CN111525136A - Composite binder and application thereof in silicon cathode of lithium ion battery - Google Patents

Composite binder and application thereof in silicon cathode of lithium ion battery Download PDF

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Publication number
CN111525136A
CN111525136A CN202010365423.9A CN202010365423A CN111525136A CN 111525136 A CN111525136 A CN 111525136A CN 202010365423 A CN202010365423 A CN 202010365423A CN 111525136 A CN111525136 A CN 111525136A
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lithium ion
ion battery
silicon
composite binder
binder
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王辉
刘杰
赵而英
黎艳艳
张倩
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Qingdao University of Science and Technology
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Qingdao University of Science and Technology
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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
    • H01M4/621—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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of 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
    • H01M4/628—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
    • H01M2004/027—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
    • 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 composite binder and application thereof in a silicon cathode of a lithium ion battery. The composite binder consists of a polymer A and a polymer B, wherein the polymer A is polycarboxyl nitrile rubber, and the polymer B is guar gum; the weight percentage of the polymer A in the composite binder is 30-70%, and the weight percentage of the polymer B in the composite binder is 30-70%; the invention also provides a preparation method of the composite binder and application of the composite binder in a silicon cathode of a lithium ion battery. When the composite binder is used in a silicon cathode of a lithium ion battery, the polycarboxyl nitrile rubber and the guar gum form a hydrogen bond cross-linked three-dimensional network through in-situ thermal polymerization, so that the binding strength of the binder is improved, the binder has high elasticity, high viscosity and good mechanical property, the volume expansion of the silicon cathode is inhibited, and the cycling stability of the silicon cathode is obviously improved; the obtained lithium ion battery has high charge-discharge specific capacity, high coulombic efficiency and long service life.

Description

Composite binder and application thereof in silicon cathode of lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a composite binder and application thereof in a silicon cathode of a lithium ion battery.
Background
Currently, the energy problem and the environmental pollution problem are increasingly prominent, and there is an urgent need to develop an electrochemical storage device with environmental protection and high energy density. Since the last 90 s of the century, lithium ion batteries have been commercialized successfully, and are widely used in the field of portable electronic products such as notebook computers, cameras, smart phones, and the like, and are actively expanding to the fields of electric vehicles, wearable smart devices, and the like.
The lithium ion battery mainly comprises a positive electrode, a negative electrode, an electrolyte, a diaphragm and the like. At present, graphite is a commonly used negative electrode material in lithium ion batteries, but the theoretical specific capacity (375mA · h/g) is low, so that the application requirement of electric automobiles on high-energy density batteries cannot be met. However, silicon has excellent theoretical specific capacity which reaches 4200mA · h/g, and the silicon can replace graphite to become the most promising lithium ion battery negative electrode material.
Unfortunately, silicon has a fatal defect, silicon particles expand greatly when lithium ions are inserted into the silicon crystal, and silicon shrinks volumetrically to easily generate a large gap when the lithium ions are extracted from the silicon crystal; when silicon is used as a lithium ion battery cathode material, the lithium ion battery can undergo volume change of up to 300% in the lithium intercalation/lithium deintercalation process; such a large volume change easily causes separation of a part of the silicon particles from the conductive agent or the current collector, resulting in loss of active materials; the constant expansion and contraction of the silicon particles damages a Solid Electrolyte Interface (SEI) film on the surface of the electrode, and the thickness of the SEI film increases with the increase of cycle times, so that irreversible capacity is caused, the capacity of the battery is rapidly attenuated, the cycle stability is poor, and the commercial application of the battery is restricted.
In the lithium ion battery, the binder is an indispensable key material of the electrode, mainly plays a role in connecting an electrode active substance, a conductive agent and an electrode current collector, and maintains the structural integrity of the electrode, so that the impedance of the electrode is reduced. In addition, the binder is beneficial to promoting the mechanical property and the processability of the battery and meets the requirement of actual production. The silicon-based negative electrode material undergoes huge volume expansion in the charge and discharge processes, so that the requirement on the performance of the binder is stricter; conventional binders in silicon-based anode materials, such as: carboxymethyl cellulose/styrene butadiene rubber composite material (CMC/SBR), alginate ester and polyacrylic acid (PAA), the bonding strength of the binding agents is low, so that the charge-discharge specific capacity of the lithium ion battery is low; moreover, the silicon can not resist the cracking of the silicon and the disintegration of the electrode, thereby influencing the structural stability of the silicon cathode and reducing the service life of the lithium ion battery.
Disclosure of Invention
The invention provides a composite binder and application thereof in a lithium ion battery silicon negative electrode, and aims to solve the problems of low charge-discharge specific capacity, unstable structure and short service life of the binder for the lithium ion battery negative electrode in the prior art due to low bonding strength.
In order to solve the technical problems, the invention is mainly realized by the following technical scheme:
in one aspect, the composite binder for the lithium ion battery cathode consists of a polymer A and a polymer B, wherein the polymer A is polycarboxyl nitrile rubber, and the polymer B is guar gum; the weight percentage of the polymer A in the composite binder is 30-70%, and the weight percentage of the polymer B in the composite binder is 30-70%.
According to the invention, the polycarboxy nitrile rubber (XNBR) and the Guar Gum (GG) form a composite binder, the composite binder takes the guar gum as a framework, the high-elasticity and high-viscosity polycarboxy nitrile rubber is filled in the guar gum framework, the high elasticity and high viscosity of the polycarboxy nitrile rubber and the firm and good mechanical property of the guar gum are combined, the hard guar gum framework can inhibit the volume expansion of a silicon cathode, the high-elasticity polycarboxy nitrile rubber buffers the obvious volume change of the silicon anode, the high-viscosity polycarboxy nitrile rubber resists the breakage of silicon and the disintegration of an electrode, and the structural stability of the silicon cathode is fully ensured. The composite binder has high bonding strength and good tensile property, and the obtained silicon negative electrode sheet has a firm structure, is well suitable for the volume expansion of a silicon negative electrode, improves the charge-discharge specific capacity of a lithium ion battery, has high coulombic efficiency, improves the cycle stability of the lithium ion battery, and prolongs the service life of the lithium ion battery.
