CN111916692A - Preparation method of lithium battery negative electrode material - Google Patents

Preparation method of lithium battery negative electrode material Download PDF

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CN111916692A
CN111916692A CN202010576390.2A CN202010576390A CN111916692A CN 111916692 A CN111916692 A CN 111916692A CN 202010576390 A CN202010576390 A CN 202010576390A CN 111916692 A CN111916692 A CN 111916692A
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lithium
composite fiber
gelatin
silicon
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戴嘉
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Shao Zhengye
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Shao Zhengye
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Abstract

The invention discloses a preparation method of a lithium battery cathode material, and belongs to the technical field of new energy. The lithium battery cathode material prepared by the invention is prepared by mixing liquid lithium alloy and a silicon-carbon composite material according to the mass ratio of 1: 3-1: 20 are compounded. The liquid lithium alloy is dispersed and filled in the pores of the silicon-carbon composite material, and the liquid lithium alloy is adopted to replace a lithium source embedded in a conventional negative electrode, so that the formation of lithium dendrites in the long-term charge-discharge cycle process of the battery can be effectively avoided, the existence of the liquid lithium alloy can also effectively buffer the expansion of the silicon-carbon negative electrode in the charge-discharge cycle process. By controlling the types of elements in the lithium alloy and the preparation process of the silicon-carbon composite material, the liquid lithium alloy can be effectively filled in the silicon-carbon composite material to form a structure similar to gel.

Description

Preparation method of lithium battery negative electrode material
Technical Field
The invention discloses a preparation method of a lithium battery cathode material, and belongs to the technical field of new energy.
Background
Among the many alternatives for lithium ion battery negative electrode materials, silicon is one of the most likely substitutes for commercial graphite negative electrodes for the following reasons: (1) silicon has the highest theoretical specific mass capacity (4200 mAh/g) in many alternative negative electrodes; (2) the discharge platform of the silicon cathode is about 0.4V, which finds balance in keeping normal open-circuit voltage and avoiding poor lithium plating; (3) the silicon storage capacity is sufficient (the earth crust content is listed as the second), the economic cost is low, and the environment is protected.
However, silicon still has a great problem as a negative electrode of a lithium ion battery. Alloy chimeras such as alloy phase Li4.4Si and the like generate extremely obvious volume expansion (more than 360%) during the formation process, and generate huge stress during the lithium intercalation/deintercalation, and the following consequences can be caused: (1) the electrode structure can be gradually crushed along with the action of stress in the cycle of lithium removal/lithium insertion, which is a problem existing in the alloying negative electrode; (2) under the action of interfacial stress, the active material splits from the current collector and is no longer effective; (3) the motor structure is continuously destroyed due to the volume expansion and the internal stress, and new interfaces are continuously exposed to the electrolyte, so that a Solid Electrolyte Interface (SEI) repeats a cycle of generation-destruction-reformation, and lithium ions in the battery are continuously consumed. The above processes all result in collapse of the motor structure and degradation of the battery capacity. In addition to the huge volume expansion, the poor conductivity of silicon not only affects the transmission efficiency of electron ions, but also causes the interface impedance to be large.
Since 1990, researchers have made many researches to solve the above problems of the silicon negative electrode, and the main principles include utilization of a matrix for relieving internal stress, nanocrystallization of the silicon negative electrode, fabrication of a change in physical void volume, and the like.
Disclosure of Invention
The invention mainly solves the technical problems that: aiming at the problems of the traditional lithium battery cathode, the application provides a lithium battery cathode material and a preparation method thereof.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a lithium battery negative electrode material comprises 30-50 parts of current collectors and 10-15 parts of active material coatings;
the active material layer is prepared from liquid lithium alloy and a silicon-carbon composite material according to the mass ratio of 1: 3-1: 20 are compounded.
