Method for preparing lithium battery negative electrode material by using phosphate fertilizer solid waste and application of lithium battery negative electrode material

Abstract

The invention relates to a method for preparing a lithium battery negative electrode material by using phosphate fertilizer solid waste and application. The method comprises the following steps: dissolving fluorine-containing silica gel powder in a sulfuric acid solution for pickling, carrying out suction filtration and water washing on a reactant for multiple times after pickling is completed until the pH is neutral, and drying to obtain pickled fluorine-containing silica gel powder with the fluorine content of 1-7%; mixing the acid-washed fluorine-containing silica gel powder and silicon powder according to a mass ratio of 1: 1 to obtain mixed powder; and grinding the mixed powder in a ball milling tank to obtain silicon monoxide powder, wherein the silicon monoxide powder is the lithium battery negative electrode material. The phosphorus fertilizer byproduct fluorine-containing silica gel is used as a raw material and mixed with the silicon powder after being subjected to acid pickling, different atmospheres are used in the ball milling process, the silicon monoxide negative electrode material with good cycle stability or high initial coulombic efficiency can be obtained, the production process can be adjusted according to the use scene, and the production cost is reduced. The silicon monoxide negative electrode materials with different electrochemical performance deviations are obtained.

Description

Technical Field

[0001] This invention relates to the field of lithium battery materials technology, specifically to a method and application for preparing lithium battery anode materials using phosphate fertilizer solid waste. Background Technology

[0002] Phosphate fertilizer production generates a byproduct called fluorinated silica gel. Currently, the only treatment method for this byproduct is simple processing followed by dumping, resulting in economically worthless phosphate fertilizer solid waste that only occupies land and creates environmental pressure. However, the silica gel and fluorine elements contained in this fluorinated silica gel, as phosphate fertilizer solid waste, are not effectively recycled. If a reasonable process design and resource recycling are implemented to achieve the harmless treatment of fluorides, the treatment of fluorinated silica gel can not only achieve environmental goals but also create significant economic benefits.

[0003] Currently, the recycling and processing of fluorinated silica gel involves areas with low economic value. CN1092790A, CN101462726A, and CN105036144A disclose three methods for preparing silica using fluorinated silica gel; CN119143166A discloses a method for preparing silica and co-producing calcium fluoride using fluorinated silica gel; CN101462732A discloses a method for preparing sodium silicate using fluorinated silica gel; and CN116589312A discloses a method for preparing liquid silicon fertilizer using fluorinated silica gel. The economic value of the products prepared using fluorinated silica gel is low, and the selling price is below 20,000 yuan / ton.

[0004] Silicon suboxide (SiOx) is a relatively ideal anode material for lithium-ion batteries, possessing high specific capacity (2600 mAh / g), good cycle stability, and environmental friendliness, and is considered a highly promising next-generation lithium-ion battery anode material. Currently, domestically produced silicon suboxide anodes can fetch up to 300,000 yuan / ton, exhibiting high added value. However, due to the significant volume change effect encountered by SiOx materials during cycling, the SEI film on the material surface exhibits poor stability. Repeated rupture and growth of the SEI film leads to substantial consumption of active lithium, thus affecting the cycle life of lithium-ion batteries.

[0005] To improve the stability of the SEI film in silicon suboxide materials and reduce irreversible active lithium loss during the first charge-discharge cycle, existing technologies typically enhance battery stability and extend lithium battery life by adding functional additives to the electrolyte or constructing an artificial SEI film on the silicon-based material surface. Functional additives added to the electrolyte mainly include carbonate additives, sulfur-containing additives, and fluorine-containing additives. However, carbonate additives are prone to gas generation, sulfur-containing additives are expensive, and the introduction of fluorine-containing additives enables the formation of a LiF-rich SEI film on the surface of the silicon-oxygen anode during charge-discharge. LiF possesses high mechanical strength and good ionic conductivity, significantly improving the stability and density of the SEI film. However, the synthesis and use of traditional fluorine-containing electrolyte additives are costly, and they are introduced into the electrode material via the electrolyte to form the SEI, rather than being directly constructed on the silicon-oxygen anode material. This undoubtedly increases manufacturing costs and operational steps, and also introduces a degree of instability.

