Preparation method of polymer-coated silicon-based negative electrode material
Through the preparation method of polymer-coated silicon-based negative electrode material, the volume expansion and alkalinity of silicon-based materials in lithium-ion batteries are solved, the energy density and cycle stability of the battery are improved, and more efficient electrochemical performance is achieved .
Patent Information
- Application Number
- CN202310682909.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-09
- Publication Date
- 2024-12-10
AI Technical Summary
Traditional graphite negative electrode materials have low capacity, and the volume expansion effect and surface alkalinity problems of silicon-based materials during charging and discharging limit their application, affecting the energy density and cycling stability of the battery.
The preparation method of polymer-coated silicon-based negative electrode material is adopted. The silicon-based material is coated by carbon and mixed with a lithium source, and then calcined, and polymer coating is carried out. Polymers such as PMMA, PEO, PVA, etc. are used to improve the material's Compatibility and stability.
The first Coulomb efficiency was improved, the volume expansion was limited, the cycling and electrochemical performance of the electrodes were improved, and the energy density and stability of the battery were improved.
Smart Images
Figure CN119108518A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the fields of energy storage materials and electrochemistry, and in particular to a method for preparing a polymer-coated silicon-based negative electrode material. Background Art
[0002] With the popularization of new energy vehicles, there is a huge demand for high energy density, endurance and low cost of power batteries. The specific capacity of traditional graphite negative electrodes is too low to meet the needs of high specific capacity lithium-ion batteries, while the theoretical specific capacity of silicon-based materials is much higher than that of graphite, which is close to its performance limit, and the voltage to lithium is not high. Therefore, silicon-based materials are expected to become the negative electrode materials for the next generation of high energy density lithium batteries. Among them, silicon oxide has a higher theoretical capacity (2400mAh / g) and a relatively low volume expansion effect (200%), and is a new type of negative electrode material for lithium-ion batteries. However, compared with graphite, the volume expansion effect of silicon oxide during the charging and discharging process is still an important obstacle to its application. At the same time, due to the presence of oxygen, the lithium ions provided by the positive electrode react with oxygen during the first charging and discharging process to generate electrochemically inactive lithium silicate (Li x Si y O z ) and lithium oxide (Li 2 O), rather than forming an electrochemically active lithium-silicon alloy (Li x Si y ), which consumes the number of reversible lithium ions, resulting in a low first coulomb efficiency. The low first efficiency directly affects the capacity of the positive electrode, thereby reducing the energy density of the battery.
[0003] In addition, due to the hydrolysis of lithium silicate and the presence of lithium oxide, the alkalinity of the negative electrode aqueous slurry is relatively strong, which will partially react with the carboxyl -COOH in the mainstream silicon-carbon polymer binder (such as polyacrylic acid, etc.), affecting the binder performance and the long-term cycle stability of the battery cell. At the same time, the strong alkalinity of the slurry will also react with the nano-silicon particles in silicon oxide and release gas, affecting the coating process, causing the activity of nano-silicon to decrease and reducing the material capacity. Therefore, how to modify the surface of high-first-effect silicon oxide and reduce the surface alkalinity is of great significance to improving the cycle stability of the electrode. Summary of the invention
[0004] The purpose of the present invention is to solve at least one of the above-mentioned deficiencies in the prior art. For example, one of the purposes of the present invention is to provide a method for preparing a polymer-coated silicon-based negative electrode material that can improve the initial coulombic efficiency, limit volume expansion, and improve the cycle performance of the electrode.
[0005] In order to achieve the above objectives, the present invention provides a method for preparing a polymer-coated silicon-based negative electrode material.
[0006] The preparation method of the polymer-coated silicon-based negative electrode material comprises the following steps: carbon-coating the silicon-based material, and then evenly mixing it with a lithium source to obtain a pre-lithiated silicon negative electrode precursor; calcining the pre-lithiated silicon negative electrode precursor under a protective gas to obtain a pre-lithiated silicon negative electrode material; and acid-washing the pre-lithiated silicon negative electrode material, and then polymer-coating it; wherein the polymer is one or more of PMMA, PEO, PVA, PVDF-HFP, PANI, PPY, PBS, and PEDOT:PSS.
