CN117199268A - Preparation method of pre-lithiation buffer film of silicon oxide anode - Google Patents
Preparation method of pre-lithiation buffer film of silicon oxide anode Download PDFInfo
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- CN117199268A CN117199268A CN202311455332.4A CN202311455332A CN117199268A CN 117199268 A CN117199268 A CN 117199268A CN 202311455332 A CN202311455332 A CN 202311455332A CN 117199268 A CN117199268 A CN 117199268A
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 172
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- 238000006138 lithiation reaction Methods 0.000 title claims abstract description 82
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
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- 229910052799 carbon Inorganic materials 0.000 claims abstract description 41
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 35
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- PAZHGORSDKKUPI-UHFFFAOYSA-N lithium metasilicate Chemical compound [Li+].[Li+].[O-][Si]([O-])=O PAZHGORSDKKUPI-UHFFFAOYSA-N 0.000 description 1
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 description 1
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- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a preparation method of a pre-lithiation buffer film of a silicon oxide anode, belonging to the technical field of pre-lithiation. The preparation method comprises the steps of mixing a biomass material, an activating agent and water, performing activation treatment and first drying, then carbonizing, pickling, washing and second drying to obtain biomass porous carbon, dispersing the biomass porous carbon, a polymer and lithium salt in an organic solvent, preparing a pre-lithiation buffer film of a silicon oxide negative electrode which can conduct lithium ions and transmit electrons in different thicknesses through a coating process, and introducing the pre-lithiation buffer film between the silicon oxide negative electrode piece and a lithium foil, wherein lithium is pre-supplemented through different potential differences when pressure is applied; the pre-lithiation buffer film is introduced for pre-lithiation, so that the irreversible capacity consumed by the first cycle can be effectively compensated, the first cycle coulomb efficiency of the silicon-oxygen negative electrode material can be improved, and the energy density of the battery can be further improved.
Description
Technical Field
The invention relates to the technical field of prelithiation, in particular to a preparation method of a prelithiation buffer film of a silicon oxide negative electrode.
Background
Lithium ion batteries are considered as battery energy storage systems with the best comprehensive performance in recent years, and are used as the sole chelating agents in new energy automobiles, portable electronic products and the like. Along with the continuous improvement of the energy technical requirements of the human society, in order to meet the development requirements of high and new devices, development of a lithium ion battery anode and cathode material system with higher energy density is urgently needed. While in the negative electrode, silicon oxide (SiO x ) The negative electrode material is certainly one of the best candidates. However, as the silicon oxide negative electrode can generate irreversible conversion reaction (lithium oxide and lithium silicate are generated) in the primary lithiation process, and simultaneously an SEI film is formed on the surface of the material, a large amount of electrolyte and lithium ions extracted from the positive electrode material are consumed, the silicon oxide negative electrode material shows lower primary coulombic efficiency, and the irreversible capacity loss affects the electrochemical performance of the battery in the subsequent cycle. Therefore, irreversible capacity loss during the first cycle is one of the bottlenecks faced by current commercialization of silicon oxide anode materials.
In order to improve the coulombic efficiency of materials and electrodes, the pre-lithiation technology can provide additional active lithium for the battery, reduce the irreversible conversion reaction of the silicon oxide negative electrode, and reduce the loss of the positive electrode lithium source caused by the formation of an SEI film, thereby improving the reversible capacity of the battery. At present, the reported pre-lithiation methods of the lithium ion battery cathode materials mainly comprise the following steps: (1) electrochemical prelithiation: the method for reducing the first irreversible capacity of the anode and cathode materials is commonly used, and can accurately control the lithium supplementing quantity by controlling the cut-off potential, the current density and the like to compensate for the irreversible capacity loss or completely lithiate the irreversible capacity loss, and the expandability is still a main problem, because the method needs to realize the pre-deposition process of a matrix through a half-cell system for assembling lithium foil and electrolyte or temporarily, the time cost is increased in the related assembling and disassembling processes, and the mass production significance is reduced; (2) a prelithiation additive: the lithium silicon alloy is synthesized by adopting a heating melting method, and almost all anode materials can be lithiated, but the lithium silicon alloy is extremely unstable in air and humid environment due to low potential and high chemical reactivity and can only be operated in a glove box; (3) chemical prelithiation: the lithium-containing reagent with strong reducibility is used for transferring active lithium onto a negative electrode material through oxidation-reduction reaction, the method is based on the prelithiation of a solution process, homogeneous phase and rapid prelithiation can be realized, the prelithiation degree is regulated by controlling the soaking time of chemical prelithiation, but the electrode is unstable in air after the chemical prelithiation is carried out, and the electrode needs to be carried out in inert gas in the cleaning and subsequent battery assembly processes, so that the industrial application of the electrode is restricted, and the lithiation agent used in the chemical prelithiation method generally has certain toxicity and danger, so that the chemical lithiation environmental risk and the safety risk are high; (4) contact prelithiation: the method is efficient, simple and quick in operation, low-cost lithium foil can be adopted, the pre-lithiation amount can be adjusted by controlling the reaction time, but the method has the problems of uneven pre-lithiation and difficult precise control of the pre-lithiation degree, and meanwhile, for thick electrodes, the reaction time required by lithium ions to diffuse into the electrodes is longer.
