CN112201787A - High-capacity negative electrode bonding system, negative electrode and lithium ion battery - Google Patents
High-capacity negative electrode bonding system, negative electrode and lithium ion battery Download PDFInfo
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- CN112201787A CN112201787A CN202010972711.0A CN202010972711A CN112201787A CN 112201787 A CN112201787 A CN 112201787A CN 202010972711 A CN202010972711 A CN 202010972711A CN 112201787 A CN112201787 A CN 112201787A
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- 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
- 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
- H01M4/134—Electrodes based on metals, Si or alloys
-
- 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
- H01M4/621—Binders
- H01M4/622—Binders being polymers
-
- 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
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
-
- 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
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a high-capacity cathode bonding system, a cathode and a lithium ion battery. The high capacity anode binding system for binding an anode active material to form an anode active material layer includes: the negative electrode comprises an elastic wrapping layer wrapping the surface of the negative electrode active material and a water-soluble polymer connected with the elastic wrapping layer. The elastic wrapping layer and the water-soluble polymer form a high-capacity negative electrode bonding system, and the high-capacity negative electrode bonding system can expand and contract along with a negative electrode active material and inhibit the negative electrode active material from expanding and cracking.
Description
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a high-capacity negative electrode bonding system, a negative electrode and a lithium ion battery.
Background
Lithium ion batteries are widely used in consumer electronics, power batteries, and energy storage products due to their advantages of high energy density, no memory effect, long cycle life, and environmental friendliness.
With the continuous multifunctionalization and refinement of various electric devices, people also put forward higher and higher requirements on the energy density of lithium ion batteries. In order to improve the energy density of lithium ion batteries, researchers have conducted extensive studies on high-capacity negative active materials, and negative electrodes and lithium batteries using the same. At present, graphite cathodes are commonly used in lithium ion batteries on the market, the reversible capacity reaches 360mAh/g, and gradually approaches to the theoretical limit of 372 mAh/g. The theoretical capacity of the high-capacity cathode active material, particularly the silicon cathode material, can reach more than 3600mAh/g, and the energy density of the lithium ion battery can be effectively improved.
However, the high-capacity negative electrode active material has large lithium insertion amount and large expansion-contraction ratio in the charging and discharging process, which can reach more than 300% (the expansion-contraction ratio of the graphite negative electrode is about 10%), so that the active material is easy to crack and the negative electrode active layer structure is cracked and damaged by using the conventional binder in the charging and discharging process, the battery expansion in the using process can be greatly increased, and the cycle life of the battery can be greatly shortened.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a high-capacity negative electrode binder system, a negative electrode, and a lithium ion battery, which are intended to solve the problem of the prior art that an active material is easily broken.
A high capacity anode binding system for binding an anode active material to form an anode active material layer, comprising: the negative electrode comprises an elastic wrapping layer wrapping the surface of the negative electrode active material and a water-soluble polymer connected with the elastic wrapping layer.
The high-capacity negative electrode bonding system is characterized in that the elastic modulus of the elastic wrapping layer is 0.1-200 MPa, and the elongation at break of the elastic wrapping layer is more than 20%.
The high-capacity negative electrode bonding system is characterized in that the thickness of the elastic wrapping layer is 10-500 nm.
The high capacity negative electrode bonding system, wherein the elastic wrapping comprises an elastic material;
the elastic material includes: at least one of a polyether amine elastic material, an epoxy resin elastic material, a polyether resin elastic material, a polyurethane elastic material, a polystyrene elastic material, a polyacrylate elastic material, a polyethylene elastic material, a polypropylene elastic material, a polyamide elastic material, a styrene butadiene rubber material, a natural rubber material, a nitrile butadiene rubber material, an ethylene propylene rubber material and a silicone rubber material.
The high capacity negative electrode binder system, wherein the water soluble polymer comprises: at least one of sodium carboxymethylcellulose, sodium alginate, polyacrylic acid, polymethacrylic acid, polyacrylamide and polysaccharide polymer.
A lithium ion battery negative electrode, comprising: a negative electrode current collector, a negative electrode active material layer formed on the negative electrode current collector;
wherein the anode active material layer includes: the high-capacity negative electrode comprises a negative electrode active material, an elastic wrapping layer wrapping the surface of the negative electrode active material, a water-soluble polymer connected with the elastic wrapping layer to form the high-capacity negative electrode bonding system, and a conductive agent and an auxiliary additive which are dispersed in the negative electrode active material layer.
The lithium ion battery negative electrode, wherein the auxiliary additive comprises: at least one of multifunctional aziridine, multifunctional polycarbodiimide, multifunctional isocyanate, multifunctional epoxy resin, iron ion, copper ion and organic tin catalyst.
The lithium ion battery cathode is characterized in that the cathode active material is a silicon active material.
