CN116864613A - Positive pole piece containing core-shell structure microspheres and battery - Google Patents
Positive pole piece containing core-shell structure microspheres and battery Download PDFInfo
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- CN116864613A CN116864613A CN202310995069.1A CN202310995069A CN116864613A CN 116864613 A CN116864613 A CN 116864613A CN 202310995069 A CN202310995069 A CN 202310995069A CN 116864613 A CN116864613 A CN 116864613A
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- 239000004005 microsphere Substances 0.000 title claims abstract description 130
- 239000011258 core-shell material Substances 0.000 title claims abstract description 104
- 239000006258 conductive agent Substances 0.000 claims abstract description 39
- 239000011149 active material Substances 0.000 claims abstract description 27
- 239000011230 binding agent Substances 0.000 claims abstract description 17
- 229920000642 polymer Polymers 0.000 claims abstract description 15
- 239000002861 polymer material Substances 0.000 claims abstract description 11
- 239000013543 active substance Substances 0.000 claims abstract description 10
- 239000004020 conductor Substances 0.000 claims abstract description 6
- 239000000155 melt Substances 0.000 claims abstract description 6
- 239000000463 material Substances 0.000 claims description 29
- -1 polyethylene Polymers 0.000 claims description 19
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- 229920000573 polyethylene Polymers 0.000 claims description 16
- 239000004698 Polyethylene Substances 0.000 claims description 15
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 13
- 239000002033 PVDF binder Substances 0.000 claims description 13
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 13
- 238000001035 drying Methods 0.000 claims description 13
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 13
- 238000003825 pressing Methods 0.000 claims description 13
- 238000004080 punching Methods 0.000 claims description 13
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 11
- 239000000178 monomer Substances 0.000 claims description 10
- 239000007774 positive electrode material Substances 0.000 claims description 10
- 239000011248 coating agent Substances 0.000 claims description 9
- 238000000576 coating method Methods 0.000 claims description 9
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- PAYRUJLWNCNPSJ-UHFFFAOYSA-N N-phenyl amine Natural products NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 claims description 8
- KAESVJOAVNADME-UHFFFAOYSA-N Pyrrole Chemical compound C=1C=CNC=1 KAESVJOAVNADME-UHFFFAOYSA-N 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 8
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 claims description 8
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 claims description 8
- 238000002360 preparation method Methods 0.000 claims description 7
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- 238000002156 mixing Methods 0.000 claims description 4
- 229920001155 polypropylene Polymers 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
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- 229920000089 Cyclic olefin copolymer Polymers 0.000 claims description 3
- 239000004952 Polyamide Substances 0.000 claims description 3
- 239000004793 Polystyrene Substances 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 239000002134 carbon nanofiber Substances 0.000 claims description 3
- 229910021389 graphene Inorganic materials 0.000 claims description 3
- 239000002048 multi walled nanotube Substances 0.000 claims description 3
- 239000007800 oxidant agent Substances 0.000 claims description 3
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- 229920003229 poly(methyl methacrylate) Polymers 0.000 claims description 3
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 3
- 229920002647 polyamide Polymers 0.000 claims description 3
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- 229920006149 polyester-amide block copolymer Polymers 0.000 claims description 3
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- 239000004627 regenerated cellulose Substances 0.000 claims description 3
- 239000002109 single walled nanotube Substances 0.000 claims description 3
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 claims description 3
- 125000002490 anilino group Chemical group [H]N(*)C1=C([H])C([H])=C([H])C([H])=C1[H] 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 abstract description 11
- 239000010410 layer Substances 0.000 description 16
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 15
- 229910052782 aluminium Inorganic materials 0.000 description 15
- 239000011162 core material Substances 0.000 description 14
- 239000000243 solution Substances 0.000 description 11
- 239000003792 electrolyte Substances 0.000 description 10
- 239000011888 foil Substances 0.000 description 10
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 8
- 229910001416 lithium ion Inorganic materials 0.000 description 8
- 230000000903 blocking effect Effects 0.000 description 7
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- 238000002844 melting Methods 0.000 description 7
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 5
- 239000002174 Styrene-butadiene Substances 0.000 description 5
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 5
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 5
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- 239000011889 copper foil Substances 0.000 description 5
- 239000008367 deionised water Substances 0.000 description 5