Disclosure of Invention
The invention aims to provide a preparation method of a pre-lithiation buffer film of a silicon oxide negative electrode, and the method provided by the invention is used for realizing controllable, efficient and uniform pre-lithiation of a silicon oxide negative electrode plate of a lithium ion battery.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a pre-lithiation buffer film of a silicon oxide anode, which comprises the following steps:
(1) Mixing a biomass material, an activating agent and water, and then sequentially performing activation treatment and first drying to obtain an activated biomass material;
sequentially carbonizing, acid washing, water washing and secondary drying the activated biomass material to obtain biomass porous carbon;
(2) Mixing the biomass porous carbon obtained in the step (1) with a polymer, lithium salt and an organic solvent, and sequentially carrying out mechanical stirring and ultrasonic dispersion to obtain a mixed solution;
and (3) scraping the mixed solution on a substrate, and performing vacuum drying to obtain the pre-lithiation buffer film of the silicon oxide anode.
Preferably, the biomass material in the step (1) is at least one of bamboo wood powder, peanut shells, walnut shells, straw, coconut shells, starch and grains.
Preferably, the temperature rising speed of carbonization in the step (1) is 1-10 ℃/min, the temperature of carbonization is 600-1100 ℃, and the time of carbonization is 0.5-6 h.
Preferably, the polymer in the step (2) is at least one of PVDF-HFP, EVA, PE, PPO, PVC, PVMA.
Preferably, the lithium salt in the step (2) is LiTFSI, liClO, liBOB, liBF 4 、LiFSI、LiDFP、LiDFOB、LiPO 2 F 2 At least one of them.
Preferably, in the step (2), the mass ratio of the biomass porous carbon, the polymer and the lithium salt is (3-12): (0.6-12): (1-22).
Preferably, the rotation speed of mechanical stirring in the step (2) is 500-1000 r/min, and the time of mechanical stirring is 10-48 h.
The invention also provides the pre-lithiation buffer film of the silicon oxide anode prepared by the preparation method.
The invention also provides a method for pre-lithiation of the pre-lithiation buffer film of the silicon oxide anode by adopting the technical scheme, which comprises the following steps: and under the inert atmosphere condition, sequentially placing a silicon-oxygen negative electrode plate, a pre-lithiation buffer film and a lithium foil of the silicon-oxygen negative electrode from bottom to top, and dropwise adding electrolyte at the interface of the silicon-oxygen negative electrode to perform pre-lithiation treatment to obtain the pre-lithiated silicon-oxygen negative electrode.
Preferably, the pressure of the pre-lithiation treatment is 0.5-10 kg, and the time of the pre-lithiation treatment is 0.5-24 h.
The invention provides a preparation method of a pre-lithiation buffer film of a silicon oxide negative electrode, which comprises the steps of mixing a biomass material, an activating agent and water, performing activation treatment and first drying, carbonizing, pickling, washing and second drying to obtain biomass porous carbon, dispersing the biomass porous carbon, a polymer and lithium salt in an organic solvent, and preparing the pre-lithiation buffer film of the silicon oxide negative electrode with different thicknesses through a coating process. According to the invention, the pre-lithiation buffer film is introduced between the silicon oxide negative electrode piece and the lithium foil, and lithium is pre-supplemented through the difference of potential differences when pressure is applied; the pre-lithiation buffer film is introduced for pre-lithiation, so that the irreversible capacity consumed by the first cycle can be effectively compensated, the first cycle coulomb efficiency of the silicon-oxygen negative electrode material can be improved, and the energy density of the battery can be further improved. The results of the examples show that, compared with the non-prelithiated silicon oxide negative electrode, the prelithiated silicon oxide negative electrode prepared in application example 1 has a specific charge capacity of 957mAh/g after being cycled for 100 weeks, and a capacity retention rate of 90.9%, which indicates that the prelithiation treatment operation in application example 1 is beneficial to improving the electrochemical performance of the silicon oxide negative electrode; compared with the non-prelithiated silicon oxide cathode, the lithium intercalation capacity of the prelithiated silicon oxide cathode prepared in application example 2 is reduced from 2170.5mAh/g to 1498mAh/g, and the first-week efficiency is improved from 76.3% to 112.2%.
