Metal phosphorus-doped negative electrode material, preparation method thereof and lithium ion battery

Abstract

The invention provides a metal phosphorus-doped negative electrode material, a preparation method thereof and a lithium ion battery, and belongs to the technical field of phosphorus negative electrode materials. The preparation method comprises the following steps: in an inert atmosphere, mixing excessive elemental phosphorus with metal powder through first mechanical oscillation to obtain a mixture of metal phosphide and elemental phosphorus; under the inert atmosphere, the mixture and a carbon material are mixed through second mechanical oscillation, so that the phosphorus elementary substance and the carbon material interact with each other, phosphorus-carbon composite particles are obtained, and the metal phosphide is evenly dispersed in the phosphorus-carbon composite particles; the metal is at least one of iron, cobalt, nickel and copper. The negative electrode material provided by the invention has relatively high specific capacity and capacity retention rate, and has relatively good mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of phosphorus anode material technology, and in particular to a metal-doped phosphorus anode material, its preparation method, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density and stable cycle life, and are widely used in mobile electronic devices, electric vehicles, and large-scale energy storage. However, with the continuous improvement of battery performance requirements, current lithium-ion battery systems using graphite as the anode are increasingly unable to meet application demands. Graphite has a theoretical specific capacity of 372 mAh / g and a lithium intercalation plateau voltage of 0.1V vsLi. + / Li. With the expansion of lithium-ion battery applications, especially in the field of electric vehicles, the requirements for their low-temperature performance and fast-charging performance are gradually increasing, while the properties of graphite anodes restrict the further development of anode materials.

[0003] To address these challenges, researchers are continuously developing new high-performance material systems. Phosphorus boasts a theoretical specific capacity of up to 2596 mAh / g and a lithium intercalation plateau potential of 0.7 V vs. Li. + / Li can adapt to charging / discharging processes with larger currents. However, phosphorus has poor electronic conductivity, making it difficult to achieve stable cycling; in addition, the alloying / dealloying reactions that occur in phosphorus during charging / discharging are usually accompanied by the destruction of the material structure and volume expansion, causing phosphorus to fail during charging / discharging. Summary of the Invention

[0004] In view of this, in order to at least partially solve at least one of the aforementioned technical problems, the present invention provides a phosphorus-doped metal anode material, a method for preparing the same, and a lithium-ion battery.

[0005] According to one aspect of the present invention, a method for preparing a phosphorus-doped anode material is provided, comprising: mixing excess elemental phosphorus with metal powder by a first mechanical vibration under an inert atmosphere to obtain a mixture of metal phosphide and elemental phosphorus; mixing the mixture with carbon material by a second mechanical vibration under an inert atmosphere, such that elemental phosphorus and carbon material interact to obtain phosphorus-carbon composite particles, wherein the metal phosphide is uniformly dispersed within the phosphorus-carbon composite particles; wherein the metal is at least one selected from iron, cobalt, nickel, and copper.

[0006] According to an embodiment of the present invention, the mass ratio of metal to phosphorus is 1:19 to 19:1, preferably 9:91 to 2:3.

[0007] According to an embodiment of the present invention, the mass ratio of the mixture to the carbon material is 1:19 to 19:1, preferably 2:3 to 7:3.

[0008] According to an embodiment of the present invention, the temperature of the first mechanical vibration mixing and / or the second mechanical vibration mixing is room temperature; the frequency of the first mechanical vibration is 25~35Hz, and the vibration time is 5~7h;

[0009] The second mechanical oscillation frequency is 25~35Hz, and the oscillation time is 11~13h.

[0010] According to embodiments of the present invention, the carbon material includes one or more of graphite, graphene, porous carbon, Ketjen black, carbon nanotubes, carbon fibers, carbon black, amorphous carbon, carbon nanospheres, and pitch cracking carbon.

[0011] According to embodiments of the present invention, elemental phosphorus includes one or more of white phosphorus, red phosphorus, black phosphorus, blue phosphorus, and purple phosphorus.

[0012] According to another aspect of the present invention, a negative electrode material prepared by the above-described preparation method is provided. The negative electrode material includes a metal phosphide and phosphorus-carbon composite particles. The phosphorus-carbon composite particles are formed by the interaction between elemental phosphorus and carbon in the carbon material. The metal phosphide is uniformly dispersed in the phosphorus-carbon composite particles, and the metal is at least one of iron, cobalt, nickel, and copper.