In a preferred embodiment, the weight percentage of the polymer A in the composite binder is 40-60%, and the weight percentage of the polymer B in the composite binder is 40-60%. In the composite binder, the content of the polycarboxyl nitrile rubber and the content of the guar gum can be further adjusted, so that the proportion of the polycarboxyl nitrile rubber and the guar gum is optimized, the interaction of the polycarboxyl nitrile rubber and the guar gum is promoted, the interaction effect between the polycarboxyl nitrile rubber and the guar gum is improved, and the comprehensive performance of the composite binder is further improved.
As a preferred embodiment, the solids content of the polymer A is from 40 to 45%. In the composite binder, the polycarboxy nitrile rubber exists in a latex form, the solid content of the polycarboxy nitrile rubber is 40-45%, and the solid content of the polycarboxy nitrile rubber is preferably 42% under normal conditions; the solid content of the polycarboxy nitrile rubber is controlled, so that the preparation of the composite binder is facilitated, and the operation is convenient; the guar gum is in a powder state, and the common guar gum in the market is selected as the guar gum.
In another aspect, the invention provides a preparation method of a composite binder for a lithium ion battery anode, comprising the following steps: and mixing and uniformly stirring the polymer A and the polymer B to obtain the composite binder. The preparation method of the composite binder is obtained by mixing and stirring the polymer A and the polymer B, and the preparation method of the composite binder is simple, convenient to operate and easy to realize industrialization; the obtained composite binder is convenient to store and easy to use.
In another aspect, the lithium ion battery negative plate comprises a negative current collector and an active coating coated on the surface of the negative current collector, wherein the active coating comprises the following components in parts by weight: 60-80 parts of silicon-based active substances; 10-20 parts of a conductive agent; 10-20 parts of the composite binder for the lithium ion battery negative electrode.
The lithium ion battery negative plate is also called as a silicon negative electrode, the silicon negative electrode comprises a negative electrode current collector and an active coating, the active coating is formed by bonding a silicon-based active substance, a conductive agent and a composite binder to the negative electrode current collector; the silicon cathode has firm structure and good cycling stability, and the lithium ion battery obtained by the silicon cathode has high charge-discharge specific capacity, good cycling stability and long service life.
As a preferred embodiment, the thickness of the active coating is 50 to 1500 μm; preferably, the loading amount of the silicon-based active material on the negative plate is 0.3-2.0mg/cm2. The thickness of the active coating in the lithium ion battery negative plate is regulated and controlled within the range of 50-1500 mu m, and the thickness of the active coating is regulated according to actual requirements, so that the lithium ion batteries with different purposes are obtained; the load capacity of the silicon-based active substance on the negative plate in the active coating of the negative plate of the lithium ion battery is usually 0.1-3mg/cm2The larger the load is, the smaller the cycle period of the lithium ion battery is, and the load of the silicon-based active substance on the negative plate is 3mg/cm2Then, the cycle period of the lithium ion battery is 50; preferably, the loading amount of the silicon-based active material on the negative plate is 0.3-2.0mg/cm2The lithium ion battery with the load has long cycle period and long service life.
As a preferred embodiment, the silicon-based active material is a silicon material or a silicon-carbon composite material. The silicon-based active substance can be a pure silicon material or a composite material of silicon and carbon. The silicon-based active substance is powder, namely silicon powder, and the silicon material has good specific capacity; the silicon-carbon composite material is composite powder of silicon and carbon, and has good electrical conductivity.
As a preferred embodiment, the silicon material is any one or more of nano silicon, micro silicon, porous silicon or amorphous silicon. The silicon material is used as the silicon-based active substance, and can be nano silicon particles, micron silicon particles, porous silicon particles or amorphous silicon particles, and the silicon material has the advantages of wide application range, convenient material taking, low price and easy obtainment.
As a preferred embodiment, the conductive agent is any one or more of graphite, acetylene black, Super P, Super S, graphene, carbon fiber, carbon nanotube, or ketjen black. The conductive agent of the invention can be selected from a plurality of types, is convenient to select materials, and has good conductivity, low price and good use performance.
In another aspect, the invention provides a method for preparing a lithium ion battery negative electrode sheet, which comprises the following steps: 1) adding a silicon-based active substance, a conductive agent and a composite binder into water, and uniformly grinding to obtain slurry; 2) coating the slurry obtained in the step 1) on the front and back surfaces of a negative current collector, performing vacuum drying, and cutting to obtain a negative plate.
In the preparation method of the lithium ion battery negative plate, the silicon-based active substance, the conductive agent and the composite binder are firstly added into water to prepare slurry, and the water is removed in the vacuum drying process, so that an active coating is formed on the surface of a negative current collector, and the negative plate with a stable structure is obtained; the preparation method of the lithium ion battery negative plate has the advantages of short process flow, simple preparation method, convenient operation, mild condition, no special requirement on equipment and easy realization of industrialization.
As a preferred embodiment, in the step 1), the viscosity of the slurry is 1000-4000 cp. In the preparation process of the lithium ion battery negative plate, water is only a dissolving medium, and the water is added to form slurry by the silicon-based active substance, the conductive agent and the composite binder, so that the slurry is easily coated on a negative current collector; the water can volatilize out during the subsequent vacuum drying, and the using amount of the water is usually 1000-4000 parts by weight; the viscosity of the slurry is controlled to be proper, so that the slurry is conveniently coated on the negative current collector, and the convenience of operation is improved.
As a preferred embodiment, in the step 1), the content of the composite binder in the slurry is 1-40% by weight. The invention can also control the use amount of the composite binder in the slurry by controlling the weight percentage content of the composite binder in the slurry, so as to obtain the lithium ion battery negative plate with firmer performance, further improve the cycle stability and prolong the service life of the lithium ion battery.
As a preferable embodiment, in the step 2), during vacuum drying, the vacuum degree is 0.1-1MPa, the drying temperature is 80-120 ℃, and the drying time is 10-15 h. The invention controls the vacuum drying process by controlling the vacuum degree, the drying temperature and the drying time, avoids the influence of overhigh temperature on the silicon-based active substance and the conductive agent, and leads the water in the slurry to be quickly volatilized so as to form a firm active coating on the surface of the negative current collector, and simultaneously, the active ingredients of the active coating cannot be damaged.
A lithium ion battery comprising the lithium ion battery negative electrode tab of any of the above. The lithium ion battery has the advantages of large first-cycle discharge capacity, good battery cycle stability, high capacity retention rate and long service life.
