Negative electrode material, manufacturing method thereof, and battery

Abstract

The present invention relates to the field of negative electrode materials and provides a negative electrode material, a manufacturing method thereof, and a battery. The negative electrode material includes a silicon-based active material and a lithium silicate, and further includes Mg, Al, and P, wherein the mass content of Mg in the negative electrode material is a%, the mass content of Al in the negative electrode material is b%, and the mass content of P in the negative electrode material is c%, and a, b, and c in the negative electrode material satisfy the relationship 0.3≦(a+b) / c≦1.5 and 0.5≦a+b+c≦10. The introduction of Mg, Al, and P into the negative electrode material provided by the present invention is beneficial to the formation of lithium ion transmission channels and can improve the rate performance of the negative electrode material.

Description

[Technical Field]

[0001] This application claims priority based on a Chinese patent application filed with the State Intellectual Property Office on September 28, 2023, bearing application number 202311294348.1 and entitled "Negative electrode material and manufacturing method thereof, and battery," the disclosure of which is incorporated herein in its entirety.

[0002] The present application relates to the technical field of negative electrode materials, and more particularly to negative electrode materials and methods for producing the same, and batteries. [Background technology]

[0003] As the application of lithium-ion batteries expands and deepens, the performance requirements for lithium-ion batteries are also increasing. Traditional graphite anode materials are no longer able to meet the increasingly high market demands, particularly in terms of battery energy density. Silicon-oxygen materials have recently attracted attention as anode materials with high specific capacity. While silicon-oxygen materials have specific capacities exceeding 2000 mAh / g, they have lower initial coulombic efficiency and inferior conductivity, cycle performance, and rate performance compared to graphite materials.

[0004] To improve the performance of silicon-oxygen materials, lithium is typically doped into the silicon-oxygen material to increase the initial coulombic efficiency. However, this changes the distribution of silicon within the silicon-oxygen material, causing silicon aggregation and an increase in silicon grain size of over 50%, resulting in a deterioration in the rate performance and cycle performance of the material. Furthermore, the lithium-doped silicon-oxygen material contains lithium silicate, which, due to hydrolysis, becomes highly alkaline, destroying the polymer binder during aqueous slurry preparation, resulting in poor slurry stability and precipitation, which can affect battery manufacturing. Summary of the Invention [Problem to be solved by the invention]

[0005] Embodiments of the present application provide a negative electrode material and a manufacturing method thereof, and a battery, which are advantageous for forming a lithium ion transmission channel by introducing Mg, Al, and P elements into the negative electrode material, and can improve the rate performance and cycle performance of the negative electrode material.

Means for Solving the Problems

[0006] In a first aspect, embodiments of the present application provide a negative electrode material including a silicon-based active material and lithium silicate, further including Mg element, Al element, and P element, where the mass content of Mg element in the negative electrode material is a%, the mass content of Al element in the negative electrode material is b%, the mass content of P element in the negative electrode material is c%, and in the negative electrode material, a, b, and c satisfy the following formula. 0.3 ≦ (a + b) / c ≦ 1.5, and 0.5 ≦ a + b + c ≦ 10

[0007] In some embodiments, the silicon-based active material includes silicon crystallites with a size of 20 nm.

[0008] In some embodiments, the silicon-based active material includes silicon and / or silicon oxide.

[0009] In some embodiments, the silicon-based active material includes silicon oxide represented by the general formula SiOx (0 < x ≦ 2).

[0010] In some embodiments, the lithium silicate includes at least one of Li2SiO3, Li2Si2O5, and Li4SiO4.

[0011] In some embodiments, in the negative electrode material, 0.002 ≦ a / b ≦ 2.

[0012] In some embodiments, the mass content of Mg element in the negative electrode material is a%, and 0.001 ≦ a ≦ 0.065.

[0013] In some embodiments, the mass content of Al element in the negative electrode material is b%, where 0.09≦b≦0.55.

[0014] In some embodiments, the mass content of the P element in the negative electrode material is c%, where 0.15≦c≦0.65.

[0015] In some embodiments, the negative electrode material further comprises a carbon layer.

[0016] In some embodiments, the carbon layer comprises at least one of an amorphous carbon material and a graphitized carbon material.

[0017] In some embodiments, the carbon layer comprises an amorphous carbon material, the amorphous carbon material comprising at least one of amorphous carbon, carbon black, and activated carbon.

[0018] In some embodiments, the carbon layer comprises a graphitized carbon material, the graphitized carbon material comprising at least one of conductive graphite, graphene.

[0019] In some embodiments, the particle size distribution of the negative electrode material is D 10 ≧1.0μm, 3μm≦D 50 ≦10μm, D 90 Meets the requirement of ≦25.0 μm.

[0020] In some embodiments, the mass content of lithium silicate in the negative electrode material is 30% to 80%.

[0021] In some embodiments, the carbon layer has a thickness of 10 nm to 2000 nm.

[0022] In some embodiments, the mass percentage of carbon element in the negative electrode material is 1% to 50%.

[0023] In some embodiments, the specific surface area of ​​the negative electrode material is 0.1 m 2 / g~50m 2 / g.

[0024] In some embodiments, the tap density of the negative electrode material is 0.5 g / cm 3 ~1.5g / cm 3 is.

[0025] In some embodiments, the specific capacity of the negative electrode material is measured within a voltage range of 0 V to 1.5 V, and when the cutoff voltage is 0.3 V, the specific capacity of the negative electrode material is A; when the cutoff voltage is 0.4 V, the specific capacity of the negative electrode material is B; and when the cutoff voltage is 0.5 V, the specific capacity of the negative electrode material is C, satisfying the following formula: 0.7≦(CB) / (BA)≦1.3

[0026] In some embodiments, the negative electrode material has a pH of 9-12.

[0027] In a second aspect, the present application provides a method for producing a negative electrode material, the method comprising the steps of: The silicon-based raw material is immersed in a phosphoric acid solution, subjected to a surface modification treatment, and then subjected to solid-liquid separation to obtain a precursor. A mixture containing a precursor, a lithium source, a magnesium source, and an aluminum source is heat-treated to obtain a negative electrode material containing a silicon-based active material and a lithium silicate, the negative electrode material further containing an Mg element, an Al element, and a P element, wherein the mass content of the Mg element in the negative electrode material is a %, the mass content of the Al element in the negative electrode material is b %, and the mass content of the P element in the negative electrode material is c %, and in the negative electrode material, a, b, and c satisfy the following formula: 0.3≦(a+b) / c≦1.5, and 0.5≦a+b+c≦10

[0028] In some embodiments, the silicon-based active material comprises silicon grains that are 20 nm or less in size.

[0029] In some embodiments, the silicon-based active material comprises silicon and / or silicon oxide.

[0030] In some embodiments, the silicon-based active material contains silicon oxide SiOx (0 < x ≦ 2).

[0031] In some embodiments, the lithium silicate contains at least one of Li2SiO3, Li2Si2O5, and Li4SiO4.

[0032] In some embodiments, in the negative electrode material, 0.002 ≦ a / b ≦ 2.

[0033] In some embodiments, the concentration of the phosphoric acid solution is 0.05 mol / L to 5 mol / L.

[0034] In some embodiments, the time of the immersion treatment is 2 hours to 10 hours.

[0035] In some embodiments, the solid-liquid separation includes at least one of filtration and centrifugation.

[0036] In some embodiments, the lithium source contains at least one of Li2O, Li2CO3, LiOH, Li, LiH, LiAlH4, and LiBH4.

