Negative electrode material and method for manufacturing the same, 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 National Intellectual Property Administration on September 28, 2023, with an application number of 202311294348.1 and an invention title of "Negative Electrode Material and Its Manufacturing Method, and Battery", and incorporates all of its disclosures herein.

[0002] This application relates to the technical field of negative electrode materials, particularly to negative electrode materials and their manufacturing methods, and batteries.

Background Art

[0003] With the expansion and deepening of the application of lithium-ion batteries, the requirements for the performance of lithium-ion batteries are also increasing. Particularly in terms of the energy density of the battery, conventional graphite negative electrode materials can no longer meet the increasingly high market requirements. As a negative electrode material with a high specific capacity, in recent years, silicon oxygen materials have recently attracted attention. Although the specific capacity of silicon oxygen materials exceeds 2000 mAh / g, compared with graphite materials, the initial Coulomb efficiency is low, and the conductivity, cycle performance, and rate performance are inferior.

[0004] In order to improve the performance of silicon oxygen materials, usually, the initial Coulomb efficiency is improved by doping lithium into the silicon oxygen materials. However, after lithium is doped, the original distribution of silicon inside the silicon oxygen materials changes, causing silicon aggregation, and the crystal grain size of silicon increases by more than 50%, leading to the deterioration of the rate performance and the decline of the cycle performance of the material. Also, after lithium is doped, the silicon oxygen material contains lithium silicate, and due to the hydrolysis of lithium silicate, the alkalinity increases, destroying the polymer binder when preparing an aqueous slurry, resulting in poor slurry stability, causing slurry precipitation, and being likely to affect the manufacturing of the battery.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Embodiments of the present application provide a negative electrode material and a method for manufacturing the same, 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, wherein 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 crystal grains 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 in the negative electrode material is b%, where 0.09 ≤ b ≤ 0.55.

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

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

[0016] In some embodiments, the carbon layer comprises at least one of amorphous carbon material and 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 and 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 The size must be ≤25.0 μm.

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

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

[0022] In some embodiments, the mass percentage of carbon 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 m². 2 / g~50m 2It is / g.

[0024] In some embodiments, the tap density of the negative electrode material is 0.5 g / cm³. 3 ~1.5g / cm 3 That is the case.

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

[0026] In some embodiments, the pH of the negative electrode material is 9 to 12.

[0027] In a second aspect, the present invention provides a method for manufacturing a negative electrode material, comprising the following steps: Silicon-based raw materials are immersed in a phosphoric acid solution, subjected to surface modification treatment, and then solid-liquid separation is performed 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, wherein the negative electrode material further contains Mg, Al, and P elements, 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 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 includes silicon crystal grains having a size of 20 nm or less.

[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 protective atmosphere gas includes at least one of nitrogen, helium, neon, argon, and krypton.

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

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

[0045] In some embodiments, the carbon coating treatment includes gas-phase carbon coating and / or solid-phase carbon coating.

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

[0047] The proposed technology has at least the following beneficial effects.

[0048] First, the negative electrode material according to this application incorporates Mg, Al, and P elements. These elements coordinate with the O element in the silicon-based active material or lithium silicate, which is advantageous for the formation of lithium ion transmission channels and improves the rate performance of the negative electrode material. By controlling the range of (a+b) / c, the combination of Mg, Al, P elements, silicon-based active material, and lithium silicate allows for the formation of faster and more lithium ion transmission channels, lowering the energy barrier for lithium ion transmission and improving the rate performance and cycle performance of the negative electrode material. Furthermore, the introduction of Mg, Al, and P elements reduces the hydrolysis of lithium silicate, thereby lowering the pH of the negative electrode material, reducing the breakdown of the binder in the electrode sheet due to the alkaline environment, which is advantageous for improving the processing stability of the pre-lithium negative electrode material. The slurry prepared with the negative electrode material is more stable, less prone to sedimentation, and less prone to gas generation.

[0049] Next, the method for manufacturing the 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, and then mixing and heat-treating the silicon-based raw material with the uniformly deposited phosphate ions with a lithium source, a magnesium source, and an aluminum source. During the heat treatment process, the content ratios of Mg, Al, and P elements are controlled, and the range of (a+b) / c is further controlled so that the lithium source and the silicon-based active material form a lithium silicate, and in some of the lithium in the lithium silicate, lithium is replaced by magnesium and aluminum, and silicon is replaced by phosphorus. Note that Mg and Al elements have larger radii than Li, and phosphorus can provide more bonding sites than silicon, and by combining Mg, Al, P elements, the silicon-based active material, and lithium silicate, it is possible to form a faster and larger number of lithium ion transmission channels, thereby lowering the lithium ion transmission energy barrier.

[0050] The method for manufacturing a negative electrode material according to this application can not only improve the electrochemical performance of the material, but is also suitable for large-scale production, can manufacture negative electrode materials, and can effectively improve the rate performance and cycle stability of batteries. [Brief explanation of the drawing]

[0051] [Figure 1] This is a process flow diagram of the method for manufacturing the negative electrode material according to an embodiment of the present application. [Figure 2] This is a comparative diagram of the cycle performance of the negative electrode materials manufactured in Example 1 and Comparative Example 1 of this application. [Figure 3] This is a schematic diagram illustrating the cycle capacity retention state of the negative electrode material manufactured in Example 1 of the present application. [Modes for carrying out the invention]

[0052] The following are preferred embodiments of the embodiments of the present application, and it should be noted that a person skilled in the art can make several modifications and improvements without departing from the principles of the embodiments of the present application, all of which fall within the scope of protection of the embodiments of the present application.