Drawings
FIG. 1 is an SEM image of biomass porous carbon prepared in example 1 of the invention;
FIG. 2 is an SEM image of a cross section of a pre-lithiated buffer film of a silicon oxide anode prepared in example 1 of the present invention;
FIG. 3 is a schematic diagram showing the pre-lithiation treatment of the pre-lithiation buffer film of the silicon oxide negative electrode prepared in examples 1 to 5 of the present invention;
fig. 4 is a graph of the first charge and discharge of a button half cell assembled from a pre-lithiated silicon oxide negative electrode and a non-pre-lithiated silicon oxide negative electrode prepared in application example 1 of the present invention, wherein the solid line is the non-pre-lithiated silicon oxide negative electrode and the dotted line is the pre-lithiated silicon oxide negative electrode prepared in application example 1;
FIG. 5 is a graph showing the cycle performance of a button half cell assembled from a pre-lithiated silicon oxide negative electrode and a non-pre-lithiated silicon oxide negative electrode prepared in application example 1 of the present invention, wherein the solid line is the non-pre-lithiated silicon oxide negative electrode and the dotted line is the pre-lithiated silicon oxide negative electrode prepared in application example 1;
fig. 6 is a graph of the first charge and discharge of a button half cell assembled from a pre-lithiated silicon oxide negative electrode and a non-pre-lithiated silicon oxide negative electrode prepared in application example 2 of the present invention, wherein the solid line is the non-pre-lithiated silicon oxide negative electrode and the dotted line is the pre-lithiated silicon oxide negative electrode prepared in application example 2;
fig. 7 is a graph of the first charge and discharge of a button half cell assembled from a pre-lithiated silicon oxide negative electrode and a non-pre-lithiated silicon oxide negative electrode prepared in application example 3 of the present invention, wherein the solid line is the non-pre-lithiated silicon oxide negative electrode and the dotted line is the pre-lithiated silicon oxide negative electrode prepared in application example 3;
fig. 8 is a graph of the first charge and discharge of a button half cell assembled from a pre-lithiated silicon oxide negative electrode and a non-pre-lithiated silicon oxide negative electrode prepared in application example 4 of the present invention, wherein the solid line is the non-pre-lithiated silicon oxide negative electrode and the dotted line is the pre-lithiated silicon oxide negative electrode prepared in application example 4;
fig. 9 is a graph of the first charge and discharge of a button half cell assembled from a pre-lithiated silicon oxide negative electrode and a non-pre-lithiated silicon oxide negative electrode prepared in application example 5 of the present invention, wherein the solid line is the non-pre-lithiated silicon oxide negative electrode and the dotted line is the pre-lithiated silicon oxide negative electrode prepared in application example 5.
Detailed Description
The invention provides a preparation method of a pre-lithiation buffer film of a silicon oxide anode, which comprises the following steps:
(1) Mixing a biomass material, an activating agent and water, and then sequentially performing activation treatment and first drying to obtain an activated biomass material;
sequentially carbonizing, acid washing, water washing and secondary drying the activated biomass material to obtain biomass porous carbon;
(2) Mixing the biomass porous carbon obtained in the step (1) with a polymer, lithium salt and an organic solvent, and sequentially carrying out mechanical stirring and ultrasonic dispersion to obtain a mixed solution;
and (3) scraping the mixed solution on a substrate, and performing vacuum drying to obtain the pre-lithiation buffer film of the silicon oxide anode.
In the present invention, the raw materials used are all conventional commercial products in the art unless otherwise specified.
The method comprises the steps of mixing a biomass material, an activating agent and water, and then sequentially carrying out activation treatment and first drying to obtain the activated biomass material.
In the present invention, the biomass material is preferably at least one of bamboo wood powder, peanut shells, walnut shells, straw, coconut shells, starch, and grains. In the present invention, the biomass material is preferably subjected to washing, drying and crushing treatment before use.
In the present invention, the activator is preferably KOH, naOH, liOH, znCl 2 、NaCl、KCl、K 2 CO 3 、H 3 PO 4 At least one of them.
In the invention, the mass ratio of the biomass material to the activating agent is preferably (0.6-12): (1 to 42), more preferably (1 to 10): (2-40). The invention controls the mass ratio of the biomass material to the activator in the range, thereby preparing the three-dimensional biomass carbon material with a proper multi-stage pore canal structure, enabling lithium salt to enter the pore canal structure, realizing uniform and continuous transmission of ions and electrons, and finally achieving the effect of uniform prelithiation.
In the present invention, the activation treatment is preferably performed under stirring conditions; the time of the activation treatment is preferably 1-24 hours; the temperature of the activation treatment is preferably room temperature.
In the present invention, the temperature of the first drying is preferably 80 to 150 ℃. The present invention is not limited in the first drying time, and the removal of water can be achieved.
After the activated biomass material is obtained, the activated biomass material is carbonized, acid-washed, water-washed and second dried in sequence to obtain the biomass porous carbon.
In the invention, the heating rate of carbonization is preferably 1-10 ℃/min, the temperature of carbonization is preferably 600-1100 ℃, and the time of carbonization is preferably 0.5-6 h. The invention controls the temperature rising speed, temperature and time of carbonization in the above range, can prepare biomass porous carbon with a multi-level pore structure comprising small pores, medium pores and large pores, is more beneficial to the dispersion of lithium salt into the pore structure, and realizes the continuity of a lithium guide passage and uniform pre-lithium supplementation.
In the invention, the acid used for acid washing is preferably hydrochloric acid solution with the concentration of 1-9 mol/L. In the present invention, the water used for the water washing is preferably deionized water. The invention has no special limit to the times of water washing, and can realize water washing to be neutral. The second drying mode is not limited in character, and the water removal can be realized.
After the biomass porous carbon is obtained, the biomass porous carbon is mixed with the polymer, the lithium salt and the organic solvent, and then the mechanical stirring and the ultrasonic dispersion are sequentially carried out to obtain a mixed solution.
In the present invention, the polymer is preferably at least one of PVDF-HFP, EVA, PE, PPO, PVC, PVMA.
In the present invention, the lithium salt is preferably LiTFSI, liClO, liBOB, liBF 4 、LiFSI、LiDFP、LiDFOB、LiPO 2 F 2 At least one of them.