[0007] In an exemplary embodiment of the method for preparing a polymer-coated silicon-based negative electrode material of the present invention, the silicon-based material may be silicon oxide, or one or more of silicon monoxide, silicon oxide, and metal element-doped silicon oxide compounds, wherein the chemical formula of the silicon oxide may be SiO x , where 0<x<2.
[0008] In an exemplary embodiment of the method for preparing a polymer-coated silicon-based negative electrode material of the present invention, the carbon coating may be prepared by chemical vapor deposition, which may include: reacting the silicon-based material and an organic gas carbon source at high temperature under a protective gas to prepare a carbon-coated silicon-based material, wherein the structure of the carbon-coated silicon-based material may be SiO x @C.
[0009] In an exemplary embodiment of the method for preparing a polymer-coated silicon-based negative electrode material of the present invention, the organic gas carbon source may be one or more of methane, acetylene and ethylene, and the mixing ratio of the organic gas carbon source and the protective gas may be 1:0.2 to 5.
[0010] In an exemplary embodiment of the method for preparing the polymer-coated silicon-based negative electrode material of the present invention, the high-temperature reaction temperature may be 600-1000° C., the heating rate may be 1-20° C. / min, and the insulation time may be 10-300 min.
[0011] In an exemplary embodiment of the preparation method of the polymer-coated silicon-based negative electrode material of the present invention, the preparation method may also include: naturally cooling to room temperature after the calcination step to obtain a pre-lithiation silicon negative electrode material, the calcination heating rate may be 3 to 10°C / min, the insulation temperature after calcination may be 600 to 1000°C, and the insulation time may be 3 to 10 hours.
[0012] In an exemplary embodiment of the preparation method of the polymer-coated silicon-based negative electrode material of the present invention, the amount of the carbon-coated silicon-based material may be 1 to 10 g, and the molar ratio of the carbon-coated silicon-based material to the lithium source may be 10:1 to 3:2; the lithium source may be one or more of lithium amide, lithium hydride, lithium hydroxide, lithium nitride, lithium fluoride, lithium oxide, lithium peroxide, and lithium sulfide.
[0013] In an exemplary embodiment of the preparation method of the polymer-coated silicon-based negative electrode material of the present invention, the acid pickling may include: dispersing the pre-lithiation silicon negative electrode material in an acidic solution, stirring, filtering, washing until the washing liquid is neutral and drying, and the stirring time may be 3 to 10 minutes.
[0014] In an exemplary embodiment of the method for preparing the polymer-coated silicon-based negative electrode material of the present invention, the solute of the acid solution used for the pickling may be one or more of sodium citrate, oxalic acid, glacial acetic acid, perchloric acid, sodium tetraborate and sodium hypochlorite.
[0015] In an exemplary embodiment of the method for preparing the polymer-coated silicon-based negative electrode material of the present invention, the mass of the pre-lithiation silicon negative electrode material can be 0.5-3 g, the concentration of the acidic solution used for the pickling can be 1-5 mol / L, and the volume can be 10 mL-80 mL.
[0016] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:
[0017] (1) The present invention uses lithium-containing compounds to supplement carbon-coated silicon oxide, replenishing the number of reversible lithium ions and improving the initial coulombic efficiency. In addition, the higher initial efficiency directly affects the performance of the positive electrode capacity, thereby improving the overall battery energy density.
[0018] (2) The present invention uses an acid solution of a certain concentration to pickle the pre-lithiated silicon dioxide negative electrode, thereby improving the binder failure and slurry bubbling problems caused by the excessive alkalinity of the sample, thereby improving the cycle performance of the electrode.
[0019] (3) The polymer coating layer of the present invention improves the compatibility between silicon monoxide and the organic electrolyte, limits the volume expansion of the material to a certain extent, avoids material cracking, and more effectively improves the cycle stability of the electrode. In addition, the coated polymer layer further prevents the active material silicon particles in the material from reacting, thereby improving the electrochemical performance of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The above and other objects and / or features of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, in which:
[0021] Figure 1A flow chart showing an example of a method for preparing a polymer-coated silicon-based negative electrode material of the present invention.
