared from the lithium ion secondary battery pole piece slurry and a preparation method thereof, a lithium ion secondary battery comprising the lithium ion secondary battery pole piece, a battery module comprising the lithium ion secondary battery, a battery pack comprising the battery module, and an electric device comprising the lithium ion secondary battery, the battery module and/or the battery pack.

Background

A secondary battery is also called a rechargeable battery or a secondary battery, and refers to a battery that can be continuously used by activating an active material by charging after the battery is discharged. The main secondary batteries on the market include nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid (or lead-storage) batteries, lithium ion secondary batteries, polymer lithium ion secondary batteries, and the like.

Lithium ion secondary batteries have been commercialized for about 30 years, and originally have been mainly used in consumer electronics products such as cameras, notebook computers, mobile phones, and the like. With the increasing concern about environmental problems, the replacement of fossil energy with clean energy is becoming an increasingly urgent need, and with the advancement of lithium ion secondary battery technology, lithium ion secondary batteries have rapidly entered the field of electric vehicles in recent years. With the widespread use of lithium ion secondary batteries, high capacity and small volume have become a trend in their development.

The positive electrode sheet of a lithium ion secondary battery generally contains an electrode active material conductive agent and a binder. The electrode active material can be selected from lithium iron phosphate, lithium nickel manganese oxide, lithium manganese iron phosphate, lithium cobalt oxide and the like, and the material is mainly inorganic nano or micron particles. In order to pursue high energy density of the cell, the active particle usage is typically over 95%. Most of the conductive agent is nano carbon black particles. The active particles and the conductive agent are bonded by the binder while being bonded to the surface of the metal current collector. The binder is dissolved in a solvent, mixed with the active particles and the conductive agent to form slurry, coated on the surface of the metal current collector, dried, and the solvent is volatilized, so that the materials are bonded on the surfaces of the particles to form a bonding network.

To reduce volume, a high compaction density (e.g., lithium iron phosphate compaction density greater than or equal to 2.55 g/cm) is typically prepared ³ The compacted density of the ternary positive electrode active material is greater than or equal to 3.5g/cm ³ ) And (3) a positive pole piece. However, high compactionAfter the positive pole piece is wound and hot-pressed, the corners of the pole piece are easy to crack, so that the yield of the high-compaction-density pole piece is high, even the pole piece cannot be produced, and the energy density of a battery cell is difficult to improve.

In the prior art, people try to add a toughening agent to improve the flexibility of the electrode plate when preparing the electrode plate. However, some toughening agents have too high boiling points, and are difficult to dry in the process of preparing the pole piece, and the residual toughening agents can cause the increase of the interface resistance and influence the electrode dynamics. Some toughening agents are difficult to dissolve in an N-methyl pyrrolidone (NMP) solvent, and are difficult to disperse uniformly in the process of preparing slurry, so that the positions of the pole piece parts are hard and brittle, and meanwhile, the electrode dynamics can be influenced by local enrichment of the toughening agents. Some toughening agents have insulativity, so that the resistance of an electrode plate is obviously increased, and the performance of the battery is influenced.

Accordingly, there remains a need in the art for a high compaction density flexible pole piece that overcomes the above-mentioned deficiencies.

Disclosure of Invention

The inventor of the present disclosure provides a high compaction density flexible pole piece through extensive and intensive research, which can be prepared without changing the existing preparation process, and can significantly improve the toughness of the high compaction density flexible pole piece and maintain excellent electrochemical properties. Correspondingly, the disclosure also provides a slurry for preparing the high-compaction-density flexible pole piece, and a lithium ion secondary battery, a battery module, a battery pack and an electric device comprising the high-compaction-density flexible pole piece.

According to a first aspect of the present disclosure, there is provided a lithium ion secondary battery pole piece slurry comprising an electrode material and a solvent, the electrode material comprising an electrode active material and a polymer additive, the polymer additive having an aspect ratio of 500.

In some embodiments, the aspect ratio of the polymeric additive is from 500 to 60000, optionally from 500 to 50000.

In some embodiments, the polymeric additive is selected from one or more of Polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polypyrrole (PPY), polythiophene (PTh), and derivatives thereof.

In some embodiments, the electrode active material is selected from one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide.

In some embodiments, the electrode material comprises 95 to 99.7 parts by weight of the electrode active material and 0.1 to 1.0 part by weight of the polymeric additive.

In some embodiments, the electrode material further comprises a conductive agent and a binder.

In some embodiments, the electrode material comprises 95 to 99.7 parts by weight of an electrode active material, 0.1 to 2.0 parts by weight of a conductive agent, 0.1 to 2.0 parts by weight of a binder, and 0.1 to 1.0 parts by weight of a polymer additive.

In some embodiments, the slurry comprises 60 to 90 parts by weight of the electrode material and 10 to 40 parts by weight of the solvent.

According to a second aspect of the present disclosure, there is provided a method for manufacturing the above-mentioned lithium ion secondary battery pole piece slurry, which comprises:

mixing an electrode material with a solvent, wherein the electrode material comprises an electrode active material and a polymer additive,

shearing and stirring are carried out, so that the aspect ratio of the polymer additive is more than 500.

The inventor of the application finds that when the pole piece slurry is prepared, the added high polymer additive forms a one-dimensional fiber structure under the action of shearing and stirring, and the high-compaction-density pole piece prepared by using the slurry has excellent flexibility and does not crack during hot pressing. The one-dimensional fiber structure can also bind electrode active substance particles and a conductive agent, so that the dosage of a binding agent (such as PVDF) is allowed to be reduced, and the thickness of the binding agent wrapped on the surfaces of the electrode active substance particles is reduced, thereby reducing the migration resistance of lithium ions, being beneficial to improving the migration of the lithium ions in a pole piece, and finally enabling the obtained lithium ion secondary battery to show good rate performance.