[0053] As the applications of lithium-ion batteries expand and deepen, the demands on their performance are increasing, and conventional graphite anode materials are no longer able to meet the ever-increasing market demands, particularly in terms of energy density. Recently, silicon-oxygen materials have attracted attention as anode materials with high specific capacity. Although silicon-oxygen materials have a specific capacity exceeding 2000 mAh / g, they have lower initial Coulomb 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 material to enhance the initial Coulombic efficiency. However, after lithium doping, the distribution of silicon within the silicon-oxygen material changes, causing silicon aggregation, which degrades the material's rate performance, reduces its cycle performance, and increases its volume. Furthermore, after lithium doping, the silicon-oxygen material contains lithium silicate, and the hydrolysis of lithium silicate increases alkalinity. This destroys polymer binders when preparing aqueous slurries, leading to poor slurry stability, slurry precipitation, and potentially impacting battery manufacturing.

[0055] Specifically, this application provides a negative electrode material comprising a silicon-based active material and an active material containing lithium silicate; The negative electrode material further contains Mg, Al, and P elements, with a mass content of Mg in the negative electrode material being a%, a mass content of Al in the negative electrode material being b%, and a mass content of P in the negative electrode material being c%, such that 0.3 ≤ (a + b) / c ≤ 1.5 and 0.5 ≤ a + b + c ≤ 10.

[0056] The anode material according to this application, after the introduction of Mg, Al, and P elements into the anode material, allows the applicant to coordinate with the O element in the silicon-based active material or lithium silicate, which is advantageous for the formation of lithium ion transmission channels and improves the rate performance of the anode material. By controlling the range of (a+b) / c, the blending of Mg, Al, P elements, silicon-based active material, and lithium silicate can form more lithium ion transmission channels faster and more abundantly, lowering the lithium ion transmission energy barrier. Furthermore, the introduction of Mg, Al, and P elements can reduce the hydrolysis of lithium silicate, thereby lowering the pH of the anode material, reducing the breakdown of the binder in the electrode sheet due to the alkaline environment, which is advantageous for improving the processing stability of the pre-lithium anode material. It is hypothesized that the slurry prepared with the anode material will be more stable, less prone to sedimentation, and less prone to gas generation. Through numerous experiments, the applicant discovered that the desired technical effect can be achieved and the technical problem of the present application can be solved as long as the elements Mg, Al, and P are present and the equations 0.3 ≤ (a+b) / c ≤ 1.5 and 0.5 ≤ a+b+c ≤ 10 are satisfied.

[0057] In the above proposed technology, (a+b) / c may specifically be 0.3, 0.5, 0.7, 0.8, 0.9, 1.0, 1.2, 1.3, 1.4, or 1.5, and of course, it may be any other value within the above range, but is not limited to these. If (a+b) / c is less than 0.3, the amounts of Mg and Al are too small, and the remaining P combines with the Li doped into the anode material by prelithiation to form a large amount of lithium phosphate, leading to the loss of active lithium ions and reducing the initial efficiency of the anode material. If (a+b) / c is greater than 1.5, the amount of P is too small, and the remaining Mg and Al combine excessively with Si and O to form substances such as magnesium silicate and aluminum silicate, leading to the loss of silicon and reducing the specific capacity of the anode material. Therefore, controlling the balance of the mixing ratio of Mg, Al, and P is advantageous for forming an effective lithium ion transmission channel and improves the initial Coulomb efficiency and rate performance of the anode material. Preferably, 0.6 ≤ (a+b) / c ≤ 1.2.

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

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

[0060] In some embodiments, the applicant speculated that the portion containing Al, Mg, and P elements may include, but is not limited to, at least one of aluminosilicate, magnesium silicate, aluminum phosphate, magnesium phosphate, magnesium oxide, aluminum oxide, phosphorus oxide, and phosphate. Specifically, the applicant speculated that, but is not limited to, the portion containing Al, Mg, and P elements may include, but is not limited to, at least one of LiAlSiO4, Al2SiO5, Al2O3, P2O5, Li3PO4, AlPO4, Al(PO3)3, LiAlO2, MgO, MgSiO3, Mg2SiO4, Mg3(PO4)2, and Li2Mg2O9Si3. Furthermore, in light of current detection technology, the applicant cannot fully confirm the specific forms in which Al, Mg, and P elements exist. However, based on the explanation of the principle described above, the data from the examples, and the analysis of beneficial effects, the applicant can find that by controlling the content of Al, Mg, and P elements in the present application to the above range, the technical problem of the present application can already be solved, and that there is no clear relationship with the specific forms in which Al, Mg, and P elements exist.

[0061] In some embodiments, the Al element in the composite anode material exists at least partially in a +3 valence state.

[0062] In some embodiments, the Mg element in the composite anode material exists at least partially in a +2 valence state.