In the invention, the mass ratio of the biomass porous carbon, the polymer and the lithium salt is preferably (3-12): (0.6-12): (1-22), more preferably (4-10): (1-10): (2-20). The invention controls the mass ratio of biomass porous carbon, polymer and lithium salt in the above range, can form a pre-lithiation buffer film of the silicon oxide anode with a self-supporting film structure with better mechanical property, and simultaneously has high ionic conductivity and electronic conductivity.
In the present invention, the organic solvent is preferably at least one of N, N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, ethyl acetate, dimethyl sulfoxide, dioxane, N-hexane, acetone, acetonitrile. In the invention, the ratio of the mass of the biomass porous carbon to the volume of the organic solvent is preferably (4-10) g: (10-24) mL. The invention controls the mass of biomass porous carbon and the volume ratio of organic solvent in the above range, so that each component material can be uniformly dispersed in the organic solvent, and the smoothness and flatness of the prepared pre-lithiation buffer film structure of the silicon oxide anode are ensured.
In the invention, the rotating speed of the mechanical stirring is preferably 500-1000 r/min, and the time of the mechanical stirring is preferably 10-48 h. The invention controls the rotation speed and time of mechanical stirring in the above range, can uniformly disperse each component material, and simultaneously allows lithium salt to enter the pore structure of the biological porous carbon more uniformly.
In the invention, the power of ultrasonic dispersion is preferably 50-100W, and the time of ultrasonic dispersion is preferably 0.5-3 h. The invention controls the power and time of ultrasonic dispersion in the above range, and further disperses the biological porous carbon, lithium salt and polymer uniformly, so that the prepared pre-lithiation buffer film of the silicon oxide negative electrode can perform pre-lithiation uniformly.
After the mixed solution is obtained, the mixed solution is coated on a substrate in a scraping way, and vacuum drying is carried out to obtain the pre-lithiation buffer film of the silicon oxide cathode.
In the invention, the thickness of the film of the blade-coated product obtained after blade coating is preferably 100-500 μm. The thickness of the film of the scratch-coated product obtained after the scratch coating is controlled in the range, so that the integrity of the film structure can be ensured in the pre-lithium process, and meanwhile, the ion conductivity and the electron conductivity of the pre-lithiation buffer film of the silicon oxide anode can be ensured to be basically unchanged.
In the present invention, the substrate is preferably a stainless steel foil. In the invention, the temperature of the vacuum drying is preferably 45-150 ℃. The time of vacuum drying is not particularly limited, and the solvent can be removed.
The invention also provides the pre-lithiation buffer film of the silicon oxide anode prepared by the preparation method.
The invention also provides a method for pre-lithiation of the pre-lithiation buffer film of the silicon oxide anode by adopting the technical scheme, which comprises the following steps: and under the inert atmosphere condition, sequentially placing a silicon-oxygen negative electrode plate, a pre-lithiation buffer film and a lithium foil of the silicon-oxygen negative electrode from bottom to top, and dropwise adding electrolyte at the interface of the silicon-oxygen negative electrode to perform pre-lithiation treatment to obtain the pre-lithiated silicon-oxygen negative electrode.
In the invention, the pressure of the pre-lithiation treatment is preferably 0.5-10 kg, and the time of the pre-lithiation treatment is preferably 0.5-24 h.
The method for prelithiation provided by the invention is simple to operate, mild in reaction condition and suitable for large-scale production and application.
The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The preparation method of the pre-lithiation buffer film of the silicon oxide cathode comprises the following steps:
(1) Mixing and dispersing 5g of washed, dried and crushed bamboo wood powder and 10g of KOH into water, performing activation treatment for 10 hours under the stirring condition, and performing first drying at the temperature of 80 ℃ to obtain an activated biomass material; the mass ratio of the bamboo wood powder biomass material to the KOH activator is 1:2;
carbonizing the activated biomass material for 2 hours under inert gas at a temperature of 800 ℃ at a temperature rising speed of 5 ℃/min, washing the carbonized product with 100mL of 1mol/L hydrochloric acid solution, washing with deionized water to be neutral, and performing secondary drying to obtain biomass porous carbon;
(2) Dispersing the biomass porous carbon obtained in the step (1), PVDF-HFP and LiTFSI into 10mL of N, N-Dimethylformamide (DMF) according to the mass ratio of 4:1:2, mechanically stirring for 12h and ultrasonically dispersing for 0.5h to obtain a uniform and stable mixed solution; the ratio of the mass of the biomass porous carbon to the volume of the N, N-dimethylformamide organic solvent is 2g:5mL;
and (3) directly scraping the mixed solution on a stainless steel foil according to the thickness of a scraping product film of 100 mu m, and drying in vacuum at 80 ℃ to obtain the pre-lithiation buffer film of the silicon oxide anode.
The SEM image of the biomass porous carbon prepared in example 1 was obtained by observing the biomass porous carbon prepared in example 1 with a scanning electron microscope, and as shown in fig. 1, the biomass porous carbon was composed of three different pore structures, the pore diameter of the macropores was about 12 μm, the pore diameter of the mesopores was 2 μm, and the surface of the macropores was dispersed with nano-scale micropores.
The cross section of the pre-lithiated buffer film of the silicon oxide anode prepared in example 1 was observed by a scanning electron microscope, and an SEM image of the cross section of the pre-lithiated buffer film of the silicon oxide anode prepared in example 1 was obtained, as shown in fig. 2, and as apparent from fig. 2, the thickness of the pre-lithiated buffer film of the silicon oxide anode prepared in example 1 was 150 μm, and the components were uniformly dispersed.