[0022] Figure 2 A SEM image showing an example of a method for preparing a polymer-coated silicon-based negative electrode material of the present invention.
[0023] Figure 3 A SEM image showing an example of a method for preparing a polymer-coated silicon-based negative electrode material of the present invention.
[0024] Figure 4 An XRD diagram of an example of a method for preparing a polymer-coated silicon-based negative electrode material of the present invention is shown.
[0025] Figure 5 A first cycle charge and discharge curve diagram of an example of a method for preparing a polymer-coated silicon-based negative electrode material of the present invention is shown. DETAILED DESCRIPTION
[0026] Hereinafter, the method for preparing the polymer-coated silicon-based negative electrode material of the present invention will be described in detail in conjunction with exemplary embodiments.
[0027] It should be noted that the terms "S1", "S2", "S3", etc. used in the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.
[0028] The huge change in volume of silicon during the charge and discharge process causes particle breakage, loss of electrical contact, and loss of active substances, resulting in low initial efficiency and poor cycle performance of silicon-based negative electrode materials, which greatly limits the practical application of silicon-based negative electrode materials. In addition, the continuous consumption of active lithium leads to lithium loss, and the early pre-lithiation causes the surface alkalinity of the material to be higher during the pulping process, which destroys the stability of lithium silicate in silicon-based materials. These problems have a great negative impact on the electrochemical performance of the battery.
[0029] In response to the above problems, the inventors proposed a method for preparing a polymer-coated silicon-based negative electrode material, which can better solve the above problems and make the high-stability silicon composite material have a very broad application scenario.
[0030] Exemplary Embodiment 1
[0031] This exemplary embodiment provides a method for preparing a polymer-coated silicon-based negative electrode material. The method comprises the following steps (eg Figure 1 shown):
[0032] S1. Carbon-coating the silicon-based material, and then evenly mixing it with a lithium source to obtain a pre-lithiated silicon negative electrode precursor.
[0033] Optionally, the silicon-based material is silicon monoxide, or one or more of silicon monoxide, silicon oxide, and metal element-doped silicon oxide compounds, wherein the chemical formula of silicon monoxide is SiO x , where 0<x<2. For example, x can be 0.2, 0.8, 1 and 1.2.
[0034] More specifically, silicon monoxide may include one or more of silicon monoxide, silicon oxide, and silicon oxide compounds doped with metal elements.
[0035] Optionally, the carbon coating is prepared by chemical vapor deposition, including: reacting a silicon-based material and an organic gas carbon source at high temperature under a protective gas to prepare a carbon-coated silicon-based material, wherein the structure of the carbon-coated silicon-based material is SiO x @C.
[0036] Optionally, the organic gas carbon source may be one or more of methane, acetylene and ethylene, and the mixing ratio of the organic gas carbon source to the protective gas may be 1:0.2 to 5. For example, the mixing ratio of the organic gas carbon source to the protective gas may be 1:0.2, 1:1, 1:2, 1:3, 1:4 and 1:5.
[0037] Optionally, the high temperature reaction temperature may be 600-1000°C, the heating rate may be 1-20°C / min, and the holding time may be 10-300min. For example, the high temperature reaction temperature may be 600°C, 700°C, 800°C, 900°C and 1000°C, the heating rate may be 1°C / min, 2°C / min, 5°C / min, 10°C / min, 15°C / min, 20°C / min, and the holding time may be 10min, 50min, 100min, 150min, 200min, 250min, 300min.
[0038] Optionally, the amount of carbon-coated silicon-based material can be 1 to 10 g, and the molar ratio of the carbon-coated silicon-based material to the lithium source can be 10:1 to 3:2; for example, the amount of silicon-based material can be 10 g, and the molar ratio of the carbon-coated silicon-based material to the lithium source can be 1:1.5. The lithium source can be one or more of lithium amide, lithium hydride, lithium hydroxide, lithium nitride, lithium fluoride, lithium oxide, lithium peroxide, and lithium sulfide.