The beneficial effects are that: the liquid lithium alloy and the silicon-carbon composite material are compounded, the liquid lithium alloy is dispersed and filled in pores of the silicon-carbon composite material, and the liquid lithium alloy is used for replacing a lithium source embedded in a conventional negative electrode, so that the formation of lithium dendrites and the existence of the liquid lithium alloy in the long-term charge-discharge cycle process of the battery can be effectively avoided, and the expansion of the silicon-carbon negative electrode in the charge-discharge cycle process can be effectively buffered.
Preferably, the liquid lithium alloy is a lithium tin alloy; in the lithium tin alloy, the mass ratio of lithium to tin is 1: 3-1: 5.
the beneficial effects are that: the lithium tin alloy is adopted, so that the conductivity of lithium is guaranteed, and the alloy is kept in a liquid state all the time at the normal circulation temperature of the battery.
Preferably, the lithium tin alloy comprises boron with the mass of 3-5% of that of lithium.
The beneficial effects are that: by adding boron, the infiltration capacity of the lithium tin alloy to the silicon-carbon cathode is further improved, the liquid alloy is limited by the pore structure of the silicon-carbon cathode to form gel-like bodies, and the liquid holding capacity (liquid alloy) of the silicon-carbon cathode is improved laterally.
As optimization, a fast ion conductor with the mass of 0.1 time that of the lithium-tin alloy and modified tetratitanic acid with the mass of 0.1 time that of the lithium-tin alloy can be added into the liquid lithium alloy and the silicon-carbon composite material obtained in the step (1); the fast ion conductor is Li2S-P2S5，Li2S-SiS2，Li2S-GeS2，Li10GeP2S12Or Li10SnP2S12Any one of them; the modified titanic acid is prepared by mixing and reacting modified titanium dioxide and titanic acid; the modified titanium dioxide is aminated silicon dioxide.
The beneficial effects are that: on one hand, the viscosity of the liquid lithium alloy can be changed by adding the fast ion conductor, so that the liquid lithium alloy can be stably stored in a system, and on the other hand, the conductivity of the product can be increased by adding the fast ion conductor.
Preferably, the silicon-carbon composite material is prepared by mixing gelatin, chitosan, ethyl orthosilicate, bacterial cellulose and glutaraldehyde, reacting, and then performing electrostatic spinning and calcining.
The beneficial effects are that: gelatin, bacterial cellulose and chitosan are adopted to form gel-like fibers under the action of glutaraldehyde, tetraethoxysilane is used as a silicon source and is hydrolyzed to form silicon dioxide, once the silicon dioxide is formed, the gel is adsorbed and fixed, so that a nano silicon dioxide layer is formed on the surface of the gel, firstly, the organic gel is pyrolyzed and carbonized to form a porous fiber framework under a high-temperature environment, the porous carbon fiber framework is gradually shrunk along with the further rise of the temperature, the silicon dioxide layer coated on the surface plays a good supporting role, and after the internal and external interaction force, the fibers are twisted to enable the surface of the fibers to be in a wave-shaped wrinkle shape; with the further increase of the temperature, the silicon dioxide is reduced by carbon and is converted into silicon protoxide or simple substance silicon, and finally the silicon-carbon composite material is formed.
As optimization, the lithium battery negative electrode material comprises the following raw material components in parts by weight: 35 parts current collector and 15 parts active material coating.
As optimization, the preparation method of the lithium battery negative electrode material comprises the following specific preparation steps:
(1) preparing a carbon-silicon composite material;
(2) preparing an active material coating;
(3) compounding the current collector with the active material coating;
(4) and (4) performing index analysis on the product obtained in the step (3).
The beneficial effects are that: and through negative pressure impregnation, the liquid lithium alloy is effectively impregnated, permeated and immersed into the silicon-carbon composite material and is effectively adsorbed and fixed by the silicon-carbon composite material.