According to a third aspect of the present disclosure, there is provided a lithium ion secondary battery pole piece comprising a current collector and an electrode material on the current collector, the electrode material comprising an electrode active material and a polymeric additive, the polymeric additive having an aspect ratio of 500.

In some embodiments, the current collector is aluminum foil; the electrode active material is selected from one or more of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

According to a fourth aspect of the present disclosure, there is provided a method for preparing the above lithium ion secondary battery pole piece, comprising applying the above lithium ion secondary battery pole piece slurry to a current collector.

According to a fifth aspect of the present disclosure, there is provided a lithium ion secondary battery comprising the above lithium ion secondary battery pole piece.

According to a sixth aspect of the present disclosure, there is provided a battery module including the above-described lithium-ion secondary battery.

According to a seventh aspect of the present disclosure, there is provided a battery pack including the above battery module.

According to an eighth aspect of the present disclosure, there is provided an electric device including at least one of the above-described lithium ion secondary battery, the above-described battery module, and the above-described battery pack.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required to be used in the embodiments of the present disclosure will be briefly described below. It should be apparent that the drawings in the embodiments of the present disclosure described below are merely examples, and that other drawings may be obtained from the drawings by those of ordinary skill in the art without inventive effort.

Fig. 1 is a schematic view of an embodiment of a lithium-ion secondary battery according to the present application.

Fig. 2 is an exploded view of the lithium ion secondary battery shown in fig. 1.

Fig. 3 is a schematic view of an embodiment of a battery module according to the present application.

Fig. 4 is a schematic view of an embodiment of a battery pack according to the present application.

Fig. 5 is an exploded view of the battery pack shown in fig. 4.

Fig. 6 is a schematic diagram of an embodiment of an apparatus using the lithium-ion secondary battery of the present application as a power source.

Fig. 7 is an SEM image of the pole piece prepared in comparative example 1.

Fig. 8 is an SEM image of the pole piece prepared in comparative example 2.

Fig. 9 is an SEM image of the pole piece prepared in example 1.

Fig. 10 is an SEM image of the pole piece prepared in example 7.

Description of reference numerals:

1, a battery pack; 2, putting the box body on the box body; 3, a lower box body; 4 a battery module; 5 a secondary battery; 51 a housing; 52 an electrode assembly; 53 a cap assembly.

Detailed Description

Embodiments of the present disclosure are described in further detail below with reference to the drawings and examples. The following detailed description of the embodiments and the accompanying drawings are intended to illustrate the principles of the disclosure, but are not intended to limit the scope of the disclosure, i.e., the disclosure is not limited to the described embodiments.

As disclosed herein, a "range" is defined in terms of lower and upper limits, with a given range being defined by the selection of one lower limit and one upper limit that define the boundaries of the particular range. Ranges defined in this manner may or may not include endpoints and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Further, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, unless otherwise noted, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 to 5" have been listed herein, and "0 to 5" is only a shorthand representation of the combination of these numbers. In addition, when a parameter is an integer of 2 or more, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, or the like.

In the present disclosure, all embodiments and preferred embodiments mentioned herein may be combined with each other to form a new technical solution, if not specifically stated.

In the present disclosure, all the technical features mentioned herein as well as preferred features may be combined with each other to form new technical solutions, if not specifically stated.

In the present disclosure, all steps mentioned herein may be performed sequentially or randomly, if not specifically stated, but preferably sequentially. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, and may also comprise steps (b) and (a) performed sequentially. For example, reference to the process further comprising step (c) means that step (c) may be added to the process in any order, for example, the process may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.

In the present disclosure, the terms "include" and "comprise" as used herein mean open or closed unless otherwise specified. For example, the terms "comprising" and "comprises" may mean that other components not listed may also be included or included, or that only listed components may be included or included.

In the description herein, it is to be noted that, unless otherwise specified, "above" and "below" are inclusive and "one or more" mean "several" two or more. In the description herein, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description herein, the term "or" is inclusive, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or not present); a is false (or not present) and B is true (or present); or both a and B are true (or present).

Lithium ion secondary battery pole piece slurry

The lithium ion secondary battery pole piece slurry disclosed by the invention comprises an electrode material and a solvent, wherein the electrode material comprises an electrode active substance and a polymer additive, and the polymer additive has an aspect ratio of 500.

The electrode active material may be selected from positive electrode active materials. The positive active material includes, but is not limited to, one or more of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The lithium iron phosphate may be, for example, liFePO ₄ (LFP). The lithium nickel cobalt manganese oxide may be, for example, liNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM333)、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523)、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (NCM211)、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622)、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811)、LiNi _0.5 Co _0.3 Mn _0.2 O ₂ (NCM532)。

The polymer additive is one or more selected from Polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polypyrrole (PPY), polythiophene (PTh) and their derivatives. The derivative of polythiophene may be, for example, 3,4-Polymer of Ethylenedioxythiophene (PEDOT). Without being limited to any particular theory, the applicant believes that through the shearing action of external force, the high polymer additives can realize a fiber structure, reduce the particle sliding resistance in the winding and tabletting process and solve the problem of hot pressing cracking of the high-compaction-density pole piece; meanwhile, the dosage of PVDF is reduced, the film forming thickness of PVDF on the surface of active particles is reduced, the diffusion impedance of lithium ions in the active particles is improved, and the pole piece dynamics is improved.

