Composite electrode material and preparation method thereof

Abstract

This invention relates to the field of lithium-ion battery technology, specifically to a composite electrode material and its preparation method. The preparation method includes the following steps: using tin, red phosphorus, and lithium salt in a molar ratio of 3.5–3.9:3:0.5–0.1 as raw materials, ball milling is performed in an inert gas to obtain lithium-doped tin phosphide material; the lithium-doped tin phosphide material and carbon nanotube material are mixed uniformly, and calcined under a protective atmosphere to construct a carbon conductive network on the surface of the lithium-doped tin phosphide material to obtain modified tin phosphide material; the modified tin phosphide material is mixed uniformly with additives to obtain the composite electrode material. This invention achieves multi-dimensional modification of tin phosphide anode material through stepwise synergistic processing, solving the technical problem of decreased electrochemical performance of existing tin phosphide anode materials due to volume expansion and lithium loss.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a composite electrode material and its preparation method. Background Technology

[0002] With the rapid development of portable electronic devices and electric vehicles, the demand for high-performance lithium-ion batteries is increasing. The performance of lithium-ion batteries largely depends on the characteristics of the anode material, but currently commercially available graphite anode materials are limited by their theoretical specific capacity and are unable to meet the growing demand for high energy density. Tin phosphide, due to its high theoretical specific capacity and low operating potential, is considered a highly promising next-generation anode material.

[0003] However, tin phosphide materials face numerous challenges in practical applications: First, significant volume expansion occurs during charge and discharge, leading to electrode material pulverization and structural damage; second, its inherently poor conductivity limits electron transport efficiency; furthermore, repeated rupture and regeneration of the SEI film during cycling continuously consumes active lithium, severely impacting battery cycle life. These problems severely restrict the commercial application of tin phosphide anode materials. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composite electrode material and its preparation method, which solves the technical problem of decreased electrochemical performance of existing tin phosphide anode materials due to volume expansion and lithium loss.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing a composite electrode material, comprising the following steps:

[0007] Using tin, red phosphorus, and lithium salt in a molar ratio of 3.5–3.9:3:0.5–0.1 as raw materials, lithium-doped tin phosphide material was prepared by ball milling in an inert gas atmosphere. The lithium-doped tin phosphide material and carbon nanotube material were mixed evenly and calcined under a protective atmosphere to construct a carbon conductive network on the surface of the lithium-doped tin phosphide material, thus obtaining modified tin phosphide material. The modified tin phosphide material was then mixed evenly with additives to obtain a composite electrode material.

[0008] In one possible implementation, the grinding media for the ball milling process are stainless steel balls, and the ball-to-material ratio is 1 to 10:1.

[0009] In one possible implementation, the ball milling time is 4h to 8h, and the ball milling speed is 300r / min to 800r / min.

[0010] In one possible implementation, the lithium salt is at least one of LiF, LiCl, Li3N, and Li3PO4.

[0011] In one possible implementation, the calcination temperature of the calcination treatment is 200℃~400℃, and the calcination time is 1h~3h.

[0012] In one possible implementation, the carbon nanotube material is at least one of single-walled carbon nanotubes or multi-walled carbon nanotubes, and the mass ratio of the lithium-doped tin phosphide material to the carbon nanotube material is 98.6–99.5:0.4–0.9.

[0013] In one possible implementation, before uniformly mixing the modified tin phosphide material with the additive, the step further includes: sieving the modified tin phosphide material; wherein the sieve used for sieving is a 500-mesh sieve.

[0014] In one possible implementation, the additive is at least one of AlPO4, Al(OH)3, Na3PO4 and Na2HPO4, and the additive accounts for 0.1% to 0.5% of the mass of the composite electrode material.

[0015] This invention also provides a composite electrode material, prepared using the above-described method, wherein the composite electrode material has a D... 50 It ranges from 4µm to 6µm.

[0016] In one possible implementation, the lithium-doped tin phosphide material accounts for 98.6% to 99.5% of the mass of the composite electrode material, the carbon nanotube material accounts for 0.4% to 0.9% of the mass, and the additive accounts for 0.1% to 0.5% of the mass.