[0013] According to embodiments of the present invention, the interactions include van der Waals forces or covalent bonds.

[0014] According to embodiments of the present invention, van der Waals forces include the tight binding of elemental phosphorus and carbon in carbon materials through physical adsorption; covalent bonds include the bonding of elemental phosphorus and carbon in carbon materials through one or more of PC and POC.

[0015] According to another aspect of the present invention, a lithium-ion battery is provided, comprising a negative electrode, wherein the negative electrode comprises the aforementioned negative electrode material, a conductive agent, and a binder.

[0016] According to an embodiment of the present invention, excess elemental phosphorus is subjected to a first mechanical vibration with metal powder, transforming the metal powder into a metal phosphide state. The remaining elemental phosphorus forms a tight bond with carbon material through a second mechanical vibration. Utilizing the lithium storage capacity of elemental phosphorus helps improve the lithium storage capacity of the anode material. This invention, by adding excess elemental phosphorus and using two mechanical vibrations, helps to form a composite morphology where 10-50 nanometer-sized metal phosphides are uniformly dispersed within phosphorus-carbon composite particles. During lithium intercalation, nickel phosphide decomposes to produce metallic nickel smaller than 10 nanometers, which can act as anchor points in the phosphorus anode, increasing the strain resistance of the anode material. During the delithiation stage, elemental nickel preferentially forms nickel phosphide crystals, serving as central sites for PP bond recovery, thereby restoring the volume expansion of the phosphorus anode during lithium storage to its initial state. This results in smaller volume changes and expansion of the anode material, reducing structural damage during charging or discharging, helping to reduce volume changes in lithium-ion batteries and lower the post-cycle volume expansion rate. Metal phosphides help improve the mechanical properties of lithium-ion batteries, thereby extending their service life.

[0017] According to embodiments of the present invention, the composite morphology formed by the phosphorus-doped metal anode material exhibits superior low-temperature performance (e.g., -30 to -10°C) and fast-charging performance. Furthermore, no lithium-ion deposition occurs during long-term cycling, contributing to the stable cycle stability of the lithium-ion battery. The positive-to-negative electrode capacity ratio of the anode material of the present invention can be controlled at around 1, eliminating the need for higher anode capacity and saving resources. Attached Figure Description

[0018] Figure 1 A flowchart illustrating a method for preparing a phosphorus-doped metal anode material according to an embodiment of the present invention is shown;

[0019] Figure 2 A transmission electron microscope (TEM) image of the nickel-doped red phosphorus anode material 1 prepared in Example 1 of the present invention is shown.

[0020] Figure 3 A high-resolution transmission electron microscope image of nickel phosphide in the negative electrode material 1 of Embodiment 1 of the present invention is shown;

[0021] Figure 4 The X-ray photoelectron spectrum of the nickel-doped red phosphorus anode material 1 prepared in Example 1 of the present invention is shown.

[0022] Figure 5 A bar chart showing the Young's modulus of the negative electrode materials prepared in Example 1 and Comparative Example 1 of the present invention is shown; and

[0023] Figure 6 The diagram shows the thickness changes of the negative electrode materials of Embodiment 1 and Comparative Example 1 after being fabricated into electrode sheets and then charged and discharged. Detailed Implementation

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0026] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0027] In related technologies, phosphorus has a high specific capacity and lithium intercalation platform, and it has the advantage of fast ion transport and electrochemical reactions. However, phosphorus is prone to alloying or dealloying reactions during charging or discharging, which can cause damage to the material structure, lead to volume changes, and reduce the cycle performance of phosphorus anode materials.

[0028] In realizing the concept of this invention, it was discovered that mixing excess elemental phosphorus with metal powder facilitates the formation of metal phosphides. Further addition of carbon materials promotes the interaction between elemental phosphorus and carbon, enhancing the electronic conductivity of both the metal phosphides and elemental phosphorus, accelerating the reaction and mass transfer, and reducing polarization. Simultaneously, it mitigates structural damage caused by volume changes during charging / discharging, improving the cycle stability and rate performance of the negative electrode material.