Compared with the prior art, the invention has the beneficial effects that: according to the composite binder, the polycarboxy nitrile rubber and the guar gum are used for forming the composite binder, the guar gum is used as a framework, the polycarboxy nitrile rubber is filled in the guar gum framework, the high elasticity and high viscosity of the polycarboxy nitrile rubber and the firm mechanical property of the guar gum are integrated, the hard guar gum framework can inhibit the volume expansion of a silicon cathode, the high elasticity polycarboxy nitrile rubber buffers the obvious volume change of a silicon anode, and the high viscosity polycarboxy nitrile rubber resists the breakage of silicon and the disintegration of an electrode; the composite binder has high bonding strength and good tensile property, and fully ensures the structural stability of the negative plate; the lithium ion battery obtained by the method has the advantages of large first-period discharge specific capacity, high coulombic efficiency, good battery cycle stability, high capacity retention rate and long service life. The composite binder and the preparation method of the negative plate prepared from the composite binder are simple to operate, mild in condition, free of special requirements for equipment, easy to realize industrialization, convenient to store and easy to use.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The composite binder for the lithium ion battery cathode comprises a polymer A and a polymer B, wherein the polymer A is polycarboxyl nitrile rubber, and the polymer B is guar gum; the weight percentage of the polymer A in the composite binder is 30-70%, and the weight percentage of the polymer B in the composite binder is 30-70%.
Preferably, the weight percentage of the polymer A in the composite binder is 40-60%, and the weight percentage of the polymer B in the composite binder is 40-60%.
Further, the solid content of the polymer A is 40-45%.
The invention relates to a preparation method of a composite binder for a lithium ion battery cathode, which comprises the following steps: and mixing and uniformly stirring the polymer A and the polymer B to obtain the composite binder.
The invention relates to a lithium ion battery negative plate, which comprises a negative current collector and an active coating coated on the surface of the negative current collector, wherein the active coating comprises the following components in parts by weight: 60-80 parts of silicon-based active substances; 10-20 parts of a conductive agent; 10-20 parts of the composite binder for the lithium ion battery negative electrode.
Preferably, the thickness of the active coating is 50-1500 μm; preferably, the loading amount of the silicon-based active material on the negative plate is 0.3-2.0mg/cm2。
Further, the silicon-based active substance is a silicon material or a silicon-carbon composite material.
Furthermore, the silicon material is any one or more of nano silicon, micron silicon, porous silicon or amorphous silicon.
Preferably, the conductive agent is any one or more of graphite, acetylene black, Super P, Super S, graphene, carbon fiber, carbon nanotube or Ketjen black.
The invention relates to a preparation method of a lithium ion battery negative plate, which comprises the following steps: 1) adding a silicon-based active substance, a conductive agent and a composite binder into water, and uniformly grinding to obtain slurry; 2) coating the slurry obtained in the step 1) on the surface of a negative current collector, vacuum drying, and cutting to obtain the electrode plate.
Preferably, in the step 1), the viscosity of the slurry is 1000-4000 cp.
Specifically, in the step 1), the weight percentage of the composite binder in the slurry is 1-40%.
Further, in the step 2), during vacuum drying, the vacuum degree is 0.1-1MPa, the drying temperature is 80-120 ℃, and the drying time is 10-15 h.
A lithium ion battery comprising the lithium ion battery negative electrode tab of any of the above.
Example 1
The invention relates to a preparation method of a lithium ion battery negative plate, which comprises the following steps:
1) mixing polycarboxyl nitrile rubber and guar gum according to the weight ratio of 4:6, and uniformly stirring to obtain a composite binder;
2) dispersing nano silicon powder, conductive agent carbon black (Super P) and the composite binder obtained in the step 1) in water, wherein the weight ratio of the nano silicon powder, the conductive agent carbon black (Super-P) and the composite binder obtained in the step 1) is 6:2:2, and uniformly grinding in a mortar to obtain slurry;
3) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 0.13MPa and the drying temperature of 80 ℃ for 12h, and then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely nano silicon powder, on the negative electrode plate is 0.6mg/cm2；
4) And (3) assembling the negative plate obtained in the step 3) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 11
The application of pure GG as a binder in a silicon negative electrode of a lithium battery is as follows:
1) dispersing nano silicon powder, conductive agent carbon black (Super-P) and a binder (GG) in water, wherein the weight ratio of the nano silicon powder to the conductive agent carbon black (Super-P) to the binder (GG) is 6:2:2, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 0.13MPa and the drying temperature of 80 ℃ for 12h, and then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely nano silicon powder, on the negative electrode plate is 0.6mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 12
The application of pure XNBR as a binder in a lithium battery silicon negative electrode is as follows:
1) dispersing nano silicon powder, conductive agent carbon black (Super-P) and a binder (XNBR) in water, wherein the weight ratio of the nano silicon powder to the conductive agent carbon black (Super-P) to the binder (XNBR) is 6:2:2, and uniformly grinding the nano silicon powder, the conductive agent carbon black (Super-P) and the binder (XNBR) in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 0.13MPa and the drying temperature of 80 ℃ for 12h, and then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely nano silicon powder, on the negative electrode plate is 0.6mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 13
The application of the existing commercially available binder in the lithium battery silicon negative electrode is that the binder is a sodium carboxymethylcellulose/styrene butadiene rubber composite material (CMC/SBR), and the weight ratio of the sodium carboxymethylcellulose to the styrene butadiene rubber in the binder is 5:
1) dispersing nano silicon powder, conductive agent carbon black (Super-P) and a binder (CMC/SBR) in water, wherein the weight ratio of the nano silicon powder, the conductive agent carbon black (Super-P) and the binder (CMC/SBR) is 6:2:2, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 0.13MPa and the drying temperature of 80 ℃ for 12h, and then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely nano silicon powder, on the negative electrode plate is 0.6mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Example 2
The invention relates to a preparation method of a lithium ion battery negative plate, which comprises the following steps:
1) mixing polycarboxyl nitrile rubber and guar gum according to the weight ratio of 5:5, and uniformly stirring to obtain a composite binder;
2) taking 60 parts of porous silicon powder, 10 parts of conductive agent acetylene black and 10 parts of composite binder obtained in the step 1), dispersing in 1000 parts of water, and uniformly grinding in a mortar to obtain slurry;
3) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 0.1MPa and the drying temperature of 120 ℃ for 10h, then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely porous silicon powder, on the negative electrode plate is 0.80mg/cm2；