Application examples 1-5 schematic diagrams of the pre-lithiation treatment performed by using the pre-lithiation buffer film of the silicon oxide anode prepared in examples 1-5 are shown in fig. 3, and in the pre-lithiation treatment process, the silicon oxide anode, the pre-lithiation buffer film (of the silicon oxide anode of the lithium ion battery) and the lithium foil are placed in sequence from bottom to top.
Application example 1
The method for prelithiation using the prelithiation buffer film for a silicon oxide negative electrode described in example 1 comprises the following steps: under the inert atmosphere condition, sequentially placing a silicon oxide negative electrode, the pre-lithiation buffer film and the lithium foil from bottom to top, dropwise adding 10 mu L of electrolyte at the interface of the silicon oxide negative electrode, and performing pre-lithiation treatment for 1h under the pressure condition of 3kg to obtain a pre-lithiated silicon oxide negative electrode;
the electrolyte is a mixed solution of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) with the volume ratio of 1:1:1, and the lithium salt is LiPF with the volume ratio of 1mol/L 6 Adding 5% fluoroethylene carbonate (FEC) (mass fraction);
and the specific parameters of the silicon oxide negative electrode plate are as follows: the negative electrode material current collector adopts a single-light copper foil with the thickness of 10 mu m, the negative electrode active material is a silicon oxide material, the unit capacity is 1600mAh/g, and the current collector also comprises conductive agent carbon black, CMC (sodium carboxymethyl cellulose) and SBR (styrene butadiene rubber); wherein, the mass ratio of the silicon oxide material to the conductive agent carbon black to the CMC to the SBR is 80:10:5:5.
the button half cell was assembled using the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 1, respectively, i.e., the positive electrode case, the silicon oxide negative electrode, the separator, the lithium foil, the spacer, and the negative electrode case were placed in this order.
The initial charge-discharge curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 1 is detected by using a new wire test cabinet CT-4000 under the voltage range of 0.05-1.5 and V by adopting a constant-current constant-voltage charge-discharge method, and is shown in fig. 4, wherein a solid line is the initial charge-discharge curve of the button half cell assembled by the non-pre-lithiated silicon oxide negative electrode, and a dotted line is the initial charge-discharge curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode prepared in application example 1. As can be seen from fig. 4, the lithium intercalation capacity of the pre-lithiated silicon oxide negative electrode was reduced from 2170.5mAh/g to 1902mAh/g, and the first-week efficiency was improved from 76.3% to 87.4% as compared with the non-pre-lithiated silicon oxide negative electrode.
The cycle diagram of the button half cell assembled by the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 1 is detected by using a new wire test cabinet CT-4000 under the voltage range of 0.05-1.5 and V by adopting a constant-current constant-voltage charge-discharge method, and is shown in fig. 5, wherein a solid line is a cycle curve of the button half cell assembled by the non-pre-lithiated silicon oxide negative electrode, and a dotted line is a cycle curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode prepared in application example 1. As can be seen from fig. 5, the charge specific capacity after 100 weeks of cycle of the pre-lithiated silicon oxide negative electrode was 957mAh/g, and the capacity retention rate was 90.9%, compared with the non-pre-lithiated silicon oxide negative electrode, indicating that the pre-lithiated treatment operation in application example 1 is advantageous for improving the electrochemical performance of the silicon oxide negative electrode.
Example 2
The preparation method of the pre-lithiation buffer film of the silicon oxide cathode comprises the following steps:
(1) Washing, drying and crushing 5g of bamboo powder and 40g of ZnCl 2 Mixing and dispersing the mixture into an aqueous solution, performing activation treatment for 12 hours under the stirring condition, and performing first drying at the temperature of 100 ℃ to obtain an activated biomass material; the bamboo wood powder biomass material and ZnCl 2 The mass ratio of the activator is 1:6, preparing a base material;
carbonizing the activated biomass material for 3 hours under inert gas at the temperature of 900 ℃ according to the heating speed of 2 ℃/min, washing the carbonized product with 500mL of 2mol/L hydrochloric acid solution, washing with deionized water to be neutral, and drying to obtain biomass porous carbon;
(2) The biomass porous carbon, EVA and LiPO obtained in the step (1) are treated by 2 F 2 Dispersing into 20mL of N, N-Dimethylformamide (DMF) according to the mass ratio of 4:1:4, mechanically stirring for 24 hours and ultrasonically dispersing for 1 hour to obtain uniform and stable mixed solution; the ratio of the mass of the biomass porous carbon to the volume of the N, N-dimethylformamide organic solvent is 1g:5mL;
and (3) directly scraping the mixed solution on a stainless steel foil according to the thickness of a scraping product film of 100 mu m, and drying in vacuum at 120 ℃ to obtain the pre-lithiation buffer film of the silicon oxide anode.
Application example 2
The method for prelithiation using the prelithiation buffer film for a silicon oxide negative electrode described in example 2 was as follows: and under the inert atmosphere condition, sequentially placing a silicon oxide negative electrode plate, the pre-lithiation buffer film and the lithium foil from bottom to top, dropwise adding 20 mu L of electrolyte at the interface of the silicon oxide negative electrode, and performing 3h pre-lithiation treatment under the pressure condition of 5kg to obtain the pre-lithiated silicon oxide negative electrode.
