CN113363589A - Lithium ion battery and preparation method thereof - Google Patents

Lithium ion battery and preparation method thereof Download PDF

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Publication number
CN113363589A
CN113363589A CN202110547849.0A CN202110547849A CN113363589A CN 113363589 A CN113363589 A CN 113363589A CN 202110547849 A CN202110547849 A CN 202110547849A CN 113363589 A CN113363589 A CN 113363589A
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lithium
lithium ion
negative electrode
ion battery
battery cell
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李莉
胡小勇
杜晨树
陶德瑜
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Dongguan Weike Battery Co ltd
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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • H01M4/602—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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative 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
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    • Y02E60/10—Energy storage using batteries
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Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery and a preparation method thereof, wherein the preparation method comprises the following steps: step (A): mixing graphite, conductive carbon black, lithium carboxymethyl cellulose, N-methyl pyrrolidone, styrene butadiene rubber and water according to a certain mass ratio to prepare a negative electrode material, and coating the negative electrode material on the surface of a foil to prepare a negative electrode sheet; step (B): assembling the positive plate, the diaphragm and the negative plate into a battery cell, and putting the battery cell into a formed aluminum-plastic film to be dried until the water content is less than 150ppm to obtain a semi-finished battery cell; step (C): preparing an electrolyte; step (D): and injecting the electrolyte into the semi-finished product battery cell, standing at 40-50 ℃, forming, shaping and grading to obtain the lithium ion battery. The preparation method can improve the lithium ion transmission efficiency and the utilization rate of active substances, effectively reduce flatulence and improve the high-temperature performance.

Description

Lithium ion battery and preparation method thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery and a preparation method thereof.
Background
With the continuous development of modern society, electronic products are widely applied, and lithium ion batteries, as a novel green energy source, have the advantages of high energy density, good safety performance, long cycle life, low self-discharge and the like, and are widely applied to 3C electronic products. However, in the intense competition of the market, the demand of 3C electronic products is continuously increasing. Taking a lithium ion battery for a notebook computer as an example, the lithium ion battery can not be used at a high environmental temperature, the battery is easy to have a gas expansion problem, the electrical performance is greatly damaged, and the user experience is seriously influenced.
Disclosure of Invention
The invention aims to: aiming at the defects of the prior art, the preparation method of the lithium ion battery is provided, the lithium ion transmission efficiency and the utilization rate of active substances can be improved, the flatulence is effectively reduced, and the high-temperature performance is improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a lithium ion battery comprises the following steps:
step (A): graphite, conductive carbon black, lithium carboxymethyl cellulose, styrene butadiene rubber, N-methyl pyrrolidone and water are mixed according to the mass part ratio of 40-50: 0.2-0.5: 0.5-1.0: 1-1.5: 0.4-0.6:
mixing 50-55 to prepare a negative electrode material, and coating the negative electrode material on the surface of the foil to prepare a negative electrode sheet;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is less than 150ppm to prepare a semi-finished battery cell;
step (C): preparing an electrolyte;
step (D): and (4) injecting the electrolyte prepared in the step (C) into the semi-finished product battery core prepared in the step (B), standing at 40-50 ℃, forming, shaping and grading to prepare the lithium ion battery.
Preferably, the electrolyte comprises the following components in a mass ratio of 80-90: 5-10: 0.1-10 of lithium salt, organic solvent and additive.
Preferably, the lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis oxalate borate, lithium bis (trifluoromethyl) sulfonyl imide and lithium bis fluorosulfonyl imide, and the concentration of the lithium salt is 0.7-1.5 mol/L.
Preferably, the organic solvent includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl n-butyrate, and γ -butyrolactone.
Preferably, each part of the additive comprises 0.1-2.5 parts of organic film-forming additive and 0.1-1.5 parts of overcharge protection agent by mass.
Preferably, the organic film-forming additive is one or a mixture of vinylene carbonate and 1, 3-propane sultone; the overcharge protective agent is one or a mixture of 1, 3-propenyl-propane sultone and dinitramide ammonium salt.
Preferably, the foil is one of aluminum material, copper material and tin material.