[0017] The beneficial effects of this invention are that, compared with the prior art, it achieves multi-dimensional modification of tin phosphide anode materials through step-by-step synergistic processing. First, by limiting the raw material molar ratio and using a ball milling process, lithium ions are pre-intercalated into the crystal lattice to compensate for lithium loss during cycling. Second, carbon nanotubes are calcined to construct a coated conductive network, simultaneously improving conductivity and buffering volume expansion. Finally, additives are used to optimize the electrode interface stability, solving the technical problem of decreased electrochemical performance of existing tin phosphide anode materials due to volume expansion and lithium loss. Attached Figure Description

[0018] Figure 1 The graphs show the rate testing results of the composite electrode materials prepared in Examples 1-3 and Comparative Example 1 of this invention at different current densities.

[0019] Figure 2The first charge-discharge curve of the composite electrode material prepared in Example 1 of this invention at a current density of 0.1 A / g is shown. Detailed Implementation

[0020] To address the aforementioned technical problems, this invention provides a composite electrode material and its preparation method. The technical solution and embodiments of this invention will now be described in detail with reference to the accompanying drawings.

[0021] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0022] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation", "connection" and "joining" should be interpreted broadly, for example, they can refer to fixed connection, detachable connection, or integral connection; for those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0023] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0024] In traditional lithium-ion battery anode material systems, tin phosphide-based materials undergo periodic volume deformation during charge and discharge due to their crystal structure, resulting in a lattice expansion coefficient of 280%–300%. This volume effect leads to contact failure between active material particles, causing disruption of electron transport paths. The intrinsic conductivity of the material is below 10⁻⁶. -3 The charge transfer impedance (S / cm) exhibits diffusion-controlled characteristics in the low-frequency region, causing the electrode polarization voltage to rise above 0.25V. Regarding cycle stability, the dynamic reconstruction process of the SEI film consumes lithium ions in the electrolyte, resulting in a capacity decay rate exceeding 15% per 100 cycles.

[0025] If the above problems are not addressed, the structural integrity of the electrode materials will continue to deteriorate during cycling, and the utilization rate of active materials will drop below a critical value. The progressive destruction of the conductive network will lead to an exponential increase in the battery's internal resistance, causing an irreversible shift in the operating voltage plateau. Continuous lithium-ion loss will accelerate electrolyte decomposition, ultimately causing thermodynamic instability in the battery system. These technical defects will severely restrict the practical application of high-energy-density batteries in the power supply field.

[0026] To address the aforementioned issues, this application first analyzes the failure mechanism of traditional tin phosphide materials, finding that continuous lithium-ion loss stems from the irreversible consumption of active lithium during cycling, while the destruction of the conductive network is directly related to structural disintegration caused by volume expansion. To resolve this, this application considers compensating for the lithium source through pre-doping while simultaneously constructing a three-dimensional conductive framework to suppress structural deformation. Regarding the material modification path, chemical deposition of a carbon layer was attempted, but insufficient interfacial bonding was found; solid-state sintering for lithium doping was also tested, but uneven distribution issues existed. Ultimately, high-energy ball milling was chosen to achieve atomic-level doping, combined with in-situ composite formation of carbon nanotubes to form a continuous conductive pathway. The ball milling process parameters were optimized through orthogonal experiments to ensure uniform lithium embedding in the lattice, and the calcination temperature was controlled to prevent tin phosphide decomposition while promoting carbon network cross-linking.

[0027] This invention provides a method for preparing a composite electrode material, comprising the following steps:

[0028] Using tin, red phosphorus, and lithium salt in a molar ratio of 3.5–3.9:3:0.5–0.1 as raw materials, lithium-doped tin phosphide material was prepared by ball milling in an inert gas atmosphere. The lithium-doped tin phosphide material and carbon nanotube material were mixed evenly and calcined under a protective atmosphere to construct a carbon conductive network on the surface of the lithium-doped tin phosphide material, thus obtaining modified tin phosphide material. The modified tin phosphide material was then mixed evenly with additives to obtain a composite electrode material.

[0029] The core innovation of this application lies in achieving multi-dimensional modification of tin phosphide anode materials through step-by-step synergistic processing. First, lithium-ion lattice pre-intercalation is achieved by limiting the raw material molar ratio and using a ball milling process to compensate for lithium loss during cycling. Second, a coated conductive network is constructed using carbon nanotube calcination, simultaneously improving conductivity and buffering volume expansion. Finally, electrode interface stability is optimized through additives. These three steps sequentially address lithium compensation, conductivity enhancement, and interface regulation, forming a synergistic and efficient technical path.