[0037] In some embodiments, the magnesium source contains at least one of Mg2O, Mg, Mg(OH)2, and MgCl2.

[0038] In some embodiments, the aluminum source contains at least one of Al2O3, Al, Al(OH)3, and AlCl3.

[0039] In some embodiments, the temperature of the heat treatment is 400°C to 900°C.

[0040] In some embodiments, the heat preservation time of the heat treatment is 2 hours to 12 hours.

[0041] In some embodiments, the heat treatment is performed in a protective atmosphere.

[0042] In some embodiments, the gas of the protective atmosphere comprises at least one of nitrogen, helium, neon, argon, and krypton.

[0043] In some embodiments, before immersing the silicon-based raw material in a phosphoric acid solution to perform the surface modification treatment, the method further includes: coating the silicon-based raw material with carbon to obtain a silicon carbon composite, and using the silicon carbon composite as the silicon-based raw material.

[0044] In some embodiments, after heat treating the mixture comprising the precursor, a lithium source, a magnesium source, and an aluminum source, the method further comprises carbon coating the heat-treated product.

[0045] In some embodiments, the carbon coating process comprises a gas phase carbon coating process and / or a solid phase carbon coating process.

[0046] In a third aspect, the present application provides a battery including the negative electrode material or a negative electrode material produced by the method for producing the negative electrode material. [Effects of the Invention]

[0047] The technical solution of the present application has at least the following beneficial effects:

[0048] First, the present invention provides a negative electrode material incorporating Mg, Al, and P elements. These elements coordinate with the oxygen in the silicon-based active material or lithium silicate, favoring the formation of lithium ion transmission channels and improving the rate performance of the negative electrode material. By controlling the (a + b) / c range, the combination of Mg, Al, and P elements with the silicon-based active material and lithium silicate allows for faster and more lithium ion transmission channels to be formed, lowering the energy barrier for lithium ion transmission and improving the rate and cycle performance of the negative electrode material. Furthermore, the incorporation of Mg, Al, and P reduces the hydrolysis of the lithium silicate, thereby lowering the pH of the negative electrode material and reducing the damage to the binder in the electrode sheet due to an alkaline environment. This is beneficial for improving the processing stability of pre-lithiated negative electrode materials. The slurry prepared with the negative electrode material is more stable, less susceptible to settling, and less prone to gas generation.

[0049] The method for producing a negative electrode material according to the present invention involves immersing a silicon-based raw material in a phosphoric acid solution to uniformly deposit phosphate ions on the surface of the silicon-based raw material, then mixing and heat-treating the silicon-based raw material with a lithium source, a magnesium source, and an aluminum source. During the heat-treatment process, the content ratios of Mg, Al, and P are controlled, and the range of (a+b) / c is controlled. The lithium source and the silicon-based active material form a lithium silicate, and some of the lithium in the lithium silicate is replaced by magnesium and aluminum, and some of the silicon is replaced by phosphorus. Note that Mg and Al have larger radii than Li, and phosphorus can provide more connection points than silicon. The combination of Mg, Al, P, the silicon-based active material, and the lithium silicate can form faster and more lithium ion transmission channels, lowering the energy barrier for lithium ion transmission.

[0050] The method for producing the negative electrode material according to the present invention not only improves the electrochemical performance of the material, but also is suitable for large-scale production of the negative electrode material, and can effectively improve the rate performance and cycle stability of the battery. [Brief explanation of the drawings]

[0051] [Figure 1] FIG. 1 is a process flow diagram of a method for producing a negative electrode material according to an embodiment of the present application. [Figure 2] FIG. 2 is a comparison diagram of the cycle performance of the negative electrode materials produced in Example 1 and Comparative Example 1 of the present application. [Figure 3] FIG. 2 is a schematic diagram showing the cycle capacity retention state of the negative electrode material produced in Example 1 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0052] It should be noted that the following are preferred embodiments of the present invention, and those skilled in the art may make some modifications and improvements without departing from the principles of the present invention, all of which fall within the scope of protection of the present invention.

[0053] As the application of lithium-ion batteries expands and deepens, the performance requirements for lithium-ion batteries are also increasing. Traditional graphite anode materials are no longer able to meet the increasingly high market demands, particularly in terms of battery energy density. Silicon-oxygen materials have recently attracted attention as anode materials with high specific capacity. While silicon-oxygen materials have specific capacities exceeding 2000 mAh / g, they have lower initial coulombic efficiency and inferior conductivity, cycle performance, and rate performance compared to graphite materials.

[0054] To improve the performance of silicon-oxygen materials, lithium is typically doped into the silicon-oxygen material to increase the initial coulombic efficiency. However, this changes the distribution of silicon within the silicon-oxygen material, causing silicon aggregation, resulting in a deterioration in the material's rate performance, cycle performance, and volume increase. Furthermore, the lithium-doped silicon-oxygen material contains lithium silicate, which, due to hydrolysis, becomes highly alkaline, destroying the polymer binder during aqueous slurry preparation, resulting in poor slurry stability and precipitation, which can affect battery manufacturing.

[0055] Specifically, the present application provides a negative electrode material including a silicon-based active material and an active material including lithium silicate; The negative electrode material further contains Mg, Al, and P, the mass content of the Mg element in the negative electrode material is a%, the mass content of the Al element in the negative electrode material is b%, and the mass content of the P element in the negative electrode material is c%, and 0.3≦(a+b) / c≦1.5 and 0.5≦a+b+c≦10.

[0056] In the present invention, after introducing Mg, Al, and P into the negative electrode material, the applicant believes that the Mg, Al, and P coordinate with the O element in the silicon-based active material or lithium silicate, favoring the formation of lithium ion transmission channels and improving the rate performance of the negative electrode material. By controlling the (a+b) / c range, the combination of Mg, Al, and P with the silicon-based active material and lithium silicate can form more rapid lithium ion transmission channels and lower the energy barrier for lithium ion transmission. Furthermore, the introduction of Mg, Al, and P can reduce the hydrolysis of the lithium silicate, thereby lowering the pH of the negative electrode material and reducing the damage to the binder in the electrode sheet caused by an alkaline environment. This is beneficial for improving the processing stability of pre-lithiated negative electrode materials. The applicant also believes that the slurry prepared with the negative electrode material will be more stable, less susceptible to settling, and less prone to gas generation. Through extensive experiments, the applicant has discovered that as long as the elements Mg, Al and P are present and the formulas 0.3≦(a+b) / c≦1.5 and 0.5≦a+b+c≦10 are satisfied, the desired technical effects can be achieved and the technical problem of the present application can be solved.

[0057] In the above technical solution, (a + b) / c may be, for example, 0.3, 0.5, 0.7, 0.8, 0.9, 1.0, 1.2, 1.3, 1.4, or 1.5, and may be other values ​​within the above range, but is not limited thereto. When (a + b) / c is less than 0.3, the amount of Mg and Al is too small, and the remaining P combines with Li doped in the negative electrode material through prelithiation to form a large amount of lithium phosphate, resulting in the loss of active lithium ions and a decrease in the initial efficiency of the negative electrode material. When (a + b) / c is greater than 1.5, the amount of P is too small, and the remaining Mg and Al combine with Si and O to form substances such as magnesium silicate and aluminum silicate, resulting in the loss of silicon and a decrease in the specific capacity of the negative electrode material. Therefore, controlling the balance of the Mg, Al, and P composition ratios is beneficial to the formation of effective lithium ion transmission channels and improves the initial coulombic efficiency and rate performance of the negative electrode material. Preferably, 0.6≦(a+b) / c≦1.2.