Preferably, the degree of substitution of the lithium carboxymethyl cellulose is 90 to 99, and the number average molecular weight of the lithium carboxymethyl cellulose is 1.2 x 105～1.5×105。
Preferably, the viscosity of the negative electrode material is 1500-4000 mPa & s.
Another object of the present invention is to: a lithium ion battery effectively reduces flatulence and improves high-temperature performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a lithium ion battery is prepared by the preparation method of the lithium ion battery.
Compared with the prior art, the invention has the beneficial effects that: according to the preparation method of the lithium ion battery, the lithium is supplemented to the negative electrode by using the lithium carboxymethyl cellulose, so that the dispersion stability of the graphite slurry can be improved, the lithium ion transmission efficiency and the utilization rate of active substances are improved, and the service life is prolonged; an organic film forming additive and an overcharge protective agent are added into the electrolyte, so that a damaged SEI film can be repaired, the negative electrode and the electrolyte are prevented from reacting to generate gas, and the high-temperature performance of the electrolyte is improved; the manufacturing process is strictly controlled, the water content of the naked electric core and the shell is controlled to be below 150ppm before liquid injection, high-temperature standing is carried out after liquid injection, the process of side reaction between partial components in electrolyte and a negative electrode is accelerated, gas is prevented from being generated by reaction in a high-temperature environment in the later stage, and the high-temperature performance is improved.
Drawings
FIG. 1 is a graph showing the thickness expansion rate at a temperature of 85 ℃ as a function of storage time for example 1 and comparative examples 1 to 7.
FIG. 2 is a graph showing the capacity retention rate at 45 ℃ according to the number of cycles of charge and discharge in this example 1 and comparative examples 1 to 7.
Detailed Description
1. A preparation method of a lithium ion battery comprises the following steps:
step (A): graphite, conductive carbon black, lithium carboxymethyl cellulose, styrene butadiene rubber, N-methyl pyrrolidone and water are mixed according to the mass part ratio of 40-50: 0.2-0.5: 0.5-1.0: 1-1.5: 0.4-0.6:
mixing 50-55 to prepare a negative electrode material, and coating the negative electrode material on the surface of the foil to prepare a negative electrode sheet;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is less than 150ppm to prepare a semi-finished battery cell;
step (C): preparing an electrolyte;
step (D): and (4) injecting the electrolyte prepared in the step (C) into the semi-finished product battery core prepared in the step (B), standing at 40-50 ℃, forming, shaping and grading to prepare the lithium ion battery.
Wherein, each part of additive comprises 0.1 to 2.5 parts of organic film forming additive and 0.1 to 1.5 parts of overcharge protection agent by mass; the organic film-forming additive is one or a mixture of two of vinylene carbonate and 1, 3-propane sultone; the overcharge protection agent is one or two of 1, 3-propenyl-propane sultone and dinitramide ammonium salt. When the battery is stored at high temperature and full power, the SEI protective film of the negative electrode is damaged, and the film-forming additive in the electrolyte can repair the damaged SEI film, so that the side reaction of gas generation between the negative electrode and the electrolyte is avoided, and the high-temperature performance of the battery is improved. The overcharge protection agent can protect the battery from overcharge when the battery is overcharged. The organic film-forming additive is one or a mixture of vinylene carbonate and 1, 3-propane sultone, and preferably, each part of the organic film-forming additive comprises 1 part of vinylene carbonate and 2.5 parts of 1, 3-propane sultone by mass. The overcharge protection agent is one or a mixture of two of 1, 3-propenyl-propane sultone and dinitramide ammonium salt, and preferably, each overcharge protection agent comprises 0.5 part of 1, 3-propenyl-propane sultone and 1.5 parts of dinitramide ammonium salt. The step (A) is mainly from the perspective of lithium supplement, the step (B) and the step (D) are mainly from the perspective of a manufacturing process, the step (C) is mainly from the perspective of electrolyte improvement, the step (B) and the step (D) complement each other and jointly improve the high-temperature performance, if only a single measure is used, the improvement effect is very limited, and meanwhile, the technical scheme has no loss on the energy density of the battery, does not need to transform equipment and has the capacity of mass production. The shell can be one of a formed aluminum-plastic film, an aluminum shell or a stainless steel shell.
Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis oxalato borate, lithium bis (trifluoromethyl) sulfonimide and lithium bis fluorosulfonimide.
Preferably, the concentration of the lithium salt is 0.7-1.5 mol/L.
Preferably, the organic solvent includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl n-butyrate, and γ -butyrolactone.
Preferably, the foil is one of aluminum material, copper material and tin material.
Preferably, the degree of substitution of the lithium carboxymethyl cellulose is 90 to 99, and the number average molecular weight of the lithium carboxymethyl cellulose is 1.2 × 105～1.5×105。
Preferably, the viscosity of the negative electrode material is 1500-4000 mPa & s.
2. A lithium ion battery is prepared by the preparation method of the lithium ion battery.
The present invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the embodiments of the invention are not limited thereto.
Example 1
A preparation method of a lithium ion battery comprises the following steps:
step (A): graphite, conductive carbon black, lithium carboxymethyl cellulose, SBR (styrene butadiene rubber), N-methyl pyrrolidone and water are mixed according to the mass part ratio of 50: 0.5: 0.7: 1.2: 0.5: 50, mixing to obtain a negative electrode material, and coating the negative electrode material on the surface of the foil to obtain a negative electrode plate;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is less than 150ppm to prepare a semi-finished battery cell;
step (C): lithium salt, organic solvent and additive are mixed according to the mass ratio of 85: 10: 1.5 mixing to prepare electrolyte;
step (D): injecting the electrolyte into the semi-finished product battery cell prepared in the step (B), standing for 24 hours at 40 ℃, forming, shaping and grading to prepare the lithium ion battery;
wherein, each part of additive comprises 0.1 part of organic film forming additive and 1.5 parts of overcharge protection agent by mass; each part of the organic film-forming additive comprises 1 part of vinylene carbonate and 2.5 parts of 1, 3-propane sultone by mass. Each part of overcharge protection agent comprises 0.5 part of 1, 3-propenyl-propane sultone and 1.5 parts of dinitramide ammonium salt. When the battery is stored at high temperature and full power, the SEI protective film of the negative electrode is damaged, and the film-forming additive in the electrolyte can repair the damaged SEI film, so that the side reaction of gas generation between the negative electrode and the electrolyte is avoided, and the high-temperature performance of the battery is improved. The overcharge protection agent can protect the battery from overcharge when the battery is overcharged.
Preferably, the lithium salt is lithium hexafluorophosphate.
Preferably, the concentration of the lithium salt is 1.2 mol/L.
Preferably, the organic solvent is ethylene carbonate.
Preferably, the foil is an aluminum material.
Preferably, the degree of substitution of the lithium carboxymethyl cellulose is 95, and the number average molecular weight of the lithium carboxymethyl cellulose is 1.4 × 105。
Preferably, the viscosity of the negative electrode material is 3000mPa · s.
Example 2
A lithium ion battery and a preparation method thereof comprise the following steps:
step (A): graphite, conductive carbon black, lithium carboxymethyl cellulose, SBR (styrene butadiene rubber), N-methyl pyrrolidone and water are mixed according to the mass part ratio of 40: 0.3: 0.6: 1.1: 0.4: 50, mixing to obtain a negative electrode material, and coating the negative electrode material on the surface of the foil to obtain a negative electrode plate;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is 100ppm to prepare a semi-finished battery cell;
step (C): lithium salt, organic solvent and additive are mixed according to the mass ratio of 80: 5: 0.1, mixing to prepare an electrolyte;
step (D): injecting the electrolyte into the semi-finished product battery cell prepared in the step (B), standing for 24 hours at 40 ℃, forming, shaping and grading to prepare the lithium ion battery;
wherein, each part of additive comprises 0.1 part of organic film forming additive and 0.1 part of overcharge protection agent by mass; each part of the organic film-forming additive comprises 1 part of vinylene carbonate and 2.5 parts of 1, 3-propane sultone by mass. Each part of overcharge protection agent comprises 0.5 part of 1, 3-propenyl-propane sultone and 1.5 parts of dinitramide ammonium salt.
Preferably, the lithium salt is lithium tetrafluoroborate.