As a later preparation method of the lithium battery negative electrode material, the preparation method comprises the following specific steps:
(1) mixing gelatin and water according to a mass ratio of 1: 10-1: 20, mixing and dispersing, stirring and dissolving, adding bacterial cellulose accounting for 1-3% of the mass of gelatin, chitosan accounting for 4-8% of the mass of gelatin, glutaraldehyde accounting for 0.3-0.5% of the mass of gelatin and ethyl orthosilicate accounting for 10-15% of the mass of gelatin, heating, stirring and reacting, carrying out electrostatic spinning to obtain composite fibers, heating the composite fibers to 1480-1500 ℃ at the speed of 0.8-1.2 ℃/min under the nitrogen atmosphere, carrying out heat preservation reaction for 4-6 h, cooling to room temperature at the speed of 20-30 ℃/min by using dry ice, discharging, pressing, and cutting into sheets with the thickness of 1-3 mm;
(2) mixing the substance obtained in the step (1) with liquid lithium under the protection of inert gas, adding a fast ion conductor with the mass of 0.1 time that of the liquid lithium alloy and modified tetratitanic acid with the mass of 0.1 time that of the liquid lithium alloy into the mixture of the substance obtained in the step (1) and the liquid lithium, vacuumizing to 600-800 Pa, and carrying out pressure-maintaining impregnation for 30-60 min;
(3) and (3) mixing a current collector with the substance obtained in the step (2) according to the mass ratio of 2: 1, mixing, and bonding by using a bonding agent with the mass of 0.2-0.4 times of that of a current collector;
(4) and (4) performing index analysis on the product obtained in the step (3).
As optimization, the binder in the step (3) is a PVDF solution; the PVDF solution is prepared by mixing PVDF and a solvent according to a mass ratio of 1: 8-1: 10 are compounded; the solvent is any one of NMP, DMF, DMSO, TEP or DMAc.
The beneficial effects are that: by adopting the solvent, the PVDF is favorably and effectively dissolved, the flowability and the wettability of the binder on the surfaces of the current collector and the silicon-carbon composite material impregnated sheet are improved, the organic combination of the interface of the current collector and the silicon-carbon composite material impregnated sheet is favorably realized, the interface impedance is reduced, and the separation of the current collector and the silicon-carbon composite material impregnated sheet in the charge-discharge cycle process can be effectively avoided.
Preferably, the preparation method of the modified titanic acid in the step (2) comprises the following steps of mixing titanium dioxide and potassium carbonate according to a mass ratio of 3: 1, mixing and grinding, and calcining for 13 hours at the temperature of 800 ℃ to obtain potassium tetratitanate, wherein the mass ratio of the potassium tetratitanate to 10% hydrochloric acid is 1: 10, mixing, soaking, filtering, washing and drying to obtain the titanic acid, wherein the titanic acid and the deionized water are mixed according to the mass ratio of 1: 50, adding aminated titanium dioxide with the mass of 0.1-0.3 times that of the titanic acid, performing ultrasonic dispersion, filtering, and drying to obtain modified titanic acid; the aminated titanium dioxide is prepared by mixing nano titanium dioxide and water according to the mass ratio of 1: 10, adding aminopropyltriethoxysilane accounting for 1-2 times of the mass of the nano titanium dioxide and ammonia water accounting for 0.1-0.3 time of the mass of the nano titanium dioxide, stirring for reaction, and filtering to obtain the aminated titanium dioxide.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious 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.
In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe the method for testing each index of the lithium battery negative electrode material manufactured in the following examples as follows:
firstly, a metal lithium sheet is taken as a counter electrode, an electrolyte is an EC/DMC (v/v =1/1) electrolyte containing 1.0MLiPF6, a polyethylene diaphragm is adopted as the diaphragm, and a button cell is assembled in a glove box according to a positive electrode shell, a working electrode pole piece, the diaphragm, the lithium sheet, foamed nickel, a stainless steel gasket and a negative electrode shell.
And (3) testing the battery: and (3) observing the electrochemical performance of the button cell by adopting a Wuhan blue electricity test system, wherein the charge-discharge multiplying power is 0.1C, and the charging voltage range is 5 mV-1.5V.