[0058] In the above technical solution, the value of a+b+c may be specifically, but not limited to, 0.5, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, or 10, and may of course be other values ​​within the above range. If the value of a+b+c is too small, it indicates that the content of doping elements in the negative electrode material is too low, and the magnesium aluminum phosphate-related substances formed on the surface and / or inside of the silicon-based active material are insufficient, which reduces the pH of the negative electrode material and reduces the stability of the slurry after preparing the negative electrode material to form a slurry.

[0059] In some embodiments, the content of Al, Mg, P elements can be measured by ICP method (Agilent 5800VDV, ICP-OES).

[0060] In some embodiments, the applicant believes that the portion containing Al, Mg, and P elements can include, but is not limited to, at least one of aluminosilicate, magnesium silicate, aluminum phosphate, magnesium phosphate, magnesium oxide, aluminum oxide, oxide of phosphorus, and phosphate. Specifically, the applicant believes that the portion containing Al, Mg, and P elements can include, but is not limited to, at least one of LiAlSiO4, Al2SiO5, Al2O3, PO5, Li3PO4, AlPO4, Al(PO3)3, LiAlO2, MgO, MgSiO3, Mg2SiO4, Mg3(PO4)2, and Li2Mg2O9Si3. In view of current detection technology, the applicant cannot completely confirm the specific forms of existence of Al, Mg, and P elements. However, based on the explanation of the above principles, the data of the examples, and an analysis of the beneficial effects, the applicant can find that controlling the contents of Al, Mg, and P elements in the present application within the above ranges can solve the technical problem of the present application, and there is no obvious relationship with the specific forms of existence of Al, Mg, and P elements.

[0061] In some embodiments, the Al element in the composite negative electrode material is at least partially present in the +3 valent form.

[0062] In some embodiments, the Mg element in the composite negative electrode material is at least partially present in the +2 valent form.

[0063] In some embodiments, the mass content of Mg element in the negative electrode material is a% (0.001≦a≦0.065), specifically, but not limited to, 0.001%, 0.004%, 0.006%, 0.008%, 0.01%, 0.03%, 0.035%, 0.038%, 0.040%, 0.041%, 0.045%, 0.05%, 0.055%, 0.065%, etc.

[0064] In some embodiments, the mass content of Al element in the negative electrode material is b% (0.09≦b≦0.55), specifically, but not limited to, 0.09%, 0.095%, 0.1%, 0.12%, 0.15%, 0.2%, 0.25%, 0.35%, 0.39%, 0.40%, 0.42%, 0.50%, 0.55%, etc.

[0065] In some embodiments, the mass content of the P element in the negative electrode material is c% (0.15≦c≦0.70), such as, but not limited to, 0.15%, 0.18%, 0.22%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, or 0.65%.

[0066] In some embodiments, the silicon-based active material includes silicon crystal grains, and the size of the silicon crystal grains is 20 nm or less, such as, but not limited to, 20 nm, 19 nm, 18 nm, 15 nm, 12 nm, 10 nm, 8 nm, 5 nm, or 2 nm.

[0067] In some embodiments, the silicon-based active material comprises silicon and / or silicon oxide.

[0068] In some embodiments, the silicon-based active material has the general formula SiO x (0≦x≦2). In some explanations, silicon oxide may be a material in which silicon particles are dispersed in SiO2, or may be a material having a tetrahedral structural unit in which a silicon atom is located at the center of the tetrahedral structural unit and oxygen atoms are located at the four vertices of the tetrahedral structural unit. Silicon oxide specifically includes SiO 0.2 , SiO 0.4 , SiO 0.6 , SiO 0.8 , SiO or SiO 1.2 etc. Preferably, the silicon oxide is SiO.

[0069] In some embodiments, the lithium silicate comprises at least one of Li2SiO3, Li2SiO5, and Li4SiO4. It is understood that a prelithiated silicon-based active material produces a certain amount of lithium silicate, and most of this lithium silicate is located on the surface and / or inside the silicon-based active material, or the silicon-based active material is interspersed with the lithium silicate.

[0070] In some embodiments, the mass content of Mg in the negative electrode material is a%, and the mass content of Al in the negative electrode material is b%, with 0.002≦a / b≦2. Specifically, the a / b ratio may be 0.002, 0.005, 0.008, 0.01, 0.02, 0.03, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8, 1, 1.5, or 2, and may also be other values ​​within the above ranges, without being limited thereto. It is understood that the atomic radii of Mg and Al are larger than those of Li, allowing Mg and Al to occupy the crystal lattice of Li, which is beneficial for the formation of larger ion channels, better doping reactivity of Mg, and more uniform and effective doping of metal elements. Controlling the a / b ratio within the above ranges allows for the Mg 2+ and Al 3+ The doping can be balanced, preventing any one element from occupying too much of the Li crystal lattice, and the formed magnesium aluminum phosphate and lithium silicate can be more uniformly dispersed on the surface and / or inside of the silicon-based active material. By adding Mg and Al simultaneously, the crystal grains of the lithium silicate crystals can be made more uniform, resulting in better lithium ion transport performance.

[0071] In some embodiments, the negative electrode material further comprises a carbon layer, which is understood to coat at least a portion of the surface of the core containing the silicon-based active material and lithium silicate.

[0072] In some embodiments, the thickness of the carbon layer is 10 nm to 2000 nm, and more specifically, may be, but is not limited to, 10 nm, 50 nm, 100 nm, 300 nm, 500 nm, 800 nm, 1000 nm, 1500 nm, 1800 nm, or 2000 nm. Controlling the thickness of the carbon layer is beneficial for improving lithium ion transmission efficiency, favoring high-rate charging and discharging of the material, improving the volume expansion of the material, and improving the cycling performance of the negative electrode material.

[0073] In some embodiments, the carbon layer comprises at least one of an amorphous carbon material and a graphitized carbon material.

[0074] In some embodiments, the carbon layer comprises an amorphous carbon material including at least one of amorphous carbon, carbon black, and activated carbon.

[0075] In some embodiments, the carbon layer comprises a graphitized carbon material comprising at least one of conductive graphite, graphene.

[0076] In some embodiments, the tap density of the negative electrode material is 0.5 g / cm 3 ~1.5g / cm 3 , e.g., 0.2 g / cm 3 , 0.3g / cm 3 , 0.5g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 1.0g / cm 3 , 1.2g / cm 3 etc. Preferably, 0.7 g / cm 3 ~1.3g / cm 3 is.

[0077] In some embodiments, the particle size distribution of the negative electrode material is D 10 ≧1.0μm, 3μm≦D 50 ≦10μm, D 90 Meets the requirement of ≦25.0 μm.

[0078] Specifically, the average particle size D of the negative electrode material 50 The particle size D of the negative electrode material may be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. 10 The particle size D of the negative electrode material may be 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 2.9 μm, or 3 μm. 90 The particle size of the negative electrode material may be, but is not limited to, 25 μm, 20 μm, 18 μm, 15 μm, 12 μm, 10 μm, or the like. Controlling the particle size of the negative electrode material within the above range is advantageous for improving the cycle performance and rate performance of the negative electrode material.

[0079] In some embodiments, the specific surface area of ​​the negative electrode material is less than 0.1 m 2 / g~50m 2 / g. Preferably, the specific surface area of ​​the composite negative electrode material is 1 m 2 / g, 5m 2 / g, 8m 2 / g, 10m 2 / g, 15m 2 / g, 20m 2 / g, 25m 2 / g, 30m 2 / g, 35m 2 / g, 40m 2 / g, 45m 2 / g, or 50m 2 / g, etc. It is understood that controlling the specific surface area within the above range is advantageous in reducing the consumption of irreversibly activated lithium ions and improving the initial coulomb efficiency of the battery.