[0063] In some embodiments, the mass content of Mg element in the negative electrode material is a% (0.001 ≤ a ≤ 0.065). Specifically, it may be, but is 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 anode material is b% (0.09 ≤ b ≤ 0.55). Specifically, it may be 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., and is not limited thereto.

[0065] In some embodiments, the mass content of P element in the anode material is c% (0.15 ≤ c ≤ 0.70). Specifically, it may be 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%, etc., and is not limited thereto.

[0066] In some embodiments, the silicon-based active material contains silicon crystallites, and the size of the silicon crystallites is 20 nm or less. Specifically, it may be 20 nm, 19 nm, 18 nm, 15 nm, 12 nm, 10 nm, 8 nm, 5 nm or 2 nm, etc., and is not limited thereto.

[0067] In some embodiments, the silicon-based active material contains 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 descriptions, the silicon oxide may be a material in which silicon particles are dispersed in SiO2, or a material having a tetrahedral structural unit in which silicon atoms are located at the centers of the tetrahedral structural units and oxygen atoms are located at the four vertices of the tetrahedral structural units may also be used. Specifically, the silicon oxide may be 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.

[0069] In some embodiments, the lithium silicate comprises at least one of Li2SiO3, Li2Si2O5, and Li4SiO4. It is understood that pre-lithified silicon-based active materials generate a certain amount of lithium silicate, the majority of which is located on the surface and / or within the silicon-based active material, or the silicon-based active material is dispersed within the lithium silicate.

[0070] In some embodiments, the mass content of element Mg in the anode material is a%, the mass content of element Al in the anode material is b%, and 0.002 ≤ a / b ≤ 2. Specifically, it 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 of course, it may be other values ​​within the above range, but is not limited to these. 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 advantageous for the formation of larger ion channels, resulting in better doping reaction activity of Mg and promoting more uniform and effective doping of the metal element. By controlling the a / b ratio within the above range, Mg 2+ and Al 3+ By doping with these elements in a balanced manner, it is possible to avoid any element excessively occupying the Li crystal lattice, and the formed magnesium aluminum phosphate and lithium silicate can be more uniformly dispersed on and / or within the silicon-based active material. By adding Mg and Al simultaneously, the crystal grains of the lithium silicate crystal can be made more uniform, resulting in improved lithium ion transport performance.

[0071] In some embodiments, the negative electrode material further includes a carbon layer. It is understood that the carbon layer covers 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 10 nm, 50 nm, 100 nm, 300 nm, 500 nm, 800 nm, 1000 nm, 1500 nm, 1800 nm, or 2000 nm, but is not limited to these. Controlling the thickness of the carbon layer is advantageous for improving lithium-ion transmission efficiency, for high-rate charging and discharging of the material, for improving the volume expansion of the material, and for improving the cycle performance of the negative electrode material.

[0073] In some embodiments, the carbon layer comprises at least one of amorphous carbon material and 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 containing at least one of conductive graphite and graphene.

[0076] In some embodiments, the tap density of the negative electrode material is 0.5 g / cm³. 3 ~1.5g / cm 3 For example, 0.2 g / cm³ 3 0.3 g / cm³ 3 , 0.5 g / cm 3 , 0.6 g / cm³ 3 , 0.7 g / cm³ 3 , 0.8 g / cm³ 3 1.0 g / cm³ 3 , 1.2 g / cm³ 3 And so on. Preferably, 0.7 g / cm³. 3 ~1.3g / cm 3 That is the case.

[0077] In some embodiments, the particle size distribution of the negative electrode material is D 10 ≥1.0μm, 3μm≦D 50 ≤10μm, D 90 The size must be ≤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, etc. 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, etc. 90 The particle size may be 25 μm, 20 μm, 18 μm, 15 μm, 12 μm, or 10 μm, etc., but is not limited to these. 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 0.1 m². 2 / g~50m 2 The value is / g. Preferably, the specific surface area of ​​the composite anode material is 1m². 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 It may also be / g, etc., but is not limited to these. It is understood that controlling the specific surface area within the above range is advantageous in reducing the consumption of irreversibly active lithium ions and improving the initial Coulombic efficiency of the battery.

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

[0081] In some embodiments, the mass content of lithium silicate in the anode 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 pre-lithifying the silicon-based active material, the initial Coulombic efficiency of the anode material can be effectively improved.

[0082] In some embodiments, lithium silicates are uniformly distributed on and / or within the silicon-based active material, and at least some of the lithium silicates are located in the carbon layer.

[0083] In some embodiments, the specific capacitance of the negative electrode material is measured within a voltage range of 0V to 1.5V, and during the lithium desorption process of the negative electrode material, if the cutoff voltage is 0.3V, the specific capacitance of the negative electrode material is A; if the cutoff voltage is 0.4V, the specific capacitance of the negative electrode material is B; and if the cutoff voltage is 0.5V, the specific capacitance of the negative electrode material is C, satisfying the following equation. 0.7 ≤ (CB) / (BA) ≤ 1.3 (CB) / (BA) may be specifically 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, or 1.3, and of course, it may be any other value within the above range. If (CB) / (BA) is less than 0.7, there is a certain loss in the capacity of the negative electrode material, and the initial efficiency decreases. If (CB) / (BA) is greater than 1.3, many crystal grains aggregate inside the negative electrode material, affecting lithium ion transfer inside the negative electrode material and worsening the room temperature cycling performance of the negative electrode material.