- 229910021641 deionized water Inorganic materials 0.000 description 5
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- 229910002804 graphite Inorganic materials 0.000 description 5
- 239000010439 graphite Substances 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- 238000004806 packaging method and process Methods 0.000 description 5
- 239000002985 plastic film Substances 0.000 description 5
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- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 229920000767 polyaniline Polymers 0.000 description 3
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 2
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- 238000010586 diagram Methods 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 238000007719 peel strength test Methods 0.000 description 2
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- 229910001870 ammonium persulfate Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
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- 238000011160 research Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a positive electrode plate containing core-shell structure microspheres and a battery, and relates to the technical field of batteries. The positive electrode plate comprises a current collector and an active material layer coated on the surface of the current collector, wherein the active material layer comprises an active material, a core-shell structure microsphere, a first conductive agent and a binder, the inner core of the core-shell structure microsphere is a polymer material, and the shell layer of the core-shell structure microsphere is a conductive material; when the temperature reaches the set temperature, the polymer material of the microsphere core with the core-shell structure melts and overflows to cover the active substances, the whole body which is originally unstable is divided into discontinuous areas, and the chain reaction when the thermal runaway occurs is blocked. According to the invention, the core-shell structure polymer microspheres are added in the pole piece, and the active substances with poor thermal stability are covered by the molten overflow when heated, so that the originally unstable whole body is divided into discontinuous areas, the chain reaction when thermal runaway occurs is blocked, and the heating safety of the battery is improved.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a positive pole piece containing microspheres with a core-shell structure and a battery.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
With the rapid development of the electric automobile industry, the technology of the lithium ion battery for the automobile is gradually focused towards the direction of high energy density, wherein the positive electrode adopts high nickel ternary as a main mode for realizing the high energy density. However, the most significant problem of the high nickel ternary material is poor thermal stability and unstable structure at high temperature, which greatly deteriorates intrinsic safety of the battery, and thus, improving the safety of the battery is an important task of current researches.
There are many ways to improve the safety of the battery, and among them, studies on two ways of blending the current collector surface coating and the positive electrode material are particularly extensive. Chinese patent publication No. CN113764612a discloses a positive electrode sheet containing a heat-sensitive coating layer disposed between a current collector and a positive electrode active material layer, wherein when the temperature of a battery increases, a heat-sensitive material melts to form an electron blocking layer, blocking the connection of the active material layer and the current collector, and thus blocking the occurrence of thermal runaway in a large area.
The inventors found that the application of such a thermosensitive material in a pole piece is very much, basically, the blocking and isolation of the active material is realized by utilizing the characteristic that the thermal resistance of the thermosensitive material is increased or insulated, but the direct introduction of the thermosensitive material into the pole piece generally increases the resistance of the pole piece or reduces the duty ratio of the active material, so that the loss of the electrical performance is caused, or the thermosensitive material is introduced into the pole piece as a separate coating, so that the increase of the manufacturing process and the increase of the internal resistance are also caused. Therefore, how to make the heat sensitive material have the effect of safety improvement and not lose the electrical property as much as possible becomes the key of whether the technology can be applied on a large scale.
Disclosure of Invention
The invention aims to provide a positive electrode plate and a battery containing core-shell structure microspheres, wherein the core-shell structure polymer microspheres are added in the electrode plate, the polymer microspheres have certain cohesiveness, and meanwhile, the surface of the polymer microspheres contains a conductive shell layer and can also serve as a conductive agent, active substances with poor thermal stability are covered by fusion overflow when heated, the original unstable whole body is divided into discontinuous areas, the chain reaction when thermal runaway occurs is blocked, the heating safety of the battery is improved, and the problems in the prior art are solved.