The lithium ion battery negative electrode is characterized in that the weight of the water-soluble polymer in the negative electrode active material layer is 1-10% of the weight of the negative electrode active material.
A lithium ion battery comprises the lithium ion battery cathode.
Has the advantages that: first, the high capacity negative electrode binding system can reduce lithium ion battery negative electrode swelling. Due to the existence of the elastic wrapping layer and the formation of the continuous network structure of the whole bonding system, the expansion of the active material and the active layer and the expansion of the lithium ion battery can be effectively inhibited; second, the high capacity negative electrode binding system improves the long cycle life of lithium ion batteries. On one hand, the elastic wrapping layer inhibits the active material from cracking, and the service life of the active material is prolonged; due to the existence of the elastic wrapping layer and the formation of the continuous network structure of the whole bonding system, the whole structure damage of the cathode active layer is inhibited, the bonding strength and the long-term stability of the bonding agent to the active material are enhanced, and the service lives of the cathode and the lithium ion battery are prolonged.
Drawings
Fig. 1 is a schematic structural diagram of a negative electrode of a lithium ion battery according to the present invention.
Detailed Description
The present invention provides a high capacity negative electrode binder system, a negative electrode, and a lithium ion battery, and the purpose, technical scheme, and effect of the present invention are more clear and definite, and the present invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The present invention provides a high capacity anode binding system for binding an anode active material to form an anode active material layer, comprising: an elastic coating layer (cross-linked polymer elastic coating layer) coated on the surface of the negative active material and a water-soluble polymer (water-soluble polymer) connected with the elastic coating layer.
The elastic wrapping layer and the water-soluble polymer form a high-capacity negative electrode bonding system, and the high-capacity negative electrode bonding system can expand and contract along with a negative electrode active material and inhibit the negative electrode active material from expanding and cracking. Specifically, the elastic wrapping layer wraps the anode active material, and due to good elasticity of the elastic wrapping layer, the elastic wrapping layer can contract along with the expansion of the active material and inhibit the expansion and the fragmentation of the active material; the active material shell interface formed by the elastic wrapping layer is more stable and is more firmly bonded with the water-soluble polymer, so that bonding failure generated in the expansion and contraction process is inhibited; because the elastic wrapping layer is matched with the water-soluble polymer, a continuous network structure of a bonding system can be ensured to be formed, and the stable structure of the long-term circulation of the negative active layer is ensured.
The elastic wrapping layer (crosslinked polymer elastic wrapping layer) is wrapped on the negative active material, wherein the elastic wrapping layer has good elasticity and can expand and contract along with the negative active material and inhibit the negative active material from expanding and cracking. The elastic coating of the present invention is desirably elastic and is typically a crosslinked polymeric elastic coating. If the elastic modulus is too low, expansion and chipping of the active material cannot be effectively inhibited; if the elastic modulus is too high, the internal stress is too large, and the active particles may be broken. In one embodiment of the present invention, the elastic modulus of the elastic coating layer is 0.1 to 200MPa, and the elastic modulus of the elastic coating layer is 1 to 50 MPa.
In the present invention, if the elongation at break of the elastic wrapping layer is too low, the crosslinked polymeric elastic layer may crack during the expansion process, and the expansion and the fragmentation of the active material may not be effectively inhibited. In one embodiment of the invention, the elastic wrap layer has an elongation at break of greater than 20%. Further, the elongation at break of the elastic wrapping layer is greater than 50%.
In the present invention, if the thickness of the elastic wrapping layer is too thin, expansion and fragmentation of the active material may not be effectively inhibited; if the thickness of the elastic wrapping layer is too thick, diffusion and entering of lithium ions are influenced, and therefore capacity, multiplying power and low-temperature performance are influenced. In one embodiment of the invention, the thickness of the elastic wrapping layer is 10nm to 500 nm; further, the thickness of the elastic wrapping layer is 20 nm-200 nm.
In one embodiment of the invention, the elastic wrap layer comprises an elastic material. Specifically, the elastic material in the present invention may specifically be an elastomer including one or more high molecular polymers (crosslinked polymers). The main component of the elastic wrapping layer is a high-molecular elastomer. In one embodiment of the present invention, the elastic material is selected from at least one of polyetheramine elastic material, epoxy resin elastic material, polyether resin elastic material, polyurethane elastic material, polystyrene elastic material, polyacrylate elastic material, polyethylene elastic material, polypropylene elastic material, copolyester elastic material, polyamide elastic material, styrene-butadiene rubber, natural rubber, nitrile rubber, ethylene-propylene rubber, and silicone rubber. Further, the elastic wrapping layer comprises: at least one of a polyether amine elastic wrapping layer, an epoxy resin elastic wrapping layer, a polyether resin elastic wrapping layer, a polyurethane elastic wrapping layer, a polystyrene elastic wrapping layer, a polyacrylate elastic wrapping layer, a polyethylene elastic wrapping layer, a polypropylene elastic wrapping layer, a polyamide elastic wrapping layer, a styrene butadiene rubber wrapping layer, a natural rubber wrapping layer, a nitrile butadiene rubber wrapping layer, an ethylene propylene rubber wrapping layer and a silicon rubber wrapping layer.