Testing the expansion rate of the working electrode piece: and (5) disassembling the battery after the battery is circulated for 500 weeks, measuring the thickness of the working electrode pole piece, and calculating the expansion rate of the pole piece.
Example 1
The lithium battery negative electrode material mainly comprises the following raw material components in parts by weight: 35 parts current collector and 15 parts active material coating.
A preparation method of a lithium battery negative electrode material mainly comprises the following preparation steps:
(1) mixing gelatin and water according to a mass ratio of 1: 10, standing and swelling for 6h at room temperature, stirring and dissolving for 10min at the speed of 300r/min by using a stirrer, then sequentially adding bacterial cellulose accounting for 1% of the mass of gelatin, chitosan accounting for 4% of the mass of gelatin, glutaraldehyde accounting for 0.3% of the mass of gelatin and ethyl orthosilicate accounting for 10% of the mass of gelatin, heating and stirring for reacting for 4h at the temperature of 55 ℃ and the stirring speed of 400r/min to obtain a spinning solution, and spinning the obtained spinning solution into fibers with the average diameter of 0.4mm to obtain composite fibers; heating the obtained composite fiber to 1480 ℃ at the speed of 0.8 ℃/min in a nitrogen atmosphere, carrying out heat preservation reaction for 4 hours, taking out the composite fiber when the composite fiber is hot, cooling the composite fiber to room temperature at the speed of 20 ℃/min by using dry ice, discharging the composite fiber, pressing the composite fiber under the pressure of 0.3MPa, and cutting the composite fiber into slices with the thickness of 1 mm;
(2) according to the mass ratio of 1: 3, mixing the liquid lithium alloy and the substance obtained in the step (1), adding a fast ion conductor with the mass of 0.1 time that of the liquid lithium alloy and modified tetratitanic acid with the mass of 0.1 time that of the liquid lithium alloy into the mixture of the substance obtained in the step (1) and the liquid lithium alloy, mixing under the protection of inert gas, vacuumizing to 600Pa, and carrying out pressure maintaining impregnation for 30 min;
(3) the method comprises the steps of coating a PVDF solution on the surface of a current collector by using a copper foil as the current collector, and controlling the coating amount to be 5mg/cm2Bonding the substance obtained in the step (2) with the mass of 0.5 time of that of the current collector to the surface of the current collector coated with the PVDF solution under the protection of inert gas, rolling under the pressure of 0.2MPa, and then drying in vacuum;
(4) and (4) performing index analysis on the product obtained in the step (3).
Preferably, the liquid lithium alloy in the step (2) is a lithium tin alloy. In the lithium tin alloy, the mass ratio of lithium to tin is 1: 3. the lithium tin alloy comprises boron with the mass percent of 3 percent of lithium.
Optimally, the PVDF solution in the step (2) is prepared by mixing PVDF and a solvent according to a mass ratio of 1: 8, compounding; the solvent is NMP.
Preferably, the preparation method of the modified titanic acid in the step (2) comprises the following steps of mixing titanium dioxide and potassium carbonate according to a mass ratio of 3: 1, mixing and grinding, and calcining for 13 hours at the temperature of 800 ℃ to obtain potassium tetratitanate, wherein the mass ratio of the potassium tetratitanate to 10% hydrochloric acid is 1: 10, mixing, soaking, filtering, washing and drying to obtain the titanic acid, wherein the titanic acid and the deionized water are mixed according to the mass ratio of 1: 50, adding aminated titanium dioxide with the mass of 0.3 time that of the titanic acid, performing ultrasonic dispersion, filtering and drying to obtain modified titanic acid; the aminated titanium dioxide is prepared by mixing nano titanium dioxide and water according to the mass ratio of 1: 10, adding aminopropyl triethoxysilane which is 2 times of the mass of the nano titanium dioxide and ammonia water which is 0.3 times of the mass of the nano titanium dioxide, stirring for reaction, and filtering to obtain the aminated titanium dioxide.
Preferably, the fast ion conductor is Li2S-P2S5。
Example 2 (without addition of lithium tin alloy compared to example 1)
The lithium battery negative electrode material mainly comprises the following raw material components in parts by weight: 30 parts current collector and 15 parts active material coating.