[0084] In some embodiments, the pH of the negative electrode material is 9 to 12, specifically 9, 9.5, 10, 10.5, 11, 11.5, or 12, and of course, other values ​​within the above range are also acceptable. Slurries prepared with the negative electrode material according to this application are more stable, less prone to sedimentation, and less prone to gas generation.

[0085] The present invention further provides a method for manufacturing a composite anode material, the method comprising the following steps S10 to S20, as shown in Figure 1. S10: Silicon-based raw materials are immersed in a phosphoric acid solution, subjected to surface modification treatment, and then solid-liquid separation is performed 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 contains Mg, Al, and P elements, with a mass content of Mg in the negative electrode material being a%, a mass content of Al in the negative electrode material being b%, and a mass content of P in the negative electrode material being c%, where a, b, and c satisfy the following equation. 0.3 ≤ (a+b) / c ≤ 1.5, and 0.5 ≤ a + b + c ≤ 10

[0086] The present invention relates to a method for producing a negative electrode material, in which a silicon-based raw material is immersed in a phosphoric acid solution to uniformly deposit phosphate ions on the surface of the silicon-based raw material, and then the silicon-based raw material with uniformly deposited phosphate ions on its surface is mixed and heat-treated 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 lithium silicate, and in some of the lithium in the lithium silicate, lithium is replaced by magnesium and aluminum, and silicon is replaced by phosphorus. The elements Mg and Al have larger radii than Li, and phosphorus can provide more bonding sites than silicon. By combining Mg, Al, P elements, the silicon-based active material, and lithium silicate, it is possible to form more lithium ion transmission channels faster and more efficiently, thereby lowering the lithium ion transmission energy barrier.

[0087] The proposed technology will be explained in detail below.

[0088] S10: Silicon-based raw materials are immersed in a phosphoric acid solution, subjected to surface modification treatment, and then solid-liquid separation is performed to obtain a precursor.

[0089] In some embodiments, the silicon-based raw material contains silicon oxide SiOy (where 0 < y ≤ 2), and the silicon oxide is specifically SiO 0.2 、SiO 0.4 、SiO 0.6 、SiO 0.8 、SiO or SiO 1.2 etc. may be used. 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 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., and is not limited thereto.

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

[0092] In some embodiments, the means of solid-liquid separation includes at least one of filtration and centrifugation. The filtration may be 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 crystal grains 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 contains 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 protective atmosphere gas includes at least one of nitrogen, helium, neon, argon, and krypton.

[0103] In some embodiments, the lithium silicate comprises at least one of Li2SiO3, Li2Si2O5, and Li4SiO4. It is understood that pre-lithified silicon-based active materials generate a certain amount of lithium silicate, the majority of which is located on the surface and / or within the silicon-based active material, or the silicon-based active material is dispersed within the lithium silicate.

[0104] In some embodiments, the mass content of element Mg in the anode material is a%, the mass content of element Al in the anode material is b%, and 0.002 ≤ a / b ≤ 2. Specifically, it 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 of course, it may be other values ​​within the above range, but is not limited to these. 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 advantageous for the formation of larger ion channels, resulting in better doping reaction activity of Mg and promoting more uniform and effective doping of the metallic element. By controlling the a / b ratio within the above range, Mg 2+ and Al 3+ By doping with these elements in a balanced manner, it is possible to avoid any element excessively occupying the Li crystal lattice, and the formed magnesium aluminum phosphate and lithium silicate can be more uniformly dispersed on and / or within the silicon-based active material. By adding Mg and Al simultaneously, the crystal grains of the lithium silicate crystal can be made more uniform, resulting in improved lithium ion transport performance.

[0105] In some embodiments, prior to S10, the method further includes carbon coating the silicon-based active material to obtain a silicon-carbon composite, and using the silicon-carbon composite as the silicon-based active material.

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

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

[0108] When the carbon coating treatment is a gas-phase carbon coating treatment, it may specifically involve 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 600°C to 1000°C. Specifically, the temperature may be 600°C, 700°C, 800°C, 850°C, 900°C, 950°C, or 1000°C, and is not limited to these. Preferably, the deposition temperature is 700°C to 900°C.

[0110] In some embodiments, the heat retention time for deposition is 0.5 to 10 hours. Specifically, the heat retention time may be 0.5 hours, 1 hour, 3 hours, 6 hours, 8 hours, 9 hours, or 10 hours, and is not limited to these. Preferably, the heat retention time for deposition is 3 to 9 hours.

[0111] In some embodiments, the carbon source gas includes at least one of alkanes, cycloalkanes, alkenes, alkynes, and aromatic hydrocarbons. Specifically, the carbon source gas includes 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, it 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 carbon source gas of a certain concentration is introduced as a gas source for the carbon material, and after being kept warm for a certain period of time, the carbon material is deposited on the surface of the silicon-based active material.

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

[0114] In some embodiments, the second carbon source includes 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 also be 20:10, 30:15, 50:60, 80:30, 90:20, 100:10, etc., and of course, it may be other values ​​within the above range, but is not limited to these.