Preferably, the concentration of the lithium salt is 0.7 mol/L.
Preferably, the organic solvent is ethylene carbonate.
Preferably, the foil is an aluminum material.
Preferably, the degree of substitution of the lithium carboxymethyl cellulose is 90, and the number average molecular weight of the lithium carboxymethyl cellulose is 1.2 × 105。
Preferably, the viscosity of the negative electrode material is 1500mPa · s.
Example 3
A lithium ion battery and a preparation method thereof comprise the following steps:
step (A): graphite, conductive carbon black, lithium carboxymethyl cellulose, styrene butadiene rubber, N-methyl pyrrolidone and water are mixed according to the mass part ratio of 48: 0.4: 0.67: 1.3: 0.45: 52, mixing to obtain a negative electrode material, and coating the negative electrode material on the surface of the foil to obtain a negative plate;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is 120ppm to prepare a semi-finished battery cell;
step (C): lithium salt, organic solvent and additive are mixed according to the mass ratio of 85: 8: 6 mixing to prepare electrolyte;
step (D): injecting the electrolyte into the semi-finished product battery cell prepared in the step (B), standing for 24 hours at 45 ℃, forming, shaping and grading to prepare the lithium ion battery;
wherein, each part of additive comprises 2 parts of organic film forming additive and 1 part of overcharge protection agent by mass; each part of the organic film-forming additive comprises 1 part of vinylene carbonate and 2.5 parts of 1, 3-propane sultone by mass. Each part of overcharge protection agent comprises 0.5 part of 1, 3-propenyl-propane sultone and 1.5 parts of dinitramide ammonium salt.
Preferably, the lithium salt is lithium tetrafluoroborate.
Preferably, the concentration of the lithium salt is 1.2 mol/L.
Preferably, the organic solvent is propylene carbonate.
Preferably, the foil is copper material.
Preferably, the degree of substitution of the lithium carboxymethyl cellulose is 95, and the number average molecular weight of the lithium carboxymethyl cellulose is 1.3 × 105。
Preferably, the viscosity of the negative electrode material is 2500mPa · s.
Example 4
A lithium ion battery and a preparation method thereof comprise the following steps:
step (A): graphite, conductive carbon black, lithium carboxymethyl cellulose, SBR (styrene butadiene rubber), N-methyl pyrrolidone and water are mixed according to the mass part ratio of 46: 0.35: 0.7: 1.4: 0.5: 55, mixing to obtain a negative electrode material, and coating the negative electrode material on the surface of the foil to obtain a negative plate;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is 100ppm to prepare a semi-finished battery cell;
step (C): lithium salt, organic solvent and additive are mixed according to the mass ratio of 85: 6: 2 mixing to prepare an electrolyte;
step (D): injecting the electrolyte into the semi-finished product battery cell prepared in the step (B), standing for 24 hours at 46 ℃, forming, shaping and grading to prepare the lithium ion battery;
wherein, each part of additive comprises 1.5 parts of organic film forming additive and 0.5 part of overcharge protection agent by mass; each part of the organic film-forming additive comprises 1 part of vinylene carbonate and 2.5 parts of 1, 3-propane sultone by mass. Each part of overcharge protection agent comprises 0.5 part of 1, 3-propenyl-propane sultone and 1.5 parts of dinitramide ammonium salt.
Preferably, the lithium salt is lithium bis (oxalato) borate.
Preferably, the concentration of the lithium salt is 1.2 mol/L.
Preferably, the organic solvent is diethyl carbonate.
Preferably, the foil is an aluminum material.
Preferably, the degree of substitution of the lithium carboxymethyl cellulose is 99, and the number average molecular weight of the lithium carboxymethyl cellulose is 1.5 × 105。
Preferably, the viscosity of the negative electrode material is 4000mPa · s.