4) And (3) assembling the negative plate obtained in the step 3) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 21
The application of pure GG as a binder in a silicon negative electrode of a lithium battery is as follows:
1) taking 60 parts of porous silicon powder, 10 parts of conductive agent acetylene black and 10 parts of binder (GG), dispersing in 1000 parts of water, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, and performing vacuum drying and vacuum treatmentDrying at 120 deg.C for 10h under 0.1MPa, and cutting into circular electrode plate with diameter of 12mm to obtain negative electrode plate with loading of active substance porous silicon powder of 0.80mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 22
The application of pure XNBR as a binder in a lithium battery silicon negative electrode is as follows:
1) taking 60 parts of porous silicon powder, 10 parts of conductive agent acetylene black and 10 parts of binder (XNBR), dispersing in 1000 parts of water, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 0.1MPa and the drying temperature of 120 ℃ for 10h, then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely porous silicon powder, on the negative electrode plate is 0.80mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 23
The application of the existing commercially available binder in the lithium battery silicon negative electrode is that the binder is a sodium carboxymethylcellulose/styrene butadiene rubber composite material (CMC/SBR), and the weight ratio of the sodium carboxymethylcellulose to the styrene butadiene rubber in the binder is 5:
1) taking 60 parts of porous silicon powder, 10 parts of conductive agent acetylene black and 10 parts of binder (CMC/SBR), dispersing in 1000 parts of water, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 0.1MPa and the drying temperature of 120 ℃ for 10h, then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely porous silicon powder, on the negative electrode plate is 0.80mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Example 3
The invention relates to a preparation method of a lithium ion battery negative plate, which comprises the following steps:
1) mixing polycarboxyl nitrile rubber and guar gum according to the weight ratio of 6:4, and uniformly stirring to obtain a composite binder;
2) taking 80 parts of amorphous silicon powder, 20 parts of conductive agent carbon black (Super S) and 20 parts of composite binder obtained in the step 1), dispersing in 4000 parts of water, and uniformly grinding in a mortar to obtain slurry;
3) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 1.0MPa and the drying temperature of 90 ℃ for 15h, then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely amorphous silicon powder, on the negative electrode plate is 1.20mg/cm2；
4) And (3) assembling the negative plate obtained in the step 3) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 31
The application of pure GG as a binder in a silicon negative electrode of a lithium battery is as follows:
1) taking 80 parts of amorphous silicon powder, 20 parts of conductive agent carbon black (Super S) and 20 parts of binder (GG), dispersing in 4000 parts of water, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 1.0MPa and the drying temperature of 90 ℃ for 15h, then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely amorphous silicon powder, on the negative electrode plate is 1.20mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 32
The application of pure XNBR as a binder in a lithium battery silicon negative electrode is as follows:
1) taking 80 parts of amorphous silicon powder, 20 parts of conductive agent carbon black (Super S) and 20 parts of binder (XNBR), dispersing in 4000 parts of water, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 1.0MPa and the drying temperature of 90 ℃ for 15h, then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely amorphous silicon powder, on the negative electrode plate is 1.20mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 33
The application of the existing commercially available binder in the lithium battery silicon negative electrode is that the binder is a sodium carboxymethylcellulose/styrene butadiene rubber composite material (CMC/SBR), and the weight ratio of the sodium carboxymethylcellulose to the styrene butadiene rubber in the binder is 5:
1) taking 80 parts of amorphous silicon powder, 20 parts of conductive agent carbon black (Super S) and 20 parts of binder (CMC/SBR), dispersing in 4000 parts of water, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the vacuum degree of 1.0MPa and the drying temperature of 90 ℃ for 15h, then cutting the copper foil into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely amorphous silicon powder, on the negative electrode plate is 1.20mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Example 4
The invention relates to a preparation method of a lithium ion battery negative plate, which comprises the following steps:
1) mixing polycarboxyl nitrile rubber and guar gum according to the weight ratio of 7:3, and uniformly stirring to obtain a composite binder;
2) dispersing a silicon-carbon composite material (nano silicon powder and asphalt composite material), a conductive agent carbon nano tube and the composite binder obtained in the step 1) in water, wherein the weight ratio of the silicon-carbon composite material to the conductive agent carbon nano tube to the composite binder obtained in the step 1) is 6:2:2, and uniformly grinding in a mortar to obtain slurry;
3) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the drying temperature of 110 ℃ for 12h, and then cutting into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of the active substance-silicon-carbon composite material on the negative electrode plate is 2.0mg/cm2；
4) And (3) assembling the negative plate obtained in the step 3) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 41
The application of pure GG as a binder in a silicon negative electrode of a lithium battery is as follows:
1) 80 parts of silicon-carbon composite material (nano silicon powder and asphalt composite material), conductive agent carbon nano tube and adhesive (GG) are dispersed in water, the weight ratio of the silicon-carbon composite material to the conductive agent carbon nano tube to the adhesive (GG) is 6:2:2, and the silicon-carbon composite material, the conductive agent carbon nano tube and the adhesive (GG) are uniformly ground in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the drying temperature of 110 ℃ for 12h, and then cutting into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of the active substance-silicon-carbon composite material on the negative electrode plate is 2.0mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 42
The application of pure XNBR as a binder in a lithium battery silicon negative electrode is as follows:
1) 80 parts of silicon-carbon composite material (nano silicon powder and asphalt composite material), conductive agent carbon nano tube and binder (XNBR) are taken and dispersed in water, the weight ratio of the silicon-carbon composite material to the conductive agent carbon nano tube to the binder (XNBR) is 6:2:2, and the materials are uniformly ground in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the drying temperature of 110 ℃ for 12h, and then cutting into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of the active substance-silicon-carbon composite material on the negative electrode plate is 2.0mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 43
The application of the existing commercially available binder in the lithium battery silicon negative electrode is that the binder is a sodium carboxymethylcellulose/styrene butadiene rubber composite material (CMC/SBR), and the weight ratio of the sodium carboxymethylcellulose to the styrene butadiene rubber in the binder is 5:
1) taking 80 parts of silicon-carbon composite material (nano silicon powder and asphalt composite material), conductive agent carbon nano tube and binder (CMC/SBR), dispersing in water, wherein the weight ratio of the silicon-carbon composite material to the conductive agent carbon nano tube to the binder (CMC/SBR) is 6:2:2, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at the drying temperature of 110 ℃ for 12h, and then cutting into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of the active substance-silicon-carbon composite material on the negative electrode plate is 2.0mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Example 5
The invention relates to a preparation method of a lithium ion battery negative plate, which comprises the following steps:
1) mixing polycarboxyl nitrile rubber and guar gum according to the weight ratio of 3:7, and uniformly stirring to obtain a composite binder;
2) dispersing micron silicon powder, conductive agent carbon black (Super-P) and the composite binder obtained in the step 1) in water, wherein the weight ratio of the micron silicon powder, the conductive agent carbon black (Super-P) and the composite binder obtained in the step 1) is 6:2:2, and uniformly grinding in a mortar to obtain slurry;
3) coating the slurry obtained in the step 2) on the surface of copper foil, vacuum drying at 80 ℃ for 12h, and then cutting into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely micron silicon powder, on the negative electrode plate is 0.3mg/cm2；
4) And (3) assembling the negative plate obtained in the step 3) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 51
The application of pure GG as a binder in a silicon negative electrode of a lithium battery is as follows:
1) dispersing micrometer silicon powder, conductive agent carbon black (Super-P) and a binder (GG) in water, wherein the weight ratio of the nanometer silicon powder, the conductive agent carbon black (Super-P) and the binder (GG) is 6:2:2, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at 80 ℃ for 12h, and then cutting into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely micron silicon powder, on the negative electrode plate is 0.3mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 52
The application of pure XNBR as a binder in a lithium battery silicon negative electrode is as follows:
1) dispersing micron silicon powder, conductive agent carbon black (Super-P) and a binder (XNBR) in water, wherein the weight ratio of the nano silicon powder, the conductive agent carbon black (Super-P) and the binder (XNBR) is 6:2:2, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at 80 ℃ for 12h, and then cutting into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely micron silicon powder, on the negative electrode plate is 0.3mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Comparative example 53
The application of the existing commercially available binder in the lithium battery silicon negative electrode is that the binder is a sodium carboxymethylcellulose/styrene butadiene rubber composite material (CMC/SBR), and the weight ratio of the sodium carboxymethylcellulose to the styrene butadiene rubber in the binder is 5:
1) dispersing micrometer silicon powder, conductive agent carbon black (Super-P) and binder (CMC/SBR) in water, wherein the weight ratio of the nanometer silicon powder, the conductive agent carbon black (Super-P) and the binder (CMC/SBR) is 6:2:2, and uniformly grinding in a mortar to obtain slurry;
2) coating the slurry obtained in the step 2) on the surface of a copper foil, drying in vacuum at 80 ℃ for 12h, and then cutting into a circular electrode plate with the diameter of 12mm to obtain a negative electrode plate, wherein the loading capacity of an active substance, namely micron silicon powder, on the negative electrode plate is 0.3mg/cm2；
3) And (3) assembling the negative plate obtained in the step 2) into a 2016 button cell by using a lithium plate as a counter electrode.
Experiment 1
The composite binder, the pure binder GG and the XNBR are respectively prepared into aqueous solutions, wherein the weight ratio of the GG to the XNBR is 3:7, 4:6, 5:5, 6:4, 7:3, 1:0 and 0:1, and the existing binder is a mixture of sodium carboxymethylcellulose and styrene butadiene rubber according to the weight ratio of 5: 5; stirring the obtained aqueous solution, placing the aqueous solution in a mould, and drying the aqueous solution in vacuum at the drying temperature of 80 ℃ for 12 hours to obtain a sample; the sample was cut out to obtain a test piece having dimensions of 30mm × 5mm × 0.4mm (length × width × thickness), and subjected to a tensile test at a tensile rate of 10mm/min, and the elongation at break thereof was recorded, and the results are shown in table 1.
TABLE 1 elongation at break of different binders
Figure BDA0002476387030000141
As can be seen from Table 1, pure GG is hard and brittle, and has low elongation at break and high breaking strength; pure XNBR has high elasticity and elongation at break of more than 200 percent; the elongation at break of the composite binder is between 180 and 190 percent under the buffering action of the XNBR; therefore, the elongation at break of the composite binder is obviously greater than that of pure GG and is close to that of XNBR; this demonstrates the excellent flexibility of the composite binder of the present invention.
As can be seen from table 1, the elongation at break of the composite binder of the present invention is much greater than that of the existing commercially available binder (sodium carboxymethylcellulose and styrene butadiene rubber composite), and therefore, the composite binder of the present invention has very good flexibility.
Experiment 2
The assembled 2016 button cells obtained in examples 1 to 5, comparative examples 11 to 13, comparative examples 21 to 23, comparative examples 31 to 33, comparative examples 41 to 43, and comparative examples 51 to 53 were put in an electrolyte solution of 1M LiPF for performance test, respectively6The electrolyte is a solution of ethylene carbonate EC/dimethyl carbonate DMC/diethyl carbonate DEC with a volume ratio of lithium salt of 1:1:1, the assembled battery is stood for 12 hours, and the stood battery is subjected to constant-current charging and discharging on a blue-ray test system, wherein the charging and discharging current is 1000mA/g, and the voltage range is 0.01-1.2V. Measuring the first-period discharge capacity, the cycle period and the discharge capacity after the cycle of the battery, and calculating the discharge capacity retention rate of the battery; and measuring the expansion rate of the negative pole piece in the battery on the market, wherein the expansion rate is calculated by testing the change condition of the thickness of the negative pole piece before and after the first cycle, and the experimental results are listed in tables 2-6.
TABLE 2 discharge Performance test results of nano-silicon cells
Figure BDA0002476387030000151
As can be seen from Table 2, when the lithium ion battery obtained by the composite binder provided by the invention takes the nano silicon powder as the silicon-based active material, the first-cycle specific discharge capacity of the lithium ion battery is 3006mA · h/g, the first-cycle specific discharge capacity of the lithium ion battery obtained in the comparative example 11 is 2814mA · h/g, the first-cycle specific discharge capacity of the lithium ion battery obtained in the comparative example 12 is only 1654mA · h/g, and the first-cycle specific discharge capacity of the lithium ion battery obtained in the comparative example 13 is mA 962 · h/g; the result shows that the composite binder has high bonding strength, the negative plate obtained from the composite binder has a firm structure, and the first-cycle specific discharge capacity of the obtained lithium ion battery is large, which is far greater than that of the lithium ion battery (namely comparative example 13) obtained by adopting the existing commercially available composite binder (CMC/SBR).