[0030] The working process and principle of this application are as follows: This technical solution improves the intrinsic defects of tin phosphide materials through a step-by-step synergistic process. First, ball milling is performed using a specific molar ratio of tin, red phosphorus, and lithium salt. High-energy mechanical force is used to achieve uniform doping of lithium atoms into the tin phosphide lattice, replenishing the lithium source in advance to compensate for lithium-ion loss during cycling. An inert gas environment prevents oxidation of the raw materials and ensures the stability of the doping process. Subsequently, the lithium-doped material is mixed with carbon nanotubes and calcined. The two-dimensional structure of carbon nanotubes forms a three-dimensional conductive network on the material surface, enhancing electron transport efficiency and buffering the volume expansion effect. A protective atmosphere ensures stable bonding between the carbon nanotubes and the substrate material. Finally, additives are used to regulate interface properties, promoting the processing performance of the electrode slurry and the stable formation of the SEI film. These three steps sequentially address lithium compensation, conductivity improvement, and interface optimization, forming a synergistic technical path.

[0031] Specifically, the grinding media used in the ball milling process are stainless steel balls, and the ball-to-material ratio is 1 to 10:1.

[0032] The use of stainless steel as the milling media avoids wear and tear on ceramic or polymer materials during high-speed collisions. For example, zirconia ceramic balls may break and produce micron-sized particles that contaminate the raw materials, while polyurethane balls are prone to thermal degradation under prolonged friction. When the ball mass is insufficient, the mechanical energy transfer efficiency decreases, leading to incomplete material crushing. Conversely, when the ball mass is excessive, the high probability of collisions may cause local temperatures to rise above 80°C, resulting in the thermal decomposition of lithium salts.

[0033] Using stainless steel balls as the milling media prevents contamination of the raw materials by other materials due to wear during high-speed ball milling. An appropriate ball-to-material ratio ensures efficient transfer of mechanical energy, promotes thorough crushing and mixing of the raw materials, and avoids over-grinding or heat buildup. These optimized milling process parameters facilitate the construction of uniformly lithium-doped tin phosphide materials, thereby improving the electrochemical stability of the final material.

[0034] Specifically, the ball milling time is 4h to 8h, and the ball milling speed is 300r / min to 800r / min.

[0035] By controlling the ball milling time between 4 and 8 hours, it is possible to ensure that tin, red phosphorus, and lithium salts fully contact each other under mechanical force and complete lithium-ion intercalation. Setting the ball milling speed to 300 to 800 rpm allows for control of temperature rise while ensuring particle fineness.

[0036] Specifically, the lithium salt is at least one of LiF, LiCl, Li3N, and Li3PO4. Optimized selection of the lithium salt type effectively improves the lithium-ion release efficiency and doping uniformity.

[0037] Specifically, the calcination temperature for the calcination treatment is 200℃~400℃, and the calcination time is 1h~3h.

[0038] The lower limit of the calcination temperature is set at 200℃ based on the critical temperature at which effective bonding reactions begin between carbon nanotubes and lithium-doped tin phosphide. Below this critical value, a continuous conductive network cannot form on the material surface. The upper limit of the calcination temperature is set at 400℃ based on the thermal stability threshold of carbon nanotubes; exceeding this temperature will damage the carbon nanotube structure. This temperature-time combination is compatible with the lithium-doped tin phosphide material ball-milled in the preceding step. The nanoscale rough surface formed by ball milling provides more anchoring points for the carbon nanotubes, allowing them to more uniformly coat the material surface within the defined temperature range.

[0039] Specifically, the carbon nanotube material is at least one of single-walled carbon nanotubes or multi-walled carbon nanotubes, and the mass ratio of lithium-doped tin phosphide material to carbon nanotube material is 98.6–99.5:0.4–0.9.

[0040] The addition of carbon nanotubes improves the coverage density and uniformity of the conductive network, thereby enhancing the overall conductivity of the composite material. Simultaneously, by controlling the amount of carbon nanotubes added, the problem of a loose material structure caused by excessive carbon nanotube introduction is avoided, ensuring the mechanical stability of the composite material.