[0006] Currently, the main technology for directly constructing artificial SEIs on silicon-based material surfaces is through the introduction of polymer groups. For example, CN 114039042 B discloses a method for constructing an artificial SEI film on a silicon anode surface using a 3(3-nitrophenyl)acrylonitrile / olefin sulfonic acid copolymer; CN 119050272 A discloses a method for constructing an artificial SEI using phospholipid vesicle coating and anionic polymer complexes. However, there are few studies on directly constructing fluorinated artificial SEIs on silicon-oxygen anode surfaces. Patent CN 119650597 A discloses a method for constructing an artificial SEI on a silicon anode surface using 2-fluorosulfonyl difluoroacetic acid, but this method is mainly for pure silicon anodes rather than silicon-oxygen anodes, and the raw materials are relatively expensive and the construction steps are complex, which greatly limits its application on silicon anodes.

[0007] Based on the above analysis, if fluorinated silica gel from phosphate fertilizer waste could be prepared as a silicon suboxide anode material for use in the lithium-ion battery industry, it would greatly enhance the added value of recycling fluorinated silica gel. Fluorinated silica gel contains fluorine; if fluorine is introduced in situ during the synthesis of silicon suboxide materials and used in lithium-ion batteries, the introduced fluorine will react with lithium elements extracted from the electrolyte or cathode during cycling, forming an SEI film on the surface of the silica material, thereby improving the material's electrochemical performance. However, there are currently no reports on preparing fluorinated silica gel from phosphate fertilizer waste as a silicon suboxide anode material for use in the lithium-ion battery industry. Summary of the Invention

[0008] To address the above problems, this invention proposes a method and application for preparing lithium battery anode materials using phosphate fertilizer solid waste.

[0009] This invention discloses a method for preparing lithium battery anode materials using fluorinated silica gel, comprising the following steps:

[0010] S1. Dissolve the fluorinated silica gel powder in a 30%-40% sulfuric acid solution for acid washing. After acid washing, the reactant is filtered and washed with water multiple times until the pH is neutral. After drying, acid-washed fluorinated silica gel powder with a fluorine content of 1%-7% is obtained.

[0011] S2. Mix the acid-washed fluorinated silica gel powder and silica powder obtained in S1 at a mass ratio of 1:1 to obtain a mixed powder;

[0012] S3. The mixed powder obtained in S2 is ground in a ball mill to obtain silicon suboxide powder, which is the lithium battery anode material; wherein...

[0013] When the ball milling atmosphere is air, the silicon suboxide powder has good cycle stability when used as a lithium battery anode material;

[0014] When the ball milling atmosphere is argon, the silicon suboxide powder has a high initial coulombic efficiency when used as a lithium battery anode material.

[0015] Furthermore, the pickling temperature in S1 is 80°C.

[0016] Furthermore, the pickling time in S1 is 30~150 min, and the fluorine content of the pickled fluorinated silica gel powder is negatively correlated with the pickling time.

[0017] Furthermore, the pickling in S1 is carried out in a constant temperature water bath magnetic stirrer at a speed of 600 rpm.

[0018] Furthermore, the grinding in S3 involves adding grinding balls to a grinding jar and grinding at a grinding speed of 600 rpm / min for 4 hours.

[0019] Furthermore, the mass ratio of the grinding beads to the mixed powder in S3 is 8:1.

[0020] Furthermore, the concentration of the sulfuric acid solution is 38.5%.

[0021] The silicon suboxide powder prepared by the method of the present invention is used in lithium batteries.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention uses fluorinated silica gel, a byproduct of phosphate fertilizer, as raw material. After acid washing, it is mixed with silicon powder, and silicon suboxide anode materials with different electrochemical properties are obtained by ball milling. This invention finds that by using different atmospheres during the ball milling process, silicon suboxide anode materials with good cycle stability or high initial coulombic efficiency can be obtained. The production process can be adjusted according to the application scenario to obtain silicon suboxide anode materials with different electrochemical performance biases.