As can be seen from table 2, the specific discharge capacity of the lithium ion battery obtained by the composite binder of the present invention after 100 charge and discharge cycles is still 2012mA · h/g, the specific discharge capacity of the lithium ion battery obtained in comparative example 11 after 100 charge and discharge cycles is only 675mA · h/g, the specific discharge capacity of the lithium ion battery obtained in comparative example 12 after 100 charge and discharge cycles is only 938mA · h/g, and the specific discharge capacity of the lithium ion battery obtained in comparative example 13 after 100 charge and discharge cycles is only 613mA · h/g; therefore, the specific discharge capacity of the lithium ion battery obtained by the composite binder is far higher after 100 charge and discharge cycles than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
As can be seen from table 2, the specific discharge capacity retention rate of the lithium ion battery obtained from the composite binder is 67% after 100 charge and discharge cycles, the specific discharge capacity retention rate of the lithium ion battery of comparative example 11 is only 23% after 100 charge and discharge cycles, the specific discharge capacity retention rate of the lithium ion battery of comparative example 12 is only 56% after 100 charge and discharge cycles, and the specific discharge capacity retention rate of the lithium ion battery of comparative example 13 is 63% after 100 charge and discharge cycles; therefore, the specific discharge capacity retention rate of the lithium ion battery obtained by the composite binder is far higher than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
As can be seen from table 2, the lithium ion battery obtained by using the composite binder of the present invention has a negative electrode sheet expansion rate of 126% after 100 charge and discharge cycles, the lithium ion battery of comparative example 11 has a negative electrode sheet expansion rate of 173% after 100 charge and discharge cycles, the lithium ion battery of comparative example 12 has a negative electrode sheet expansion rate of 139% after 100 charge and discharge cycles, and the lithium ion battery of comparative example 13 has a negative electrode sheet expansion rate of 208% after 100 charge and discharge cycles; therefore, the lithium ion battery obtained by the composite binder disclosed by the invention has the negative plate expansion rate after 100 charge and discharge cycles which is far smaller than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
Therefore, the lithium ion battery prepared by the composite binder has the advantages of good cycle stability, large charge-discharge specific capacity, high discharge capacity retention rate, low negative plate expansion rate and long service life.
TABLE 3 discharge Performance test results for porous silicon cells
Figure BDA0002476387030000171
As can be seen from Table 3, when the porous silicon powder is used as the silicon-based active material, the first-cycle specific discharge capacity of the lithium ion battery obtained by the composite binder is 3166mA · h/g, the first-cycle specific discharge capacity of the lithium ion battery obtained by the comparative example 11 is 2988mA · h/g, the first-cycle specific discharge capacity of the lithium ion battery obtained by the comparative example 12 is 1756mA · h/g, and the first-cycle specific discharge capacity of the lithium ion battery obtained by the comparative example 13 is only 964mA · h/g; the composite binder has high bonding strength, the obtained negative plate has a firm structure, and the first-period discharge specific capacity of the obtained lithium ion battery is large.
As can be seen from table 3, the specific discharge capacity of the lithium ion battery obtained by the composite binder of the present invention after 100 charge and discharge cycles is still 1825mA · h/g, the specific discharge capacity of the lithium ion battery obtained by comparative example 11 after 100 charge and discharge cycles is 1013mA · h/g, the specific discharge capacity of the lithium ion battery obtained by comparative example 12 after 100 charge and discharge cycles is only 865mA · h/g, and the specific discharge capacity of the lithium ion battery obtained by comparative example 13 after 100 charge and discharge cycles is only 569mA · h/g; therefore, the specific discharge capacity of the lithium ion battery obtained by the composite binder is far higher after 100 charge and discharge cycles than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
As can be seen from table 3, the specific discharge capacity retention rate of the lithium ion battery obtained from the composite binder is 58% after 100 charge and discharge cycles, the specific discharge capacity retention rate of the lithium ion battery of comparative example 11 is only 34% after 100 charge and discharge cycles, the specific discharge capacity retention rate of the lithium ion battery of comparative example 12 is only 49% after 100 charge and discharge cycles, and the specific discharge capacity retention rate of the lithium ion battery of comparative example 13 is only 49% after 100 charge and discharge cycles; therefore, the specific discharge capacity retention rate of the lithium ion battery obtained by the composite binder is far higher than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
As can be seen from table 3, the lithium ion battery obtained by using the composite binder of the present invention has an expansion rate of 135% of the negative electrode sheet after 100 charge and discharge cycles, the lithium ion battery of comparative example 11 has an expansion rate of 185% of the negative electrode sheet after 100 charge and discharge cycles, the lithium ion battery of comparative example 12 has an expansion rate of 147% of the negative electrode sheet after 100 charge and discharge cycles, and the lithium ion battery of comparative example 13 has an expansion rate of 214% of the negative electrode sheet after 100 charge and discharge cycles; therefore, the lithium ion battery obtained by the composite binder disclosed by the invention has the negative plate expansion rate after 100 charge and discharge cycles which is far smaller than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
Therefore, the lithium ion battery prepared by the composite binder has the advantages of good cycle stability, large charge-discharge specific capacity, high discharge capacity retention rate, low negative plate expansion rate and long service life.
TABLE 4 discharge Performance test results of amorphous silicon cells
Figure BDA0002476387030000181
As can be seen from Table 4, when amorphous silicon powder is used as a silicon-based active material, the first-cycle specific discharge capacity of the lithium ion battery obtained by the composite binder is 3155mA · h/g, the first-cycle specific discharge capacity of the lithium ion battery obtained by the comparative example 11 is 2897mA · h/g, the first-cycle specific discharge capacity of the lithium ion battery obtained by the comparative example 12 is 1365mA · h/g, and the first-cycle specific discharge capacity of the lithium ion battery obtained by the comparative example 13 is only 1074mA · h/g; the composite binder has high bonding strength, the obtained negative plate has a firm structure, and the first-period discharge specific capacity of the obtained lithium ion battery is large.