The electrolyte is Ethylene Carbonate (EC), dimethyl carbonate (DMC) andmixed solution of methyl ethyl carbonate (EMC) with volume ratio of 1:1:1 and LiPF with lithium salt of 1mol/L 6 5% fluoroethylene carbonate (FEC) was added;
and the specific parameters of the silicon oxide negative electrode plate are as follows: the negative electrode material current collector adopts a single-light copper foil with the thickness of 10 mu m, the negative electrode active material is a silicon oxide material, the unit capacity is 1600mAh/g, and the current collector also comprises conductive agent carbon black, CMC (sodium carboxymethyl cellulose) and SBR (styrene butadiene rubber); wherein, the mass ratio of the silicon oxide material to the conductive agent carbon black to the CMC to the SBR is 80:10:5:5.
the button half cell was assembled using the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 2, respectively, i.e., the positive electrode case, the silicon oxide negative electrode, the PP separator, the lithium foil, the gasket, and the negative electrode case were placed in this order.
The initial charge-discharge curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 2 is detected by using a new wire test cabinet CT-4000 under the voltage range of 0.05-1.5V by adopting a constant-current constant-voltage charge-discharge method, and is shown in fig. 6, wherein a solid line is the initial charge-discharge curve of the button half cell assembled by the non-pre-lithiated silicon oxide negative electrode, and a dotted line is the initial charge-discharge curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode prepared in application example 2. As can be seen from fig. 6, the lithium intercalation capacity of the pre-lithiated silicon oxide negative electrode was reduced from 2170.5mAh/g to 1498mAh/g, and the first-week efficiency was increased from 76.3% to 112.2% as compared with the non-pre-lithiated silicon oxide negative electrode.
Example 3
The preparation method of the pre-lithiation buffer film of the silicon oxide cathode comprises the following steps:
(1) Mixing and dispersing 5g of washed, dried and crushed bamboo wood powder and 20g of KOH into an aqueous solution, performing activation treatment for 24 hours under the stirring condition, and performing first drying at 120 ℃ to obtain an activated biomass material; the mass ratio of the bamboo wood powder biomass material to the KOH activator is 1:4, a step of;
carbonizing the activated biomass material for 1h under inert gas at a temperature of between 1000 ℃ and 10 ℃/min; washing the carbonized product with 100mL of 1mol/L hydrochloric acid solution, washing with deionized water to be neutral, and performing secondary drying to obtain biomass porous carbon;
(2) Dispersing the biomass porous carbon, PVMA and LiTFSI obtained in the step (1) into 10mL of N, N-Dimethylformamide (DMF) according to the mass ratio of 4:10:15, mechanically stirring for 24 hours and ultrasonically dispersing for 0.5 hour to obtain a uniform and stable mixed solution; the ratio of the mass of the biomass porous carbon to the volume of the N, N-dimethylformamide organic solvent is 2g:5mL;
and (3) directly scraping the mixed solution on a stainless steel foil according to the thickness of a scraping product film of 100 mu m, and drying in vacuum at 150 ℃ to obtain the pre-lithiation buffer film of the silicon oxide anode.
Application example 3
The method for pre-lithiation using the pre-lithiation buffer film of a silicon oxide anode described in example 3, comprises the steps of: under the inert atmosphere condition, sequentially placing a silicon oxide negative electrode plate, the pre-lithiation buffer film and the lithium foil from bottom to top, dropwise adding 10 mu L of electrolyte at the interface of the silicon oxide negative electrode, and performing 2h pre-lithiation treatment under the pressure condition of 5kg to finally obtain a pre-lithiated silicon oxide negative electrode;
the electrolyte is a mixed solution of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) with the volume ratio of 1:1:1, and the lithium salt is LiPF with the volume ratio of 1mol/L 6 5% fluoroethylene carbonate (FEC) was added;
and the specific parameters of the silicon oxide negative electrode plate are as follows: the negative electrode material current collector adopts a single-light copper foil with the thickness of 10 mu m, the negative electrode active material is a silicon oxide material, the unit capacity is 1600mAh/g, and the current collector also comprises conductive agent carbon black, CMC (sodium carboxymethyl cellulose) and SBR (styrene butadiene rubber); wherein, the mass ratio of the silicon oxide material to the conductive agent carbon black to the CMC to the SBR is 80:10:5:5.
the button half cell was assembled using the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 3, respectively, i.e., the positive electrode case, the silicon oxide negative electrode, the separator, the lithium foil, the spacer, and the negative electrode case were placed in this order.
The initial charge-discharge curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 3 is detected by using a new wire test cabinet CT-4000 under the voltage range of 0.05-1.5V by adopting a constant-current constant-voltage charge-discharge method, and is shown in fig. 7, wherein a solid line is the initial charge-discharge curve of the button half cell assembled by the non-pre-lithiated silicon oxide negative electrode, and a dotted line is the initial charge-discharge curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode prepared in application example 3. As can be seen from fig. 7, the lithium intercalation capacity of the pre-lithiated silicon oxide negative electrode was reduced from 2170.5mAh/g to 1721mAh/g, and the first-week efficiency was improved from 76.3% to 97.5% as compared with the non-pre-lithiated silicon oxide negative electrode.