[0029] Figure 1 A flowchart illustrating a method for preparing a phosphorus-doped metal anode material according to an embodiment of the present invention is shown.

[0030] Specifically, according to one embodiment of the present invention, a method for preparing a phosphorus-doped metal anode material is provided, with reference to... Figure 1 As shown, it includes steps S101 to S102.

[0031] In step S101, under an inert atmosphere, excess elemental phosphorus is mixed with metal powder by a first mechanical vibration to obtain a mixture of metal phosphide and elemental phosphorus.

[0032] According to embodiments of the present invention, elemental phosphorus is mixed with metal powder to form metal phosphides. Metal phosphides have a high theoretical capacity and, as active materials in lithium-ion batteries, can insert and extract lithium ions during charging / discharging, providing high energy density. Fixing a portion of elemental phosphorus into metal phosphides helps improve the stability of phosphorus, enhances the mechanical properties of the negative electrode material, reduces volume changes and expansion of the negative electrode material, and minimizes structural damage during charging or discharging.

[0033] In step S102, under an inert atmosphere, the mixture and carbon material are mixed by a second mechanical vibration, so that elemental phosphorus interacts with the carbon material to obtain phosphorus-carbon composite particles, and metal phosphides are uniformly dispersed in the phosphorus-carbon composite particles.

[0034] According to an embodiment of the present invention, the remaining elemental phosphorus is mixed with carbon material, causing the two to interact. The carbon material has good electrical conductivity, which helps to enhance the electronic conductivity of the metal phosphide, further improving the cycle stability and rate performance of the anode material.

[0035] According to embodiments of the present invention, the metal is at least one selected from iron, cobalt, nickel, and copper. The incorporated metal facilitates the formation of metal phosphides, and the secondary mechanical vibration helps to uniformly disperse the metal phosphides, enhancing the overall structural stability of the negative electrode material, improving its mechanical properties, and thus extending the battery's lifespan. By adjusting the type and content of the aforementioned metals, the corresponding battery specific capacity and capacity retention rate can be adjusted, thereby adapting to different application scenarios.

[0036] According to embodiments of the present invention, the mass ratio of metal to elemental phosphorus is 1:19 to 19:1. Adjusting the mass ratio within this range helps to control the ratio of metal phosphide to elemental phosphorus in the resulting mixture, ensuring more complete formation of the metal phosphide. This is beneficial for improving the electrochemical performance of the anode material, while also satisfying the requirement of having suitable elemental phosphorus to increase the lithium storage capacity of the anode material. Furthermore, it improves the conductivity of the anode material while ensuring its mechanical stability. The mass ratio of metal to elemental phosphorus can be, for example, 1:19, 1:15, 1:12, 1:9, 1.7:10.8, 2:5, 1:2, 7:13, 1:1, 3:1, 6:1, 9:1, 12:1, 15:1, or 19:1, preferably 9:91 to 2:3.

[0037] According to embodiments of the present invention, the mass ratio of the mixture to the carbon material is 1:19 to 19:1. The carbon material has good electrical conductivity, which helps to promote electron transport and improve the conductivity of the negative electrode material. By controlling the mass ratio of the mixture to the carbon material within the above range, it helps to provide a certain mechanical support to the negative electrode material while maintaining good electron conductivity. The mass ratio can be, for example, 1:19, 1:15, 1:12, 1:9, 2:5, 1:2, 1:1, 3:1, 6:1, 9:1, 12:1, 15:1, or 19:1, preferably 2:3 to 7:3, and more preferably, 6:4.

[0038] According to an embodiment of the present invention, the temperature for the first mechanical vibration mixing and / or the second mechanical vibration mixing is room temperature. Performing mechanical vibration mixing at room temperature makes the process gentler, safer, and has lower energy consumption. The frequency of the first mechanical vibration is 25-35 Hz, and the vibration time is 5-7 h; the frequency of the second mechanical vibration is 25-35 Hz, and the vibration time is 11-13 h. Controlling the frequency and vibration time of the first / second mechanical vibration within the above ranges helps to promote a more uniform and thorough mixing between the metal powder and elemental phosphorus, and promotes the formation of more contact points between the particles, which is beneficial for the formation of metal phosphides. The frequency of the first / second mechanical vibration can be, for example, 25 Hz, 26 Hz, 27 Hz, 28 Hz, 29 Hz, 30 Hz, 31 Hz, 32 Hz, 33 Hz, 34 Hz, or 35 Hz, preferably 30 Hz. The frequencies of the first and second mechanical vibrations can be the same or different. The vibration time of the first mechanical vibration can be, for example, 5 h, 6 h, or 7 h, preferably 6 h. The oscillation time of the second mechanical oscillation can be, for example, 11h, 12h or 13h, preferably 12h.