In order to solve the technical problems, the invention is realized by the following technical scheme:
the first aspect of the invention provides a positive electrode plate containing core-shell structure microspheres.
The positive electrode plate containing the core-shell structure microsphere is characterized by comprising a current collector and an active material layer coated on the surface of the current collector, wherein the active material layer comprises an active material, the core-shell structure microsphere, a first conductive agent and a binder, the inner core of the core-shell structure microsphere is a polymer material, and the shell layer of the core-shell structure microsphere is a conductive material; when the temperature reaches the set temperature, the polymer material of the microsphere core with the core-shell structure melts and overflows to cover active substances, so that the original unstable whole is divided into discontinuous areas, and the chain reaction when thermal runaway occurs is blocked;
in the active material layer, the mass percentages of the active material, the core-shell structure microsphere, the first conductive agent and the binder are as follows:
active material: 90 to 98 percent
And (2) a binder: 0.5% -2%;
a first conductive agent: 0.5% -2%;
microsphere with core-shell structure: 1% -6%.
Preferably, the core-shell structure microsphere is formed by compounding a thermosensitive microsphere and a second conductive agent.
Preferably, the thermosensitive microsphere is at least one of polyethylene, polypropylene, polyamide, polyesteramide, polystyrene, polyvinyl chloride, polyester, polyurethane, olefin copolymer or monomer modified copolymer thereof.
Preferably, the second conductive agent is polyaniline or polypyrrole.
Preferably, the polymer material of the microsphere core with the core-shell structure is melted and overflowed at a set temperature of 100-150 ℃.
Preferably, the binder is at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, regenerated cellulose, polyvinyl chloride, polymethyl methacrylate, polyacrylonitrile and styrene butadiene rubber.
Preferably, the first conductive agent is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, vapor grown carbon fibers, superconducting carbon, and graphene.
Preferably, the preparation method of the microsphere with the core-shell structure comprises the following steps:
step one: dispersing the thermosensitive microspheres into a solution prepared from a second conductive agent monomer, and uniformly dispersing to prepare a mixed dispersion liquid;
step two: dropwise adding 2M hydrochloric acid into the dispersion liquid obtained in the step one, dropwise adding 50mL hydrochloric acid into a second conductive agent monomer with the proportion of 4.6mL, placing the mixed dispersion liquid into an ice bath, and after the temperature is reduced to below 5 ℃, adding 25mL 2M ammonium persulfate aqueous solution, and magnetically stirring for 1h after the slow dropwise addition is completed; the method comprises the steps of carrying out a first treatment on the surface of the
Step three: and separating and washing the reaction product from the solution to obtain the microsphere material with the core-shell structure.
Preferably, the preparation method of the positive electrode plate containing the core-shell structure microsphere comprises the following steps:
step one: 1.2 percent of binder, first conductive agent, core-shell structure microsphere and positive electrode material: 1.5 percent to 2 percent: sequentially adding 95.3% of the mixture into N-methylpyrrolidone, and fully stirring and uniformly mixing to obtain uniform slurry;
step two: and coating the slurry on a current collector, and drying, cold pressing and punching to obtain the positive electrode plate.
A second aspect of the invention provides a battery.
A battery comprising the positive electrode sheet comprising core-shell structured microspheres of the first aspect.