[0041] Specifically, before uniformly mixing the modified tin phosphide material with the additives, the process includes a step of sieving the modified tin phosphide material. The sieve used for sieving is a 500-mesh sieve.

[0042] Specifically, the additive is at least one of AlPO4, Al(OH)3, Na3PO4 and Na2HPO4, and the mass percentage of the additive in the composite electrode material is 0.1% to 0.5%.

[0043] The additives work synergistically with the lithium-doped tin phosphide and carbon conductive network formed in the preceding steps: lithium doping increases the lithium-ion diffusion rate in the bulk material, the carbon conductive network maintains overall conductivity, and the additives further reduce lithium-ion diffusion resistance by optimizing interfacial reactions. These three factors work together to achieve a balance between material structural stability and electrochemical performance. Precise control of the additive content maintains optimal contact between the active material and the conductive network while avoiding electron transport path blockage caused by the aggregation of inactive materials, thus achieving an optimized balance between cycle stability and rate performance.

[0044] This invention also provides a composite electrode material, prepared using the above-described method, wherein the composite electrode material has a D... 50 It ranges from 4µm to 6µm.

[0045] D50 The particle size range is achieved through the coordinated control of ball milling, calcination conditions, and sieving. In ball milling, the raw material is crushed to a preset particle size range by adjusting the rotation speed and time. Sieving uses a 500-mesh sieve to directly remove particles exceeding the particle size range, ensuring the final material contains the desired D particle size. 50 The particle size is in the range of 4µm to 6µm. This particle size range was selected as the critical point for balancing specific surface area and volume expansion, where 4µm is the minimum threshold for suppressing side reactions and 6µm is the maximum threshold for maintaining lithium-ion diffusion efficiency.

[0046] Specifically, in the composite electrode material, the mass percentage of lithium-doped tin phosphide material is 98.6% to 99.5%, the mass percentage of carbon nanotube material is 0.4% to 0.9%, and the mass percentage of additives is 0.1% to 0.5%.

[0047] While maintaining a high proportion of active materials, the conductive network forms a continuous three-dimensional structure by precisely controlling the carbon nanotube content. At the same time, excessive carbon materials are avoided from blocking the lithium-ion diffusion channels. The addition of trace amounts of additives effectively promotes the uniform deposition of inorganic components in the SEI film and reduces the occurrence of interfacial side reactions. The synergistic effect of these three factors enables the composite material to maintain structural integrity during cycling.

[0048] The present invention will now be described in detail through specific embodiments. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0049] In the following embodiments, unless otherwise specified, the methods described are conventional methods; and unless otherwise specified, the reagents and materials described are commercially available.

[0050] Example 1

[0051] This invention provides a method for preparing a composite electrode material, comprising the following steps:

[0052] Step 1: Preparation of lithium-doped tin phosphide material.

[0053] Step 1.1 Weigh 22g of metallic tin, 4.65g of red phosphorus, and 0.64g of LiCl in a glove box, mix them briefly in an agate mortar, and then pour them into a ball mill jar.

[0054] Step 1.2 Add stainless steel balls to the grinding jar at a ball-to-material ratio of 4:1, tighten the grinding jar lid, and seal it with a sealing strip.

[0055] Step 1.3 Place the ball milling jar into the ball mill, set the ball milling time to 4 hours and the ball milling speed to 400 r / min to obtain lithium-doped tin phosphide material.

[0056] Step 2, Preparation of modified tin phosphide material.

[0057] Step 2.1 Take out the tin phosphide material obtained in Step 1.3, weigh out 20g, and weigh out 0.14g of single-walled carbon nanotubes. Mix them in an agate mortar and place them in a corundum crucible after mixing.

[0058] Step 2.2 Place the corundum crucible into a tube furnace, heat at a rate of 5℃ / min, calcine at 300℃, and hold for 2 hours to obtain modified tin phosphide material.

[0059] Step 3, preparation of composite electrode material.

[0060] The modified tin phosphide material obtained in step 2.2 was mixed with 0.06 g of Na3PO4 in an agate mortar for 0.5 h to obtain a composite electrode material.

[0061] Example 2

[0062] This invention provides a method for preparing a composite electrode material, comprising the following steps:

[0063] Step 1: Preparation of lithium-doped tin phosphide material.