[0039] According to embodiments of the present invention, the carbon material includes one or more of graphite, graphene, porous carbon, Ketjen black, carbon nanotubes, carbon fibers, carbon black, amorphous carbon, carbon nanospheres / microspheres, and pitch cracking carbon. These carbon materials each possess different properties and advantages, and can be combined with elemental phosphorus for various lithium battery applications. Preferably, the carbon material is Ketjen black.

[0040] According to embodiments of the present invention, the elemental phosphorus includes one or more of white phosphorus, red phosphorus, black phosphorus, blue phosphorus, and purple phosphorus. The aforementioned elemental phosphorus can combine with metal powder to form metal phosphides, and the remaining elemental phosphorus can interact with carbon materials, contributing to improved stability of the lithium-ion battery. This stable combination provides stable and long-lasting conductivity, thereby extending the battery's lifespan. Preferably, the elemental phosphorus is red phosphorus.

[0041] According to another aspect of the present invention, a negative electrode material prepared by the preparation method described above is provided, comprising a metal phosphide and phosphorus-carbon composite particles; the phosphorus-carbon composite particles are formed by the interaction between elemental phosphorus and carbon in the carbon material; the metal phosphide is uniformly dispersed in the phosphorus-carbon composite particles, wherein the metal is at least one of iron, cobalt, nickel, and copper.

[0042] According to embodiments of the present invention, the aforementioned phosphorus-doped anode material, compared to anode materials without phosphorus doping, can ensure rapid completion of lithiation / delithiation reactions and mass transfer at low temperatures, reducing the negative effects of polarization. Combined with the high reaction potential of metal phosphides, it can accommodate more polarization reduction space during charging. The present invention solves the problems of rapid capacity decay and lithium metal deposition at low temperatures and during fast charging, expanding the selection space for electrode design and charging strategies. Using the aforementioned phosphorus-doped anode material, compared to anode materials without phosphorus doping, superior low-temperature and fast-charging performance can be achieved. Using the aforementioned phosphorus-doped anode material can improve the mechanical properties of the anode, increasing the average Young's modulus of the anode by more than 200%. Using the aforementioned phosphorus-doped anode material, compared to anode materials without phosphorus doping, the post-cycle volume expansion rate can be reduced by more than 50%.

[0043] In one embodiment, the anode material of the present invention exhibits high mechanical properties, good rate performance, high cycle stability, and good low-temperature performance, avoiding drastic capacity decay and lithium-ion deposition during low-temperature and fast charging. Compared to phosphorus anodes without metal phosphides, it achieves better stable cycling and rate operation even with reduced use of fluoroethylene carbonate (an additive in lithium-ion battery electrolytes that helps form a solid electrolyte interphase (SEI) film). Specifically, the phosphorus-doped anode material achieves stable cycling with only about 10% fluoroethylene carbonate in the electrolyte compared to anode materials without phosphorus doping. Furthermore, since fluoroethylene carbonate is expensive and fluorine is prone to pollution, reducing its usage helps save costs and protect the environment.

[0044] According to embodiments of the present invention, the interactions include van der Waals forces or covalent bonds. The interactions formed after the mechanical mixing of elemental phosphorus and carbon materials can solve the problem of poor conductivity when used alone, and also improve the mechanical properties of the anode material. The stable bonding brought about by van der Waals forces and covalent bonds can fully utilize the conductivity of carbon materials, thereby improving the chemical stability of the anode material and extending the cycle life of the lithium-ion battery.