The molecular weight of the polymer additive is not particularly limited as long as the high aspect ratio fibers can be formed by shear stirring. By way of non-limiting example, the weight average molecular weight of the PTFE can be from 2,000,000 to 4,000,000g/mol, alternatively from 2,500,000 to 3,500,000g/mol, e.g., 3,000,000g/mol; the PEO may have a weight average molecular weight of 50,000 to 200,000g/mol, alternatively 80,000 to 150,000g/mol, for example 100,000g/mol; the weight average molecular weight of the PAN may be 150,000 to 350,000g/mol, alternatively 200,000 to 300,000g/mol, for example 250,000g/mol; the PVA can have a weight average molecular weight of 30,000 to 70,000g/mol, alternatively 40,000 to 60,000g/mol, for example 50,000g/mol; the weight average molecular weight of PPY may be from 50,000 to 200,000g/mol, alternatively from 80,000 to 150,000g/mol, for example 100,000g/mol; the weight average molecular weight of the PTH can be from 50,000 to 200,000g/mol, alternatively from 80,000 to 150,000g/mol, for example 100,000g/mol. In the present disclosure, the polymeric additive is sheared and agitated to form high aspect ratio polymeric fibers. The length-to-diameter ratio of the polymer fiber can be in the range of from 500 to 6001, 600. Fiber aspect ratio refers to the ratio of the length to the diameter of the fiber.

The electrode material may further include a conductive agent and a binder. Non-limiting examples of the conductive agent may include one or more of superconducting carbon, carbon black (e.g., acetylene black, ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Non-limiting examples of binders may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymers, tetrafluoroethylene-hexafluoropropylene copolymers, and fluorine-containing acrylate resins.

The solvent may be a conventional solvent for preparing a lithium ion secondary battery pole piece slurry, including solvents known in the art and solvents developed in the future, such as N-methylpyrrolidone (NMP).

In some embodiments, the electrode material comprises 95 to 99.7 parts by weight of the electrode active material and 0.1 to 1.0 part by weight of the polymeric additive. Although the content of the electrode active material in the electrode material is not limited to the above range, the amount within the range ensures the highest amount of the electrode active material and the maximum cell energy density. In some embodiments, the weight fraction of the electrode active material is 95 to 99.7 parts by weight, for example, 95 parts by weight, 95.5 parts by weight, 96 parts by weight, 96.5 parts by weight, 97 parts by weight, 97.5 parts by weight, 98 parts by weight, 98.5 parts by weight, 99 parts by weight, 99.1 parts by weight, 99.2 parts by weight, 99.3 parts by weight, 99.4 parts by weight, 99.5 parts by weight, 99.6 parts by weight, 99.7 parts by weight, and ranges inclusive. In some embodiments, the weight fraction of the polymeric additive is 0.1 to 1.0 parts by weight, such as 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1.0 parts by weight, and ranges inclusive of any two of the foregoing. In some embodiments, the electrode material further comprises a conductive agent and a binder. In some embodiments, the electrode material includes 95 to 99.7 parts by weight of an electrode active material, 0.1 to 2.0 parts by weight of a conductive agent, 0.1 to 2.0 parts by weight of a binder, and 0.1 to 1.0 part by weight of a polymer additive. In some embodiments, the weight fraction of the conductive agent is 0.1 to 2.0 parts by weight, such as 0.1 part by weight, 0.2 part by weight, 0.3 part by weight, 0.4 part by weight, 0.5 part by weight, 0.6 part by weight, 0.7 part by weight, 0.8 part by weight, 0.9 part by weight, 1.0 part by weight, 1.1 part by weight, 1.2 parts by weight, 1.3 parts by weight, 1.4 parts by weight, 1.5 parts by weight, 1.6 parts by weight, 1.7 parts by weight, 1.8 parts by weight, 1.9 parts by weight, 2.0 parts by weight, and ranges bounded by any two of the foregoing. In some embodiments, the binder is present in an amount of 0.1 to 2.0 parts by weight, such as 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1.0 parts by weight, 1.1 parts by weight, 1.2 parts by weight, 1.3 parts by weight, 1.4 parts by weight, 1.5 parts by weight, 1.6 parts by weight, 1.7 parts by weight, 1.8 parts by weight, 1.9 parts by weight, 2.0 parts by weight, and any two of the foregoing ranges.

In some embodiments, the slurry comprises 60 to 90 parts by weight of the electrode material and 10 to 40 parts by weight of the solvent. Although the amounts of the electrode material and the solvent are not limited to the above ranges, the amounts of the electrode material and the solvent within the above ranges ensure uniform dispersion of the electrode active material, the conductive agent, the binder, and the polymer fiber additive in the solvent. In some embodiments, the weight part of the electrode material is 65 to 85 parts by weight, optionally 70 to 80 parts by weight, for example 75 parts by weight. In some embodiments, the solvent is present in an amount of 15 to 35 parts by weight, optionally 20 to 30 parts by weight, for example 25 parts by weight.

The lithium ion secondary battery pole piece slurry disclosed by the invention can also comprise other optional additives, such as a thickening agent (such as sodium carboxymethylcellulose (CMC-Na), a PTC thermistor material and the like.

In some embodiments, the lithium ion secondary battery pole piece slurry of the present disclosure is a positive pole piece slurry for preparing a positive pole piece of a lithium ion secondary battery, comprising a positive electrode material and a solvent.

The present disclosure also provides a method for manufacturing the above lithium ion secondary battery pole piece slurry, which comprises: mixing an electrode material and a polymer additive with a solvent, wherein the electrode material contains an electrode active substance and the polymer additive, and shearing and stirring the mixture to obtain an aspect ratio of the polymer additive of 500.

Shear agitation may be performed using shear agitation devices known in the art and developed in the future, such as a double planetary agitation apparatus. By way of non-limiting example, the dispersion disk speed of the double planetary stirring apparatus may be 1000 to 3000rpm, alternatively 1500 to 2000rpm, and the kneading disk speed may be 10 to 30rpm, alternatively 15 to 25rpm. By way of non-limiting example, the temperature of agitation may be controlled to be in the range of 25-30 deg.C and the time of agitation may be in the range of 60-130 minutes, alternatively 70-120 minutes, 80-110 minutes, or 90-100 minutes.