Example 5
A lithium ion battery and a preparation method thereof comprise the following steps:
step (A): graphite, conductive carbon black, lithium carboxymethyl cellulose, SBR (styrene butadiene rubber), N-methyl pyrrolidone and water are mixed according to the mass part ratio of 47: 0.3: 0.7: 1.2: 0.5: 52, mixing to obtain a negative electrode material, and coating the negative electrode material on the surface of the foil to obtain a negative plate;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is 90ppm to prepare a semi-finished battery cell;
step (C): lithium salt, organic solvent and additive are mixed according to the mass ratio of 90: 90: 7 mixing to prepare an electrolyte;
step (D): injecting the electrolyte into the semi-finished product battery cell prepared in the step (B), standing for 24 hours at 50 ℃, forming, shaping and grading to prepare the lithium ion battery;
wherein, each part of additive comprises 2 parts of organic film forming additive and 1.5 parts of overcharge protection agent by mass; each part of the organic film-forming additive comprises 1 part of vinylene carbonate and 2.5 parts of 1, 3-propane sultone by mass. Each part of overcharge protection agent comprises 0.5 part of 1, 3-propenyl-propane sultone and 1.5 parts of dinitramide ammonium salt.
Preferably, the lithium salt is lithium bis (trifluoromethyl) sulfonimide.
Preferably, the concentration of the lithium salt is 1.2 mol/L.
Preferably, the organic solvent is ethyl propionate.
Preferably, the foil is a tin material.
Preferably, the degree of substitution of the lithium carboxymethyl cellulose is 90, and the carboxymethyl cellulose isThe number average molecular weight of the lithium element is 1.4X 105。
Preferably, the viscosity of the negative electrode material is 2000mPa · s.
Example 6
A lithium ion battery and a preparation method thereof comprise the following steps:
step (A): graphite, conductive carbon black, lithium carboxymethyl cellulose, styrene butadiene rubber, N-methyl pyrrolidone and water are mixed according to the mass part ratio of 48: 0.25: 0.7: 1.4: 0.5: 52, mixing to obtain a negative electrode material, and coating the negative electrode material on the surface of the foil to obtain a negative plate;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is 100ppm to prepare a semi-finished battery cell;
step (C): lithium salt, organic solvent and additive are mixed according to the mass ratio of 80: 5: 5 mixing to prepare electrolyte;
step (D): injecting the electrolyte into the semi-finished product battery cell prepared in the step (B), standing for 24 hours at 45 ℃, forming, shaping and grading to prepare the lithium ion battery;
wherein, each part of additive comprises 2.5 parts of organic film forming additive and 1.5 parts of overcharge protection agent by mass; the organic film-forming additive is one or a mixture of two of vinylene carbonate and 1, 3-propane sultone; each part of the organic film-forming additive comprises 1 part of vinylene carbonate and 2.5 parts of 1, 3-propane sultone by mass. Each part of overcharge protection agent comprises 0.5 part of 1, 3-propenyl-propane sultone and 1.5 parts of dinitramide ammonium salt.
Preferably, the lithium salt is lithium bis (fluorosulfonyl) imide.
Preferably, the concentration of the lithium salt is 0.7 mol/L.
Preferably, the organic solvent is ethyl n-butyrate.
Preferably, the foil is an aluminum material.
Preferably, the degree of substitution of the lithium carboxymethyl cellulose is 99, and the number average molecular weight of the lithium carboxymethyl cellulose is 1.4 × 105。
Preferably, the viscosity of the negative electrode material is 3500mPa · s.
Comparative example 1
The difference from example 1 is that:
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is 300ppm to prepare a semi-finished battery cell;
step (D): and (C) injecting the electrolyte into the semi-finished product battery cell prepared in the step (B), standing for 24 hours at normal temperature, forming, shaping and grading to obtain the lithium ion battery.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 2
The difference from example 1 is that:
step (C): lithium salt and an organic solvent are mixed according to the mass part ratio of 85: 10 mixing to prepare an electrolyte;
the rest is the same as embodiment 1, and the description is omitted here.
Comparative example 3
The difference from example 1 is that:
step (A): graphite, conductive carbon black, sodium carboxymethyl cellulose, styrene butadiene rubber, N-methyl pyrrolidone and water are mixed according to the mass part ratio of 42: 0.5: 0.7: 1.3: 0.5: 50, mixing to obtain a negative electrode material, and coating the negative electrode material on the surface of the foil to obtain a negative electrode plate;
the rest is the same as embodiment 1, and the description is omitted here.