[0080] In some embodiments, the mass content of carbon element in the negative electrode material is 1% to 50%. Specifically, it may be, but is not limited to, 1%, 5%, 8%, 10%, 15%, 20%, 30%, 35%, 40%, 45%, or 50%. The carbon in the negative electrode material is derived from the carbon material in the carbon layer.

[0081] In some embodiments, the mass content of lithium silicate in the negative electrode material is 30% to 80%. Specifically, it may be, but is not limited to, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or 80%. By prelithiating the silicon-based active material, the initial coulombic efficiency of the negative electrode material can be effectively improved.

[0082] In some embodiments, the lithium silicate is uniformly distributed on and / or within the silicon-based active material, with at least a portion of the lithium silicate being located in the carbon layers.

[0083] In some embodiments, the specific capacity of the negative electrode material is measured within a voltage range of 0 V to 1.5 V, and during the lithium desorption process of the negative electrode material, when the cutoff voltage is 0.3 V, the specific capacity of the negative electrode material is A; when the cutoff voltage is 0.4 V, the specific capacity of the negative electrode material is B; and when the cutoff voltage is 0.5 V, the specific capacity of the negative electrode material is C, satisfying the following formula: 0.7≦(CB) / (BA)≦1.3 Specifically, (CB) / (BA) may be 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, or 1.3, and may also be other values ​​within the above range. If (CB) / (BA) is less than 0.7, there will be a certain loss in the capacity of the negative electrode material, and the initial efficiency will decrease. If (CB) / (BA) is greater than 1.3, many crystal grains will aggregate within the negative electrode material, affecting the lithium ion transport within the negative electrode material and resulting in poor cycle performance at room temperature.

[0084] In some embodiments, the pH of the negative electrode material is 9 to 12, and may be specifically 9, 9.5, 10, 10.5, 11, 11.5, or 12, or other values ​​within the above range. Slurries prepared with the negative electrode materials according to the present application are more stable, less susceptible to settling, and less susceptible to gas generation.

[0085] The present application further provides a method for manufacturing a composite negative electrode material, and as shown in FIG. 1, the method includes the following steps S10 to S20. S10: Immerse the silicon-based raw material in a phosphoric acid solution, perform surface modification treatment, and then perform solid-liquid separation to obtain a precursor; S20: A mixture containing a precursor, a lithium source, a magnesium source, and an aluminum source is heat-treated to obtain a negative electrode material containing a silicon-based active material and a lithium silicate, the negative electrode material further containing Mg, Al, and P, the mass content of the Mg element in the negative electrode material being a%, the mass content of the Al element in the negative electrode material being b%, and the mass content of the P element in the negative electrode material being c%, and in the negative electrode material, a, b, and c satisfy the following formula: 0.3≦(a+b) / c≦1.5, and 0.5≦a+b+c≦10

[0086] The method for producing an anode material according to the present invention involves immersing a silicon-based raw material in a phosphoric acid solution to uniformly attach phosphate ions to the surface of the silicon-based raw material, and then mixing and heat-treating the silicon-based raw material with a lithium source, a magnesium source, and an aluminum source. During the heat-treatment process, the lithium source and the silicon-based active material form a lithium silicate, and some of the lithium in the lithium silicate is replaced by magnesium and aluminum, and the silicon is replaced by phosphorus. Furthermore, Mg and Al have larger radii than Li, and phosphorus can provide more bonding points than silicon. The combination of Mg, Al, P, the silicon-based active material, and the lithium silicate can form faster and more lithium ion transmission channels, thereby lowering the energy barrier for lithium ion transmission.

[0087] The present technical solution will be described in detail below.

[0088] S10: The silicon-based raw material is immersed in a phosphoric acid solution, subjected to a surface modification treatment, and subjected to solid-liquid separation to obtain a precursor.

[0089] In some embodiments, the silicon-based raw material contains silicon oxide SiOy (where 0 < y ≤ 2), and specifically, the silicon oxide is, for example, SiO 0.2 、SiO 0.4 、SiO 0.6 、SiO 0.8 、SiO or SiO 1.2 and so on. Preferably, the silicon oxide is SiO.

[0090] In some embodiments, the concentration of the phosphoric acid solution is 0.05 mol / L to 5 mol / L. Specifically, it may be, but is not limited to, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, etc.

[0091] In some embodiments, the time of the immersion treatment is 2 hours to 10 hours. Specifically, it may be, but is not limited to, 2 hours, 3 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.

[0092] In some embodiments, the means of solid-liquid separation includes at least one of filtration and centrifugation. The filtration may be, for example, vacuum suction filtration, filtration by filter paper, etc.

[0093] S20: Heat-treat a mixture containing a precursor, a lithium source, a magnesium source, and an aluminum source to obtain a negative electrode material containing a silicon-based active material and lithium silicate. The negative electrode material further contains Mg element, Al element, and P element. The mass content of the Mg element in the negative electrode material is a%, the mass content of the Al element in the negative electrode material is b%, and the mass content of the P element in the negative electrode material is c%. In the negative electrode material, a, b, and c satisfy the following formula. 0.3 ≤ (a + b) / c ≤ 1.5, and 0.5 ≤ a + b + c ≤ 10

[0094] In some embodiments, the silicon crystallites in the silicon-based active material are 20 nm or less, specifically, they may be 20 nm, 19 nm, 18 nm, 15 nm, 12 nm, 10 nm, 8 nm, 5 nm, 2 nm, etc., and are not limited thereto.

[0095] In some embodiments, the silicon-based active material contains nanosilicon and / or silicon oxide.

[0096] In some embodiments, the silicon-based active material is silicon oxide SiO x (where 0 < x ≦ 2). Silicon oxide specifically includes SiO 0.2 , SiO 0.4 , SiO 0.6 , SiO 0.8 , SiO or SiO 1.2 etc. Preferably, the silicon oxide is SiO.

[0097] In some embodiments, the lithium source contains at least one of Li2O, Li2CO3, LiOH, Li, LiH, LiAlH4, and LiBH4.

[0098] In some embodiments, the magnesium source contains at least one of Mg2O, Mg, Mg(OH)2, and MgCl2.

[0099] In some embodiments, the aluminum source contains at least one of Al2O3, Al, Al(OH)3, and AlCl3.

[0100] In some embodiments, the heat treatment temperature is 400°C to 900°C, and the heat treatment time is 2 hours to 10 hours. Specifically, the heat treatment temperature may be 400°C, 500°C, 600°C, 650°C, 700°C, 750°C, 800°C, or 900°C. The heat treatment time may specifically be 2 hours, 4 hours, 6 hours, 8 hours, 9 hours, or 10 hours, and is not limited thereto.

[0101] In some embodiments, the heat treatment is performed in a protective atmosphere.

[0102] In some embodiments, the gas of the protective atmosphere comprises at least one of nitrogen, helium, neon, argon, and krypton.

[0103] In some embodiments, the lithium silicate comprises at least one of Li2SiO3, Li2SiO5, and Li4SiO4. It is understood that a prelithiated silicon-based active material produces a certain amount of lithium silicate, and most of this lithium silicate is located on the surface and / or inside the silicon-based active material, or the silicon-based active material is interspersed with the lithium silicate.