A preparation method of a lithium battery negative electrode material mainly comprises the following preparation steps:
(1) mixing gelatin and water according to a mass ratio of 1: 10, standing and swelling for 6h at room temperature, stirring and dissolving for 10min at the speed of 300r/min by using a stirrer, then sequentially adding bacterial cellulose accounting for 1% of the mass of gelatin, chitosan accounting for 4% of the mass of gelatin, glutaraldehyde accounting for 0.3% of the mass of gelatin and ethyl orthosilicate accounting for 10% of the mass of gelatin, heating and stirring for reacting for 4h at the temperature of 55 ℃ and the stirring speed of 400r/min to obtain a spinning solution, and spinning the obtained spinning solution into fibers with the average diameter of 0.4mm to obtain composite fibers; heating the obtained composite fiber to 1480 ℃ at the speed of 0.8 ℃/min in a nitrogen atmosphere, carrying out heat preservation reaction for 4 hours, taking out the composite fiber when the composite fiber is hot, cooling the composite fiber to room temperature at the speed of 20 ℃/min by using dry ice, discharging the composite fiber, pressing the composite fiber under the pressure of 0.3MPa, and cutting the composite fiber into slices with the thickness of 1 mm;
(2) the method comprises the steps of coating a PVDF solution on the surface of a current collector by using a copper foil as the current collector, and controlling the coatingThe coverage is 5mg/cm2Bonding the substance obtained in the step (1) with the mass of 0.5 time of that of the current collector to the surface of the current collector coated with the PVDF solution under the protection of inert gas, rolling under the pressure of 0.2MPa, and then drying in vacuum;
(3) and (3) performing index analysis on the product obtained in the step (2).
Optimally, the PVDF solution is prepared by mixing PVDF and a solvent according to a mass ratio of 1: 8, compounding; the solvent is NMP.
Example 3 (using liquid lithium magnesium alloy as compared to example 1)
The lithium battery negative electrode material mainly comprises the following raw material components, by weight, 35 parts of current collector and 12 parts of active material coating.
A preparation method of a lithium battery negative electrode material mainly comprises the following preparation steps:
(1) mixing gelatin and water according to a mass ratio of 1: 10, standing and swelling for 6h at room temperature, stirring and dissolving for 10min at the speed of 300r/min by using a stirrer, then sequentially adding bacterial cellulose accounting for 1% of the mass of gelatin, chitosan accounting for 4% of the mass of gelatin, glutaraldehyde accounting for 0.3% of the mass of gelatin and ethyl orthosilicate accounting for 10% of the mass of gelatin, heating and stirring for reacting for 4h at the temperature of 55 ℃ and the stirring speed of 400r/min to obtain a spinning solution, and spinning the obtained spinning solution into fibers with the average diameter of 0.4mm to obtain composite fibers; heating the obtained composite fiber to 1480 ℃ at the speed of 0.8 ℃/min in a nitrogen atmosphere, carrying out heat preservation reaction for 4 hours, taking out the composite fiber when the composite fiber is hot, cooling the composite fiber to room temperature at the speed of 20 ℃/min by using dry ice, discharging the composite fiber, pressing the composite fiber under the pressure of 0.3MPa, and cutting the composite fiber into slices with the thickness of 1 mm;
(2) according to the mass ratio of 1: 3, mixing the liquid lithium alloy and the substance obtained in the step (1), adding a fast ion conductor with the mass of 0.1 time that of the liquid lithium alloy and modified tetratitanic acid with the mass of 0.1 time that of the liquid lithium alloy into the mixture of the substance obtained in the step (1) and the liquid lithium alloy, mixing under the protection of inert gas, vacuumizing to 600Pa, and carrying out pressure maintaining impregnation for 30 min;
(3) the method comprises the steps of coating a PVDF solution on the surface of a current collector by using a copper foil as the current collector, and controlling the coating amount to be 5mg/cm2Bonding the substance obtained in the step (2) with the mass of 0.5 time of that of the current collector to the surface of the current collector coated with the PVDF solution under the protection of inert gas, rolling under the pressure of 0.2MPa, and then drying in vacuum;
(4) and (4) performing index analysis on the product obtained in the step (3).