The water-soluble polymer is used for matching with the elastic wrapping layer to form a continuous network structure of a bonding system. The water-soluble polymer is in a strip shape or a chain shape, is positioned among the elastic wrapping layers and is connected with the crosslinking points on the surfaces of the elastic wrapping layers. In one embodiment of the present invention, the water-soluble polymer is at least one selected from the group consisting of sodium carboxymethylcellulose and derivatives thereof, sodium alginate and derivatives thereof, polyacrylic acid and copolymers thereof, polymethacrylic acid and copolymers thereof, polyacrylamide and copolymers thereof, polysaccharide polymers and derivatives thereof, and diisocyanate and derivatives thereof. Further, the water-soluble polymer includes: at least one of sodium carboxymethylcellulose, sodium alginate, polyacrylic acid, polymethacrylic acid, polyacrylamide and polysaccharide polymer.
Referring to fig. 1, the present invention also provides a lithium ion battery cathode, including: the method comprises the following steps: a negative electrode current collector 1, a negative electrode active material layer 2 formed on the negative electrode current collector 1;
wherein the anode active material layer 2 includes: the negative electrode active material comprises a negative electrode active material 210, an elastic wrapping layer 221 wrapping the surface of the negative electrode active material 210, a water-soluble polymer 222 connected with the elastic wrapping layer 221 to form the high-capacity negative electrode bonding system 220, and a conductive agent and an auxiliary additive which are dispersed in the negative electrode active material layer 2.
The anode active material layer 2 of the present invention includes the high capacity anode binder system 220 as described above. The high-capacity negative electrode bonding system 220 of the present invention is a network bonding system, and particularly refers to a bonding agent part for assisting an active material to be bonded into an active layer, and does not include the negative electrode active material 210, a conductive agent, and other auxiliary materials. That is, the network bonding system is composed of an elastic wrapping layer 221 and a water-soluble polymer 222. The high-capacity negative electrode bonding system 220 does not include a conductive agent part, and then the high-capacity negative electrode bonding system, the negative electrode active material 210, the conductive agent and the like form a negative electrode active layer 2 to complete the charge and discharge functions. Further, the elastic wrapping layer 221 and the water-soluble polymer 222 are connected by the cross-linking points 230. The crosslinking points are mainly bonded by chemical bonds, including ionic bonds, covalent bonds, and the like. As can be seen, the elastic wrapping layer is wrapped 221 on the negative active material 210 and connected with the water-soluble polymer 222 to form a continuous network structure in the present invention.
In the negative electrode active material layer 2 of the negative electrode of the lithium ion battery, a plurality of the elastic wrapping layers 221 are connected with the water-soluble polymers at the cross-linking points 230, and the cross-linking points 230 are formed among the water-soluble polymers 222, so that a network bonding system is formed. The shell interface of the negative active material 210 formed by the cross-linked elastic wrapping layer 221 is more stable, the bonding with the water-soluble polymer 222 is firmer, and the bonding failure generated in the expansion and shrinkage process is inhibited; due to the existence of the cross-linked elastic wrapping layer 221, the continuous network structure of a bonding system can be ensured to be formed by matching with the water-soluble polymer 222, and the stable structure of the long-term circulation of the negative active layer 2 is ensured.
Compared with the prior art, the lithium ion battery cathode at least has the following advantages: first, low expansion. Due to the existence of the high-molecular elastic wrapping layer 221 and the formation of the continuous network structure of the whole binding system, the expansion of the negative electrode active material 210 and the negative electrode active layer 2 and the expansion of the final lithium ion battery can be effectively inhibited; second, long cycle life. On the one hand, the cross-linked polymer coating layer 221 suppresses cracking of the active material 210, and improves the life of the negative active material 210; due to the existence of the cross-linked polymer wrapping layer 220 and the formation of the continuous network structure of the whole bonding system, the whole structure damage of the cathode active layer 2 is inhibited, the bonding strength and the long-term stability of the bonding agent to the active material 210 are enhanced, and the service lives of the cathode and the lithium ion battery are prolonged.
In one embodiment of the present invention, the negative active material 210 is a silicon active material. The silicon active material is in the form of particles, which can also be referred to as silicon active powder.
The water-soluble polymer 222 can be dissolved in water, and can be used for preparing a lithium ion battery cathode in an aqueous environment. The water-soluble polymer 222 may also be referred to as a water-soluble polymer. The water-soluble polymer is used as a thickener, a crosslinking agent, a dispersant and a binder.
In one embodiment of the present invention, the conductive agent includes one or more of conductive carbon black, carbon nanotubes, graphene, carbon fibers.