[0104] In some embodiments, the mass content of Mg in the negative electrode material is a%, and the mass content of Al in the negative electrode material is b%, with 0.002≦a / b≦2. Specifically, the a / b ratio may be 0.002, 0.005, 0.008, 0.01, 0.02, 0.03, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8, 1, 1.5, or 2, and may also be other values ​​within the above ranges, without being limited thereto. It is understood that the atomic radii of Mg and Al are larger than those of Li, allowing Mg and Al to occupy the crystal lattice of Li, which is beneficial for the formation of larger ion channels, better doping reactivity of Mg, and more uniform and effective doping of metal elements. Controlling the a / b ratio within the above ranges allows for the formation of Mg and Al. 2+ and Al 3+ The doping can be balanced, preventing any one element from occupying too much of the Li crystal lattice, and the formed magnesium aluminum phosphate and lithium silicate can be more uniformly dispersed on the surface and / or inside of the silicon-based active material. By adding Mg and Al simultaneously, the crystal grains of the lithium silicate crystals can be made more uniform, resulting in better lithium ion transport performance.

[0105] In some embodiments, before S10, the method further includes performing a carbon coating treatment on the silicon-based active material to obtain a silicon carbon composite, and treating the silicon carbon composite as the silicon-based active material.

[0106] In some embodiments, after S20, the method further includes performing a carbon coating treatment on the heat-treated product.

[0107] In some embodiments, the carbon coating process includes a gas phase carbon coating process and / or a solid phase carbon coating process.

[0108] When the carbon coating process is a gas-phase carbon coating process, it may specifically include depositing a silicon-based active material with a carbon source gas under a protective atmosphere to obtain a composite.

[0109] In some embodiments, the deposition temperature is between 600° C. and 1000° C. Specific examples of the temperature include, but are not limited to, 600° C., 700° C., 800° C., 850° C., 900° C., 950° C., or 1000° C. Preferably, the deposition temperature is between 700° C. and 900° C.

[0110] In some embodiments, the incubation time for vapor deposition is 0.5 to 10 hours. Specific examples of the incubation time include, but are not limited to, 0.5, 1, 3, 6, 8, 9, or 10 hours. Preferably, the incubation time for vapor deposition is 3 to 9 hours.

[0111] In some embodiments, the carbon source gas comprises at least one of an alkane, a cycloalkane, an alkene, an alkyne, and an aromatic hydrocarbon. Specifically, the carbon source gas comprises at least one of acetylene, methane, benzene, toluene, cyclohexane, ethanol, ethylene, and propylene.

[0112] In some embodiments, the concentration of the carbon source gas is 0.1 L / min to 10 L / min. Specifically, the concentration may be, but is not limited to, 0.1 L / min, 0.4 L / min, 0.6 L / min, 0.8 L / min, 1.0 L / min, 2 L / min, 5 L / min, 6 L / min, 8 L / min, 9 L / min, or 10 L / min. A certain concentration of carbon source gas is introduced as a gas source for the carbon material, and after maintaining the temperature for a certain period of time, the carbon material is deposited on the surface of the silicon-based active material.

[0113] When the carbon coating treatment is a solid-phase carbon coating treatment, specifically, the process may include mixing a silicon-based raw material with a second carbon source, and performing a carbonization treatment to obtain a silicon carbon composite.

[0114] In some embodiments, the second carbon source comprises at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt.

[0115] In some embodiments, the mass ratio of the silicon-based raw material to the second carbon source is (20-100):(10-80). The mass ratio of the silicon-based active material to the second carbon source may be, but is not limited to, 20:10, 30:15, 50:60, 80:30, 90:20, 100:10, etc., and may of course be other values ​​within the above range.

[0116] In some embodiments, the carbonization temperature is 600°C to 1000°C. Specific examples of the temperature include, but are not limited to, 600°C, 700°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 950°C, and 1000°C. Preferably, the carbonization temperature is 700°C to 900°C.

[0117] In some embodiments, the incubation time for the carbonization treatment is 0.5 to 10 hours. Specifically, the incubation time may be, but is not limited to, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 hours. Preferably, the incubation time for the carbonization treatment is 3 to 5 hours.

[0118] In some embodiments, the carbonization process is carried out in a protective atmosphere, and the gas of the protective atmosphere comprises at least one of nitrogen, helium, neon, argon, and krypton.

[0119] In some embodiments, the silicon carbon composite after the carbon coating treatment is further subjected to at least one of crushing, sieving, and demagnetization. Preferably, the composite after the carbon coating treatment is crushed, sieved, and demagnetized in this order.

[0120] It should be noted that whether the carbon coating is performed before step S10 or after step S20 does not have a significant effect on the present invention. This is because the carbon layer formed by the coating does not affect the contact between the silicon-based raw material and phosphoric acid, and phosphoric acid can penetrate the carbon layer and uniformly adhere to the surface of the silicon-based raw material. During the subsequent heat treatment process, the lithium source and the silicon-based raw material form lithium silicate, and some of the lithium in the lithium silicate is replaced by magnesium and aluminum, and silicon is replaced by phosphorus. Furthermore, divalent Mg and trivalent Al have larger radii than Li, and phosphorus can provide more bonding points than silicon. After Mg, A, P, and O are coordinated, a magnesium aluminum phosphate-based material and lithium silicate are formed on the surface and / or inside of the silicon-based active material. The combination of lithium silicate and magnesium aluminum phosphate can form faster and more lithium ion transmission channels. In addition, the carbon coating process further improves the volume expansion of the material, improving lithium ion transmission efficiency, which is beneficial for high-rate charge and discharge of the material and improves the cycle performance of the negative electrode material.

[0121] The present invention also provides a battery employing the negative electrode material according to the above-described embodiment or the negative electrode material manufactured by the method for manufacturing the negative electrode material according to the above-described embodiment. The battery according to the embodiment has advantages of high capacity, high initial efficiency, long cycle life, excellent rate performance, and low expansion.

[0122] The present invention will be further described below with reference to several examples. Note that the present invention is not limited to the specific examples below. The present invention can be implemented by making appropriate modifications within the scope of the present invention. [Example]

[0123] Example 1 The method for preparing the negative electrode material includes the following steps: (1) SiO powder (D 50 1 kg of carbon-coated SiO2 (=6.3 μm) was taken and placed in a tubular furnace, heated to 900°C in a nitrogen atmosphere, acetylene was introduced, and the temperature was maintained for 3 hours, after which the material was cooled to obtain a carbon-coated SiO2 material. (2) 100 g of phosphoric acid was taken and uniformly mixed with 950 g of water to obtain a phosphoric acid solution, and the carbon-coated SiO material was immersed in the phosphoric acid solution for 6 hours, and then suction filtered to obtain the precursor; (3) 100 g of Li2O, 3 g of MgCl2, and 30.3 g of AlCl3 were mixed with the precursor, then placed in a box furnace in a nitrogen atmosphere, heated to 800°C, and kept at that temperature for 4 hours. After that, the mixture was removed and sieved to obtain the negative electrode material.

[0124] The negative electrode material prepared in the examples of the present application includes an active material and a carbon layer located on at least a portion of the surface of the active material, and the active material includes a silicon-based active material and a lithium silicate.

[0125] Other parameters of the negative electrode material are detailed in Table 1.