As can be seen from table 4, the specific discharge capacity of the lithium ion battery obtained by the composite binder of the present invention after 100 charge and discharge cycles is still 1825mA · h/g, the specific discharge capacity of the lithium ion battery obtained by comparative example 11 after 100 charge and discharge cycles is 1324mA · h/g, the specific discharge capacity of the lithium ion battery obtained by comparative example 12 after 100 charge and discharge cycles is only 539mA · h/g, and the specific discharge capacity of the lithium ion battery obtained by comparative example 13 after 100 charge and discharge cycles is only 547mA · h/g; therefore, the specific discharge capacity of the lithium ion battery obtained by the composite binder is far higher after 100 charge and discharge cycles than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
As can be seen from table 4, the specific discharge capacity retention rate of the lithium ion battery obtained from the composite binder is 59% after 100 charge and discharge cycles, the specific discharge capacity retention rate of the lithium ion battery of comparative example 11 is 46% after 100 charge and discharge cycles, the specific discharge capacity retention rate of the lithium ion battery of comparative example 12 is only 40% after 100 charge and discharge cycles, and the specific discharge capacity retention rate of the lithium ion battery of comparative example 13 is 51% after 100 charge and discharge cycles; therefore, the specific discharge capacity retention rate of the lithium ion battery obtained by the composite binder is far higher than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
As can be seen from table 4, the lithium ion battery obtained by using the composite binder of the present invention has an expansion rate of 125% of the negative electrode sheet after 100 charge and discharge cycles, the lithium ion battery of comparative example 11 has an expansion rate of 191% of the negative electrode sheet after 100 charge and discharge cycles, the lithium ion battery of comparative example 12 has an expansion rate of 147% of the negative electrode sheet after 100 charge and discharge cycles, and the lithium ion battery of comparative example 13 has an expansion rate of 204% of the negative electrode sheet after 100 charge and discharge cycles; therefore, the lithium ion battery obtained by the composite binder disclosed by the invention has the negative plate expansion rate after 100 charge and discharge cycles which is far smaller than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
Therefore, the lithium ion battery prepared by the composite binder has the advantages of good cycle stability, large charge-discharge specific capacity, high discharge capacity retention rate and long service life.
TABLE 5 test results of discharge performance of silicon-carbon composite battery
Figure BDA0002476387030000191
As can be seen from table 5, when the silicon-carbon composite material is used as the silicon-based active material, the first-cycle specific discharge capacity of the lithium ion battery obtained by the composite binder of the present invention is 2122mA · h/g, the first-cycle specific discharge capacity of the lithium ion battery obtained in comparative example 11 is 2096mA · h/g, the first-cycle specific discharge capacity of the lithium ion battery obtained in comparative example 12 is 1745mA · h/g, and the first-cycle specific discharge capacity of the lithium ion battery obtained in comparative example 13 is only 1076mA · h/g; the composite binder has high bonding strength, the obtained negative plate has a firm structure, and the first-period discharge specific capacity of the obtained lithium ion battery is large.
As can be seen from table 5, the specific discharge capacity of the lithium ion battery obtained by the composite binder of the present invention after 100 charge and discharge cycles is still 1539mA · h/g, the specific discharge capacity of the lithium ion battery obtained by comparative example 11 after 100 charge and discharge cycles is 1035mA · h/g, the specific discharge capacity of the lithium ion battery obtained by comparative example 12 after 100 charge and discharge cycles is 823mA · h/g, and the specific discharge capacity of the lithium ion battery obtained by comparative example 13 after 100 charge and discharge cycles is only 587mA · h/g; therefore, the specific discharge capacity of the lithium ion battery obtained by the composite binder is far higher after 100 charge and discharge cycles than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
As can be seen from table 5, the specific discharge capacity retention rate of the lithium ion battery obtained from the composite binder is 72% after 100 charge and discharge cycles, the specific discharge capacity retention rate of the lithium ion battery of comparative example 11 is 49% after 100 charge and discharge cycles, the specific discharge capacity retention rate of the lithium ion battery of comparative example 12 is only 47% after 100 charge and discharge cycles, and the specific discharge capacity retention rate of the lithium ion battery of comparative example 13 is 55% after 100 charge and discharge cycles; therefore, the specific discharge capacity retention rate of the lithium ion battery obtained by the composite binder is far higher than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
As can be seen from table 5, the lithium ion battery obtained by using the composite binder of the present invention has an expansion rate of only 104% of the negative electrode sheet after 100 charge and discharge cycles, the lithium ion battery of comparative example 11 has an expansion rate of 185% of the negative electrode sheet after 100 charge and discharge cycles, the lithium ion battery of comparative example 12 has an expansion rate of 137% of the negative electrode sheet after 100 charge and discharge cycles, and the lithium ion battery of comparative example 13 has an expansion rate of 197% of the negative electrode sheet after 100 charge and discharge cycles; therefore, the lithium ion battery obtained by the composite binder disclosed by the invention has the negative plate expansion rate after 100 charge and discharge cycles which is far smaller than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 100 charge and discharge cycles.
Therefore, the lithium ion battery prepared by the composite binder has the advantages of good cycle stability, large charge-discharge specific capacity, high discharge capacity retention rate and long service life.
TABLE 6 discharge Performance test results for micron silicon cells
Figure BDA0002476387030000211
As can be seen from table 6, when the lithium ion battery obtained by using the composite binder of the present invention uses the micron silicon powder as the silicon-based active material, the first cycle specific discharge capacity of the lithium ion battery is 2133mA · h/g, the first cycle specific discharge capacity of the lithium ion battery obtained in comparative example 11 is 2067mA · h/g, the first cycle specific discharge capacity of the lithium ion battery obtained in comparative example 12 is 1698mA · h/g, and the first cycle specific discharge capacity of the lithium ion battery obtained in comparative example 13 is only 965mA · h/g; the composite binder has high bonding strength, the obtained negative plate has a firm structure, and the first-period discharge specific capacity of the obtained lithium ion battery is large.