The invention has the following beneficial effects:
1. the invention provides a positive electrode plate and a battery containing core-shell structure microspheres, wherein the core-shell structure polymer microspheres have conducting and bonding functions, the dosage of conventional conducting agents and bonding agents can be properly reduced by introducing the core-shell structure polymer microspheres into the electrode plate, the proportion of active substances is not influenced, and the influence on the internal resistance of the electrode plate is very small, so that the influence on the energy density is small, and the core-shell structure polymer microspheres are different from the increase of the internal resistance and the decrease of the energy density caused by the introduction of other thermosensitive materials;
2. before thermal runaway, the core-shell structure microsphere has a low melting point, and the core material is melted and overflowed in advance to cover active substances with poor thermal stability, so that the original unstable whole is divided into discontinuous areas, the chain reaction when the thermal runaway occurs is blocked, and the heating safety of the battery is improved;
3. the invention only adds core-shell structure microsphere material when pole piece slurry is mixed, has no extra working procedure, has no change to pole piece structure, has no newly added coating, and has simple process.
Of course, it is not necessary for any one product to practice the invention to achieve all of the advantages set forth above at the same time.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a normal state and a thermal runaway state structure of a positive electrode plate in the prior art;
fig. 2 is a schematic diagram of the structure of the positive electrode plate in the normal state and the thermal runaway state of the invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The positive electrode plate comprises a current collector and an active material layer coated on the surface of the current collector, wherein the active material layer comprises an active material, a core-shell structure microsphere, a first conductive agent and a binder, the inner core of the core-shell structure microsphere is a polymer material, and the shell layer of the core-shell structure microsphere is a conductive material; when the temperature reaches the set temperature, the polymer material of the microsphere core with the core-shell structure melts and overflows to cover the active substances, the whole body which is originally unstable is divided into discontinuous areas, and the chain reaction when the thermal runaway occurs is blocked.
Further, the core-shell structure microsphere is formed by compounding a thermosensitive microsphere and a second conductive agent.
Further, the thermosensitive microsphere is at least one of polyethylene, polypropylene, polyamide, polyesteramide, polystyrene, polyvinyl chloride, polyester, polyurethane, olefin copolymer or a monomer modified copolymer thereof.
Further, the second conductive agent is an aniline solution or a pyrrole monomer solution.
Further, the set temperature of the polymer material of the microsphere core with the core-shell structure for melt overflow is 100-150 ℃.
Further, the binder is at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, regenerated cellulose, polyvinyl chloride, polymethyl methacrylate, polyacrylonitrile and styrene butadiene rubber.
Further, the first conductive agent is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, vapor grown carbon fibers, superconducting carbon, and graphene.
Further, the preparation method of the microsphere with the core-shell structure comprises the following steps:
step one: dispersing the thermosensitive microspheres into a solution prepared by a second conductive agent, and uniformly dispersing to prepare a mixed dispersion liquid;
step two: adding an oxidant into the mixed dispersion liquid, and controlling the reaction time and the reaction concentration to prepare a reaction product;
step three: and separating and washing the reaction product from the solution to obtain the microsphere material with the core-shell structure.
Further, the preparation method of the positive electrode plate containing the core-shell structure microsphere comprises the following steps:
step one: sequentially adding a binder, a first conductive agent, core-shell structure microspheres and a positive electrode material into N-methyl pyrrolidone according to a proportion, and fully stirring and uniformly mixing to prepare uniform slurry;
step two: and coating the slurry on a current collector, and drying, cold pressing and punching to obtain the positive electrode plate.
The battery comprises the positive electrode plate containing the core-shell structure microsphere.
The invention provides a battery pole piece and a battery comprising the same, wherein the pole piece comprises a current collector and an active material layer coated on the surface of the current collector, the active material layer comprises an active material, core-shell structure microspheres, a conductive agent and a binder, the core of the core-shell structure microspheres is made of a low-melting-point polymer material, and a shell layer is made of a conductive material.
Compared with the conventional pole piece, the pole piece provided by the invention is added with the core-shell structure polymer microsphere, and the polymer microsphere has certain cohesiveness, and meanwhile, the surface of the polymer microsphere contains a conductive shell layer and can also serve as a conductive agent, so that the addition of the core-shell structure polymer microsphere can properly reduce the dosage of the conventional conductive agent and the binder, and the proportion of active substances is not influenced. As shown in figure 2, more importantly, the core material in the microsphere is a low-melting point polymer, the melting at different temperatures can be realized by controlling the structure, the type and the crystallinity of the polymer, the melting is mainly realized within the range of 100-150 ℃, when the battery is heated to a specific temperature (generally more than 100 ℃), the low-melting point polymer melts and overflows, active substances with poor thermal stability are covered, the originally unstable whole body is divided into discontinuous areas, the chain reaction when thermal runaway occurs is blocked, and the heating safety of the battery is improved.