The supplemental additives may be dispersed in the high capacity negative electrode binder system 220. The auxiliary additive can assist the crosslinking between the elastic wrapping layer 221 and the water-soluble polymer 222 and the crosslinking between the water-soluble polymers 222, so that an integral bonding system continuous network structure is formed, and the long-term circulating structural stability of the negative electrode active layer is ensured. In one embodiment of the present invention, the auxiliary additive comprises: at least one of multifunctional aziridine (aziridine crosslinking agent), multifunctional agglomerated carbodiimide (carbodiimide crosslinking agent), multifunctional isocyanate (isocyanate crosslinking agent), multifunctional epoxy resin (epoxy crosslinking agent), iron ions, copper ions and organic tin catalysts. Alternatively, the functional groups in the polyfunctional aziridine, polyfunctional polycarbodiimide, polyfunctional isocyanate, polyfunctional epoxy may be hydroxyl functional groups.
In one embodiment of the present invention, the weight of the water-soluble polymer is about 1% to 10% of the weight of the negative electrode active material layer. In one embodiment of the present invention, the anode active material layer includes, in parts by weight: 80-110 parts of negative electrode active material, 1-20 parts of water-soluble polymer and 1-20 parts of conductive agent. Alternatively, the anode active material layer includes, in parts by weight: 90-96 parts of negative electrode active material, 1-6 parts of water-soluble polymer and 1-3 parts of conductive agent.
The invention also provides a preparation method of the lithium ion battery cathode, which comprises the following steps:
s100, dispersing a negative electrode active material and a high-molecular elastic material into a first solvent to obtain a dispersion liquid;
s200, carrying out spray drying on the dispersion liquid to obtain a negative active composite material;
s300, mixing the negative electrode active composite material, the water-soluble polymer, the conductive agent and the second solvent, coating the mixture on a current collector, and drying to obtain the negative electrode of the lithium ion battery.
In one embodiment of the present invention, an amount of the auxiliary additive as described above may be added in the S100 for generating an elastic coating layer covering the surface of the active material; and/or a certain amount of the auxiliary additive can be added in the S200 to be used as a cross-linking agent of the negative active layer.
In the preparation process, the negative active material is put into the first solvent and stirred to fully disperse the negative active material, and then the high molecular elastic material is added and stirred uniformly; and (3) carrying out spray drying on the dispersion liquid, so that the high-molecular elastic material is coated on the negative electrode active material to form a high-molecular elastic coating layer, thereby obtaining the negative electrode active composite material. The negative active composite material is a coated negative active material, and particularly is a composite material coated with an elastic coating layer on the surface of the negative active material.
The polymer elastic material is a material for forming the polymer elastic wrapping layer, for example, a polyurethane material is correspondingly prepared into the polyurethane elastic wrapping layer. In addition, the invention can also replace the macromolecule elastic material with macromolecule elastic material prepolymer or monomer of macromolecule elastic material, and add a certain amount of initiating agent, polymerize in the course of spray drying and drying to form the elastic wrapping layer. For example, the diisocyanate may be reacted to form a polyurethane elastomer wrapping.
The S300 specifically includes:
s301, adding a second solvent and the water-soluble polymer into a stirrer according to the formula, and completely dissolving in a vacuum state to obtain a water-soluble polymer solution;
s302, adding a conductive agent into the dissolved aqueous polymer solution according to the formula, and quickly stirring until the fineness is below 5 mu m; then adding a negative active composite material according to the formula, and accelerating stirring until the fineness is below 30 mu m; and (4) uniformly stirring at a low speed in vacuum, and filtering by using a 150-mesh stainless steel screen to obtain the required cathode slurry.
S303, uniformly coating the negative electrode slurry on two surfaces of a current collector (such as copper foil), drying, removing water at high temperature in vacuum, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the negative pole piece.
The invention also provides a lithium ion battery, which comprises the lithium ion battery cathode. Specifically, the lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm arranged between the positive electrode and the negative electrode, and electrolyte, wherein the negative electrode is the lithium ion battery negative electrode.
Therefore, the invention provides a lithium ion battery high-capacity negative electrode bonding system which can effectively inhibit the expansion of a high-capacity negative electrode and improve the stability of a high-capacity negative electrode active material and an active layer so as to reduce the expansion of the negative electrode of the lithium ion battery and prolong the cycle life of the lithium ion battery, and the negative electrode and the lithium ion battery comprising the bonding system.
The present invention will be further described with reference to specific comparative examples and examples.
Comparative example 1
Preparation of a negative electrode:
the negative electrode slurry formula comprises, by weight, 1.5% of sodium carboxymethylcellulose, 1.5% of butylbenzene emulsion, 1.5% of conductive carbon black, 0.5% of carbon nanotubes and 95% of silicon active material (silicon powder). In the slurry preparation process, the solvent is water, and the water accounts for 60% of the total slurry.