[0064] Step 1.1 Weigh 23.2g of metallic tin, 4.65g of red phosphorus, and 0.13g of LiF in a glove box, mix them simply in an agate mortar, and then pour them into a ball mill jar.

[0065] Step 1.2 Add stainless steel balls to the grinding jar at a ball-to-material ratio of 3.5:1, tighten the grinding jar lid, and seal it with a sealing strip.

[0066] Step 1.3 Place the ball milling jar into the ball mill, set the ball milling time to 3 hours and the ball milling speed to 350 r / min to obtain lithium-doped tin phosphide material.

[0067] Step 2, Preparation of modified tin phosphide material.

[0068] Step 2.1 Take out the tin phosphide material obtained in step 1.3, weigh out 20g, and weigh out 0.16g of single-walled carbon nanotubes. Mix them in an agate mortar and place them in a corundum crucible after mixing.

[0069] Step 2.2 Place the corundum crucible into a tube furnace, heat at a rate of 5℃ / min, calcine at 400℃, and hold for 1 hour to obtain modified tin phosphide material.

[0070] Step 3, preparation of composite electrode material.

[0071] The modified tin phosphide material obtained in step 2.2 was mixed with 0.04 g of Na3PO4 in an agate mortar for 0.5 h to obtain a composite electrode material.

[0072] Example 3

[0073] This invention provides a method for preparing a composite electrode material, comprising the following steps:

[0074] Step 1: Preparation of lithium-doped tin phosphide material.

[0075] Step 1.1 Weigh 20.8g of metallic tin, 4.65g of red phosphorus, and 0.87g of Li3N in a glove box, mix them simply in an agate mortar, and then pour them into a ball mill jar.

[0076] Step 1.2 Add stainless steel balls to the grinding jar at a ball-to-material ratio of 5:1, tighten the grinding jar lid, and seal it with a sealing strip.

[0077] Step 1.3 Place the ball milling jar into the ball mill, set the ball milling time to 3 hours and the ball milling speed to 500 r / min to obtain lithium-doped tin phosphide material.

[0078] Step 2, Preparation of modified tin phosphide material.

[0079] Step 2.1 Take out the tin phosphide material obtained in Step 1.3, weigh out 20g, and weigh out 0.18g of single-walled carbon nanotubes. Mix them in an agate mortar and place them in a corundum crucible after mixing.

[0080] Step 2.2 Place the corundum crucible into a tube furnace, heat at a rate of 5℃ / min, calcine at 350℃, and hold for 2 hours to obtain modified tin phosphide material.

[0081] Step 3, preparation of composite electrode material.

[0082] The modified tin phosphide material obtained in step 2.2 was mixed with 0.024 g of Na3PO4 in an agate mortar for 0.5 h to obtain a composite electrode material.

[0083] Example 4

[0084] The only difference from Example 1 is that the ball-to-material ratio in step 1.2 is 10:1.

[0085] Example 5

[0086] The only difference from Example 1 is that the ball-to-material ratio in step 1.2 is 1:1.

[0087] Example 6

[0088] The only difference from Example 1 is that the amount of single-walled carbon nanotubes used in step 2.1 is 0.08g.

[0089] Example 7

[0090] The only difference from Example 1 is that the calcination temperature in step 2.2 is 200°C and the holding time is 3 hours.

[0091] Example 8

[0092] The only difference from Example 1 is that the amount of Na3PO4 used in step 3 is 0.1g.

[0093] Example 9

[0094] The only difference from Example 1 is that Na3PO4 in step 3 is replaced with AlPO4.

[0095] Example 10

[0096] The only difference from Example 1 is that Na3PO4 in step 3 is replaced with Al(OH)3.

[0097] Example 11

[0098] The only difference from Example 1 is that Na3PO4 in step 3 is replaced with Na2HPO4.

[0099] It should be noted that, compared with Example 1, the performance of the composite electrode materials prepared in Examples 4 to 11 is not significantly different.

[0100] Comparative Example 1

[0101] This invention provides a method for preparing tin phosphide material, comprising the following steps:

[0102] Weigh 23.8g of metallic tin and 4.65g of red phosphorus in a glove box, mix them briefly in an agate mortar, and then pour them into a ball mill jar.

[0103] Add stainless steel balls to the grinding jar at a ball-to-material ratio of 4:1, tighten the lid of the grinding jar, and seal it with a sealing strip.