As shown in fig. 1, in the prior art, only the characteristic that the low-melting-point melting coating active material of the thermosensitive microspheres or the heated resistance is increased sharply is utilized, the active material is directly added into a pole piece or a coating is formed on a current collector to improve the heating safety of the battery, and the newly introduced thermosensitive material or the added thermosensitive coating often causes the problems of increased internal resistance of the pole piece and reduced active material ratio in two ways, so that the large-scale application of the technology is limited.
The invention innovatively prepares the low-melting-point thermosensitive microspheres and the conductive agent into the core-shell structure material, so that the pole piece mainly utilizes the conductive property of the core-shell structure material shell in normal use mode at normal temperature, and mainly utilizes the high-temperature melting insulation property of the core-shell structure material before the occurrence of thermal runaway, therefore, the low-melting-point core-shell structure material in the invention is introduced into the pole piece, has no obvious influence on the electrical property of the battery, but can obviously improve the heating safety performance of the battery.
The preparation process of the microsphere material with the core-shell structure is simple, the low-melting-point thermosensitive microsphere can be commercially purchased, such as polyethylene microsphere, polypropylene microsphere and the like, in the embodiment, the polyethylene microsphere is dispersed into an aniline solution (or pyrrole monomer solution and the like), and an initiator is added to polymerize the aniline monomer or pyrrole monomer on the surface of the polyethylene microsphere to form polyaniline or polypyrrole conductive material, so that the microsphere material with the core-shell structure is obtained.
Example 1
(1) Preparing microspheres with core-shell structures: dispersing commercially purchased polyethylene microspheres into an aniline solution, slowly adding an oxidant into the mixed dispersion liquid after uniform dispersion, controlling proper reaction time and reaction concentration, separating and washing a reaction product from the solution, and obtaining the polyaniline@polyethylene microsphere core-shell structure material.
(2) Preparing a positive electrode plate containing core-shell structure microspheres: polyvinylidene fluoride (PVDF), a conductive agent (SP), core-shell structure microspheres and a positive electrode material (NCM 811) are mixed according to the mass ratio of 1.0 percent: 0.8%:1.7%:96.5 percent of the aluminum foil is sequentially added into N-methyl pyrrolidone (NMP), fully stirred and uniformly mixed, the slurry is coated on the aluminum foil current collector, and the positive electrode plate is prepared by drying, cold pressing and punching.
(3) Preparing a cathode pole piece containing core-shell structure microspheres: sodium carboxymethylcellulose (CMC), styrene butadiene rubber emulsion (SBR), a conductive agent, core-shell structure microspheres and graphite are mixed according to the mass ratio of 1.2 percent: 1.3%:1%:1.5%:95% of the material is added into deionized water in sequence, fully stirred and uniformly mixed, the slurry is coated on a copper foil current collector, and the negative electrode plate is prepared through drying, cold pressing and punching.
(4) And stacking the diaphragm, the positive pole piece and the negative pole piece in a Z shape, packaging by adopting an aluminum plastic film to obtain a battery core to be injected with electrolyte, and injecting the electrolyte after baking to obtain the lithium ion battery with the nominal capacity of 3Ah to be tested.
Example 2
(1) Preparing microspheres with core-shell structures: the same as in example 1
(2) Preparing a positive electrode plate containing core-shell structure microspheres: polyvinylidene fluoride (PVDF), core-shell structure microspheres and a positive electrode material (NCM 811) are mixed according to the mass ratio of 1.0 percent: 2.5%:96.5 percent of the aluminum foil is sequentially added into N-methyl pyrrolidone (NMP), fully stirred and uniformly mixed, the slurry is coated on the aluminum foil current collector, and the positive electrode plate is prepared by drying, cold pressing and punching.