Example 4
The preparation method of the pre-lithiation buffer film of the silicon oxide cathode comprises the following steps:
(1) 10g of washed, dried and crushed peanut shell powder is mixed with 40g K 2 CO 3 Mixing and dispersing the mixture into an aqueous solution, performing activation treatment for 10 hours under the stirring condition, and performing first drying at the temperature of 80 ℃ to obtain an activated biomass material; the peanut shell powder biomass material and K 2 CO 3 The mass ratio of the activator is 1:4, a step of;
carbonizing the activated biomass material for 2 hours under inert gas at a temperature of between 900 ℃ and a temperature rising speed of 5 ℃/min; washing the carbonized product with 100mL of 1mol/L hydrochloric acid solution, washing with deionized water to neutrality, and drying to obtain biomass porous carbon;
(2) Dispersing the biomass porous carbon obtained in the step (1), PP and LiTFSI into 10mL of acetonitrile according to the mass ratio of 4:1:2, mechanically stirring for 5h and ultrasonically dispersing for 0.5h to obtain a uniform and stable mixed solution; the ratio of the mass of the biomass porous carbon to the volume of the N, N-dimethylformamide organic solvent is 2g:5mL;
and (3) directly scraping the mixed solution on a stainless steel foil according to the thickness of a scraping product film of 200 mu m, and drying in vacuum at 120 ℃ to obtain the pre-lithiation buffer film of the silicon oxide anode.
Application example 4
The method for prelithiation using the prelithiation buffer film for a silicon oxide negative electrode described in example 4 was as follows: under the inert atmosphere condition, sequentially placing a silicon oxide negative electrode piece, the pre-lithiation buffer film and the lithium foil from bottom to top, dropwise adding 100 mu L of electrolyte at the interface of the silicon oxide negative electrode, and performing pre-lithiation treatment for 2.5h under the pressure condition of 10kg to finally obtain a pre-lithiated silicon oxide negative electrode;
the electrolyte is a mixed solution of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) with the volume ratio of 1:1:1, and the lithium salt is LiPF with the volume ratio of 1mol/L 6 Adding 5% fluoroethylene carbonate (FEC) (mass fraction);
and the specific parameters of the silicon oxide negative electrode plate are as follows: the negative electrode material current collector adopts a single-light copper foil with the thickness of 10 mu m, the negative electrode active material is a silicon oxide material, the unit capacity is 1600mAh/g, and the current collector also comprises conductive agent carbon black, CMC (sodium carboxymethyl cellulose) and SBR (styrene butadiene rubber); wherein, the mass ratio of the silicon oxide material to the conductive agent carbon black to the CMC to the SBR is 80:10:5:5.
the button half cell was assembled using the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 4, respectively, i.e., the positive electrode case, the silicon oxide negative electrode, the separator, the lithium foil, the spacer, and the negative electrode case were placed in this order.
The initial charge-discharge curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 4 is detected by using a new wire test cabinet CT-4000 under the voltage range of 0.05-1.5V by adopting a constant-current constant-voltage charge-discharge method, and is shown in fig. 4, wherein a solid line is the initial charge-discharge curve of the button half cell assembled by the non-pre-lithiated silicon oxide negative electrode, and a dotted line is the initial charge-discharge curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode prepared in application example 4. As can be seen from fig. 8, the lithium intercalation capacity of the pre-lithiated silicon oxide negative electrode was reduced from 2170.5mAh/g to 1661.5mAh/g, and the first-week efficiency was increased from 76.3% to 101.2% as compared with the non-pre-lithiated silicon oxide negative electrode.
Example 5
The preparation method of the pre-lithiation buffer film of the silicon oxide cathode comprises the following steps:
(1) Mixing and dispersing 5g of washed, dried and crushed cereal flour (wheat flour) and 40g of KCl into an aqueous solution, performing activation treatment for 24 hours under the stirring condition, and performing first drying at the temperature of 150 ℃ to obtain an activated biomass material; the mass ratio of the cereal flour (wheat flour) biomass material to the KCl activator is 1:8, 8;
carbonizing the activated biomass material for 1h under inert gas at a temperature of between 1000 ℃ and 5 ℃/min; washing the carbonized product with 100mL of 1mol/L hydrochloric acid solution, washing with deionized water to be neutral, and performing secondary drying to obtain biomass porous carbon;
(2) Dispersing the biomass porous carbon obtained in the step (1) into 24mL of tetrahydrofuran according to the mass ratio of 4:1:2, mechanically stirring for 48 hours and ultrasonically dispersing for 0.5 hour to obtain uniform and stable mixed solution; the ratio of the mass of the biomass porous carbon to the volume of the N, N-dimethylformamide organic solvent is 1g:6mL;
and directly scraping the mixed solution on a stainless steel foil according to the thickness of a scraping product film of 500 mu m, and drying in vacuum at 120 ℃ to obtain the pre-lithiation buffer film of the silicon oxide anode.