[0126] Example 2 The method for preparing the negative electrode material includes the following steps: (1) SiO powder (D 501 kg of the carbon-coated SiO2 material (SiO2 = 6.3 μm) was placed in a tubular furnace and heated to 900°C in a nitrogen atmosphere. Acetylene was then introduced into the furnace, and the material was kept at this temperature for 3 hours and then cooled to obtain a carbon-coated SiO2 material. (2) 100 g of phosphoric acid was taken and uniformly mixed with 950 g of water to obtain a phosphoric acid solution, and the carbon-coated SiO material was immersed in the phosphoric acid solution for 6 hours, and then suction filtered to obtain the precursor; (3) 100 g of Li2O, 1.5 g of MgCl2, and 21.5 g of AlCl3 were mixed with the precursor, then placed in a box furnace in a nitrogen atmosphere, heated to 800°C, and kept at that temperature for 4 hours. After that, the mixture was removed and sieved to obtain a negative electrode material.

[0127] The negative electrode material prepared in the examples of the present application includes an active material and a carbon layer located on at least a portion of the surface of the active material, and the active material includes a silicon-based active material and a lithium silicate.

[0128] Other parameters of the negative electrode material are detailed in Table 1.

[0129] Example 3 The method for preparing the negative electrode material includes the following steps: (1) SiO powder (D 50 1 kg of the carbon-coated SiO2 material (SiO2 = 6.3 μm) was placed in a tubular furnace and heated to 900°C in a nitrogen atmosphere. Acetylene was then introduced into the furnace, and the material was kept at this temperature for 3 hours and then cooled to obtain a carbon-coated SiO2 material. (2) 150 g of phosphoric acid was taken and uniformly mixed with 950 g of water to obtain a phosphoric acid solution, and the carbon-coated SiO material was immersed in the phosphoric acid solution for 6 hours, and then suction filtered to obtain the precursor; (3) 100 g of Li2O, 1.5 g of MgCl2, and 10.5 g of AlCl3 were mixed with the precursor, then placed in a box furnace in a nitrogen atmosphere, heated to 800°C, and kept at that temperature for 4 hours. After that, the mixture was removed and sieved to obtain a negative electrode material.

[0130] The negative electrode material prepared in the examples of the present application includes an active material and a carbon layer located on at least a portion of the surface of the active material, and the active material includes a silicon-based active material and a lithium silicate.

[0131] Other parameters of the negative electrode material are detailed in Table 1.

[0132] Example 4 The method for preparing the negative electrode material includes the following steps: (1) SiO powder (D 50 1 kg of the carbon-coated SiO2 material (SiO2 = 6.3 μm) was placed in a tubular furnace and heated to 900°C in a nitrogen atmosphere. Acetylene was then introduced into the furnace, and the material was kept at this temperature for 3 hours and then cooled to obtain a carbon-coated SiO2 material. (2) 50 g of phosphoric acid was taken and uniformly mixed with 950 g of water to obtain a phosphoric acid solution, and the carbon-coated SiO material was immersed in the phosphoric acid solution for 6 hours, and then suction filtered to obtain the precursor; (3) 100 g of Li2O, 1.5 g of MgCl2, and 18 g of AlCl3 were mixed with the precursor, then placed in a box furnace in a nitrogen atmosphere, heated to 800°C, and kept at that temperature for 4 hours. After that, the mixture was removed and sieved to obtain the negative electrode material.

[0133] The negative electrode material prepared in the examples of the present application includes an active material and a carbon layer located on at least a portion of the surface of the active material, and the active material includes a silicon-based active material and a lithium silicate.

[0134] Other parameters of the negative electrode material are detailed in Table 1.

[0135] Example 5 The method for preparing the negative electrode material includes the following steps: (1) SiO powder (D 50 1 kg of the carbon-coated SiO2 material (SiO2 = 6.3 μm) was placed in a tubular furnace and heated to 900°C in a nitrogen atmosphere. Acetylene was then introduced into the furnace, and the material was kept at this temperature for 3 hours and then cooled to obtain a carbon-coated SiO2 material. (2) 80 g of phosphoric acid was taken and uniformly mixed with 950 g of water to obtain a phosphoric acid solution, and the carbon-coated SiO material was immersed in the phosphoric acid solution for 6 hours, and then suction filtered to obtain the precursor; (3) 100 g of Li2O, 1 g of MgCl2, and 35 g of AlCl were mixed with the precursor, then placed in a box furnace in a nitrogen atmosphere, heated to 800°C, and kept at that temperature for 4 hours. After that, the mixture was removed and sieved to obtain the negative electrode material.

[0136] The negative electrode material prepared in the examples of the present application includes an active material and a carbon layer located on at least a portion of the surface of the active material, and the active material includes a silicon-based active material and a lithium silicate.

[0137] Other parameters of the negative electrode material are detailed in Table 1.

[0138] Example 6 (1) 100 g of phosphoric acid was taken and uniformly mixed with 950 g of water to obtain a phosphoric acid solution, and the SiO material (D 50 1 kg of the powder (particle size: 6.3 μm) was immersed in a phosphoric acid solution for 6 hours, and then suction filtered to obtain the precursor. (2) 100 g of Li2O, 3 g of MgCl2, and 30.3 g of AlCl3 were mixed with the precursor, then placed in a box furnace in a nitrogen atmosphere, heated to 800°C, and kept at that temperature for 4 hours. After that, the mixture was removed and sieved to obtain a mixture. (3) 1.5 kg of the mixture and 120 g of asphalt were placed in a VC machine, mixed at a rotation speed of 500 rpm for 40 minutes, and then discharged. The mixture was then placed in a high-temperature box furnace and fired at 800°C for 6 hours. Nitrogen was introduced into the box furnace, and the mixture was allowed to cool naturally to room temperature. The mixture was then discharged to obtain the negative electrode material.

[0139] The negative electrode material prepared in the examples of the present application includes an active material and a carbon layer located on at least a portion of the surface of the active material, and the active material includes a silicon-based active material and a lithium silicate.

[0140] Other parameters of the negative electrode material are detailed in Table 1.

[0141] Example 7 The silicon-based raw material in step (1) is SiO 0.8 A negative electrode material was obtained in the same manner as in Example 1, except for the above.

[0142] Example 8 (3) A negative electrode material was obtained in the same manner as in Example 1, except that 100 g of Li2O, 1.3 g of MgO, and 23.1 g of Al2O3 were taken and mixed with a precursor, and then the mixture was placed in a box furnace in a nitrogen atmosphere, heated to 800°C, and kept at that temperature for 4 hours. The mixture was then removed and sieved to obtain a negative electrode material.

[0143] Comparative Example 1 (1) SiO powder (D 50 1 kg of carbon-coated SiO2 (=6.3 μm) was taken and placed in a tubular furnace, heated to 900°C in a nitrogen atmosphere, acetylene was introduced, and the temperature was maintained for 3 hours, after which it was cooled to obtain a carbon-coated SiO2 material. (2) 100 g of Li2O and a carbon-coated SiO material were mixed, then placed in a box furnace in a nitrogen atmosphere, heated to 800°C, and kept at that temperature for 4 hours. After that, the mixture was taken out and sieved to obtain a negative electrode material.

[0144] Comparative Example 2 (1) 1 kg of SiO powder (D50 = 6.3 μm) was taken, placed in a tubular furnace, and heated to 900 °C in a nitrogen atmosphere. Acetylene was introduced, and the temperature was maintained for 3 hours, after which it was cooled to obtain a carbon-coated SiO material. (2) 62.5 g of phosphoric acid was taken and uniformly mixed with 950 g of water to obtain a phosphoric acid solution, and the carbon-coated SiO material was immersed in the phosphoric acid solution for 6 hours, and then suction filtered to obtain a precursor. (3) 100 g of Li2O, 1 g of MgCl2, and 17 g of AlCl3 were mixed with the precursor, then placed in a box furnace in a nitrogen atmosphere, heated to 800°C, and kept at that temperature for 4 hours. After that, the mixture was removed and sieved to obtain the negative electrode material.