[0024] 2. The method of this invention can fully recover and utilize the fluorine and silicon resources in fluorinated silica gel, a solid waste product from phosphate fertilizer, effectively ensuring that fluorine does not leak into the external environment and achieving the goal of harmless treatment of fluorinated silica gel. This method reduces raw material costs and simplifies the complex preparation process of SEI. Unlike existing technologies, fluorine is directly introduced into the construction of silicon suboxide raw materials, resulting in good stability. Therefore, during battery cycling, fluorine in the silicon suboxide anode material can construct a stable SEI layer in situ on the electrode surface, improving the stability and cycle life of lithium batteries. It also solves the problem of difficult fluorine treatment in fluorinated silica gel, avoiding environmental damage caused by fluorine emissions and improving the electrochemical performance of silicon-oxygen anodes.

[0025] 3. It is easy to operate, low in cost, and rich in raw materials, making it easy to achieve large-scale production. The resulting silicon-oxygen anode material has high capacity, good initial coulombic efficiency, stable cycle life, and high economic value. Attached Figure Description

[0026] Figure 1 The XRD pattern of the silicon suboxide material obtained in Example 1;

[0027] Figure 2 The XRD pattern of the silicon suboxide material obtained in Example 4;

[0028] Figure 3 The image shows a TEM image of the silicon suboxide material obtained in Example 4.

[0029] Figure 4 SEM images of the silicon suboxide materials obtained in Examples 1, 2, 3, and 4;

[0030] Figure 5 Comparison of cycle stability between batteries assembled with silicon suboxide materials obtained in Examples 4, 8, and 9 and batteries assembled with two commercially available silicon suboxide materials;

[0031] Figure 6 The first charge-discharge curves of the batteries assembled with the silicon suboxide materials obtained in Examples 4, 8, and 9 are compared with those of the batteries assembled with two commercially available silicon suboxide materials. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments.

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1: Preparation of lithium battery anode material using phosphate fertilizer solid waste:

[0035] 1.1 Weigh 15g of fluorinated silica gel powder and place it in a glass beaker. Add 32.28g of deionized water and 20.22g of concentrated sulfuric acid. Then transfer the mixture to an 80℃ constant temperature water bath with a magnetic stirrer and stir at 600rpm for 80min. Subsequently, the reactants are filtered and washed with water multiple times until the pH is neutral. Then, place the mixture in a forced-air drying oven at 105℃ for 8h to obtain acid-washed and dried fluorinated silica gel powder with a final fluorine content of approximately 1%.

[0036] 1.2 Weigh 9.6g of the acid-washed and dried fluorinated silica gel powder obtained in step 1) and place it in a ball mill jar. Add pure silicon powder and mix. Add grinding balls and ball mill at 600 rpm / min for 4 hours to obtain silicon suboxide material. The silicon suboxide material is the lithium battery negative electrode material. The mass ratio of the fluorinated silica gel powder to the silicon powder is 1:1. The mass ratio of the grinding balls to the mixed powder is 8:1. The ball milling atmosphere is air.

[0037] Example 2 is the same as Example 1, except that it is ball-milled for 14 hours.

[0038] Example 3 is the same as Example 1, except that it is ball-milled for 24 hours.

[0039] Example 4 is the same as Example 1, except that it is ball-milled for 32 hours.

[0040] Example 5 is the same as Example 1, except that the molar ratio of fluorinated silica gel powder to silica powder is 1:1 and the mixture is ball-milled for 18 hours.

[0041] Example 6 is the same as Example 1, except that the molar ratio of fluorinated silica gel powder to silica powder is 1:1 and the mixture is ball-milled for 22 hours.

[0042] Example 7 is the same as Example 1, except that the molar ratio of fluorinated silica gel powder to silica powder is 1:1 and the mixture is ball-milled for 32 hours.

[0043] Example 8 is the same as Example 1, except that the molar ratio of fluorinated silica gel powder to silica powder is 1:1 and the mixture is ball-milled for 40 hours.

[0044] Example 9 is the same as Example 1, except that the ball milling is performed for 32 hours and the ball milling atmosphere is argon.

[0045] Example 10 is the same as Example 1, except that the ball milling was carried out for 32 hours, the ball milling atmosphere was argon, and the acid washing process was carried out by stirring at 600 rpm for 60 minutes in a magnetic stirrer in an 80°C constant temperature water bath. The final fluorine content was about 3%.