Firstly, adding water and sodium carboxymethylcellulose into a stirrer according to the formula, and completely dissolving the mixture in a vacuum state to obtain an aqueous polymer solution; adding the conductive carbon black and the carbon nano tube into the dissolved aqueous polymer solution according to the formula, and quickly stirring until the fineness is below 5 mu m; then adding silicon active materials according to the formula, and accelerating the stirring until the fineness is below 30 mu m; reducing the rotating speed, adding the butylbenzene emulsion, and uniformly stirring at a low speed in vacuum; and finally filtering the mixture by using a 150-mesh stainless steel screen to obtain the required cathode slurry.
Uniformly coating the slurry on two sides of a copper foil with the thickness of 8 mu m, drying, removing water at high temperature in vacuum, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the negative pole piece.
Preparation of the positive electrode:
lithium cobaltate (LiCoO) was used for the positive electrode2) As active substance. The positive electrode slurry containing the active material was prepared according to a formulation, and the solid content of the slurry contained 90% of the positive electrode active material, 5% of PVDF (polyvinylidene fluoride) binder, and 5% of conductive carbon black in terms of dry weight percentage. The slurry used N-methylpyrrolidone (NMP) as the solvent, and the solids content of the slurry was 40%.
Adding N-methyl pyrrolidone (NMP) and PVDF into a stirrer according to the formula, completely dissolving in a vacuum state to obtain a PVDF solution, adding conductive carbon black into the dissolved oily PVDF solution according to the formula, quickly stirring until the fineness is below 5 mu m, finally adding lithium cobaltate according to the formula, and uniformly stirring in a vacuum state. Filtering with a 200-mesh stainless steel screen to obtain the required anode slurry.
And uniformly coating the slurry on two sides of an aluminum foil with the thickness of 12 mu m, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the positive plate.
The separator is a Polyethylene (PE) porous membrane with the thickness of 12 um.
Preparing electrolyte:
mixing ethylene carbonate EC, propylene carbonate PC and dimethyl carbonate DMC according to a volume ratio of 3: 3: 4 preparing a mixed solvent, and then adding a solute lithium hexafluorophosphate (LiPF)6) And make LiPF6The concentration of (A) is 1M, and the electrolyte is obtained after uniform stirring.
Assembling the battery:
and winding the positive electrode, the diaphragm and the negative electrode to form a battery core, packaging the battery core by using an aluminum plastic film, injecting the electrolyte, and carrying out formation and aging tests on the battery after packaging to obtain the square flexible package battery with the length, width and thickness of 32mm, 82mm and 4.2mm respectively.
Comparative example 2
Preparation of a negative electrode:
the negative electrode slurry formula comprises, by weight, 5% of sodium carboxymethylcellulose, 1.5% of conductive carbon black, 0.5% of carbon nanotubes and 93% of silicon active materials. In the slurry preparation process, the solvent is water, and the water accounts for 60% of the total slurry.
Firstly, adding water and sodium carboxymethylcellulose into a stirrer according to the formula, and completely dissolving the mixture in a vacuum state to obtain an aqueous polymer solution; adding the conductive carbon black and the carbon nano tube into the dissolved aqueous polymer solution according to the formula, and quickly stirring until the fineness is below 5 mu m; then adding silicon active materials according to the formula, accelerating the stirring until the fineness is below 30 mu m, and uniformly stirring at a low speed in vacuum; and finally filtering the mixture by using a 150-mesh stainless steel screen to obtain the required cathode slurry.
Uniformly coating the slurry on two sides of a copper foil with the thickness of 8 mu m, drying, removing water at high temperature in vacuum, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the negative pole piece.
Preparation of the positive electrode:
lithium cobaltate (LiCoO) was used for the positive electrode2) As active substance. The positive electrode slurry containing the active material was prepared according to a formulation, and the solid content of the slurry contained 90% of the positive electrode active material, 5% of PVDF (polyvinylidene fluoride) binder, and 5% of conductive carbon black in terms of dry weight percentage. The slurry used N-methylpyrrolidone (NMP) as the solvent, and the solids content of the slurry was 40%.
Adding N-methyl pyrrolidone (NMP) and PVDF into a stirrer according to the formula, completely dissolving in a vacuum state to obtain a PVDF solution, adding conductive carbon black into the dissolved oily PVDF solution according to the formula, quickly stirring until the fineness is below 5 mu m, finally adding lithium cobaltate according to the formula, and uniformly stirring in a vacuum state. Filtering with a 200-mesh stainless steel screen to obtain the required anode slurry.
And uniformly coating the slurry on two sides of an aluminum foil with the thickness of 12 mu m, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the positive plate.
The separator is a Polyethylene (PE) porous membrane with the thickness of 12 um.