Lithium ion secondary battery pole piece

And coating the lithium ion secondary battery pole piece slurry on a current collector, and drying, cold pressing and other processes to obtain the lithium ion secondary battery pole piece.

Thus, the present disclosure provides a lithium ion secondary battery pole piece comprising a current collector and an electrode material on the current collector, the electrode material comprising an electrode active material and a polymeric additive, the polymeric additive having an aspect ratio of 500. In some embodiments, the electrode material further comprises a conductive agent and a binder.

The electrode active material, the conductive agent, the binder, and the polymer additive are as described above.

The current collector may be a positive current collector. The positive electrode current collector may be a metal foil or a composite current collector, for example, the metal foil may be an aluminum foil, and the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE, and copolymers thereof, etc.).

Lithium ion secondary battery

The present disclosure also provides a lithium ion secondary battery, which includes the above lithium ion secondary battery pole piece.

The lithium ion secondary battery generally includes a positive electrode tab, a negative electrode tab, a separator, an electrolyte, and the like. In the process of charging and discharging the battery, active ions are embedded and separated back and forth between the positive pole piece and the negative pole piece. The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece.

In some embodiments, in the lithium ion secondary battery of the present disclosure, the positive electrode sheet is made of the lithium ion secondary battery sheet slurry of the present disclosure.

The negative pole piece comprises a negative pole current collector and a negative pole film layer arranged on at least one surface of the negative pole current collector, wherein the negative pole film layer contains a negative pole active substance, a conductive agent and a binder.

The negative electrode current collector may be a metal foil or a composite current collector, and for example, the metal foil may be a foil made of copper foil, silver foil, iron foil, or an alloy of the above metals. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer, and may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on the polymer material base layer (e.g., a base layer made of polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE, and copolymers thereof).

The negative active substance is selected from one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate. As an example, the conductive agent may include one or more of superconducting carbon, carbon black (e.g., acetylene black, ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As an example, the binder may include one or more of Styrene Butadiene Rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid (PAA), sodium Polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), and carboxymethyl chitosan (CMCS). As an example, the binder may include one or more of Styrene Butadiene Rubber (SBR), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

The isolating film separates the positive electrode side from the negative electrode side of the lithium ion secondary battery, and provides selective permeation or obstruction for substances with different types, sizes and charges in a system, for example, the isolating film can insulate electrons, physically isolate positive and negative active substances of the lithium ion secondary battery, prevent internal short circuit and form an electric field in a certain direction, and enable ions in the battery to pass through the isolating film to move between the positive electrode and the negative electrode. In one embodiment of the present disclosure, the material used to prepare the separation film may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation film can be a single-layer film or a multi-layer composite film. When the barrier film is a multilayer composite film, the materials of the layers may be the same or different.

In the lithium ion secondary battery of the present disclosure, the electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolytic solution). In some embodiments, the electrolyte is an electrolyte solution. The electrolyte includes an electrolyte salt and a solvent. In some embodiments, the electrolyte salt may be selected from LiPF ₆ (lithium hexafluorophosphate), liBF ₄ Lithium tetrafluoroborate (LiClO), liClO ₄ (lithium perchlorate), liAsF ₆ (lithium hexafluoroarsenate), liFSI (lithium bis (fluorosulfonylimide), liTFSI (lithium bis (trifluoromethanesulfonylimide)), liTFS (trifluoromethyl)Lithium sulfonate), liDFOB (lithium oxalyldifluoroborate), liBOB (lithium oxalyldiborate), liPO ₂ F ₂ One or more of (lithium difluorophosphate), liDFOP (lithium difluorooxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate). In one embodiment of the present disclosure, the solvent may be selected from one or more of the following: ethylene Carbonate (EC), propylene Carbonate (PC), ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl Propyl Carbonate (MPC), ethyl Propyl Carbonate (EPC), butylene Carbonate (BC), fluoroethylene carbonate (FEC), methyl Formate (MF), methyl Acetate (MA), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB), 8978 zft 8978-butyrolactone (GBL), sulfolane (SF), dimethylsulfone (MSM), methylethylsulfone (EMS) and diethylsulfone (ESE). In one embodiment of the present disclosure, the solvent is present in an amount of 60 to 99 wt.%, such as 65 to 95 wt.%, or 70 to 90 wt.%, or 75 to 89 wt.%, or 80 to 85 wt.%, based on the total weight of the electrolyte. In one embodiment of the present disclosure, the electrolyte is present in an amount of 1 to 40 wt.%, such as 5 to 35 wt.%, or 10 to 30 wt.%, or 11 to 25 wt.%, or 15 to 20 wt.%, based on the total weight of the electrolyte.

In the lithium ion secondary battery of the present disclosure, an additive may be further optionally included in the electrolyte. For example, the additives may include one or more of the following: the negative electrode film-forming additive and the positive electrode film-forming additive can also comprise additives capable of improving certain performances of the battery, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature performance of the battery, additives for improving the low-temperature performance of the battery and the like.

In one embodiment of the present disclosure, the positive electrode tab, the negative electrode tab and the separator may be manufactured into an electrode assembly/bare cell through a winding process or a lamination process.

In one embodiment of the present disclosure, the lithium ion secondary battery may include an exterior package, which may be used to enclose the electrode assembly and the electrolyte/electrolyte solution described above. In some embodiments, the outer package of the lithium ion secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. In other embodiments, the exterior package of the lithium ion secondary battery may be a pouch, such as a pouch-type pouch. The soft bag can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS) and the like.