[0145] Comparative Example 3 (1) 1 kg of SiO powder (D50 = 6.3 μm) was taken, placed in a tubular furnace, and heated to 900 °C in a nitrogen atmosphere. Acetylene was introduced, and the temperature was maintained for 3 hours, after which the material was cooled to obtain a carbon-coated SiO material; (2) 150 g of phosphoric acid was taken and uniformly mixed with 950 g of water to obtain a phosphoric acid solution, and the carbon-coated SiO material was immersed in the phosphoric acid solution for 6 hours, and then suction filtered to obtain the precursor; (3) 100 g of Li2O, 1.3 g of MgCl2, and 7.5 g of AlCl3 were taken and mixed with the precursor, then placed in a box furnace in a nitrogen atmosphere, heated to 800°C, and kept at that temperature for 4 hours. After that, the mixture was taken out and sieved to obtain a negative electrode material.

[0146] Test Method: (1) Particle size of negative electrode material: Particle size was measured using Mastersizer 3000 laser diffraction technology. Particle size measurement is accomplished by measuring the intensity of scattered light when a laser beam passes through a dispersed particle sample. The data is then analyzed to form a scattering spectrogram, which calculates the particle size distribution. 50 is the particle size corresponding to the cumulative particle size distribution percentage of a sample reaching 50%. Its physical meaning is that particles with a particle size larger than that account for 50% and particles smaller than that account for 50%. D 50 is also called the mean diameter or median diameter. 90 Particle size, D 50 Particle size, D 10 The particle size is the equivalent diameter (average particle size) of the largest particle when the cumulative distribution is 90%, 50%, and 10% on the distribution curve, respectively. (2) Measurement method for the specific surface area of ​​the negative electrode material: After measuring the amount of gas adsorbed onto a solid surface at different relative pressures at constant temperature and low temperature, the amount of sample monolayer adsorption is determined based on the Brunauer-Emmett-Teller adsorption theory and its equation (BET equation), and the specific surface area of ​​the material is calculated. (3) Method for measuring tap density: A certain amount of sample was weighed and the tap density was measured by a Quantachrome AutoTap type tap density measuring instrument by vibrating 3000 times at 300 times / min. (4) XRD test: Silicon crystallite size test method: The XRD peaks were measured using a PANalytical X'pert Pro X-ray diffractometer, and then the Si crystallite size was calculated by performing fitting analysis on the Si peaks in the XRD using XpertHighScore software. Determination of lithium silicate content: The lithium silicate content was quantitatively analyzed using MgO as an internal standard. XRD peaks were measured using a PANalytical X'pert Pro X-ray diffractometer, and then background correction, smoothing, peak identification, and fitting analysis were performed using Jade software. The lithium silicate content was calculated by comparing it with the MgO content. (5) Carbon content measurement method: The carbon content was measured by thermogravimetric analysis. (6) Measurement of the mass content of Al, Mg, and P in the negative electrode material: The Al, Mg, and P contents of the test material were measured using ICP. Test method: 0.500 g of negative electrode material was placed in a clean platinum crucible and then calcined in an air muffle furnace at 750°C for 2 hours to completely remove carbon. After cooling, the calcined residue was thoroughly reacted with 4 mL of HNO3 and 6 mL of HF mixed acid. The platinum crucible containing the solution was then placed on a hot plate at 350°C until the solvent was completely evaporated. After the crucible cooled, an additional 6 mL of HCl was added and heated until the residue was completely dissolved. The solution was then transferred to a 100 mL plastic measuring flask and the Al, Mg, and P contents of the entire test material were measured using an ICP spectrometer (Agilent 5800VDV ICP-OES). 10,000 ppm is understood to be equivalent to 1% by mass. (7) Button battery testing: A slurry was prepared from the negative electrode material, conductive carbon black, and binder (styrene butadiene rubber and hydroxymethyl cellulose) in a ratio of 75:15:10, which was then evenly applied to copper foil and dried to produce a negative electrode sheet. A button battery was then assembled in an argon-filled glove box; the separator used was a polypropylene microporous membrane, the electrolyte used was 1 mol / L lithium hexafluorophosphate (the solvent was a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate), and the positive electrode sheet used was a metallic lithium sheet. The electrochemical performance of the battery was measured using a LAND NEWWARE 5V / 10mA type battery evaluation device, with the voltage being 1.5V and the current being 0.1C, and the initial coulombic efficiency = initial charge specific capacity / initial discharge specific capacity. (8) Cycle characteristic test: The negative electrode materials prepared in the above examples and comparative examples were mixed with graphite in a mass ratio of 15:85 to form a negative electrode material, which was then mixed with graphite in a mass ratio of 15:85 to obtain a negative electrode active material. Thereafter, the negative electrode active material, conductive carbon black, hydroxymethyl cellulose, and styrene butadiene rubber were uniformly mixed in a mass ratio of 92:4:2:2 and applied to copper foil to prepare a negative electrode sheet. A button battery was prepared using a metallic lithium sheet as a positive electrode sheet and polyethylene as a separator. The electrochemical performance of the battery was measured using a LAND NEWWARE 5V / 10mA type battery evaluation device, with the voltage being 1.5V and the current being 0.1C, and the 50-cycle retention rate was calculated as the 50th discharge specific capacity / initial discharge specific capacity. The electrochemical performance of the battery was measured using a LAND NEWWARE 5V / 10mA type battery evaluation device, with the voltage being 1.5V and the current being 0.1C and 3C, respectively, where 3C / 0.1C=3C current discharge specific capacity / 0.1C current discharge specific capacity. The specific capacity of the negative electrode material is measured within a voltage range of 0V to 1.5V. If the cutoff voltage is 0.3V, the specific capacity of the negative electrode material is A; if the cutoff voltage is 0.4V, the specific capacity of the negative electrode material is B; and if the cutoff voltage is 0.5V, the specific capacity of the negative electrode material is C. (9) Slurry stability test: The negative electrode materials produced in each example and comparative example were used as the active material, and a slurry was prepared from the negative electrode material, conductive carbon black, and binder (styrene butadiene rubber and hydroxymethyl cellulose) in a ratio of 75:15:10. This was placed in an aluminum plastic film bag, sealed, and allowed to stand. The change in shape of the aluminum plastic film bag was then monitored, with the monitoring period being one month. (10) pH test method: Use a Mettler Toledo FE20 pH meter to measure the pH of the test material and calibrate it before use. Calibration method: remove the protective liquid sleeve on the electrode, wash it with pure water several times, and then soak it in distilled water for 30 minutes. Then remove the electrode and wipe the pH electrode with tissue paper or filter paper. Then add a pH 4.01 buffer test solution to the cleaned polyethylene beaker and press the calibration key to start calibration. After the instrument test is stable (the display screen appears), add pH 7.00 and pH 9.21 buffer test solutions in sequence to perform calibration. After calibration with three types of buffer test solutions is completed, save the calibration or perform calibration again according to the calibration situation. Test: 5.00±0.01g of material powder was accurately weighed on a balance and placed in a 100ml glass beaker, 30ml of pure water was added, and the mixture was stirred evenly with a glass rod until it was completely dispersed in the pure water. After ultrasonic treatment for 5 minutes in an ultrasonic cleaner, the mixture was removed and allowed to stand. The pH of the supernatant was measured with a pH meter and the value was read.

[0147] The negative electrode materials manufactured in Examples 1 to 8 and Comparative Example 1 through the above tests correspond to sample numbers S1 to S8 and R1, and the performance parameters of the negative electrode materials are as shown in Table 1.