[0039] S2. calcining the pre-lithiated silicon negative electrode precursor under protective gas to obtain a pre-lithiated silicon negative electrode material.
[0040] More specifically, the pre-lithiated silicon negative electrode precursor and the lithium source can be ground and mixed in a mortar for 30 to 120 minutes. For example, the grinding and mixing time can be 30 minutes, 60 minutes, 90 minutes, or 120 minutes. The pre-lithiated silicon negative electrode material is then calcined in an inert atmosphere. The inert atmosphere may include at least one of argon or nitrogen.
[0041] Optionally, after the calcination step, the material can be naturally cooled to room temperature to obtain a pre-lithiated silicon negative electrode material. The heating rate of the calcination can be 3 to 10°C / min, the insulation temperature after calcination can be 600 to 1000°C, and the insulation time can be 3 to 10 hours. For example, the heating rate of the calcination can be 5°C / min, the insulation temperature after calcination can be 650°C, and the insulation time can be 3 hours. The pre-lithiated silicon negative electrode forms silicon, Li 2 SiO 3 When the heating rate of calcination is 3℃ / min, the holding temperature after calcination is 750℃, and the holding time is 6h, the pre-lithiation silicon negative electrode forms silicon, Li 2 Si 2 O 5 , carbon composites.
[0042] S3, and acid-washing the pre-lithiated silicon negative electrode material, and then coating it with a polymer.
[0043] Among them, the polymer is one or more of PMMA, PEO, PVA, PVDF-HFP, PANI, PPY, PBS, and PEDOT:PSS.
[0044] Optionally, the acid washing may include: dispersing the pre-lithiated silicon negative electrode material in an acidic solution, stirring, filtering, and washing until the washing solution is neutral and dry, and the stirring time may be 3 to 10 minutes. For example, the stirring time may be 3 minutes, 5 minutes, or 10 minutes.
[0045] Optionally, the solute of the acid solution used for pickling may be one or more of sodium citrate, oxalic acid, glacial acetic acid, perchloric acid, sodium tetraborate and sodium hypochlorite.
[0046] Optionally, the mass of the pre-lithiated silicon negative electrode material may be 0.5 to 3 g, and the concentration of the acid solution used for pickling may be 1 to 5 mol / L and the volume may be 10 to 80 mL. For example, 2 g of the pre-lithiated silicon negative electrode material may be dispersed in a 40 mL, 2 mol / L acid pickling solution.
[0047] More specifically, the concentration of the polymer solution is 0.1-30wt%, for example, the concentration of the polymer can be 0.1, 1, 5, 10, 20, 30wt%. The selected solvent can include one or more of DOL, DME, and DMC. For example, PMMA with a concentration of 1wt% is prepared in the DOL solution to form a transparent dispersion.
[0048] More specifically, the stirring time is 3 to 24 hours, the drying temperature is 40 to 100° C., and the drying time is 8 to 24 hours. For example, the stirring time is 8 hours, and the drying is performed at a temperature of 40° C. for 12 hours.
[0049] In order to better understand the above exemplary embodiments of the present invention, they are further described below with reference to specific examples and drawings.
[0050] Example 1
[0051] The preparation method of the polymer-coated silicon-based negative electrode material of this example can be achieved by the following steps:
[0052] Step 1: 20g of silicon dioxide (SiO x ) was placed in a tube furnace, and methane / argon was used as the mixed gas source, with a methane to argon mixing ratio of 1:3. The temperature was raised to 950°C at 5°C / min, kept at this temperature for 2h, and then naturally cooled to obtain SiO x / C.
[0053] Step 2: SiO x @C and lithium amide were mixed evenly in a ratio of 3:1, and then heated to 800°C at a heating rate of 5°C / min in an Ar atmosphere, kept for 2 h, and then naturally cooled to room temperature.