Comparative example 4
The difference from example 1 is that:
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is 300ppm to prepare a semi-finished battery cell;
step (C): lithium salt and an organic solvent are mixed according to the mass part ratio of 85: 10 mixing to prepare an electrolyte;
step (D): and (C) injecting the electrolyte into the semi-finished product battery cell prepared in the step (B), standing for 24 hours at normal temperature, forming, shaping and grading to obtain the lithium ion battery.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 5
The difference from example 1 is that:
step (A): graphite, conductive carbon black, sodium carboxymethyl cellulose, SBR (styrene butadiene rubber), N-methyl pyrrolidone and water are mixed according to the mass part ratio of 45: 0.4: 0.8: 1.4: 0.5: 52, mixing to obtain a negative electrode material, and coating the negative electrode material on the surface of the foil to obtain a negative plate;
step (C): lithium salt, organic solvent and additive are mixed according to the mass ratio of 85: 10: 7 mixing to prepare an electrolyte;
the rest is the same as embodiment 1, and the description is omitted here.
Comparative example 6
The difference from example 1 is that:
step (A): graphite, conductive carbon black, sodium carboxymethyl cellulose, styrene butadiene rubber, N-methyl pyrrolidone and water are mixed according to the mass part ratio of 45: 0.5: 0.8: 1.4: 0.5: 53 mixing to obtain a negative electrode material, and coating the negative electrode material on the surface of the foil to obtain a negative plate;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is 120ppm to prepare a semi-finished battery cell;
step (D): and (C) injecting the electrolyte into the semi-finished product battery cell prepared in the step (B), standing for 24 hours at the temperature of 40-50 ℃, forming, shaping and grading to obtain the lithium ion battery.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 7
The difference from example 1 is that:
a preparation method of a lithium ion battery comprises the following steps:
step (A): graphite, conductive carbon black, sodium carboxymethyl cellulose, styrene butadiene rubber, N-methyl pyrrolidone and water are mixed according to the mass part ratio of 48: 0.5: 0.7: 1.2: 0.5: 48, mixing to obtain a negative electrode material, and coating the negative electrode material on the surface of the foil to obtain a negative electrode sheet;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is 300ppm to prepare a semi-finished battery cell;
step (C): lithium salt and an organic solvent are mixed according to the mass ratio of 85: 10 mixing to prepare an electrolyte;
step (D): injecting the electrolyte into the semi-finished product battery cell prepared in the step (B), standing for 24 hours at normal temperature, forming, shaping and grading to prepare the lithium ion battery;
the rest is the same as embodiment 1, and the description is omitted here.
Performance testing
1. The prepared battery is stored in a temperature environment of 85 ℃ under the full electric condition, the thermal state thickness is recorded every 4 hours, and the expansion rate of the thermal state thickness is less than 10 percent as a judgment standard. As shown in figure 1 and table 1.
Example 1 was taken as group 8, comparative example 1 was taken as group 7, comparative example 2 was taken as group 6, comparative example 3 was taken as group 5, comparative example 4 was taken as group 4, comparative example 5 was taken as group 3, comparative example 6 was taken as group 2, and comparative example 7 was taken as group 1.
2. The prepared battery is subjected to 1C charging and 1C discharging circulation in a 45 ℃ environment, the capacity retention rate is recorded, and the capacity retention rate is larger than 80 percent and serves as a judgment standard. As shown in figure 2 and table 2.
Example 1 was taken as group 8, comparative example 1 was taken as group 7, comparative example 2 was taken as group 6, comparative example 3 was taken as group 5, comparative example 4 was taken as group 4, comparative example 5 was taken as group 3, comparative example 6 was taken as group 2, and comparative example 7 was taken as group 1.
TABLE 1
Figure BDA0003074183170000121
As can be seen from fig. 1 and table 1, group 8, i.e., example 1, can maintain the thickness expansion rate below 10% for 72 hours at high temperature, and has a longer time and excellent electrical properties compared to the prior art, i.e., group 1, which has a 24 hour expansion rate.