Preferably, the liquid lithium alloy in the step (2) is a lithium magnesium alloy; in the lithium-magnesium alloy, the mass ratio of lithium to magnesium is 1: 3; the lithium magnesium alloy comprises boron with the mass percent of 3 percent of lithium.
Optimally, the PVDF solution in the step (3) is prepared by mixing PVDF and a solvent according to a mass ratio of 1: 8, compounding; the solvent is NMP.
Preferably, the preparation method of the modified titanic acid in the step (2) comprises the following steps of mixing titanium dioxide and potassium carbonate according to a mass ratio of 3: 1, mixing and grinding, and calcining for 13 hours at the temperature of 800 ℃ to obtain potassium tetratitanate, wherein the mass ratio of the potassium tetratitanate to 10% hydrochloric acid is 1: 10, mixing, soaking, filtering, washing and drying to obtain the titanic acid, wherein the titanic acid and the deionized water are mixed according to the mass ratio of 1: 50, adding aminated titanium dioxide with the mass of 0.3 time that of the titanic acid, performing ultrasonic dispersion, filtering and drying to obtain modified titanic acid; the aminated titanium dioxide is prepared by mixing nano titanium dioxide and water according to the mass ratio of 1: 10, adding aminopropyl triethoxysilane which is 2 times of the mass of the nano titanium dioxide and ammonia water which is 0.3 times of the mass of the nano titanium dioxide, stirring for reaction, and filtering to obtain the aminated titanium dioxide.
Preferably, the fast ion conductor is Li2S-P2S5。
Example 4 (in comparison with example 1, no boron was added)
The lithium battery negative electrode material mainly comprises the following raw material components in parts by weight: 36 parts current collector and 12 parts active material coating.
A preparation method of a lithium battery negative electrode material mainly comprises the following preparation steps:
(1) mixing gelatin and water according to a mass ratio of 1: 10, standing and swelling for 6h at room temperature, stirring and dissolving for 10min at the speed of 300r/min by using a stirrer, then sequentially adding bacterial cellulose accounting for 1% of the mass of gelatin, chitosan accounting for 4% of the mass of gelatin, glutaraldehyde accounting for 0.3% of the mass of gelatin and ethyl orthosilicate accounting for 10% of the mass of gelatin, heating and stirring for reacting for 4h at the temperature of 55 ℃ and the stirring speed of 400r/min to obtain a spinning solution, and spinning the obtained spinning solution into fibers with the average diameter of 0.4mm to obtain composite fibers; heating the obtained composite fiber to 1480 ℃ at the speed of 0.8 ℃/min in a nitrogen atmosphere, carrying out heat preservation reaction for 4 hours, taking out the composite fiber when the composite fiber is hot, cooling the composite fiber to room temperature at the speed of 20 ℃/min by using dry ice, discharging the composite fiber, pressing the composite fiber under the pressure of 0.3MPa, and cutting the composite fiber into slices with the thickness of 1 mm;
(2) according to the mass ratio of 1: 3, mixing the liquid lithium alloy and the substance obtained in the step (1), adding a fast ion conductor with the mass of 0.1 time that of the liquid lithium alloy and modified tetratitanic acid with the mass of 0.1 time that of the liquid lithium alloy into the mixture of the substance obtained in the step (1) and the liquid lithium alloy, mixing under the protection of inert gas, vacuumizing to 600Pa, and carrying out pressure maintaining impregnation for 30 min;
(3) the method comprises the steps of coating a PVDF solution on the surface of a current collector by using a copper foil as the current collector, and controlling the coating amount to be 5mg/cm2Bonding the substance obtained in the step (2) with the mass of 0.5 time of that of the current collector to the surface of the current collector coated with the PVDF solution under the protection of inert gas, rolling under the pressure of 0.2MPa, and then drying in vacuum;
(4) and (4) performing index analysis on the product obtained in the step (3).