Preparing electrolyte:
mixing ethylene carbonate EC, propylene carbonate PC and dimethyl carbonate DMC according to a volume ratio of 3: 3: 4 preparing a mixed solvent, and then adding a solute lithium hexafluorophosphate (LiPF)6) And make LiPF6The concentration of (A) is 1M, and the electrolyte is obtained after uniform stirring.
Assembling the battery:
and winding the positive electrode, the diaphragm and the negative electrode to form a battery core, packaging the battery core by using an aluminum plastic film, injecting the electrolyte, and carrying out formation and aging tests on the battery after packaging to obtain the square flexible package battery with the length, width and thickness of 32mm, 82mm and 4.2mm respectively.
Example 1
Preparation of a negative electrode:
firstly, 1 kg of silicon active material is put into 4 kg of butyl acetate to be stirred, a certain amount of flexible polyether amine is added to be quickly stirred and the silicon active material is fully dispersed, and then 0.95 equivalent of bisphenol A epoxy resin (the sum of the amounts of the flexible polyether amine and the bisphenol A is about 0.25 kg) is added to be uniformly stirred. And (3) carrying out spray drying on the dispersion liquid, and collecting the dried coated silicon active material for later use.
The negative electrode slurry formula comprises, by weight, 1.5% of sodium carboxymethylcellulose, 3.5% of polyacrylic acid, 0.2% of toluene diisocyanate, 1.5% of conductive carbon black, 0.5% of carbon nanotubes and 92.8% of a silicon-coated active material. In the slurry preparation process, the solvent is water, and the water accounts for 60% of the total slurry.
Firstly, adding water, sodium carboxymethylcellulose and polyacrylic acid into a stirrer according to the formula, and completely dissolving in a vacuum state to obtain an aqueous polymer solution; adding the conductive carbon black and the carbon nano tube into the dissolved aqueous polymer solution according to the formula, and quickly stirring until the fineness is below 5 mu m; then adding the silicon-coated active material according to the formula, and accelerating the stirring until the fineness is below 30 mu m; adding toluene diisocyanate before coating, and stirring uniformly at a low speed in vacuum; and finally filtering the mixture by using a 150-mesh stainless steel screen to obtain the required cathode slurry.
Uniformly coating the slurry on two sides of a copper foil with the thickness of 8 mu m, drying, removing water at high temperature in vacuum, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the negative pole piece.
Preparation of the positive electrode:
lithium cobaltate (LiCoO) was used for the positive electrode2) As active substance. The positive electrode slurry containing the active material was prepared according to a formulation, and the solid content of the slurry contained 90% of the positive electrode active material, 5% of PVDF (polyvinylidene fluoride) binder, and 5% of conductive carbon black in terms of dry weight percentage. The slurry used N-methylpyrrolidone (NMP) as the solvent, and the solids content of the slurry was 40%.
Adding N-methyl pyrrolidone (NMP) and PVDF into a stirrer according to the formula, completely dissolving in a vacuum state to obtain a PVDF solution, adding conductive carbon black into the dissolved oily PVDF solution according to the formula, quickly stirring until the fineness is below 5 mu m, finally adding lithium cobaltate according to the formula, and uniformly stirring in a vacuum state. Filtering with a 200-mesh stainless steel screen to obtain the required anode slurry.
And uniformly coating the slurry on two sides of an aluminum foil with the thickness of 12 mu m, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the positive plate.
The separator is a Polyethylene (PE) porous membrane with the thickness of 12 um.
Preparing electrolyte:
mixing ethylene carbonate EC, propylene carbonate PC and dimethyl carbonate DMC according to a volume ratio of 3: 3: 4 preparing a mixed solvent, and then adding a solute lithium hexafluorophosphate (LiPF)6) And make LiPF6The concentration of (A) is 1M, and the electrolyte is obtained after uniform stirring.
Assembling the battery:
and winding the positive electrode, the diaphragm and the negative electrode to form a battery core, packaging the battery core by using an aluminum plastic film, injecting the electrolyte, and carrying out formation and aging tests on the battery after packaging to obtain the square flexible package battery with the length, width and thickness of 32mm, 82mm and 4.2mm respectively.
Example 2
Preparation of a negative electrode:
firstly, 1 kg of silicon active material is put into 4 kg of butyl acetate to be stirred, a certain amount of flexible hydroxyl-terminated multifunctional polyether resin is added to be quickly stirred and the silicon active material is fully dispersed, and then 1.1 equivalent of toluene diisocyanate (the sum of the amounts of the flexible hydroxyl-terminated multifunctional polyether resin and the toluene diisocyanate is about 0.25 kg) is added to be uniformly stirred. And (3) carrying out spray drying on the dispersion liquid, and collecting the dried coated silicon active material for later use.
The negative electrode slurry formula comprises, by weight, 1.5% of sodium carboxymethylcellulose, 3.5% of sodium alginate, 1.5% of conductive carbon black, 0.5% of carbon nanotubes and 93% of a silicon-coated active material. In the slurry preparation process, the solvent is water, and the water accounts for 60% of the total slurry.