[0148] [Table 1]

[0149] [Table 2] Comparison of parameter performance of each battery JPEG2025536817000003.jpg117143

[0150] As shown in Table 2, the negative electrode materials prepared in Examples 1 to 8 incorporate Mg, Al, and P elements. These elements coordinate with O in the silicon-based active material or lithium silicate, favoring the formation of lithium ion transmission channels and improving the rate performance of the negative electrode material. By controlling the range of (a + b) / c, the combination of Mg, Al, and P with the silicon-based active material and lithium silicate allows for the formation of faster and more lithium ion transmission channels, lowering the lithium ion transmission energy barrier. Furthermore, the incorporation of Mg, Al, and P reduces the hydrolysis of lithium silicate, thereby lowering the pH of the negative electrode material and reducing binder damage within the electrode sheet, which is beneficial for improving the processing stability of pre-lithiated negative electrode materials. The slurries prepared with the negative electrode materials are more stable, less susceptible to settling, and less prone to gas generation.

[0151] In Example 5, the value of a+b+c was small, and the content of the doping element in the negative electrode material was too low, so the magnesium aluminum phosphate-based material formed on the surface of the silicon-based active material was insufficient, which increased the pH of the material, i.e., made it more alkaline. After preparing the negative electrode material to form a slurry, the stability of the slurry was reduced, and a very small amount of gas was generated when the storage time was long.

[0152] In the manufacturing process of the negative electrode material of Comparative Example 1, the carbon-coated silicon-oxygen material was directly prelithiated. After lithium doping, the silicon-oxygen material contained lithium silicate, which was highly alkaline due to hydrolysis of the lithium silicate. When the aqueous slurry was prepared, the alkaline aqueous solution destroyed the polymer binder, causing the slurry to easily settle and generate gas, significantly reducing the rate performance and cycle performance of the battery.

[0153] In the negative electrode material of Comparative Example 2, (a+b) / c>1.5 and a+b+c≦0.5. Therefore, the compounding ratios of Mg, Al, and P are unbalanced, the amount of P is too small, and the remaining Mg and Al combine with Si and O in excess to form substances such as magnesium silicate and aluminum silicate, resulting in silicon loss and a decrease in the specific capacity of the negative electrode material.

[0154] In the negative electrode material of Comparative Example 3, (a+b) / c<0.3 and a+b+c≦0.5 in the negative electrode material. Therefore, the balance of the compounding ratios of Mg, Al, and P is lost, and the amounts of Mg and Al are too small. As a result, the remaining P combines with the doped Li by prelithiation to form lithium phosphate, resulting in a loss of active lithium ions and a decrease in the initial efficiency of the negative electrode material.

[0155] Although the present application has been disclosed above by the preferred embodiments, it does not limit the scope of the claims, and any person skilled in the art can make some possible changes and modifications without departing from the spirit of the present application, so the protection scope of the present application should be in accordance with the scope defined in the appended claims.

Claims

1. A negative electrode material comprising a silicon-based active material and a lithium silicate, the negative electrode material further contains Mg, Al, and P; The mass content of Mg element in the negative electrode material is a %, The mass content of Al element in the negative electrode material is b %, When the mass content of the P element in the negative electrode material is c%, A negative electrode material characterized in that a, b, and c satisfy the following formula: 0.3≦(a+b) / c≦1.5, and 0.5≦a+b+c≦10

2. The negative electrode material according to claim 1, having at least one of the following characteristics (1) to (2): (1) The silicon-based active material contains silicon crystal grains having a size of 20 nm or less. (2) The silicon-based active material contains silicon and / or silicon oxide.

3. 2. The negative electrode material according to claim 1, wherein 0.002≦a / b≦2.

4. The negative electrode material according to claim 1, having at least one of the following characteristics (1) to (3): (1) 0.001≦a≦0.065 (2) 0.09≦b≦0.55 (3) 0.15≦c≦0.70

5. 10. The negative electrode material of claim 1, further comprising a carbon layer.

6. The negative electrode material according to claim 5, having at least one of the following characteristics (1) to (3): (1) The carbon layer contains at least one of an amorphous carbon material and a graphitized carbon material. (2) The carbon layer contains an amorphous carbon material including at least one of amorphous carbon, carbon black, and activated carbon. (3) The carbon layer contains a graphitized carbon material containing at least one of conductive graphite and graphene.

7. The particle size distribution of the negative electrode material is D １０ ≧1.0μm, 3μm≦D ５０ ≦10 μm, D ９０ The negative electrode material according to claim 1 , wherein the particle size satisfies ≦25.0 μm.

8. The negative electrode material according to claim 1, having at least one of the following characteristics (1) to (3): (1) The mass content of lithium silicate in the negative electrode material is 30% to 80%. (2) The lithium silicate is Li ２ SiO ３ , Li ２ Si ２ O ５ , Li ４ SiO ４ It contains at least one of the following. (3) The pH of the negative electrode material is 9 to 12.

9. The negative electrode material according to claim 1, wherein the specific capacity of the negative electrode material is measured within a voltage range of 0 to 1.5 V, and the specific capacity of the negative electrode material when the cutoff voltage is 0.3 V is defined as A, the specific capacity of the negative electrode material when the cutoff voltage is 0.4 V is defined as B, and the specific capacity of the negative electrode material when the cutoff voltage is 0.5 V is defined as C, and the following formula is satisfied: 0.7≦(C-B) / (B-A)≦1.3

10. A step of immersing a silicon-based raw material in a phosphoric acid solution to perform a surface modification treatment, and then performing solid-liquid separation to obtain a precursor; 1. A method for producing a negative electrode material, comprising: heat-treating a mixture comprising a precursor, a lithium source, a magnesium source, and an aluminum source to obtain a negative electrode material, The negative electrode material includes a silicon-based active material and a lithium silicate, and further includes an Mg element, an Al element, and a P element; a mass content of Mg element in the negative electrode material is a %, a mass content of Al element in the negative electrode material is b %, and a mass content of P element in the negative electrode material is c %, and a, b, and c satisfy the following formula: 0.3≦(a+b) / c≦1.5, and 0.5≦a+b+c≦10

11. The manufacturing method according to claim 10, which satisfies at least one of the following characteristics (1) to (3): (1) The concentration of the phosphoric acid solution is 0.05 mol / L to 5 mol / L. (2) The immersion time is 2 to 10 hours. (3) The solid-liquid separation includes at least one of filtration and centrifugation.

12. The method according to claim 10, which satisfies one of the following characteristics (1) to (4): (1) The lithium source is Li ２ O, Li ２ CO ３ , LiOH, Li, LiH, LiAlH ４ and LiBH ４ It contains at least one of the following. (2) The magnesium source is Mg ２ O, Mg, Mg(OH) ２ and MgCl ２ It contains at least one of the following. (3) The aluminum source is Al ２ O ３ , Al, Al(OH) ３ and AlCl ３ It contains at least one of the following. (4) The temperature of the heat treatment is 400°C to 900°C.

13. The method according to claim 10, further comprising: coating the silicon-based raw material with carbon to obtain a silicon carbon composite before immersing the silicon-based raw material in a phosphoric acid solution to perform surface modification; and using the silicon carbon composite as the silicon-based active material.

14. The method according to claim 10, further comprising, after heat-treating the mixture containing the precursor, a lithium source, a magnesium source, and an aluminum source, coating the heat-treated product with carbon.

15. A battery comprising the anode material according to any one of claims 1 to 9, or the anode material produced by the production method according to any one of claims 10 to 14.

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