[0054] Step 3: Take 2 g of the powder obtained in step 2, dissolve it in 30 mL of 1 mol / L sodium citrate solution and mix and stir for 5 minutes, then filter and wash until the filtrate is neutral, and finally dry the sample at 60°C for 24 hours.
[0055] Step 4: Prepare a 1 wt% PMMA in DOL solution, then disperse the sample in step 3 in 10 ml of the PMMA solution and stir for 8 h, and then dry at 40° C. for 12 h.
[0056] Example 2
[0057] The preparation method of the polymer-coated silicon-based negative electrode material of this example can be achieved by the following steps:
[0058] Step 1: 20g of silicon dioxide (SiO x ) was placed in a tube furnace, and acetylene / argon was used as the mixed gas source, with the mixing ratio of acetylene to argon being 1:0.5. The temperature was raised to 700°C at 2°C / min, kept at this temperature for 1h, and then cooled naturally to obtain SiO x / C.
[0059] Step 2: SiO x @C and lithium hydride were mixed evenly in a ratio of 4:1, and then heated to 750°C at a heating rate of 5°C / min in a nitrogen atmosphere, kept for 6 hours, and then cooled to room temperature.
[0060] Step 3: Take 2 g of the powder obtained in step 2, dissolve it in 50 mL of 1 mol / L sodium citrate solution, mix and stir for 5 minutes, then filter and wash until the filtrate is neutral, and finally dry the sample at 60 ° C for 24 h. At this time, the SEM image of the sample is as follows Figure 2 .
[0061] Step 4: Take the sample obtained in step 3
[0062] The sample was dispersed in 15 mL of 1 wt% PEOinDOL solution and stirred for 8 h and then dried at 40 °C for 12 hours. The SEM image of the obtained sample is shown in Figure 3 , XRD pattern as Figure 4 .
[0063] Example 3
[0064] The preparation method of the polymer-coated silicon-based negative electrode material of this example can be achieved by the following steps:
[0065] Step 1: 20g of silicon dioxide (SiO x ) was placed in a tube furnace, and ethylene / argon was used as the mixed gas source, with the mixing ratio of ethylene to argon being 1:5. The temperature was raised to 600°C at 20°C / min, kept at this temperature for 0.5h, and then cooled naturally to obtain SiO x / C.
[0066] Step 2: SiO x @C and lithium hydride were mixed evenly in a ratio of 3:1, and then heated to 900°C at a heating rate of 5°C / min in an argon atmosphere, kept for 12 h, and then cooled to room temperature.
[0067] Step 3: Take 2 g of the powder obtained in step 2, dissolve it in 30 mL of 2 mol / L sodium citrate solution, mix and stir for 5 minutes, then filter and wash until the filtrate is neutral, and finally dry the sample at 60 ° C for 24 h.
[0068] Step 4: The sample obtained in step 3 was dispersed in 10 mL of 3 wt% PVAinDME solution, stirred for 8 h and then dried at 40°C for 12 h.
[0069] Example 4
[0070] The preparation method of the polymer-coated silicon-based negative electrode material of this example can be achieved by the following steps:
[0071] Step 1: 20g of silicon dioxide (SiO x ) was placed in a tube furnace, and acetylene / ethylene / argon was used as the mixed gas source, and the mixing ratio of acetylene / ethylene and argon was 1:1:5. The temperature was raised to 800°C at 5°C / min, kept at this temperature for 2h, and then cooled naturally to obtain SiOx / C.
[0072] Step 2: SiO x @C and lithium fluoride were mixed evenly in a ratio of 5:1, and then heated to 600°C at a heating rate of 5°C / min in an argon atmosphere, kept for 12 h, and then cooled to room temperature.
[0073] Step 3: Take 2 g of the powder obtained in step 2, dissolve it in 50 mL of 1 mol / L sodium citrate solution and mix and stir for 3 minutes, then filter and wash until the filtrate is neutral, and finally dry the sample at 60°C for 24 hours.
[0074] Step 4: The sample obtained in step 3 was dispersed in 10 mL of 30 wt% PVDF-HFPinDME solution, stirred for 8 h, and then dried at 50 °C for 12 h.