Preferably, the liquid lithium alloy in the step (2) is a lithium tin alloy; in the lithium tin alloy, the mass ratio of lithium to tin is 1: 3.
optimally, the PVDF solution in the step (3) is prepared by mixing PVDF and a solvent according to a mass ratio of 1: 8, compounding; the solvent is NMP.
Preferably, the preparation method of the modified titanic acid in the step (2) comprises the following steps of mixing titanium dioxide and potassium carbonate according to a mass ratio of 3: 1, mixing and grinding, and calcining for 13 hours at the temperature of 800 ℃ to obtain potassium tetratitanate, wherein the mass ratio of the potassium tetratitanate to 10% hydrochloric acid is 1: 10, mixing, soaking, filtering, washing and drying to obtain the titanic acid, wherein the titanic acid and the deionized water are mixed according to the mass ratio of 1: 50, adding aminated titanium dioxide with the mass of 0.3 time that of the titanic acid, performing ultrasonic dispersion, filtering and drying to obtain modified titanic acid; the aminated titanium dioxide is prepared by mixing nano titanium dioxide and water according to the mass ratio of 1: 10, adding aminopropyl triethoxysilane which is 2 times of the mass of the nano titanium dioxide and ammonia water which is 0.3 times of the mass of the nano titanium dioxide, stirring for reaction, and filtering to obtain the aminated titanium dioxide.
Preferably, the fast ion conductor is Li2S-P2S5。
Example 5 (comparison with example 1, without addition of Ethyl orthosilicate)
The negative electrode material of the lithium battery mainly comprises the following raw material components, by weight, 40 parts of current collector and 15 parts of active material coating.
A preparation method of a lithium battery negative electrode material mainly comprises the following preparation steps:
(1) mixing gelatin and water according to a mass ratio of 1: 10, standing and swelling for 6h at room temperature, stirring and dissolving for 10min at the speed of 300r/min by using a stirrer, sequentially adding bacterial cellulose accounting for 1% of the mass of gelatin, chitosan accounting for 4% of the mass of gelatin and glutaraldehyde accounting for 0.3% of the mass of gelatin, heating and stirring for reacting for 4h at the temperature of 55 ℃ and the stirring speed of 400r/min to obtain a spinning solution, and spinning the obtained spinning solution into fibers with the average diameter of 0.4mm to obtain composite fibers; heating the obtained composite fiber to 1480 ℃ at the speed of 0.8 ℃/min in a nitrogen atmosphere, carrying out heat preservation reaction for 4 hours, taking out the composite fiber when the composite fiber is hot, cooling the composite fiber to room temperature at the speed of 20 ℃/min by using dry ice, discharging the composite fiber, pressing the composite fiber under the pressure of 0.3MPa, and cutting the composite fiber into slices with the thickness of 1 mm;
(2) according to the mass ratio of 1: adding a liquid lithium alloy and the substance obtained in the step (1) into a reactor, adding a fast ion conductor with the mass of 0.1 time that of the liquid lithium alloy and modified tetratitanic acid with the mass of 0.1 time that of the liquid lithium alloy into the mixture of the substance obtained in the step (1) and the liquid lithium alloy, mixing under the protection of inert gas, vacuumizing to 600Pa, and carrying out pressure-maintaining impregnation for 30 min;
(3) the method comprises the steps of coating a PVDF solution on the surface of a current collector by using a copper foil as the current collector, and controlling the coating amount to be 5mg/cm2Bonding the substance obtained in the step (2) with the mass of 0.5 time of that of the current collector to the surface of the current collector coated with the PVDF solution under the protection of inert gas, rolling under the pressure of 0.2MPa, and then drying in vacuum;
(4) and (4) performing index analysis on the product obtained in the step (3).