[0046] Example 11 is the same as Example 1, except that the ball milling was carried out for 32 hours, the ball milling atmosphere was argon, and the acid washing process was carried out by stirring at 600 rpm for 30 minutes in a magnetic stirrer in an 80°C constant temperature water bath. The final fluorine content was about 7%.

[0047] Comparative Example 1: Untreated fluorinated silica gel was used directly as the negative electrode material for lithium batteries.

[0048] Comparative Example 2: Preparation of lithium battery anode material using un-acid-washed fluorinated silica gel ball milling, including the following steps:

[0049] 9.6g of un-acid-washed fluorinated silica gel powder was placed in a ball mill jar, pure silicon powder was added and mixed, and milling beads were added. The mixture was milled at 600 rpm / min for 4 h to obtain silicon suboxide material, which is the lithium battery negative electrode material. The molar ratio of fluorinated silica gel powder to silicon powder was 1:1, and the mass ratio of milling beads to mixed powder was 8:1.

[0050] Comparative Example 3: Preparation of lithium battery anode material using pure silica ball milling, including the following steps:

[0051] 9.6g of pure silicon dioxide was weighed and placed in a ball mill jar. Pure silicon powder was added and mixed. Milling balls were added, and the mixture was milled at 600 rpm / min for 32 hours to obtain silicon suboxide material. The silicon suboxide material is the negative electrode material of the lithium battery. The mass ratio of silicon dioxide to silicon powder is 1:1. The mass ratio of milling balls to mixed powder is 8:1.

[0052] Comparative Example 4: The silica suboxide material prepared in Comparative Example 3 was added to a 1% aqueous solution of 2-fluorosulfonyl difluoroacetic acid to construct a fluorinated SEI. The preparation method includes the following steps:

[0053] 1g of silicon suboxide material powder prepared in Comparative Example 3 was mixed with 100mL of 1% 2-fluorosulfonyl difluoroacetic acid aqueous solution and reacted. After centrifugation and drying, silicon suboxide material with artificial SEI containing about 1% fluorine element was obtained, which is the lithium battery negative electrode material. The reaction time was 6h and the reaction temperature was 25℃.

[0054] Example 12: Electrochemical performance testing:

[0055] The silicon suboxide anode materials obtained in Examples 1 to 11 above, and the silicon suboxide anode materials obtained in Comparative Examples 1 to 4, were subjected to electrochemical performance tests. The coin cell test conditions were: constant temperature 25℃, LR2016, initial charge / discharge rate of 0.2 C, cycle rate of 0.2 C, nominal specific capacity of 2000 mAh / g, and test voltage range of 0.001 V - 2.0 V vs Li / Li+. The results are shown in Table 1.

[0056] Table 1. Electrochemical performance of the samples prepared in Examples 1-11 and Comparative Examples 1-4

[0057] Group Ball grinding time ball mill atmosphere Raw material ratio F content First discharge specific capacity (mAh / g) Second-cycle discharge specific capacity (mAh / g) First-time Coulomb efficiency (%) Discharge specific capacity after 50 cycles Example 1 4 Air Mass ratio 1:1 1% 1759.39 1414.98 75.40% 116.43 Example 2 14 Air Mass ratio 1:1 1% 1466.28 1238.30 68.04% 157.48 Example 3 24 Air Mass ratio 1:1 1% 1448.28 957.31 51.62% 801.47 Example 4 32 Air Mass ratio 1:1 1% 1411.47 647.07 41.00% 680.39 Example 5 18 Air Molar ratio 1:1 1% 1296.43 990.77 73.46% 232.67 Example 6 22 Air Molar ratio 1:1 1% 913.54 820.97 68.39% 363.81 Example 7 32 Air Molar ratio 1:1 1% 851.68 659.66 56.45% 463.42 Example 8 40 Air Molar ratio 1:1 1% 733.44 464.57 48.48% 412.86 Example 9 32 Argon Mass ratio 1:1 1% 1863.79 1503.83 60.54% 885.58 Example 10 32 Argon Mass ratio 1:1 3% 1969.14 1334.27 65.45% 599.56 Example 11 32 Argon Mass ratio 1:1 7% 1440.82 1128.41 62.72% 454.17 Comparative Example 1 - - - - 85.91 51.45 45.07% 60.03 Comparative Example 2 4 Air Mass ratio 1:1 1% 1236.97 587.06 68.45% 113.86 Comparative Example 3 32 Air Mass ratio 1:1 0% 942.51 503.95 34.37% 539.68 Comparative Example 4 32 Air Mass ratio 1:1 1% 1189.47 623.87 39.96% 644.76