[0104] Place the ball milling jar into the ball mill, set the ball milling time to 4 hours, and the ball milling speed to 400 r / min to obtain tin phosphide material.

[0105] Electrochemical testing methods

[0106] The composite electrode materials prepared in Examples 1-3 and the tin phosphide material prepared in Comparative Example 1 were used as active materials. The active material, conductive agent (Super P), binder (SBR), and CMC were thoroughly ground into a slurry at a mass ratio of 80:10:7:3. The mixed electrode material was then coated onto copper foil to form an electrode sheet. The electrode sheet was dried in a vacuum drying oven at 60°C for 12 hours and then cut into circular pieces with a diameter of 1.5 cm for later use. Using the cut electrode sheet as the positive electrode and a lithium metal sheet as the negative electrode, a CR2025 coin cell was assembled.

[0107] The charge / discharge cutoff voltages were 2.0V and 0.005V, respectively. After three charge / discharge cycles at 0.1C to activate the battery, cycle stability testing was performed at 0.5C. The first charge / discharge curves are shown below. Figure 2 The results for specific capacity and capacity retention are shown in [the table]. Figure 1 See Table 1.

[0108] Table 1 Electrochemical test results

[0109]

[0110] Combination Figure 1 , Figure 2 As shown in Table 1, compared with Comparative Example 1, the first-cycle coulombic efficiency and cycle capacity retention of the composite electrode materials prepared in Examples 1 to 3 are significantly improved, and the first-cycle charge specific capacity does not change significantly. This indicates that the preparation method of the composite electrode material provided in this application can improve the electrochemical performance of lithium-ion batteries, thereby solving the technical problem of decreased electrochemical performance of existing tin phosphide anode materials due to volume expansion and lithium loss.

[0111] The above description is merely a preferred embodiment of the present invention, and the specific embodiments described above are not intended to limit the present invention. Various modifications and variations can be made within the scope of the technical concept of the present invention. All refinements, modifications, or equivalent substitutions made by those skilled in the art based on the above description are within the scope of protection of the present invention.

Claims

1. A method for preparing a composite electrode material, characterized in that, Includes the following steps: Lithium-doped tin phosphide material was prepared by ball milling in an inert gas using tin, red phosphorus and lithium salt in a molar ratio of 3.5-3.9:3:0.5-0.

1. Lithium-doped tin phosphide material and carbon nanotube material were mixed evenly and calcined under a protective atmosphere to construct a carbon conductive network on the surface of lithium-doped tin phosphide material, thus obtaining modified tin phosphide material. After the modified tin phosphide material and the additives are mixed evenly, the composite electrode material is obtained. The mass ratio of the lithium-doped tin phosphide material to the carbon nanotube material is 98.6–99.5:0.4–0.

9. The additive is at least one of AlPO4, Al(OH)3, Na3PO4, and Na2HPO4. The mass percentage of the additive in the composite electrode material is 0.1%–0.5%. The calcination temperature of the calcination treatment is 200℃–400℃, and the calcination time is 1h–3h.

2. The preparation method according to claim 1, characterized in that, The ball milling media used in the ball milling process are stainless steel balls, and the ball-to-material ratio is 1 to 10:

1.

3. The preparation method according to claim 2, characterized in that, The ball milling process takes 4 to 8 hours and the ball milling speed is 300 to 800 r / min.

4. The preparation method according to claim 1, characterized in that, The lithium salt is at least one of LiF, LiCl, Li3N and Li3PO4.

5. The preparation method according to claim 1, characterized in that, The carbon nanotube material is at least one of single-walled carbon nanotubes or multi-walled carbon nanotubes.

6. The preparation method according to claim 1, characterized in that, Before uniformly mixing the modified tin phosphide material with the additives, the method further includes the following steps: The modified tin phosphide material was sieved. The sieve used for the sieving process is 500 mesh.

7. A composite electrode material, characterized in that, The composite electrode material is prepared by the preparation method according to any one of claims 1 to 6, wherein the D 50 It ranges from 4µm to 6µm.

8. The composite electrode material according to claim 7, characterized in that, In the composite electrode material, the lithium-doped tin phosphide material accounts for 98.6% to 99.5% by mass, the carbon nanotube material accounts for 0.4% to 0.9% by mass, and the additives account for 0.1% to 0.5% by mass.

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