The shape of the lithium ion secondary battery of the present disclosure may be cylindrical, square, or any other shape. Fig. 1 is a lithium-ion secondary battery 5 of a square structure as an example. Fig. 2 shows an exploded view of the lithium ion secondary battery 5 of fig. 1, the outer package may include a case 51 and a cap assembly 53, and the case 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and the side plates enclosing to form a receiving cavity. The housing 51 has an opening communicating with the accommodating chamber, and the top cover assembly 53 can cover the opening to close the accommodating chamber. The positive electrode piece, the negative electrode piece and the isolating film can form an electrode assembly 52 through a winding process or a lamination process, the electrode assembly is packaged in the containing cavity, and the electrolyte is soaked in the electrode assembly 52. The number of the electrode assemblies 52 included in the lithium-ion secondary battery 5 may be one or more.

Battery module, battery pack, and electric device

In one embodiment of the present disclosure, several lithium ion secondary batteries may be assembled together to constitute a battery module, in which two or more lithium ion secondary batteries described in the present disclosure are contained, the specific number depending on the application of the battery module and the parameters of the individual battery module.

Fig. 3 is a battery module 4 as an example. Referring to fig. 3, in the battery module 4, a plurality of lithium ion secondary batteries 5 may be arranged in series along the longitudinal direction of the battery module 4. Of course, the arrangement may be in any other manner. The plurality of lithium-ion secondary batteries 5 may be further fixed by a fastener.

Alternatively, the battery module 4 may further include a case having an accommodation space in which the plurality of lithium ion secondary batteries 5 are accommodated.

In one embodiment of the present disclosure, two or more of the above-described battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack depends on the application of the battery pack and the parameters of the individual battery modules. The battery pack can include the battery box and set up a plurality of battery module in the battery box, and this battery box includes box and lower box, and the box can be covered and well match on the box down to the upper box, forms the enclosure space that is used for holding battery module. Two or more battery modules may be arranged in the battery case in a desired manner.

Fig. 4 and 5 are a battery pack 1 as an example. Referring to fig. 4 and 5, a battery pack 1 may include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery box comprises an upper box body 2 and a lower box body 3, wherein the upper box body 2 is used for covering the lower box body 3 and forming a closed space for accommodating a battery module 4. A plurality of battery modules 4 may be arranged in any manner in the battery box.

In one embodiment of the present disclosure, the electric device of the present disclosure includes at least one of the lithium ion secondary battery, the battery module, or the battery pack of the present disclosure, which may be used as a power source of the electric device and may also be used as an energy storage unit of the electric device. The electric devices include, but are not limited to, mobile digital devices (e.g., mobile phones, notebook computers, etc.), electric vehicles (e.g., electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, and the like.

Fig. 6 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle and the like. In order to meet the requirements of the electric device for high power and high energy density, a battery pack or a battery module can be adopted.

As another example, the powered device may be a mobile phone, a tablet computer, a notebook computer, or the like. The electric device is generally required to be thin and light, and a lithium ion secondary battery can be used as a power source.

Technical effects

The inventor of the present disclosure unexpectedly finds that when the pole piece slurry is prepared, the polymer additive is added, and the polymer additive material can form a one-dimensional fiber structure through proper shearing and stirring, which can provide good flexibility for the electrode active layer made of the slurry, so as to improve the flexibility of the high-compaction-density pole piece, and the corner of the pole piece does not crack after being wound and hot-pressed.

Surprisingly, by forming the polymeric additive into a one-dimensional fiber structure, the excellent electrochemical properties of the resulting pole piece are also maintained. Without being bound by any particular theory, the applicant believes that because these high molecular materials contain polar functional groups, they can well infiltrate lipid electrolytes, thereby improving the rate capability of the pole piece. Meanwhile, the fiber structure can bind the electrode active substance particles and the conductive agent, the dosage of the adhesive (such as PVDF) is allowed to be reduced, and the thickness of the adhesive coated on the surface of the electrode active substance particles is reduced, so that the migration resistance of lithium ions is reduced, the migration of the lithium ions in the pole piece is improved, and finally, the good rate performance is shown.

In addition, the method for preparing the pole piece slurry and the pole piece can utilize the existing process equipment, does not need to make great changes on the existing process route, and is favorable for saving the cost.

Examples

The present invention will be described in further detail with reference to examples. It should be understood that these examples are given for illustrative purposes only and are not intended to limit the scope of the present invention.

In the following examples and comparative examples, reagents, materials and instruments used therein were commercially available or synthetically produced, unless otherwise specified.

Lithium iron phosphate (LFP) and NCM532 (LiNi) _0.5 Co _0.3 Mn _0.2 O ₂ ) And graphite manufactured by fibrate new materials group ltd; conductive carbon (SP) is manufactured by kay chemical ltd of shanghai; the electrolyte is manufactured by Shenzhen New aegis science and technology Limited.

The stirring equipment is 10L double-planet stirring equipment produced by Macro-engineering-science technologies, inc. The stirring conditions were as follows: controlling the temperature at 25-30 ℃; stirring speed: the rotating speed of the dispersion disc is 1000-3000rpm, and the rotating speed of the kneading disc is 10-30rpm; the stirring time is 60-130min.

The length-diameter ratio of the fiber is measured by the following method: the morphology and the particle radius (R) of the pure polymer material particles are characterized by SEM, and then the radius (R) of the polymer material in the pole piece is characterized by SEM. From the principle of volume invariance, the fiber aspect ratio can be calculated:

the gram weight of the pole piece refers to the unit area (1540.25 mm) of the pole piece after being dried ² ) The mass of the electrode material film layer (i.e. the mass of the pole piece minus the mass of the aluminum foil current collector). The test method comprises the following steps: after the pole piece is dried, a punching machine is adopted to punch and cut the pole piece into the area of 1540.25mm ² The electrode disks of (2) are weighed and the mass is designated as M1. The mass of the pure aluminum foil corresponding to the area is M2, and then the gram weight of the pole piece is M1-M2. The way of adjusting the gram weight of the pole piece in extrusion coating: and adjusting the gap between the extrusion head and the current collector, wherein the larger the gap is, the larger the gram weight of the pole piece is.