As can be seen from table 6, the specific discharge capacity of the lithium ion battery obtained by the composite binder of the present invention after 50 charge and discharge cycles is still 1878mA · h/g, the specific discharge capacity of the lithium ion battery obtained by comparative example 11 after 50 charge and discharge cycles is 1436mA · h/g, the specific discharge capacity of the lithium ion battery obtained by comparative example 12 after 50 charge and discharge cycles is only 497mA · h/g, and the specific discharge capacity of the lithium ion battery obtained by comparative example 13 after 50 charge and discharge cycles is only 571 · h/g; therefore, the specific discharge capacity of the lithium ion battery obtained by the composite binder is far higher after 50 charge and discharge cycles than that of the lithium ion batteries in comparative example 11, comparative example 12 and comparative example 13 after 50 charge and discharge cycles.
As can be seen from table 6, the specific discharge capacity retention ratio of the lithium ion battery obtained from the composite binder is 88% after 50 charge and discharge cycles, the specific discharge capacity retention ratio of the lithium ion battery of comparative example 11 after 50 charge and discharge cycles is 69%, the specific discharge capacity retention ratio of the lithium ion battery of comparative example 12 after 50 charge and discharge cycles is only 29%, and the specific discharge capacity retention ratio of the lithium ion battery of comparative example 13 after 50 charge and discharge cycles is 60%; therefore, the specific discharge capacity retention rate of the lithium ion battery obtained by the composite binder is far higher than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 50 charge and discharge cycles.
As can be seen from table 6, the lithium ion battery obtained by using the composite binder of the present invention has an expansion rate of only 121% after 50 charge and discharge cycles, the lithium ion battery of comparative example 11 has an expansion rate of 193% after 50 charge and discharge cycles, the lithium ion battery of comparative example 12 has an expansion rate of 130% after 50 charge and discharge cycles, and the lithium ion battery of comparative example 13 has an expansion rate of 226% after 50 charge and discharge cycles; therefore, the lithium ion battery obtained by the composite binder disclosed by the invention has the expansion rate of the negative plate after 50 charge and discharge cycles which is far smaller than that of the lithium ion batteries in comparative examples 11, 12 and 13 after 50 charge and discharge cycles.
Therefore, the lithium ion battery prepared by the composite binder has the advantages of good cycle stability, large charge-discharge specific capacity, high discharge capacity retention rate and long service life.
Therefore, compared with the prior art, the invention has the beneficial effects that: according to the composite binder, the polycarboxy nitrile rubber and the guar gum are used for forming the composite binder, the guar gum is used as a framework, the polycarboxy nitrile rubber is filled in the guar gum framework, the high elasticity and high viscosity of the polycarboxy nitrile rubber and the firm mechanical property of the guar gum are integrated, the hard guar gum framework can inhibit the volume expansion of a silicon cathode, the high elasticity polycarboxy nitrile rubber buffers the obvious volume change of a silicon anode, and the high viscosity polycarboxy nitrile rubber resists the breakage of silicon and the disintegration of an electrode; the composite binder has high bonding strength and good tensile property, and fully ensures the structural stability of the negative plate; the lithium ion battery obtained by the method has the advantages of large first-period discharge specific capacity, high coulombic efficiency, good battery cycle stability, high capacity retention rate and long service life. The composite binder and the preparation method of the negative plate prepared from the composite binder are simple to operate, mild in condition, free of special requirements for equipment, easy to realize industrialization, convenient to store and easy to use.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (10)

1. The composite binder for the negative electrode of the lithium ion battery is characterized in that:
the composite binder consists of a polymer A and a polymer B, wherein the polymer A is polycarboxyl nitrile rubber, and the polymer B is guar gum;
the weight percentage of the polymer A in the composite binder is 30-70%, and the weight percentage of the polymer B in the composite binder is 30-70%.
2. The composite binder for a negative electrode of a lithium ion battery according to claim 1, characterized in that:
the weight percentage of the polymer A in the composite binder is 40-60%, and the weight percentage of the polymer B in the composite binder is 40-60%.
3. The composite binder for a lithium ion battery negative electrode according to claim 1 or 2, characterized in that:
the solids content of the polymer A is from 40 to 45%.
4. A method for preparing the composite binder for the negative electrode of the lithium ion battery according to any one of claims 1 to 3, comprising the steps of:
and mixing and uniformly stirring the polymer A and the polymer B to obtain the composite binder.
5. The lithium ion battery negative plate comprises a negative current collector and an active coating coated on the surface of the negative current collector, and is characterized in that the active coating comprises the following components in parts by weight:
60-80 parts of silicon-based active substances;
10-20 parts of a conductive agent;
10-20 parts of the composite binder for the negative electrode of the lithium ion battery as defined in any one of claims 1 to 3.
6. The lithium ion battery negative electrode sheet according to claim 5, characterized in that:
the thickness of the active coating is 50-1500 μm;
preferably, the loading amount of the silicon-based active material on the negative plate is 0.3-2.0mg/cm2。
7. The lithium ion battery negative electrode sheet according to claim 5, characterized in that:
the silicon-based active substance is a silicon material or a silicon-carbon composite material;
preferably, the silicon material is any one or more of nano silicon, micron silicon, porous silicon or amorphous silicon;
preferably, the conductive agent is any one or more of graphite, acetylene black, Super P, Super S, graphene, carbon fiber, carbon nanotube or Ketjen black.
8. The preparation method of the lithium ion battery negative electrode sheet according to any one of claims 5 to 7, characterized by comprising the following steps:
1) adding a silicon-based active substance, a conductive agent and a composite binder into water, and uniformly grinding to obtain slurry;
2) coating the slurry obtained in the step 1) on the surface of a negative current collector, vacuum drying, and cutting to obtain the electrode plate.
9. The preparation method of the lithium ion battery negative electrode sheet according to claim 5, characterized in that:
in the step 1), the viscosity of the slurry is 1000-4000 cP;
preferably, in the step 1), the weight percentage of the composite binder in the slurry is 1-40%;
preferably, in the step 2), the vacuum degree is 0.1-1MPa, the drying temperature is 80-120 ℃, and the drying time is 10-15h during vacuum drying.
10. A lithium ion battery, characterized by:
the negative plate of the lithium ion battery comprises the negative plate of the lithium ion battery according to any one of claims 5 to 7.
CN202010365423.9A 2020-04-30 2020-04-30 Composite binder and application thereof in silicon cathode of lithium ion battery Pending CN111525136A (en)

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