(3) Preparing a cathode pole piece containing core-shell structure microspheres: sodium carboxymethylcellulose (CMC), styrene butadiene rubber emulsion (SBR), a conductive agent, core-shell structure microspheres and graphite are mixed according to the mass ratio of 1.2 percent: 1.3%:1%:1.5%:95% of the material is added into deionized water in sequence, fully stirred and uniformly mixed, the slurry is coated on a copper foil current collector, and the negative electrode plate is prepared through drying, cold pressing and punching.
(4) And stacking the diaphragm, the positive pole piece and the negative pole piece in a Z shape, packaging by adopting an aluminum plastic film to obtain a battery core to be injected with electrolyte, and injecting the electrolyte after baking to obtain the lithium ion battery with the nominal capacity of 3Ah to be tested.
Example 3
(1) Preparing microspheres with core-shell structures: the same as in example 1
(2) Preparing a positive electrode plate containing core-shell structure microspheres: polyvinylidene fluoride (PVDF), a conductive agent (SP), core-shell structure microspheres and a positive electrode material (NCM 811) are mixed according to the mass ratio of 0.5 percent: 0.8%:2.2%:96.5 percent of the aluminum foil is sequentially added into N-methyl pyrrolidone (NMP), fully stirred and uniformly mixed, the slurry is coated on the aluminum foil current collector, and the positive electrode plate is prepared by drying, cold pressing and punching.
(3) Preparing a cathode pole piece containing core-shell structure microspheres: sodium carboxymethylcellulose (CMC), styrene butadiene rubber emulsion (SBR), a conductive agent, core-shell structure microspheres and graphite are mixed according to the mass ratio of 1.2 percent: 1.3%:1%:1.5%:95% of the material is added into deionized water in sequence, fully stirred and uniformly mixed, the slurry is coated on a copper foil current collector, and the negative electrode plate is prepared through drying, cold pressing and punching.
(4) And stacking the diaphragm, the positive pole piece and the negative pole piece in a Z shape, packaging by adopting an aluminum plastic film to obtain a battery core to be injected with electrolyte, and injecting the electrolyte after baking to obtain the lithium ion battery with the nominal capacity of 3Ah to be tested.
Comparative example 1
(1) Preparing a positive electrode plate: polyvinylidene fluoride (PVDF), a conductive agent (SP) and a positive electrode material (NCM 811) are mixed according to the mass ratio of 2 percent: 1.5%:96.5 percent of the aluminum foil is sequentially added into N-methyl pyrrolidone (NMP), fully stirred and uniformly mixed, the slurry is coated on the aluminum foil current collector, and the positive electrode plate is prepared by drying, cold pressing and punching.
(2) Preparing a negative electrode plate: sodium carboxymethylcellulose (CMC), styrene butadiene rubber emulsion (SBR), a conductive agent and graphite are mixed according to the mass ratio of 1.7 percent: 1.8%:1.5%:95% of the material is added into deionized water in sequence, fully stirred and uniformly mixed, the slurry is coated on a copper foil current collector, and the negative electrode plate is prepared through drying, cold pressing and punching.
(3) And stacking the diaphragm, the positive pole piece and the negative pole piece in a Z shape, packaging by adopting an aluminum plastic film to obtain a battery core to be injected with electrolyte, and injecting the electrolyte after baking to obtain the lithium ion battery with the nominal capacity of 3Ah to be tested.
Comparative example 2
(1) Preparing a positive electrode plate: polyvinylidene fluoride (PVDF), a conductive agent (SP), polyethylene microspheres and a positive electrode material (NCM 811) are mixed according to the mass ratio of 1%:0.8%:1.7%:96.5 percent of the aluminum foil is sequentially added into N-methyl pyrrolidone (NMP), fully stirred and uniformly mixed, the slurry is coated on the aluminum foil current collector, and the positive electrode plate is prepared by drying, cold pressing and punching.