Application example 5
The method for prelithiation using the prelithiation buffer film for a silicon oxide negative electrode described in example 5 was as follows: under the inert atmosphere condition, sequentially placing a silicon oxide negative electrode plate, the pre-lithiation buffer film and the lithium foil from bottom to top, dropwise adding 50 mu L of electrolyte at the interface of the silicon oxide negative electrode, and performing 2h pre-lithiation treatment under the pressure condition of 5kg to finally obtain a pre-lithiated silicon oxide negative electrode;
the electrolyte is a mixed solution of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) with the volume ratio of 1:1:1, and the lithium salt is LiPF with the volume ratio of 1mol/L 6 Adding 5% fluoroethylene carbonate (FEC) (mass fraction);
and the specific parameters of the silicon oxide negative electrode plate are as follows: the negative electrode material current collector adopts a single-light copper foil with the thickness of 10 mu m, the negative electrode active material is a silicon oxide material, the unit capacity is 1600mAh/g, and the current collector also comprises conductive agent carbon black, CMC (sodium carboxymethyl cellulose) and SBR (styrene butadiene rubber); wherein, the mass ratio of the silicon oxide material to the conductive agent carbon black to the CMC to the SBR is 80:10:5:5.
the button half cell was assembled using the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 5, respectively, i.e., the positive electrode case, the silicon oxide negative electrode, the separator, the lithium foil, the spacer, and the negative electrode case were placed in this order.
The initial charge-discharge curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode and the non-pre-lithiated silicon oxide negative electrode prepared in application example 5 is detected by using a new wire test cabinet CT-4000 under the voltage range of 0.05-1.5 and V by adopting a constant-current constant-voltage charge-discharge method, and is shown in fig. 9, wherein a solid line is the initial charge-discharge curve of the button half cell assembled by the non-pre-lithiated silicon oxide negative electrode, and a dotted line is the initial charge-discharge curve of the button half cell assembled by the pre-lithiated silicon oxide negative electrode prepared in application example 5. As can be seen from fig. 9, the lithium intercalation capacity of the pre-lithiated silicon oxide negative electrode was reduced from 2171.5mAh/g to 1985.7mAh/g, and the first-week efficiency was improved from 76.3% to 84.5% as compared with the non-pre-lithiated silicon oxide negative electrode.
In summary, compared with the non-prelithiated silicon oxide negative electrode, the pre-lithiated silicon oxide negative electrode prepared in application example 1 has a specific charge capacity of 957mAh/g after 100 weeks of cycle, and a capacity retention rate of 90.9%, which indicates that the pre-lithiation treatment operation in application example 1 is beneficial to improving the electrochemical performance of the silicon oxide negative electrode; compared with the non-prelithiated silicon oxide cathode, the lithium intercalation capacity of the prelithiated silicon oxide cathode prepared in application example 2 is reduced from 2170.5mAh/g to 1498mAh/g, and the first-week efficiency is improved from 76.3% to 112.2%.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A preparation method of a pre-lithiation buffer film of a silicon oxide anode comprises the following steps:
(1) Mixing a biomass material, an activating agent and water, and then sequentially performing activation treatment and first drying to obtain an activated biomass material;
sequentially carbonizing, acid washing, water washing and secondary drying the activated biomass material to obtain biomass porous carbon;
(2) Mixing the biomass porous carbon obtained in the step (1) with a polymer, lithium salt and an organic solvent, and sequentially carrying out mechanical stirring and ultrasonic dispersion to obtain a mixed solution;
and (3) scraping the mixed solution on a substrate, and performing vacuum drying to obtain the pre-lithiation buffer film of the silicon oxide anode.
2. The method of claim 1, wherein the biomass material in step (1) is at least one of bamboo powder, peanut shells, walnut shells, straw, coconut shells, starch, and grain.
3. The preparation method according to claim 1, wherein the temperature rise rate of carbonization in the step (1) is 1-10 ℃/min, the carbonization temperature is 600-1100 ℃, and the carbonization time is 0.5-6 h.
4. The method of claim 1, wherein the polymer in step (2) is at least one of PVDF-HFP, EVA, PE, PPO, PVC, PVMA.
5. The method according to claim 1, wherein the lithium salt in the step (2) is LiTFSI, liClO, liBOB, liBF 4 、LiFSI、LiDFP、LiDFOB、LiPO 2 F 2 At least one of them.
6. The preparation method of claim 1, wherein in the step (2), the mass ratio of the biomass porous carbon, the polymer and the lithium salt is (3-12): (0.6-12): (1-22).
7. The preparation method of claim 1, wherein the rotation speed of mechanical stirring in the step (2) is 500-1000 r/min, and the time of mechanical stirring is 10-48 h.
8. The pre-lithiated buffer film of a silicon oxide anode prepared by the preparation method of any one of claims 1 to 7.
9. A method of prelithiation using the prelithiation buffer film for a silicon oxide negative electrode as defined in claim 8, comprising the steps of: and under the inert atmosphere condition, sequentially placing a silicon-oxygen negative electrode plate, a pre-lithiation buffer film and a lithium foil of the silicon-oxygen negative electrode from bottom to top, and dropwise adding electrolyte at the interface of the silicon-oxygen negative electrode to perform pre-lithiation treatment to obtain the pre-lithiated silicon-oxygen negative electrode.
10. The method according to claim 9, wherein the pressure of the pre-lithiation treatment is 0.5-10 kg and the time of the pre-lithiation treatment is 0.5-24 h.
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| CN112750984A (en) * | 2021-01-06 | 2021-05-04 | 西北工业大学 | Preparation method and use method of intermediate buffer film of pre-lithiation lithium ion battery silicon-based negative electrode |
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