[0058] As can be seen from Table 1:

[0059] 1. The electrical performance results of the coin cells in Examples 1-8 show that when the ball milling atmosphere is air, regardless of whether the mass ratio of fluorinated silica gel to silicon powder is 1:1 (Examples 1-4) or the molar ratio is 1:1 (Examples 5-8), the initial charge-discharge specific capacity and initial coulombic efficiency of the synthesized silicon suboxide anode material gradually decrease with the extension of ball milling time, but the 50-cycle stability increases with the extension of ball milling time. This is because as the ball milling time increases, the silicon suboxide material tends to be more amorphous, and the oxygen in the air oxidizes the silicon suboxide material during the ball milling process, increasing the Si valence state, which is beneficial to its cycle stability. In addition, the silicon suboxide material prepared with a mass ratio of 1:1 has better cycle stability than the material prepared with a molar ratio of 1:1. This is because when the raw material ratio is 1:1, the content of fluorinated silica gel in the raw material is lower, so the O content in the prepared material is lower, resulting in poorer cycle stability. Therefore, a mass ratio of fluorinated silica gel to silicon powder of 1:1 and a ball milling time of 32 hours are preferred as the preparation process for Examples 9-11.

[0060] 2. The coin cell performance results from Examples 9-11 show that the longer the acid washing time, the lower the fluorine content of the acid-washed fluorinated silica gel powder. The fluorine content of the acid-washed fluorinated silica gel powder is negatively correlated with the acid washing time. In-situ fluorinated silicon suboxide anode materials can be prepared using acid-washed silica gel with a fluorine content of 1%-7%. The increase in F content improves the initial coulombic efficiency and charge / discharge specific capacity of the material. However, after 50 cycles, the discharge specific capacity decreases by more than 600 mAh / g compared to the second cycle. Furthermore, the decrease in the discharge specific capacity of Examples 10 and 11 is greater than that of Example 9. It is speculated that excessive F content causes a decrease in the ionic conductivity of the silicon suboxide anode material, thus reducing its cycle stability. The results from Examples 10-11 show that with a further increase in F content, the silicon suboxide anode material consumes excessive Li elements and reacts with F elements during the first charge-discharge process, thus reducing the first charge-discharge capacity. Furthermore, excessive F content causes a decrease in the ionic conductivity of the silicon suboxide anode material, thereby reducing its cycle stability. Therefore, the pickling process of Example 9 with 80 min of acid washing and a fluorine content of 1% is preferred. Based on the results of Examples 9-11, it can be inferred that the acid washing time can be extended to 150 min, and the fluorine content can be lowered, which should also yield better material performance.

[0061] 3. The coin cell electrochemical performance results from Examples 9 and 4 show that the silicon suboxide anode materials obtained by ball milling under air and argon atmospheres have different electrochemical characteristics. The material obtained by ball milling in air has a lower initial coulombic efficiency but a higher cycle retention rate due to its higher oxygen content; the material obtained by ball milling in argon atmosphere has a higher initial coulombic efficiency but a lower cycle retention rate due to its lower oxygen content. In applications, different atmospheres can be used to obtain silicon suboxide anode materials with different electrochemical performance biases depending on the application scenario requirements. Specifically, when the ball milling atmosphere is air, the silicon suboxide powder used as a lithium battery anode material exhibits good cycle stability; when the ball milling atmosphere is argon, the silicon suboxide powder used as a lithium battery anode material has a high initial coulombic efficiency.