Firstly, adding water, sodium carboxymethylcellulose and sodium alginate into a stirrer according to the formula, and completely dissolving the materials in a vacuum state to obtain an aqueous polymer solution; adding the conductive carbon black and the carbon nano tube into the dissolved aqueous polymer solution according to the formula, and quickly stirring until the fineness is below 5 mu m; then adding the silicon-coated active material according to the formula, and accelerating the stirring until the fineness is below 30 mu m; and (4) uniformly stirring at a low speed in vacuum, and filtering by using a 150-mesh stainless steel screen to obtain the required cathode slurry.
Uniformly coating the slurry on two sides of a copper foil with the thickness of 8 mu m, drying, removing water at high temperature in vacuum, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the negative pole piece.
Preparation of the positive electrode:
lithium cobaltate (LiCoO) was used for the positive electrode2) As active substance. The positive electrode slurry containing the active material was prepared according to a formulation, and the solid content of the slurry contained 90% of the positive electrode active material, 5% of PVDF (polyvinylidene fluoride) binder, and 5% of conductive carbon black in terms of dry weight percentage. The slurry used N-methylpyrrolidone (NMP) as the solvent, and the solids content of the slurry was 40%.
Adding N-methyl pyrrolidone (NMP) and PVDF into a stirrer according to the formula, completely dissolving in a vacuum state to obtain a PVDF solution, adding conductive carbon black into the dissolved oily PVDF solution according to the formula, quickly stirring until the fineness is below 5 mu m, finally adding lithium cobaltate according to the formula, and uniformly stirring in a vacuum state. Filtering with a 200-mesh stainless steel screen to obtain the required anode slurry.
And uniformly coating the slurry on two sides of an aluminum foil with the thickness of 12 mu m, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the positive plate.
The separator is a Polyethylene (PE) porous membrane with the thickness of 12 um.
Preparing electrolyte:
mixing ethylene carbonate EC, propylene carbonate PC and dimethyl carbonate DMC according to a volume ratio of 3: 3: 4 preparing a mixed solvent, and then adding a solute lithium hexafluorophosphate (LiPF)6) And make LiPF6The concentration of (A) is 1M, and the electrolyte is obtained after uniform stirring.
Assembling the battery:
and winding the positive electrode, the diaphragm and the negative electrode to form a battery core, packaging the battery core by using an aluminum plastic film, injecting the electrolyte, and carrying out formation and aging tests on the battery after packaging to obtain the square flexible package battery with the length, width and thickness of 32mm, 82mm and 4.2mm respectively.
Example 3
Preparation of a negative electrode:
firstly, 1 kg of silicon active material is put into 4 kg of butyl acetate and stirred, 0.25 kg of polyacrylate copolymer (methyl methacrylate: butyl acrylate: acrylic acid: hydroxymethyl acrylamide: 34:60:4:2) is added, and the mixture is rapidly stirred until the silicon active material is uniformly dispersed. And (3) carrying out spray drying on the dispersion liquid, and collecting the dried coated silicon active material for later use.
The negative electrode slurry formula comprises, by dry weight percent, 5% of polyacrylic acid derivatives (acrylic acid: hydroxyethyl acrylate: hydroxymethyl acrylamide: 70:25:5), 1.5% of conductive carbon black, 0.5% of carbon nanotubes and 93% of a silicon-coated active material. In the slurry preparation process, the solvent is water, and the water accounts for 60% of the total slurry.
Firstly, adding water and polyacrylic acid derivatives into a stirrer according to the formula, and completely dissolving the water and the polyacrylic acid derivatives in a vacuum state to obtain an aqueous polymer solution; adding the conductive carbon black and the carbon nano tube into the dissolved aqueous polymer solution according to the formula, and quickly stirring until the fineness is below 5 mu m; then adding the silicon-coated active material according to the formula, and accelerating the stirring until the fineness is below 30 mu m; and (4) uniformly stirring at a low speed in vacuum, and filtering by using a 150-mesh stainless steel screen to obtain the required cathode slurry.
Uniformly coating the slurry on two sides of a copper foil with the thickness of 8 mu m, drying, removing water at high temperature in vacuum, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the negative pole piece.
Preparation of the positive electrode:
lithium cobaltate (LiCoO) was used for the positive electrode2) As active substance. The positive electrode slurry containing the active material was prepared according to a formulation, and the solid content of the slurry contained 90% of the positive electrode active material, 5% of PVDF (polyvinylidene fluoride) binder, and 5% of conductive carbon black in terms of dry weight percentage. The slurry used N-methylpyrrolidone (NMP) as the solvent, and the solids content of the slurry was 40%.