[0045] According to embodiments of the present invention, van der Waals forces include the physical adsorption of phosphorus to carbon in the carbon material to form a tight bond; covalent bonds include the bonding of phosphorus to carbon in the carbon material through one or more of PC and POC. Metal and phosphorus are mixed and chemically bonded to form metal phosphide particles, while the remaining phosphorus is bonded to the carbon material through chemical covalent bonds or van der Waals forces. Van der Waals forces can be, for example, physical adsorption. Under the action of van der Waals forces or covalent bonds, the type and content of metal in the negative electrode material can be adjusted to optimize suitable specific capacity and capacity retention. The resulting lithium-ion battery exhibits a small volume change rate, high mechanical properties of the negative electrode material, and achieves good rate performance, cycle stability, and low-temperature performance. At low temperatures and during fast charging, it effectively avoids drastic capacity decay and lithium metal deposition, further optimizing battery design, adjusting the positive and negative electrode capacity ratio, and allowing for the selection of high-current pulse charging programs as needed during charging, while reducing the use of electrolyte additives.

[0046] According to another aspect of the present invention, a lithium-ion battery is provided, comprising a negative electrode, the negative electrode comprising a negative electrode material, a conductive agent and a binder as described above.

[0047] According to embodiments of the present invention, the phosphorus-doped anode exhibits excellent low-temperature and fast-charging performance while maintaining good mechanical properties. No lithium-ion deposition occurs during long-term cycling, contributing to the stable cycle stability of lithium-ion batteries. The positive-to-negative capacity ratio of the anode material of the present invention can be controlled at around 1, eliminating the need for higher anode capacity and saving resources. At a current density of 6 A / g, the capacity retention rate is 75%, and no lithium deposition occurs during cycling, demonstrating good fast-charging performance. In long-term cycle stability tests, it achieves 80% capacity retention after 600 cycles at a current density of 2 A / g, adapting to high-current pulse charging. The reversible capacity at -20°C is more than 70% of the reversible capacity at room temperature, and no lithium deposition occurs during long-term cycling at low temperatures. The phosphorus-doped anode can improve the mechanical strength of the battery anode surface, suppress volume changes during charging and discharging, and requires less film-forming additives (fluoroethylene carbonate) during battery assembly, while also exhibiting good cycle stability.

[0048] According to embodiments of the present invention, under low-temperature conditions, the phosphorus-doped negative electrode ensures rapid completion of the reaction and mass transfer, reducing the negative effects of polarization. Combined with the higher reaction potential of phosphorus, it can accommodate more polarization reduction space during charging, moving away from the lithium deposition potential and avoiding lithium deposition. The problems of rapid capacity decay and lithium metal deposition in lithium-ion batteries under low-temperature and fast-charging conditions can be solved. The selection space for electrode design and charging strategies can also be expanded, increasing the design space for the positive and negative electrode capacity ratio, and allowing for the selection of high-current pulse charging. The lithium-ion battery of the present invention can reduce and mitigate battery performance degradation and safety hazards under low-temperature and fast-charging conditions.

[0049] The present invention will be further illustrated below through embodiments, accompanying drawings, and related test experiments and results. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0050] It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of this invention is not limited thereto. The chemicals and raw materials used in the following embodiments are all commercially available or prepared using recognized processing methods.

[0051] Example 1:

[0052] Red phosphorus and nickel powder were mixed at a mass ratio of 7:13 (molar ratio 1:1) and mechanically vibrated at 30 Hz for 6 hours under an argon-filled atmosphere. Red phosphorus was continuously added during the vibration until the mass ratio reached 10.8:1.7 (molar ratio 12:1), resulting in a mixture of nickel phosphide and elemental red phosphorus. This mixture was then mixed with Ketjen black powder at a mass ratio of 6:4 and mechanically vibrated at 30 Hz for 12 hours under an argon-filled atmosphere to obtain nickel-doped red phosphorus anode material 1.

[0053] Figure 2 A transmission electron microscope (TEM) image of the nickel-doped red phosphorus anode material 1 prepared according to Example 1 of the present invention is shown. Figure 2 As shown, it can be seen that nickel phosphide ( Figure 2 The black dot-like particles were uniformly dispersed within the phosphorus-carbon composite particles (the dark, fluffy portion). High-resolution transmission electron microscopy (HRTEM) analysis was performed on the black dot-like particles. Figure 3 A high-resolution transmission electron microscope (TEM) image of nickel phosphide in the negative electrode material 1 of Embodiment 1 of the present invention is shown. Figure 3 As shown, its lattice spacing d(211) conforms to the lattice spacing of the phosphide (211) direction, confirming the formation of nickel phosphide.