[0062] 4. The electrical performance results of the coin cell in Comparative Example 1 show that the battery assembled using untreated fluorinated silicone as the negative electrode material of the lithium battery does not have charging and discharging capabilities, indicating that it cannot be used directly as the negative electrode of the lithium-ion battery.

[0063] 5. The results of the coin cell electrical performance of Example 1 and Comparative Example 2 show that: when using un-acid-washed fluorinated silica gel as raw material in Comparative Example 2, the high impurity content of the raw material results in a lower initial discharge capacity, initial coulombic efficiency, and discharge specific capacity after 50 cycles compared to the silica material prepared using acid-washed fluorinated silica gel as raw material in Example 1.

[0064] 6. The coin cell electrical performance results from Example 4 and Comparative Example 3 show that the silicon suboxide anode prepared using acid-washed fluorinated silica gel as raw material in Example 4 exhibits higher initial coulombic efficiency and higher first / second / fifty-cycle discharge capacity compared to the silicon suboxide anode prepared using pure silica as raw material in Comparative Example 3. This is because the presence of F element facilitates the formation of the SEI film, reduces the loss of active lithium, and enhances the structural stability of the sample.

[0065] 7. The coin cell performance results from Example 4 and Comparative Example 4 show that the silicon suboxide anode prepared using fluorinated silica gel (after acid washing) from Example 4 generates an artificial SEI during battery testing due to the presence of fluorine (F) in it. Therefore, it exhibits higher initial discharge specific capacity, initial coulombic efficiency, and 50-cycle discharge specific capacity compared to the silicon suboxide anode prepared using pure silica as a raw material and modified with fluorinated artificial SEI in Comparative Example 4. This indicates that using fluorinated silica gel as a raw material, the residual fluorine (F) in the silica gel itself generates a fluorinated SEI film in situ during charge and discharge, reducing the loss of active lithium and enhancing the structural stability of the sample. Compared to materials synthesized from pure silica and then surface-modified to introduce fluorine (F), this method not only has better electrochemical performance but also avoids the use of expensive raw materials, reduces manufacturing steps, and significantly lowers the cost of the synthesized silicon suboxide material.

[0066] Figure 1 The XRD pattern is obtained by direct testing of the material after ball milling for 4 hours in Example 1. Figure 1 It can be seen that the material exhibits strong crystalline behavior after ball milling for 4 hours, which is due to the incomplete reaction of the added raw material silicon powder with the fluorinated silica gel. The presence of crystalline silicon results in a better initial coulombic efficiency in Example 1, but due to the large volumetric strain of crystalline silicon, the cycle stability is poor.

[0067] Figure 2 The XRD pattern is obtained by direct testing of the material after ball milling for 32 hours in Example 4. Figure 2 It can be seen that when the ball milling time is extended to 32 hours, the resulting silicon suboxide material has basically no crystalline peaks and belongs to amorphous amorphous material. Therefore, the obtained material has good cycle stability.

[0068] Figure 3 The TEM image is obtained by direct testing of the material obtained after ball milling for 32 hours in Example 4. Figure 3 It can be seen that the material obtained after ball milling for 32 hours exhibits the characteristics of an amorphous material, without obvious lattice fringes, which is consistent with... Figure 2 The evidence corroborates each other, indicating that the obtained material has good cycle stability.

[0069] Figure 4 The images are SEM images obtained directly from the materials of Examples 1, 2, 3, and 4 after ball milling for the corresponding time. Figure 4 It can be seen that as the ball milling time increases, the particle dispersion becomes more uniform, and the particle size decreases with the ball milling time. The uniform particle dispersion leads to better contact between materials, thus improving cycle stability. However, the reduction in particle size means that the contact area between the material and the electrolyte increases, resulting in the consumption of more lithium ions and a decrease in the initial coulombic efficiency.

[0070] Example 13: Comparison with commercially available silicon suboxide anode materials:

[0071] The materials obtained from Examples 4, 8, and 9, which exhibited better electrochemical performance, were compared with those from two commercially available silicon suboxide materials after being assembled into batteries. The results are as follows: Figure 5 and Figure 6 As shown.