The test method for simulating hot pressing comprises the following steps: (1) Cutting a pole piece standard sample of 1.5cm multiplied by 15cm, (2) bending the pole piece, rolling the bent part of the pole piece by using a 2kg roller, and observing whether the folded part is transparent or not.

Comparative example 1

The positive electrode active material lithium iron phosphate, the binder PVDF (polyvinylidene fluoride) and the conductive carbon SP are fully stirred and uniformly mixed in an N-methylpyrrolidone solvent system according to the weight ratio of 97.4 to 0.8, then the mixture is coated on an Al foil (the length is 100m, the width is 350mm, and the thickness is 15 mu m) by extrusion coating or transfer coating, and the Al foil is dried and cold-pressed to obtain positive electrode pieces with different gram weights (see Table 8).

Adjusting and controlling the compaction density:

the pole pieces with different compaction densities are obtained by adjusting the pressure by a cold press (from the chen co neu neul finish rolling science and technology limited): the compacted density under the condition of 1T pressure is 2.4g/cm ³ And the compacted density under the 3T pressure condition is 2.55g/cm ³ And the compacted density under the condition of 8T pressure is 2.6g/cm ³ 。

Fig. 7 is an SEM characterization picture of the electrode sheet prepared in comparative example 1, and it can be seen that the electrode material on the aluminum foil exists in the form of particle packing.

The pole pieces were subjected to a simulated hot press test to observe the pole piece cracking (see table 8).

Comparative example 2

The positive electrode active material lithium iron phosphate, the binder PVDF (polyvinylidene fluoride), the conductive carbon SP and the hydroxyapatite are fully stirred and uniformly mixed in an N-methylpyrrolidone solvent system according to the weight ratio of 97.4 to 0.8, then are coated on an Al foil (with the length of 100m, the width of 350mm and the thickness of 15 microns) by extrusion coating or transfer coating, and are dried and cold-pressed to obtain positive electrode pieces with different gram weights (see Table 8).

Adjusting and controlling the compaction density:

the pole pieces with different compaction densities are obtained by adjusting the pressure by a cold press (from the chen co neu neul finish rolling science and technology limited): the compacted density under the condition of 1T pressure is 2.4g/cm ³ And the compacted density under the condition of 2.5T pressure is 2.55g/cm ³ And the compacted density under the condition of 7T pressure is 2.6g/cm ³ 。

Fig. 8 is an SEM picture of the electrode sheet prepared in comparative example 2, and a hydroxyapatite fibrous structure can be observed.

Example 1

Fully kneading a positive electrode active material lithium iron phosphate, a binder PVDF (polyvinylidene fluoride), conductive carbon SP and an additive PTFE in a solvent system of N-methyl pyrrolidone according to the weight ratio shown in Table 1, coating an Al foil (100 m in length, 350mm in width and 15 μm in thickness) by extrusion coating or transfer coating, drying and cold pressing to obtain a positive electrode piece. By adjusting the shearing and stirring conditions, the PTFE forms fibers with different length-diameter ratios. The aspect ratio is shown in Table 8.

TABLE 1

Adjusting and controlling the compaction density:

the following compacted densities of the pole pieces were obtained by adjusting the pressure with a cold press (from chen sieke noll finish rolling technologies gmbh): the compacted density under the pressure condition of 65T is 2.6g/cm ³ 。

Fig. 9 is an SEM picture of the pole piece prepared in example 1, from which the PTFE fiber structure can be observed.

Example 2

According to the weight ratio shown in table 2, the positive active material lithium iron phosphate, the binder PVDF (polyvinylidene fluoride), the conductive carbon SP and the additive PEO (polyethylene oxide) are fully stirred and uniformly mixed in an N-methylpyrrolidone solvent system, then are coated on an Al foil (with the length of 100m, the width of 350mm and the thickness of 15 microns) by extrusion coating or transfer coating, and are dried and cold-pressed to obtain the positive pole piece. By adjusting the shearing and stirring conditions, the PEO forms fibers with different length-diameter ratios. The aspect ratio is shown in Table 8.

TABLE 2

Numbering	Lithium iron phosphate	PVDF	SP	PEO
					2-1	97.4	1.6	0.8	0.2
2-2	97.4	1.2	0.8	0.6
					2-3	97.4	0.8	0.8	1.0

Adjusting and controlling the compaction density:

the following compacted densities of the pole pieces were obtained by adjusting the pressure with a cold press (from chen sieke noll finish rolling technologies gmbh): the compacted density under the condition of 70T pressure is 2.6g/cm ³ 。

Example 3

According to the weight ratio shown in table 3, the positive active material lithium iron phosphate, the binder PVDF (polyvinylidene fluoride), the conductive carbon SP and the additive PAN (polyacrylonitrile) are fully stirred and uniformly mixed in an N-methylpyrrolidone solvent system, then the mixture is coated on an Al foil (with the length of 100m, the width of 350mm and the thickness of 15 microns) by extrusion coating or transfer coating, and the anode plate is obtained by drying and cold pressing. By adjusting the shearing and stirring conditions, the PAN forms fibers with different length-diameter ratios. The aspect ratio is shown in Table 8.