(2) Preparing a negative electrode plate: sodium carboxymethylcellulose (CMC), styrene butadiene rubber emulsion (SBR), a conductive agent and graphite are mixed according to the mass ratio of 1.7 percent: 1.8%:1.5%:95% of the material is added into deionized water in sequence, fully stirred and uniformly mixed, the slurry is coated on a copper foil current collector, and the negative electrode plate is prepared through drying, cold pressing and punching.
(3) And stacking the diaphragm, the positive pole piece and the negative pole piece in a Z shape, packaging by adopting an aluminum plastic film to obtain a battery core to be injected with electrolyte, and injecting the electrolyte after baking to obtain the lithium ion battery with the nominal capacity of 3Ah to be tested.
Experiment
Pole piece peel strength test: according to the ASTM D3330 peel strength test standard, the peel strength of the positive plate is tested to obtain peel strength data;
testing of lithium ion batteries:
and (3) testing the internal resistance of the battery: testing the resistance of the battery by using a battery internal resistance tester to obtain direct current internal resistance data of the battery;
capacity test: charging and discharging the battery by using 0.33C and 1C respectively to obtain capacity data of the battery 0.33C and 1C;
and (3) hot box test: and (3) placing the fully charged battery in an explosion-proof oven, heating to 130 ℃ at a speed of 5 ℃ per minute from 25 ℃, keeping for 60 minutes, and recording the temperature rise and the voltage change of the battery.
TABLE 1 Pole piece peel Strength, internal Battery resistance, battery Capacity and Hot Box test data
Analysis of test results:
in comparison with comparative example 1, under the same proportion, core-shell structure microspheres and polyethylene microspheres are added into the positive electrode, the peel strength of the core-shell structure microspheres and the peel strength of the polyethylene microspheres are basically consistent, which means that the influence of the core-shell structure microspheres and the polyethylene microspheres on the peel strength of the pole piece is basically consistent, but from the aspect of internal resistance of the battery, the deterioration of the internal resistance of the battery by the pure polyethylene microspheres is obviously stronger than that of the core-shell structure microspheres, so that the battery performance of the core-shell structure microsphere set of example 1 is obviously better than that of the pure polyethylene microsphere set in the aspect of 1C/0.33C capacity ratio. In terms of heating safety, the addition blocking effect of the pure polyethylene microspheres is slightly better than that of the core-shell structure microsphere material with the conductive shell layer, so that the temperature rise of the example 1 is relatively higher than that of the comparative example 1.
In example 2, the improvement of the content of the core-shell structure microsphere replaces the conventional conductive agent, and the slight increase of the peel strength of the pole piece can be seen, which indicates that the core-shell structure microsphere can play a role in bonding to a certain extent.
In example 3, the improvement of the content of the core-shell structure microsphere replaces part of the conventional binder, so that the reduction of the peeling strength is not obvious, the internal resistance is reduced, the core-shell structure microsphere has the dual advantages of cohesiveness and conductivity, and the capacity exertion is basically not obvious.
In general, each example and comparative example 2 are compared, comparative example 2 is a conventional positive electrode sheet formula, the peel strength of each example is slightly reduced, but the increase of the internal resistance of the battery is not obvious within the range of industry standards, the capacity is close to the exertion, and most importantly, the highest temperature of a hot box is obviously reduced, which indicates that the microsphere with a core-shell structure effectively plays a blocking role in the heating process and blocks the chain reaction of thermal runaway.
As can be seen from the comparison of each example with comparative example 1, in which polyethylene microspheres were added alone, showed a remarkable increase in internal resistance and a remarkably inferior capacity performance to each example, although the highest temperature of the battery after heating was close to that of each example, and the safety blocking effect was also exhibited, compared with each example in which core-shell microspheres were added.