Adding N-methyl pyrrolidone (NMP) and PVDF into a stirrer according to the formula, completely dissolving in a vacuum state to obtain a PVDF solution, adding conductive carbon black into the dissolved oily PVDF solution according to the formula, quickly stirring until the fineness is below 5 mu m, finally adding lithium cobaltate according to the formula, and uniformly stirring in a vacuum state. Filtering with a 200-mesh stainless steel screen to obtain the required anode slurry.
And uniformly coating the slurry on two sides of an aluminum foil with the thickness of 12 mu m, compacting the pole piece by using a roller press, cutting the piece, and welding a tab to obtain the positive plate.
The separator is a Polyethylene (PE) porous membrane with the thickness of 12 um.
Preparing electrolyte:
mixing ethylene carbonate EC, propylene carbonate PC and dimethyl carbonate DMC according to a volume ratio of 3: 3: 4 preparing a mixed solvent, and then adding a solute lithium hexafluorophosphate (LiPF)6) And make LiPF6The concentration of (A) is 1M, and the electrolyte is obtained after uniform stirring.
Assembling the battery:
and winding the positive electrode, the diaphragm and the negative electrode to form a battery core, packaging the battery core by using an aluminum plastic film, injecting the electrolyte, and carrying out formation and aging tests on the battery after packaging to obtain the square flexible package battery with the length, width and thickness of 32mm, 82mm and 4.2mm respectively.
TABLE 1 gram Capacity exertion, Pole piece swelling, and cycle life of examples 1-3 and comparative examples 1-2
As can be seen from table 1, the lithium ion battery negative electrode of the present invention employs the high-capacity negative electrode bonding system of the present invention, which effectively suppresses the expansion of the electrode sheet and improves the cycle life, compared to a negative electrode employing SBR and sodium carboxymethylcellulose as the binder.
In summary, the high-capacity negative electrode bonding system of the invention is adopted in the negative electrode of the invention, and comprises the elastic wrapping layer, the water-soluble polymer and other auxiliary additives which are wrapped on the high-capacity negative electrode active material, so that the expansion of the pole piece can be effectively inhibited and the cycle life can be improved.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (10)
1. A high capacity anode binding system for binding an anode active material to form an anode active material layer, comprising: the negative electrode comprises an elastic wrapping layer wrapping the surface of the negative electrode active material and a water-soluble polymer connected with the elastic wrapping layer.
2. The high capacity negative electrode binder system of claim 1, wherein the elastic wrapping has an elastic modulus of 0.1MPa to 200MPa and an elongation at break of greater than 20%.
3. The high capacity negative electrode binder system of claim 1, wherein the thickness of the elastic wrap is between 10nm and 500 nm.
4. The high capacity negative electrode binder system of claim 1, wherein the elastic wrap comprises an elastic material;
the elastic material includes: at least one of a polyether amine elastic material, an epoxy resin elastic material, a polyether resin elastic material, a polyurethane elastic material, a polystyrene elastic material, a polyacrylate elastic material, a polyethylene elastic material, a polypropylene elastic material, a polyamide elastic material, a styrene butadiene rubber material, a nitrile butadiene rubber material, an ethylene propylene rubber material and a silicon rubber material.
5. The high capacity negative electrode binder system of claim 1, wherein the water soluble polymer comprises: at least one of sodium carboxymethylcellulose, sodium alginate, polyacrylic acid, polymethacrylic acid, polyacrylamide and polysaccharide polymer.
6. A lithium ion battery negative electrode, comprising: a negative electrode current collector, a negative electrode active material layer formed on the negative electrode current collector;
wherein the anode active material layer includes: the high-capacity negative electrode comprises a negative electrode active material, an elastic wrapping layer wrapping the surface of the negative electrode active material, a water-soluble polymer connected with the elastic wrapping layer to form the high-capacity negative electrode binding system according to claim 1, and a conductive agent and an auxiliary additive which are dispersed in the negative electrode active material layer.
7. The lithium ion battery anode of claim 6, wherein the supplemental additive comprises: at least one of multifunctional aziridine, multifunctional polycarbodiimide, multifunctional isocyanate, multifunctional epoxy resin, iron ion, copper ion and organic tin catalyst.
8. The lithium ion battery negative electrode of claim 6, wherein the negative electrode active material is a silicon active material.
9. The negative electrode for lithium ion batteries according to claim 6, wherein the weight of the water-soluble polymer in the negative electrode active material layer is 1 to 10% of the weight of the negative electrode active material.
10. A lithium ion battery comprising the negative electrode for a lithium ion battery according to claim 6.
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| CN117154101A (en) * | 2023-10-31 | 2023-12-01 | 宁德时代新能源科技股份有限公司 | Secondary battery, method for manufacturing the same, and power consumption device |
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| CN117154101B (en) * | 2023-10-31 | 2024-03-29 | 宁德时代新能源科技股份有限公司 | Secondary battery, method for manufacturing the same, and power consumption device |
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