Meanwhile, as can be seen from groups 2 to 8, when the influence factors (such as water content control, high-temperature standing, lithium supplement to the negative electrode by using lithium carboxymethyl cellulose, preparation of an electrolyte solution with an organic film-forming additive and an overcharge protection agent) in the preparation method of the lithium ion battery are reduced, the performance of the prepared battery is poor, and when the preparation method of the lithium ion battery is used, namely the factors are simultaneously controlled, the prepared battery has excellent electrical properties, and is better in performance and longer in service life compared with the battery prepared by the prior art.
TABLE 2
Group of 1 2 3 4 5 6 7 8 Remarks for note
Number of cycles ～400 ～430 ～500 ～480 ～560 ～530 ～590 ～620 The capacity retention rate is less than 10 percent
As can be seen from fig. 2 and table 2, group 8, i.e., example 1, after 1C charge and 1C discharge cycles in a 45C environment, still maintained 90% of the capacity after 600 cycles of charge and discharge, whereas the prior art had poor battery performance when the capacity decreased to below 70% after 600 cycles of charge and discharge.
Meanwhile, as can be seen from groups 2 to 8, when the influence factors (such as water content control, high-temperature standing, lithium supplement to the negative electrode by using lithium carboxymethyl cellulose, preparation of an electrolyte solution with an organic film-forming additive and an overcharge protection agent) in the preparation method of the lithium ion battery are reduced, the performance of the prepared battery is poor, and when the preparation method of the lithium ion battery is used, namely the factors are simultaneously controlled, the prepared battery has excellent electrical properties, and is better in performance and longer in service life compared with the battery prepared by the prior art.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (10)

1. A preparation method of a lithium ion battery is characterized by comprising the following steps: the method comprises the following steps:
step (A): graphite, conductive carbon black, lithium carboxymethyl cellulose, styrene butadiene rubber, N-methyl pyrrolidone and water are mixed according to the mass ratio of 40-50: 0.2-0.5: 0.5-1.0: 1-1.5: 0.4-0.6: mixing 50-55 to prepare a negative electrode material, and coating the negative electrode material on the surface of the foil to prepare a negative electrode sheet;
step (B): assembling the positive plate, the diaphragm and the negative plate prepared in the step (A) into a battery cell, and putting the battery cell into a shell and drying until the water content is less than 150ppm to prepare a semi-finished battery cell;
step (C): preparing an electrolyte;
step (D): and (4) injecting the electrolyte prepared in the step (C) into the semi-finished product battery core prepared in the step (B), standing at 40-50 ℃, forming, shaping and grading to prepare the lithium ion battery.
2. The method of claim 1, wherein the method comprises: the electrolyte comprises the following components in parts by mass: 5-10: 0.1-10 of lithium salt, organic solvent and additive.
3. The method of claim 2, wherein the step of preparing the lithium ion battery comprises: the lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium bis (trifluoromethyl) sulfimide and lithium bis (fluorosulfonyl) imide, and the concentration of the lithium salt is 0.7-1.5 mol/L.
4. The method of claim 2, wherein the step of preparing the lithium ion battery comprises: the organic solvent comprises at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl n-butyrate and gamma-butyrolactone.
5. The method of claim 2, wherein the step of preparing the lithium ion battery comprises: each part of the additive comprises 0.1-2.5 parts of organic film forming additive and 0.1-1.5 parts of overcharge protection agent by mass.
6. The method according to claim 5, wherein the method comprises the following steps: the organic film-forming additive is one or a mixture of two of vinylene carbonate and 1, 3-propane sultone; the overcharge protective agent is one or a mixture of 1, 3-propenyl-propane sultone and dinitramide ammonium salt.
7. The method of claim 1, wherein the method comprises: the foil is one of aluminum material, copper material and tin material.
8. The method of claim 1, wherein the method comprises: the degree of substitution of the lithium carboxymethyl cellulose is 90-99, and the number average molecular weight of the lithium carboxymethyl cellulose is 1.2 multiplied by 105～1.5×105。
9. The method of claim 1, wherein the method comprises: the viscosity of the negative electrode material is 1500-4000 mPa & s.
10. A lithium ion battery, characterized by: the method for preparing the lithium ion battery according to any one of claims 1 to 9.
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