In conclusion, the core-shell structure microsphere is applied to the pole piece, so that the heating safety performance of the battery is obviously improved, the electrochemical performance of the battery is extremely influenced, the process is simple and feasible, and the application prospect is provided.
In the description of the present specification, the descriptions of the terms "one embodiment," "example," "specific example," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The preferred embodiments of the invention disclosed above are intended only to assist in the explanation of the invention. The preferred embodiments are not exhaustive or to limit the invention to the precise form disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best understand and utilize the invention. The invention is limited only by the claims and the full scope and equivalents thereof.
Claims (10)
1. The positive electrode plate containing the core-shell structure microsphere is characterized by comprising a current collector and an active material layer coated on the surface of the current collector, wherein the active material layer comprises an active material, the core-shell structure microsphere, a first conductive agent and a binder, the inner core of the core-shell structure microsphere is a polymer material, and the shell layer of the core-shell structure microsphere is a conductive material; when the temperature reaches the set temperature, the polymer material of the microsphere core with the core-shell structure melts and overflows to cover active substances, so that the original unstable whole is divided into discontinuous areas, and the chain reaction when thermal runaway occurs is blocked;
in the active material layer, the mass percentages of the active material, the core-shell structure microsphere, the first conductive agent and the binder are as follows:
active material: 90 to 98 percent
And (2) a binder: 0.5% -2%;
a first conductive agent: 0.5% -2%;
microsphere with core-shell structure: 1% -6%.
2. The positive electrode sheet comprising core-shell structured microspheres of claim 1, wherein the core-shell structured microspheres are compounded by thermosensitive microspheres and a second conductive agent.
3. The positive electrode sheet comprising core-shell structured microspheres of claim 2, wherein the thermosensitive microspheres are at least one of polyethylene, polypropylene, polyamide, polyesteramide, polystyrene, polyvinyl chloride, polyester, polyurethane, olefin copolymer, or a monomer modified co-polymerized polymer thereof.
4. The positive electrode sheet comprising core-shell structured microspheres of claim 1, wherein the second conductive agent is an aniline solution or a pyrrole monomer solution.
5. The positive electrode sheet comprising core-shell structured microspheres of claim 1, wherein the polymeric material of the core-shell structured microsphere core has a set temperature of 100 ℃ to 150 ℃ for melt overflow.
6. The positive electrode sheet containing core-shell structured microspheres according to claim 1, wherein the binder is at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, regenerated cellulose, polyvinyl chloride, polymethyl methacrylate, polyacrylonitrile, and styrene butadiene rubber.
7. The positive electrode sheet comprising core-shell structured microspheres of claim 1, wherein the first conductive agent is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, vapor grown carbon fibers, superconducting carbon, and graphene.
8. The positive electrode sheet containing the core-shell structure microsphere according to claim 1, wherein the preparation method of the core-shell structure microsphere is as follows:
step one: dispersing the thermosensitive microspheres into a solution prepared by a second conductive agent, and uniformly dispersing to prepare a mixed dispersion liquid;
step two: adding an oxidant into the mixed dispersion liquid, and controlling the reaction time and the reaction concentration to prepare a reaction product;
step three: and separating and washing the reaction product from the solution to obtain the microsphere material with the core-shell structure.
9. The positive electrode sheet containing the core-shell structure microspheres according to claim 1, wherein the preparation method of the positive electrode sheet containing the core-shell structure microspheres comprises the following steps:
step one: sequentially adding a binder, a first conductive agent, core-shell structure microspheres and a positive electrode material into N-methyl pyrrolidone according to a proportion, and fully stirring and uniformly mixing to prepare uniform slurry;
step two: and coating the slurry on a current collector, and drying, cold pressing and punching to obtain the positive electrode plate.
10. A battery comprising the positive electrode sheet comprising core-shell structured microspheres of any one of claims 1-9.
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