[0075] Example 5
[0076] The preparation method of the polymer-coated silicon-based negative electrode material of this example can be achieved by the following steps:
[0077] Step 1: 20g of silicon dioxide (SiO x ) was placed in a tube furnace, and ethylene / nitrogen was used as the mixed gas source, and the ethylene / argon mixing ratio was 1:2. The temperature was raised to 600°C at 2°C / min, and the temperature was kept for 5 hours and then naturally cooled to obtain SiO x / C.
[0078] Step 2: SiO x @C and lithium nitride were mixed evenly in a ratio of 1:2, and then heated to 600°C at a heating rate of 5°C / min in a nitrogen atmosphere, kept for 12 h, and then cooled to room temperature.
[0079] Step 3: Take 2 g of the powder obtained in step 2, dissolve it in 50 mL of 1 mol / L sodium citrate solution and mix and stir for 3 minutes, then filter and wash until the filtrate is neutral, and finally dry the sample at 60°C for 24 hours.
[0080] Step 4: The sample obtained in step 3 was dispersed in 10 mL of 3 wt% PPY solution, stirred for 8 h and then dried at 50 °C for 12 h.
[0081] Example 6
[0082] The preparation method of the polymer-coated silicon-based negative electrode material of this example can be achieved by the following steps:
[0083] Select the same steps 1, 2 and 3 as in Example 1, prepare 0.5 wt% PBS in the DME solution, then disperse the sample in step 3 in 10 ml of the PBS solution, stir for 12 h, and then dry at 60° C. for 12 h.
[0084] Example 7
[0085] The preparation method of the polymer-coated silicon-based negative electrode material of this example can be achieved by the following steps:
[0086] Select the same steps 1, 2 and 3 as in Example 1, prepare 2 wt.% of PEDOT:PSS in the DMC solution, then disperse the sample in step 3 in 20 ml of the PBS solution, stir for 12 h, and then dry at 100°C for 12 h.
[0087] Example 8
[0088] The preparation method of the polymer-coated silicon-based negative electrode material of this example can be achieved by the following steps:
[0089] Select the same steps 1, 2 and 3 as in Example 2, prepare 5 wt.% PMMA and 5 wt.% PEO in the DMC solution, then disperse the sample in step 3 in 20 ml of the PMMA and PEO mixed solution, stir for 24 hours, and then dry at 100°C for 24 hours.
[0090] The samples obtained in Examples 1 to 8 above are used to prepare button half-cells. The specific steps include: mixing the silicon oxide negative electrode material with acetylene black and PAA-Li in a ratio of 8:1:1, then adding deionized water to mix into a slurry, evenly coating it on the copper foil, drying, rolling, and cutting it into pole pieces. In a glove box filled with argon, assemble it into a button cell. The battery model is 2032, the electrolyte is 1MLiPF6inEC / DMC, the counter electrode is a metal lithium sheet, and the diaphragm is a Celgard2400 microporous polypropylene membrane. Gas production: 2g of sample was added to a 5% by mass NaOH solution, and the gas production was observed at room temperature. The performance comparison of the prepared negative electrode materials is shown in Table 1 below. Among them, the first cycle charge and discharge curve of the material prepared in Example 2 is shown in Figure 5 As can be seen from the figure, it provides 1467mAh g -1 The discharge specific capacity and the first coulombic efficiency are 87%.
[0091] Table 1 Performance of negative electrodes prepared in various examples
[0092]
[0093] In summary, the beneficial effects include:
[0094] (1) The present invention uses lithium-containing compounds to supplement carbon-coated silicon oxide, replenishing the number of reversible lithium ions and improving the initial coulombic efficiency. In addition, the higher initial efficiency directly affects the performance of the positive electrode capacity, thereby improving the overall battery energy density.
[0095] (2) The present invention uses an acid solution of a certain concentration to pickle the pre-lithiated silicon dioxide negative electrode, thereby improving the binder failure and slurry bubbling problems caused by the excessive alkalinity of the sample, thereby improving the cycle performance of the electrode.