[0116] In some embodiments, the carbonization temperature is 600°C to 1000°C. Specifically, the temperature may be, but is 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, or 1000°C. Preferably, the carbonization temperature is 700°C to 900°C.

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

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

[0119] In some embodiments, the silicon-carbon composite after carbon coating is further subjected to at least one of pulverization, sieving, and demagnetization. Preferably, the composite after carbon coating is subjected to pulverization, sieving, and demagnetization in that order.

[0120] Furthermore, whether the carbon coating is performed before step S10 or after step S20 does not significantly affect 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 the phosphoric acid, the phosphoric acid can penetrate the carbon layer and adhere uniformly to the surface of the silicon-based raw material, and in the subsequent heat treatment process, the lithium source and the silicon-based raw material form lithium silicate, and in some lithium silicate, lithium is replaced by magnesium and aluminum, and silicon is replaced by phosphorus. Moreover, divalent Mg and trivalent Al have larger radii than Li, and phosphorus can provide more bonding sites than silicon, and after Mg, A and P, O coordinate, a magnesium aluminum phosphate-based material and lithium silicate are formed on the surface and / or inside the silicon-based active material, and the combination of lithium silicate and magnesium aluminum phosphate can form faster and more lithium ion transmission channels. In addition, the carbon coating treatment further improves the volume expansion of the material, improves lithium ion transmission efficiency, is advantageous for high-rate charge and discharge of the material, and improves the cycle performance of the negative electrode material.

[0121] The embodiments of the present application further provide a battery employing the negative electrode material according to the above embodiments of the present application or a negative electrode material manufactured by the method for manufacturing the negative electrode material according to the above embodiments of the present application. The battery according to the embodiments of the present application has the advantages of high capacity, high initial efficiency, long cycle life, excellent rate performance and low expansion.

[0122] The embodiments of this application will be further described below with reference to several examples. However, the present invention is not limited to the following specific embodiments. It is possible to implement the invention with appropriate modifications without altering the spirit of the invention. [Examples]

[0123] Example 1 The method for manufacturing the negative electrode material includes the following steps. (1) SiO powder (D 50 A 1 kg sample (6.3 μm) was taken, placed in a tubular furnace, heated to 900°C under a nitrogen atmosphere, acetylene was introduced, and after maintaining the temperature for 3 hours, it was cooled to obtain a carbon-coated SiO material. (2) Take 100 g of phosphoric acid and mix it uniformly with 950 g of water to obtain a phosphoric acid solution. Immerse the carbon-coated SiO material in the phosphoric acid solution for 6 hours, then filter by suction to obtain the precursor; (3) 100 g of Li2O, 23 g of MgCl, and 30.3 g of AlCl were taken and mixed with the precursor. The mixture was then placed in a box-type furnace under a nitrogen atmosphere, heated to 800°C, and maintained at this temperature for 4 hours. After removal, the mixture was sieved to obtain the negative electrode material.

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

[0125] Table 1 shows details of other parameters for the negative electrode material.

[0126] Example 2 The method for manufacturing the negative electrode material includes the following steps. (1) SiO powder (D 50(6.3 μm) 1 kg was taken, placed in a tubular furnace, heated to 900°C in a nitrogen atmosphere, acetylene was introduced, and after being kept warm for 3 hours, it was cooled to obtain carbon-coated SiO material; (2) Take 100 g of phosphoric acid and mix it uniformly with 950 g of water to obtain a phosphoric acid solution. Immerse the carbon-coated SiO material in the phosphoric acid solution for 6 hours, then filter by suction to obtain the precursor; (3) 100g of Li2O, 1.5g of MgCl2, and 1.5g of AlCl3 were taken, mixed with the precursor, placed in a box-type furnace under a nitrogen atmosphere, heated to 800°C, maintained at the temperature for 4 hours, then removed, sieved, and the negative electrode material was obtained.

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

[0128] Table 1 shows details of other parameters for the negative electrode material.

[0129] Example 3 The method for manufacturing the negative electrode material includes the following steps. (1) SiO powder (D 50 A 1 kg sample (6.3 μm) was taken, placed in a tubular furnace, heated to 900°C under a nitrogen atmosphere, acetylene was introduced, and after maintaining the temperature for 3 hours, it was cooled to obtain a carbon-coated SiO material. (2) Take 150 g of phosphoric acid and mix it uniformly with 950 g of water to obtain a phosphoric acid solution. Immerse the carbon-coated SiO material in the phosphoric acid solution for 6 hours, then filter by suction to obtain the precursor; (3) 100 g of Li2O, 1.5 g of MgCl2, and 10.5 g of AlCl3 were taken, mixed with the precursor, placed in a box-type furnace under a nitrogen atmosphere, heated to 800°C, maintained at the temperature for 4 hours, then removed, sieved, and the negative electrode material was obtained.

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

[0131] Table 1 shows details of other parameters for the negative electrode material.