[0054] The obtained negative electrode material 1 was assembled into a half-cell for testing, with an average Young's modulus of 2100 MPa. In electrolyte A (1M LiPF6 + ethylene carbonate: dimethyl carbonate = 1:1 (volume ratio) + 10% wt fluoroethylene carbonate), the reversible capacity was 1405.3 mAh / g, and the reversible capacity at a current density of 6 A / g was 1050.5 mAh / g. After cycling, the electrode thickness was 120% of its initial state, and no lithium deposition occurred. In electrolyte B (1M LiPF6 + fluoroethylene carbonate: dimethyl carbonate = 1:1 (volume ratio)), the reversible capacity at a current density of 6 A / g was 1072.5 mAh / g, with a capacity retention of 70% after 600 cycles. After 600 cycles at a current density of 2 A / g, it still retained 80% of its capacity. At -20℃, the reversible capacity of electrolyte A system is 1003.8 mAh / g, with no lithium deposition. After assembling a full battery with a commercially available lithium iron phosphate cathode, the capacity calculated based on the cathode during 5C high-current pulse charging is 144.7 mAh / g, and the capacity is 162.4 mAh / g when the cathode-to-anode capacity ratio is 1:1. This indicates that setting the cathode-to-anode capacity ratio to 1:1 achieves a larger capacity without requiring a higher anode capacity, thus conserving resources.

[0055] Example 2:

[0056] Red phosphorus and nickel powder were mixed at a mass ratio of 7:13 (molar ratio 1:1) and mechanically vibrated at 30 Hz for 6 hours under an argon-filled atmosphere. Red phosphorus was continuously added during the vibration until the mass ratio reached 61.3:38.7 (molar ratio 3:1), resulting in a mixture of nickel phosphide and elemental red phosphorus. This mixture was then mixed with Ketjen black powder at a mass ratio of 6:4 and mechanically vibrated at 30 Hz for 12 hours under an argon-filled atmosphere to obtain metal-doped red phosphorus anode material 2.

[0057] The obtained negative electrode material 2 was assembled into a half-cell for testing. In electrolyte A, the reversible capacity was 1180.1 mAh / g, and the reversible capacity at a current density of 6 A / g was 775.4 mAh / g. In electrolyte B, the reversible capacity was 805.4 mAh / g at a current density of 6 A / g, with a capacity retention of 77% after 600 cycles, and 85% capacity retention after 600 cycles at a current density of 2 A / g.

[0058] A comparison of Examples 1 and 2 shows that adjusting the ratio of metal to red phosphorus can help balance the specific capacity and stability of the battery in subsequent applications, depending on the specific application scenario.

[0059] Comparative Example 1:

[0060] Red phosphorus was mechanically vibrated at 30 Hz for 6 hours in an argon-filled atmosphere, and then mixed with Ketjen black powder at a mass ratio of 6:4 and mechanically vibrated at 30 Hz for 12 hours in an argon-filled atmosphere to obtain phosphorus anode material 1'.

[0061] The obtained phosphorus anode material 1' was assembled into a half-cell for testing, with an average Young's modulus of 521 MPa. In electrolyte A, the reversible capacity was 1456.9 mAh / g, and the capacity at a current density of 6 A / g was 490.2 mAh / g, with the electrode thickness remaining at 173% of its initial state after cycling. In electrolyte B, the reversible capacity was 553.9 mAh / g at a current density of 6 A / g, with a capacity retention of 20% after 600 cycles and 25% at a current density of 2 A / g after 600 cycles. At a low temperature of -20℃, the reversible capacity in electrolyte A was 695.5 mAh / g. After assembling a full cell with a commercially available lithium iron phosphate cathode, the capacity calculated based on the cathode during 5C high-current pulse charging was 115.5 mAh / g, and the capacity was 147.6 mAh / g when the cathode-to-anode capacity ratio was 1:1.