[0096] (3) The polymer coating layer of the present invention improves the compatibility between silicon monoxide and the organic electrolyte, limits the volume expansion of the material to a certain extent, avoids material cracking, and more effectively improves the cycle stability of the electrode. In addition, the coated polymer layer further prevents the active material silicon particles in the material from reacting, thereby improving the electrochemical performance of the electrode.
[0097] Although the present invention has been described above in conjunction with the exemplary embodiments and the accompanying drawings, it should be apparent to those skilled in the art that various modifications may be made to the above-described embodiments without departing from the spirit and scope of the claims.
Claims
1. A method for preparing a polymer-coated silicon-based negative electrode material, characterized in that: The preparation method comprises: The silicon-based material is carbon-coated and then evenly mixed with a lithium source to obtain a pre-lithiated silicon negative electrode precursor; calcining the pre-lithiated silicon negative electrode precursor under protective gas to obtain a pre-lithiated silicon negative electrode material; and The pre-lithiated silicon negative electrode material is acid-washed and then polymer-coated; Wherein, the polymer is one or more of PMMA, PEO, PVA, PVDF-HFP, PANI, PPY, PBS, and PEDOT:PSS.
2. The method for preparing a polymer-coated silicon-based negative electrode material according to claim 1, characterized in that: The silicon-based material is silicon monoxide, or one or more of silicon monoxide, silicon oxide, and metal element-doped silicon oxide compounds, wherein the chemical formula of silicon monoxide is SiO x , where 0<x<2.
3. The method for preparing a polymer-coated silicon-based negative electrode material according to claim 1, characterized in that: The carbon coating is prepared by chemical vapor deposition, including: reacting the silicon-based material and an organic gas carbon source at high temperature under a protective gas to prepare a carbon-coated silicon-based material, wherein the structure of the carbon-coated silicon-based material is SiO x @C.
4. The method for preparing a polymer-coated silicon-based negative electrode material according to claim 3, characterized in that: The organic gas carbon source is one or more of methane, acetylene and ethylene, and the mixing ratio of the organic gas carbon source to the protective gas is 1:0.2-5.
5. The method for preparing a polymer-coated silicon-based negative electrode material according to claim 3, characterized in that: The high temperature reaction temperature is 600-1000° C., the heating rate is 1-20° C. / min, and the heat preservation time is 10-300 min.
6. The method for preparing a polymer-coated silicon-based negative electrode material according to claim 1, characterized in that: The preparation method also includes: naturally cooling to room temperature after the calcination step to obtain a pre-lithiation silicon negative electrode material, the heating rate of the calcination is 3-10°C / min, the insulation temperature after calcination is 600-1000°C, and the insulation time is 3-10h.
7. The method for preparing a polymer-coated silicon-based negative electrode material according to claim 1, characterized in that: The amount of the carbon-coated silicon-based material is 1 to 10 g, and the molar ratio of the carbon-coated silicon-based material to the lithium source is 10:1 to 3:2; the lithium source is one or more of lithium amide, lithium hydride, lithium hydroxide, lithium nitride, lithium fluoride, lithium oxide, lithium peroxide, and lithium sulfide.
8. The method for preparing a polymer-coated silicon-based negative electrode material according to claim 1, characterized in that: The acid washing comprises: dispersing the pre-lithiation silicon negative electrode material in an acidic solution, stirring, filtering, washing until the washing solution is neutral and drying, and the stirring time is 3 to 10 minutes.
9. The method for preparing a polymer-coated silicon-based negative electrode material according to claim 1, characterized in that: The solute of the acid solution used for pickling is one or more of sodium citrate, oxalic acid, glacial acetic acid, perchloric acid, sodium tetraborate and sodium hypochlorite.
10. The method for preparing a polymer-coated silicon-based negative electrode material according to claim 1, characterized in that: The mass of the pre-lithiation silicon negative electrode material is 0.5-3 g, and the concentration of the acid solution used for the pickling is 1-5 mol / L and the volume is 10 mL-80 mL.