[0072] Figure 5 This compares the cycle stability of batteries assembled with the materials obtained in Examples 4, 8, and 9 with batteries assembled with two commercially available silicon suboxide materials. Figure 5 It can be seen that although the initial capacity of the silicon suboxide anode prepared by this method is not as good as that of commercially available silicon suboxide anodes, it has better cycle stability. The two products obtained by ball milling in air atmosphere (Examples 4 and 8) showed almost no capacity decay after 100 cycles, while the product obtained by ball milling in argon atmosphere (Example 9) had a cycle stability that far exceeded that of commercially available silicon suboxide materials, indicating that the product obtained by this method has strong market competitiveness.

[0073] Figure 6 The first charge-discharge curves of batteries assembled with the materials obtained in Examples 4, 8, and 9 are compared with those of batteries assembled with two commercially available silicon suboxide materials. Figure 6 It can be seen that the initial charge / discharge specific capacity of the material obtained by this method is slightly lower than that of commercially available materials. The initial coulombic efficiency (ICE) of Examples 4 and 8 is also lower than that of commercially available products. This is because ball milling in an air atmosphere increases the O content in the final material, and the increased O content reduces its initial coulombic efficiency. In contrast, Example 9 has an initial coulombic efficiency comparable to that of commercially available silicon suboxide. This is because no additional O element is introduced under an argon atmosphere, resulting in a higher initial coulombic efficiency. Figure 5 Analysis shows that Example 9 has an initial coulombic efficiency comparable to commercially available silica, and its cycle stability far exceeds that of commercially available products. While Examples 4 and 8 have lower initial coulombic efficiencies, their cycle stability far surpasses that of commercially available products. In specific applications, a suitable preparation process can be selected based on the application scenario to achieve the resource utilization of fluorinated silica gel from phosphate fertilizer solid waste.

[0074] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0075] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a negative electrode material for a lithium battery using a fluorine-containing silica gel, characterized by, The method comprises the following steps: S1, dissolving fluorine-containing silica gel powder in a 30%-40% sulfuric acid solution for acid washing, and after acid washing, the reactants are filtered and washed with water for multiple times until the pH is neutral, and then dried to obtain acid-washed fluorine-containing silica gel powder with a fluorine content of 1%-7%; S2, mixing the acid-washed fluorine-containing silica gel powder obtained in S1 and silicon powder at a mass ratio of 1:1 to obtain a mixed powder; S3, grinding the mixed powder obtained in S2 in a ball mill tank to obtain silicon monoxide powder, which is the lithium battery negative electrode material; wherein when the ball milling atmosphere is air atmosphere, the silicon monoxide powder used as the lithium battery negative electrode material has good cycle stability; when the ball milling atmosphere is argon atmosphere, the silicon monoxide powder used as the lithium battery negative electrode material has high initial coulomb efficiency.

2. The method for preparing a negative material for a lithium battery using a fluorine-containing silica gel according to claim 1, characterized in that, The temperature of the acid washing in S1 is 80°C.

3. The method of claim 1, wherein the fluorine-containing silica gel is used to prepare a negative electrode material for a lithium battery. The acid washing time in S1 is 30-150 min, and the fluorine content of the acid-washed fluorine-containing silica gel powder is negatively correlated with the acid washing time.

4. The method of claim 1, wherein the fluorine-containing silica gel is used to prepare a negative electrode material for a lithium battery. The acid washing in S1 is carried out in a constant temperature water bath magnetic stirrer at a speed of 600 rpm.

5. The method of claim 1, wherein the fluorine-containing silica gel is used to prepare a negative electrode material for a lithium battery. The grinding in S3 is carried out in a ball mill tank with ball milling beads, and the ball milling speed is 600 rpm / min for 4 h.

6. The method of claim 5, wherein the fluorine-containing silica gel is used to prepare the negative material of the lithium battery. The mass ratio of the ball milling beads to the mixed powder in S3 is 8:

1.

7. The method of claim 1, wherein the fluorine-containing silica gel is used to prepare a negative electrode material for a lithium battery. The concentration of the sulfuric acid solution is 38.5%.

8. Silicon monoxide powder prepared by the method of any one of claims 1-7.

9. Application of the silicon monoxide powder of claim 8 in lithium batteries.

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