[0062] The half-cells of Example 1, Example 2, and Comparative Example 1 were tested respectively, and the test results are shown in Table 1 below. The full cells assembled with the negative electrode materials of Example 1 and Comparative Example 1 were tested respectively, and the test results are shown in Table 2 below.

[0063] Table 1. Test results of chemical data for fast charging of half-cell materials.

[0064]

[0065] Table 2. Test results of low-temperature and full-cell electrochemical data of materials.

[0066]

[0067] As can be seen from the data in Table 1, the doping of metallic nickel in Examples 1 and 2 significantly improved the rate performance and cycle stability of the negative electrode, enabling fast charging. The amount of metallic nickel doping can be adjusted to find the appropriate ratio between reversible capacity and stability. High rate capacity and cycle stability can be achieved using a small amount of electrolyte additives. Using an electrolyte containing an appropriate amount of additives, stable operation at high currents over multiple cycles can be achieved, with significantly better stability than the undoped Comparative Example 1. This is mainly due to the improved mechanical properties brought about by metallic nickel doping, which suppresses volume changes during charging and discharging.

[0068] As can be seen from the data in Table 2, the doping of nickel in Example 1 also improved performance under low-temperature charging conditions and enabled high-current pulse charging in the full cell, exhibiting excellent capacity and stability. Furthermore, even with a 1:1 positive-to-negative electrode ratio, it met normal usage standards. Example 1 maintained good performance under low-temperature and fast-charging conditions, significantly outperforming Comparative Example 1, and avoided lithium metal deposition. While the doping of metal in Example 1 theoretically reduces capacity, the high stability of the negative electrode material in this example resulted in less lithium loss during assembly into a full cell, thus achieving a higher capacity than Comparative Example 1.

[0069] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a metal-doped phosphorous negative electrode material, characterized by, The application relates to a negative electrode material for a lithium ion battery. The excess elemental phosphorus is mixed with the metal powder by first mechanical shaking under an inert atmosphere to obtain a mixture of metal phosphide and elemental phosphorus; The mixture is mixed with a carbon material by second mechanical shaking under an inert atmosphere, so that the elemental phosphorus interacts with the carbon material to obtain phosphorus-carbon composite particles, and the metal phosphide is uniformly dispersed in the phosphorus-carbon composite particles. The metal is at least one of iron, cobalt, nickel and copper.

2. The production method according to claim 1, characterized by, The mass ratio of the metal to the elemental phosphorus is 1:19-19:1, preferably 9:91-2:

3.

3. The production method according to claim 1, characterized by, The mass ratio of the mixture to the carbon material is 1:19-19:1, preferably 2:3-7:

3.

4. The method of claim 1, wherein, The first mechanical shaking and / or the second mechanical shaking is carried out at room temperature. The frequency of the first mechanical shaking is 25-35 Hz, and the shaking time is 5-7 h. The frequency of the second mechanical shaking is 25-35 Hz, and the shaking time is 11-13 h.

5. The preparation method according to claim 1, characterized in that, The carbon material includes one or more of graphite, graphene, porous carbon, Ketjen black, carbon nanotube, carbon fiber, carbon black, amorphous carbon, carbon nanomicrosphere and pitch pyrolysis carbon.

6. The method of claim 1, wherein, The elemental phosphorus includes one or more of white phosphorus, red phosphorus, black phosphorus, blue phosphorus and purple phosphorus.

7. The negative electrode material produced by the production method according to any one of claims 1 to 6, characterized by The negative electrode material includes metal phosphide and phosphorus-carbon composite particles. The phosphorus-carbon composite particles are tightly combined by the interaction between the elemental phosphorus and carbon in the carbon material; the metal phosphide is uniformly dispersed in the phosphorus-carbon composite particles, and the metal is at least one of iron, cobalt, nickel and copper.

8. The negative electrode material according to claim 7, characterized in that, The interaction includes van der Waals force or covalent bond.

9. The negative electrode material of claim 8, wherein, The van der Waals force includes that the elemental phosphorus and carbon in the carbon material are tightly combined by physical adsorption; The covalent bond includes that the elemental phosphorus and carbon in the carbon material are bonded by one or more of P-C and P-O-C.

10. A lithium ion battery comprising a negative electrode, wherein the negative electrode comprises the negative electrode material according to any one of claims 7-9 and a conductive agent and a binder.

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