[0132] Example 4 The method for manufacturing the negative electrode material includes the following steps. (1) SiO powder (D 50 A 1 kg sample (6.3 μm) was taken, placed in a tubular furnace, heated to 900°C under a nitrogen atmosphere, acetylene was introduced, and after maintaining the temperature for 3 hours, it was cooled to obtain a carbon-coated SiO material. (2) Take 50 g of phosphoric acid and mix it uniformly with 950 g of water to obtain a phosphoric acid solution. Immerse the carbon-coated SiO material in the phosphoric acid solution for 6 hours, then filter by suction to obtain the precursor; (3) 100 g of Li2O, 1.5 g of MgCl2, and 18 g of AlCl3 were taken, mixed with the precursor, placed in a box-type furnace under a nitrogen atmosphere, heated to 800°C, maintained at the temperature for 4 hours, then removed, sieved, and the negative electrode material was obtained.

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

[0134] Table 1 shows details of other parameters for the negative electrode material.

[0135] Example 5 The method for manufacturing the negative electrode material includes the following steps. (1) SiO powder (D 50 A 1 kg sample (6.3 μm) was taken, placed in a tubular furnace, heated to 900°C under a nitrogen atmosphere, acetylene was introduced, and after maintaining the temperature for 3 hours, it was cooled to obtain a carbon-coated SiO material. (2) Take 80 g of phosphoric acid and mix it uniformly with 950 g of water to obtain a phosphoric acid solution. Immerse the carbon-coated SiO material in the phosphoric acid solution for 6 hours, then filter by suction to obtain the precursor; (3) 100 g of Li2O, 21 g of MgCl, and 35 g of AlCl were taken and mixed with the precursor. The mixture was then placed in a box-type furnace under a nitrogen atmosphere, heated to 800°C, and maintained at this temperature for 4 hours. After removal, the mixture was sieved to obtain the negative electrode material.

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

[0137] Table 1 shows details of other parameters for the negative electrode material.

[0138] Example 6 (1) Take 100g of phosphoric acid and mix it uniformly with 950g of water to obtain a phosphoric acid solution, and SiO material (D 50 1 kg of (6.3 μm) was immersed in a phosphoric acid solution for 6 hours, and then the precursor was obtained by suction filtration. (2) 100 g of Li2O, 23 g of MgCl, and 30.3 g of AlCl3 were taken, mixed with the precursor, placed in a box furnace under a nitrogen atmosphere, heated to 800°C, maintained at the temperature for 4 hours, then removed, sieved, and the mixture was obtained. (3) 1.5 kg of the mixture and 120 g of asphalt were placed in a VC machine and mixed for 40 minutes at a rotation speed of 500 rpm. After discharge, the mixture was placed in a high-temperature box-type furnace and fired at 800°C for 6 hours. Nitrogen was introduced into the box-type furnace, and it was allowed to cool naturally to room temperature. The mixture was then discharged to obtain the anode material.

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

[0140] Table 1 shows details of other parameters for the negative electrode material.

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

[0142] Example 8 (3) Take 100g of Li2O, 1.3g of MgO, and 23.1g of Al2O3, mix with the precursor, place in a box furnace under a nitrogen atmosphere, raise the temperature to 800°C, maintain the temperature for 4 hours, then remove, sift, and obtain the anode material. The anode material was obtained in the same manner as in Example 1.

[0143] Comparative Example 1 (1) SiO powder (D 50 One kilogram of material (6.3 μm) was taken, placed in a tubular furnace, heated to 900°C in a nitrogen atmosphere, acetylene was introduced, and after maintaining the temperature for 3 hours, it was cooled to obtain a carbon-coated SiO material. (2) After mixing 100g of Li2O with the carbon-coated SiO material, the mixture was placed in a box-type furnace under a nitrogen atmosphere, heated to 800°C, and maintained at that temperature for 4 hours. The mixture was then removed, sieved, and the negative electrode material was obtained.

[0144] Comparative Example 2 (1) 1 kg of SiO powder (D50 = 6.3 μm) was taken, placed in a tubular furnace, heated to 900°C in a nitrogen atmosphere, acetylene was introduced, and after being kept warm for 3 hours, 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. The carbon-coated SiO material was immersed in the phosphoric acid solution for 6 hours, and then filtered by suction to obtain the precursor. (3) 100g of Li2O, 1g of MgCl2, and 17g of AlCl3 were taken, mixed with the precursor, placed in a box-type furnace under a nitrogen atmosphere, heated to 800°C, maintained at the temperature for 4 hours, then 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, heated to 900°C under a nitrogen atmosphere, acetylene was introduced, and after maintaining the temperature for 3 hours, it was cooled to obtain a carbon-coated SiO material; (2) Take 150 g of phosphoric acid and mix it uniformly with 950 g of water to obtain a phosphoric acid solution. Immerse the carbon-coated SiO material in the phosphoric acid solution for 6 hours, then filter by suction to obtain the precursor; (3) 100 g of Li2O, 1.3 g of MgCl2, and 37.5 g of AlCl were taken and mixed with the precursor, then placed in a box-type furnace under a nitrogen atmosphere, heated to 800°C, and maintained at the temperature for 4 hours. After removal, the mixture was sieved to obtain the negative electrode material.