TABLE 3

Numbering	Lithium iron phosphate	PVDF	SP	PAN
					3-1	97.4	1.6	0.8	0.2
3-2	97.4	1.2	0.8	0.6
					3-3	97.4	0.8	0.8	1.0

Regulating and controlling the compaction density:

Example 4

According to the weight ratio shown in table 4, the positive active material lithium iron phosphate, the binder PVDF (polyvinylidene fluoride), the conductive carbon SP and the additive PVA (polyvinyl alcohol) are fully stirred and uniformly mixed in an N-methyl pyrrolidone solvent system, then are coated on an Al foil (with the length of 100m, the width of 350mm and the thickness of 15 mu m) by extrusion coating or transfer coating, and are dried and cold-pressed to obtain the positive pole piece. The PVA is formed into fibers with different length-diameter ratios by adjusting the shearing and stirring conditions. The aspect ratio is shown in Table 8.

TABLE 4

Numbering	Lithium iron phosphate	PVDF	SP	PVA
					4-1	97.4	1.6	0.8	0.2
4-2	97.4	1.2	0.8	0.6
					4-3	97.4	0.8	0.8	1.0

Adjusting and controlling the compaction density:

Example 5

According to the weight ratio shown in table 5, the positive active material lithium iron phosphate, the binder PVDF (polyvinylidene fluoride), the conductive carbon SP and the additive PPY (polypyrrole) are fully stirred and uniformly mixed in an N-methyl pyrrolidone solvent system, then are coated on an Al foil (with the length of 100m, the width of 350mm and the thickness of 15 μm) by extrusion coating or transfer coating, and are dried and cold-pressed to obtain the positive pole piece. By adjusting the shearing and stirring conditions, the PPY forms fibers with different length-diameter ratios. The aspect ratio is shown in Table 8.

TABLE 5

Numbering	Lithium iron phosphate	PVDF	SP	PPY
					5-1	97.4	1.6	0.8	0.2
5-2	97.4	1.2	0.8	0.6
					5-3	97.4	0.8	0.8	1.0

Adjusting and controlling the compaction density:

And (3) carrying out simulated hot-pressing test on the pole piece, and observing the cracking condition of the pole piece (see table 8).

Example 6

According to the weight ratio shown in table 6, the positive active material lithium iron phosphate, the binder PVDF (polyvinylidene fluoride), the conductive carbon SP and the additive PTh are fully stirred and uniformly mixed in an N-methyl pyrrolidone solvent system, then are coated on an Al foil (with the length of 100m, the width of 350mm and the thickness of 15 μm) by extrusion coating or transfer coating, and are dried and cold-pressed to obtain the positive pole piece. The PTH is formed into fibers with different length-diameter ratios by adjusting the shearing and stirring conditions. The aspect ratio is shown in Table 8.

TABLE 6

Adjusting and controlling the compaction density:

the following compacted densities of the pole pieces were obtained by adjusting the pressure with a cold press (chenchen kenuol finishing technologies, ltd): the compacted density under the condition of 75T pressure is 2.6g/cm ³ 。

Comparative example 3

The positive electrode active material nickel cobalt lithium manganate (NCM 532), binder PVDF (polyvinylidene fluoride), and conductive carbon SP are fully stirred and mixed uniformly in an N-methylpyrrolidone solvent system according to a weight ratio of 98.2, and then coated on an Al foil (length 100m, width 350mm, thickness 15 μm) by extrusion coating or transfer coating, and dried and cold-pressed to obtain positive electrode sheets with different gram weights (see table 8).

Adjusting and controlling the compaction density:

the pole pieces with different compaction densities are obtained by adjusting the pressure by a cold press (from the chen co neu neul finish rolling science and technology limited): the compacted density under the condition of 15T pressure is 3.5g/cm ³ The compacted density under the condition of 25T pressure is 3.55g/cm ³ 。

Example 7

According to the weight ratio shown in table 7, the positive active material nickel cobalt lithium manganate (NCM 532), the binder PVDF (polyvinylidene fluoride), the conductive carbon SP and the additive PTFE are fully stirred and uniformly mixed in an N-methylpyrrolidone solvent system, then coated on an Al foil (100 m in length, 350mm in width and 15 μm in thickness) by extrusion coating or transfer coating, and dried and cold-pressed to obtain the positive pole piece.

TABLE 7

Adjusting and controlling the compaction density:

the pole pieces with different compaction densities are obtained by adjusting the pressure by a cold press (from the chen co neu neul finish rolling science and technology limited): the compacted density under the condition of 10T pressure is 3.5g/cm ³ And the compacted density under the condition of 20T pressure is 3.55g/cm ³ 。

FIG. 10 is an SEM photograph of the pole piece prepared in example 7 from which the PTFE fiber structure can be observed.

Lithium ion secondary battery preparation

And (2) fully and uniformly stirring the negative active material artificial graphite, the conductive agent acetylene black and the binder PVDF in N-methyl pyrrolidone according to a weight ratio of 96.

And stacking the positive pole piece, the isolating film and the negative pole piece in sequence to enable the isolating film to be positioned between the cathode and the anode to play an isolating role, and winding to obtain the bare cell. And placing the bare cell in an outer package, injecting the prepared electrolyte and packaging. The electrolyte adopts ethylene carbonate and dimethyl carbonate as solvents, and lithium hexafluorophosphate as lithium salt. Polyethylene (PE) porous polymeric films were used as separators.

Battery core multiplying power test

A charge and discharge tester (Shenzhen New Wille electronics Limited) is adopted to measure the capacity retention rate of the battery cell under different charge and discharge multiplying factors (0.33C, 1C, 3C and 6C).

Testing conditions of the lithium iron phosphate core:

standing the prepared battery for 30 minutes in a constant temperature environment of 25 ℃, charging to 3.75V according to a constant current of 0.33C, charging at constant voltage, stopping current of 0.05C, and standing for 30 minutes; the discharge was made to 2.5V at a constant current of 0.33C and the discharge capacity C0 was recorded.