Preferably, the liquid lithium alloy in the step (2) is a lithium tin alloy; in the lithium tin alloy, the mass ratio of lithium to tin is 1: 3. the lithium tin alloy comprises boron with the mass percent of 3 percent of lithium.
Optimally, the PVDF solution in the step (3) is prepared by mixing PVDF and a solvent according to a mass ratio of 1: 8, compounding; the solvent is NMP.
Preferably, the preparation method of the modified titanic acid in the step (2) comprises the following steps of mixing titanium dioxide and potassium carbonate according to a mass ratio of 3: 1, mixing and grinding, and calcining for 13 hours at the temperature of 800 ℃ to obtain potassium tetratitanate, wherein the mass ratio of the potassium tetratitanate to 10% hydrochloric acid is 1: 10, mixing, soaking, filtering, washing and drying to obtain the titanic acid, wherein the titanic acid and the deionized water are mixed according to the mass ratio of 1: 50, adding aminated titanium dioxide with the mass of 0.3 time that of the titanic acid, performing ultrasonic dispersion, filtering and drying to obtain modified titanic acid; the aminated titanium dioxide is prepared by mixing nano titanium dioxide and water according to the mass ratio of 1: 10, adding aminopropyl triethoxysilane which is 2 times of the mass of the nano titanium dioxide and ammonia water which is 0.3 times of the mass of the nano titanium dioxide, stirring for reaction, and filtering to obtain the aminated titanium dioxide.
Preferably, the fast ion conductor is Li2S-P2S5。
Examples of effects
Table 1 below shows the results of the analysis of the retention rate and the expansion rate of the negative electrode material for lithium batteries prepared in examples 1 to 5 of the present invention.
TABLE 1
Capacity retention after 500 weeks Pole piece expansion rate after 500 weeks
Example 1 92% 60%
Example 2 80% 90%
Example 3 75% 95%
Example 4 78% 102%
Example 5 70% 130%
According to the detection results in the table 1, the product prepared by the technical scheme has good capacity retention rate, the expansion problem in the battery charge-discharge cycle process can be effectively avoided, the battery safety problem does not occur in the test process, and therefore the short circuit problem caused by lithium dendrites does not occur in the test process.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Claims (1)

1. A preparation method of a lithium battery negative electrode material is characterized by comprising the following steps: the preparation method comprises the following preparation steps:
mixing gelatin and water according to a mass ratio of 1: 10, standing and swelling for 6h at room temperature, stirring and dissolving for 10min at the speed of 300r/min by using a stirrer, then sequentially adding bacterial cellulose accounting for 1% of the mass of gelatin, chitosan accounting for 4% of the mass of gelatin, glutaraldehyde accounting for 0.3% of the mass of gelatin and ethyl orthosilicate accounting for 10% of the mass of gelatin, heating and stirring for reacting for 4h at the temperature of 55 ℃ and the stirring speed of 400r/min to obtain a spinning solution, and spinning the obtained spinning solution into fibers with the average diameter of 0.4mm to obtain composite fibers; heating the obtained composite fiber to 1480 ℃ at the speed of 0.8 ℃/min in a nitrogen atmosphere, carrying out heat preservation reaction for 4 hours, taking out the composite fiber when the composite fiber is hot, cooling the composite fiber to room temperature at the speed of 20 ℃/min by using dry ice, discharging the composite fiber, pressing the composite fiber under the pressure of 0.3MPa, and cutting the composite fiber into slices with the thickness of 1 mm;
the method comprises the steps of coating a PVDF solution on the surface of a current collector by using a copper foil as the current collector, and controlling the coating amount to be 5mg/cm2Bonding the substance obtained in the step (1) with the mass of 0.5 time of that of the current collector to the surface of the current collector coated with the PVDF solution under the protection of inert gas, rolling under the pressure of 0.2MPa, and then drying in vacuum;
performing index analysis on the product obtained in the step (2);
the PVDF solution is prepared by mixing PVDF and a solvent according to a mass ratio of 1: 8, and the solvent is NMP.
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