[0146] Test method: (1) Particle size of the negative electrode material: Particle size was measured using Mastersizer 3000 laser diffraction technology. Particle size measurement is completed by measuring the intensity of scattered light as the laser beam passes through the dispersed particle sample. Next, the data is analyzed to form a scattering spectrogram, thereby calculating the particle size distribution. 50 This is the particle size that corresponds to when the cumulative particle size distribution percentage of a single sample reaches 50%. Its physical meaning is that particles larger than this amount account for 50%, and particles smaller than this amount also account for 50%, and D 50 This is also called the 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 in the distribution curve reaches 90%, 50%, and 10%, respectively. (2) Method for measuring the specific surface area of ​​the negative electrode material: After measuring the amount of gas adsorbed onto a solid surface at constant temperature and low temperature under different relative pressures, the amount of adsorbed material in the monolayer of the sample 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: Using a Quantachrome AutoTap tap density meter, a fixed amount of sample was weighed, and the tap density was measured by vibrating it 3000 times at 300 times per minute. (4) XRD trial: Method for testing the dimensions of silicon crystallites: The Si crystallite size was calculated by measuring the XRD peak using Panathetical's X'pert Pro X-ray diffractometer and then performing a fitting analysis on the Si peak in the XRD using XpertHighScore software. Measurement 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, followed by background correction, smoothing, and peak identification using Jade software. A fitting analysis was then performed, and the lithium silicate content was calculated by comparing it with the MgO content. (5) Method for measuring carbon content: 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 content in the test material was measured using the ICP method. Test method: 0.500 g of negative electrode material was placed in a cleaned platinum crucible, then calcined in an air-atmosphere muffle furnace at 750°C for 2 hours to completely remove the carbon element. After cooling, the calcined residue was thoroughly reacted with 4 mL of HNO3 and 6 mL of HF mixed acid. The platinum crucible containing this solution was then placed on a 350°C hot plate until the solvent completely evaporated. After the crucible cooled, an additional 6 mL of HCl was added, and the mixture was heated until the residue was completely dissolved. The solution was then brought to a volume in a 100 mL plastic volumetric flask, and finally, the total Al, Mg, and P content of the test material was measured using an ICP spectrometer (Agilent 5800VDV ICP-OES). It is understood that 10,000 ppm corresponds to 1 mass%. (7) Button battery test: A slurry is prepared by mixing negative electrode material, conductive carbon black, and binder (styrene-butadiene rubber and hydroxymethylcellulose) in a ratio of 75:15:10, uniformly coating it onto copper foil and drying it to produce a negative electrode sheet. The button cell is assembled in a glove box under an argon atmosphere. The separator used is a polypropylene microporous membrane, the electrolyte is 1 mol / L lithium hexafluorophosphate (solvent is a mixture of ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate), and the positive electrode sheet is a metallic lithium sheet. The electrochemical performance of the battery was measured using a LAND NEWWARE 5V / 10mA battery evaluation device. The voltage was 1.5V, the current was 0.1C, and the initial Coulomb efficiency was calculated as initial charge ratio capacity / initial discharge ratio capacity. (8) Cycle characteristics test: The negative electrode material prepared in the above examples and comparative examples was mixed with graphite in a mass ratio of 15:85 to form the negative electrode material. The negative electrode active material was then obtained by mixing it with graphite in a mass ratio of 15:85. Subsequently, the negative electrode active material, conductive carbon black, hydroxymethylcellulose, and styrene-butadiene rubber were uniformly mixed in a mass ratio of 92:4:2:2 and applied to copper foil to prepare the negative electrode sheet. A button battery was prepared using a metallic lithium sheet as the positive electrode sheet and polyethylene as the separator. The electrochemical performance of the battery was measured using a LAND NEWWARE 5V / 10mA battery evaluation device. The voltage was 1.5V, the current was 0.1C, and the 50-cycle retention rate was calculated as the ratio of the discharge capacity at the 50th cycle to the ratio of the discharge capacity at the first cycle. The electrochemical performance of the battery was measured using a LAND NEWWARE 5V / 10mA battery evaluation device. The voltage was 1.5V, and the currents were 0.1C and 3C, respectively. The ratio of the discharge capacity at 3C current to the discharge capacity at 0.1C current is calculated as 3C / 0.1C = 3C / 0.1C. The specific capacitance 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 capacitance of the negative electrode material is A; if the cutoff voltage is 0.4V, the specific capacitance of the negative electrode material is B; and if the cutoff voltage is 0.5V, the specific capacitance 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 active materials. A slurry was prepared by mixing the negative electrode material, conductive carbon black, and binder (styrene-butadiene rubber and hydroxymethylcellulose) in a ratio of 75:15:10. This slurry was placed in an aluminum plastic film bag, sealed, and left to stand. The shape change of the aluminum plastic film bag was then monitored, with a monitoring period of one month. (10) pH test method: The pH of the test material is measured using the Mettler Toledo FE20 pH meter. Calibration is performed before use. Calibration method: Remove the protective liquid sleeve from the electrode, wash it several times with pure water, immerse it in distilled water for 30 minutes, then remove the electrode, wipe the pH electrode with tissue paper or filter paper, then put the pH 4.01 buffer test solution into a clean polyethylene beaker, press the calibration key to start calibration, and after the instrument test stabilizes (the display screen appears), add the pH 7.00 and pH 9.21 buffer test solutions in order to perform calibration. Once calibration with the three types of buffer test solutions is complete, store or recalibrate according to the calibration status. Test: 5.00 ± 0.01 g of material powder was accurately weighed onto a balance, placed in a 100 ml glass beaker, 30 ml of pure water was added, and the mixture was uniformly stirred with a glass rod to disperse completely in the pure water. After ultrasonic treatment in an ultrasonic cleaner for 5 minutes, the mixture was removed and allowed to stand. The pH of the supernatant was measured using a pH meter and the value was read.