Charging to 3.75V at constant current and constant voltage at 1C, stopping current at 0.05C, standing for 30min, discharging to 2.5V at 1C, and recording discharge capacity C1. The retention ratio of 1C discharge capacity was (C1/C0). Times.100%.

Charging to 3.75V at constant current and constant voltage according to 3C, stopping current at 0.05C, standing for 30 minutes, discharging to 2.5V at 3C, and recording discharge capacity C2. The retention ratio of the 3C discharge capacity was (C2/C0). Times.100%.

Charging to 3.75V at constant current and constant voltage at 6C, stopping current at 0.05C, standing for 30min, discharging to 2.5V at 6C, and recording discharge capacity C3. The 6C discharge capacity retention ratio was (C3/C0). Times.100%.

Ternary NCM532 cell test conditions:

standing the prepared battery for 30 minutes in a constant temperature environment of 25 ℃, charging to 4.2V according to a constant current of 0.33C, charging at a constant voltage, stopping current of 0.05C, and standing for 30 minutes; the discharge was made to 2.5V at a constant current of 0.33C and the discharge capacity C0 was recorded.

Charging to 4.2V at constant current and constant voltage at 1C, stopping current at 0.05C, standing for 30min, discharging to 2.5V at 1C, and recording discharge capacity C1. The retention ratio of the 1C discharge capacity was (C1/C0). Times.100%.

And charging to 4.2V at constant current according to 3C, charging at constant voltage, stopping current at 0.05C, standing for 30 minutes, discharging to 2.5V at 3C, and recording discharge capacity C2. The retention ratio of the 3C discharge capacity was (C2/C0). Times.100%.

Charging to 4.2V at constant current and constant voltage at 6C, stopping current at 0.05C, standing for 30min, discharging to 2.5V at 6C, and recording discharge capacity C3. The 6C discharge capacity retention ratio was (C3/C0). Times.100%.

TABLE 8

As can be seen from the above table, the presence of the high aspect ratio polymeric fibrous aid provided the resulting pole piece with no cracking during hot pressing at high compaction density, as compared to comparative examples 1 and 3, where no fibrous aid was added. The high-length-diameter ratio fiber is obtained by adding the high-molecular fiber auxiliary agent, so that not only can a high-compaction-density thick electrode be obtained, but also the prepared battery cell still keeps a very high capacity retention rate. The hydroxyapatite in comparative example 2 was also fibrous, but the corresponding high compacted density thick pole piece cracked during hot pressing. That is to say, under the conditions of higher gram weight and higher compaction density, the pole piece containing the hydroxyapatite inorganic fiber is easy to crack after being folded and hot-pressed, while the pole piece adopting the polymer material disclosed by the invention is not easy to crack, which is unexpected.

While the disclosure has been described with reference to an embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. The present disclosure is not intended to be limited to the particular embodiments disclosed herein, but rather to include all embodiments falling within the scope of the appended claims.

Claims

1. A lithium ion secondary battery pole piece slurry, which comprises an electrode material and a solvent, wherein the electrode material comprises an electrode active substance and a polymer additive, and the polymer additive has an aspect ratio of 500.

2. The lithium ion secondary battery pole piece slurry of claim 1, wherein the aspect ratio of the polymeric additive is 500 to 60000, optionally 500.

3. The lithium ion secondary battery pole piece slurry of claim 1, wherein the polymeric additive is selected from one or more of Polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polypyrrole (PPY), polythiophene (PTH), and derivatives thereof.

4. The lithium ion secondary battery pole piece slurry of any one of claims 1 to 3, wherein the electrode active material is selected from one or more of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide.

5. The lithium ion secondary battery electrode sheet slurry according to any one of claims 1 to 3, wherein the electrode material comprises 95 to 99.7 parts by weight of an electrode active material and 0.1 to 1.0 part by weight of a polymer additive.

6. The pole piece slurry for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the slurry comprises 60 to 90 parts by weight of an electrode material and 10 to 40 parts by weight of a solvent.

7. A method of making the lithium ion secondary battery pole piece slurry of any one of claims 1-6, comprising:

8. A lithium ion secondary battery pole piece, comprising a current collector and an electrode material on the current collector, wherein the electrode material comprises an electrode active material and a polymer additive, and the polymer additive has an aspect ratio of 500.

9. The lithium ion secondary battery pole piece of claim 8, wherein the aspect ratio of the polymeric additive is from 500 to 60000, optionally from 500 to 50000.

10. The lithium ion secondary battery pole piece of claim 8, wherein the polymeric additive is selected from one or more of Polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polypyrrole (PPY), polythiophene (PTh), and derivatives thereof.

11. The lithium ion secondary battery pole piece according to any one of claims 8 to 10, wherein the current collector is an aluminum foil; the electrode active material is selected from one or more of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

12. The lithium ion secondary battery electrode sheet according to any one of claims 8 to 10, wherein the electrode material comprises 93 to 99.5 parts by weight of the electrode active material and 0.1 to 1.0 part by weight of the polymer additive.

13. A method of making the lithium ion secondary battery pole piece of any one of claims 8 to 12 comprising applying the lithium ion secondary battery pole piece slurry of any one of claims 1 to 6 to a current collector.

14. A lithium ion secondary battery comprising the lithium ion secondary battery pole piece of any one of claims 8 to 12.

15. A battery module comprising the lithium-ion secondary battery of claim 14.

16. A battery pack comprising the battery module of claim 15.

17. An electric device comprising at least one of the lithium-ion secondary battery of claim 14, the battery module of claim 15, and the battery pack of claim 16.