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

[0148] [Table 1]

[0149] [Table 2] Comparison table of parameter performance of each battery JPEG0007868797000002.jpg117143

[0150] As shown in Table 2, the anode materials manufactured in Examples 1-8 have Mg, Al, and P elements introduced into them. The Mg, Al, and P elements coordinate with the O element in the silicon-based active material or lithium silicate, which is advantageous for the formation of lithium ion transmission channels and improves the rate performance of the anode material. By controlling the range of (a+b) / c, the combination of Mg, Al, and P elements with the silicon-based active material and lithium silicate can form faster and more numerous lithium ion transmission channels, lowering the lithium ion transmission energy barrier. Furthermore, the introduction of Mg, Al, and P elements can reduce the hydrolysis of lithium silicate, thereby lowering the pH of the anode material, reducing the breakdown of the binder in the electrode sheet, which is advantageous for improving the processing stability of the pre-lithium anode material. Slurries prepared with the anode material are more stable, less prone to sedimentation, and less prone to gas generation.

[0151] In Example 5, the a+b+c value is small, and the doping element content in the negative electrode material is too low. As a result, the magnesium aluminum phosphate-based material formed on the surface of the silicon-based active material is insufficient, leading to an increase in the pH of the material, i.e., greater alkalinity. After preparing the negative electrode material and forming the slurry, the stability of the slurry decreases, and if the storage time is extended, a very small amount of gas is generated.

[0152] In Comparative Example 1, the negative electrode material underwent a direct prelithiation treatment on a carbon-coated silicon-oxygen material during the manufacturing process. The lithium-doped silicon-oxygen material contained lithium silicate, and due to the hydrolysis of the lithium silicate, it became highly alkaline. When preparing the aqueous slurry, the alkaline aqueous solution destroyed the polymer binder, causing the slurry to settle easily, generating gas readily, and significantly reducing the battery's rate performance and cycle performance.

[0153] In the negative electrode material of Comparative Example 2, (a+b) / c > 1.5 and a+b+c ≤ 0.5, the balance of the mixing ratio of Mg, Al, and P is disrupted. The amount of P is too low, and the remaining Mg and Al excessively combine with Si and O to form substances such as magnesium silicate and aluminum silicate, leading to silicon loss and a decrease in the specific capacity of the negative electrode material.

[0154] In Comparative Example 3, the anode material has (a+b) / c < 0.3 and a+b+c ≤ 0.5, resulting in an imbalance in the mixing ratio of Mg, Al, and P. The amounts of Mg and Al are too low, and the remaining P combines with doped Li through prelithiation to form lithium phosphate, leading to a loss of active lithium ions and a decrease in the initial efficiency of the anode material.

[0155] Although the present application is disclosed in the above-mentioned preferred embodiments, it is not intended to limit the scope of the claims, and any person skilled in the art may make several possible changes and modifications without departing from the spirit of the present application; therefore, the scope of protection of the present application should be limited to the scope set forth in the appended claims.

Claims

1. A negative electrode material comprising a silicon-based active material and a lithium silicate, The aforementioned negative electrode material further comprises Mg, Al, and P. The mass content of Mg element in the negative electrode material is set to a%. The mass content of Al element in the negative electrode material is set to b%. When the mass content of element P in the negative electrode material is set to c%, a, b, and c are negative electrode materials characterized by satisfying the following equation. 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 features (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 comprises silicon and / or silicon oxide.

3. 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 features (1) to (3). (1) 0.001 ≤ a ≤ 0.065 (2) 0.09 ≤ b ≤ 0.55 (3) 0.15 ≤ c ≤ 0.70

5. The negative electrode material according to claim 1, further comprising a carbon layer.

6. The negative electrode material according to claim 5, having at least one of the following features (1) to (3). (1) The carbon layer comprises at least one of amorphous carbon material and graphitized carbon material. (2) The carbon layer comprises an amorphous carbon material which includes at least one of amorphous carbon, carbon black, and activated carbon. (3) The carbon layer comprises a graphitized carbon material which includes 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, satisfying ≤25.0 μm.

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

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

10. The process involves immersing a silicon-based raw material in a phosphoric acid solution to perform surface modification treatment, and then separating the solid and liquid to obtain a precursor, and A method for producing a negative electrode material, comprising the step of heat-treating a mixture containing a precursor, a lithium source, a magnesium source, and an aluminum source to obtain a negative electrode material, The anode material comprises a silicon-based active material and a lithium silicate, and further comprises Mg, Al and P elements. A manufacturing method characterized in that when the mass content of Mg element in the anode material is a%, the mass content of Al element in the anode material is b%, and the mass content of P element in the anode material is c%, 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 features (1) to (3). (1) The concentration of the phosphoric acid solution is 0.05 mol / L to 5 mol / L. (2) The duration of the immersion treatment is 2 to 10 hours. (3) The solid-liquid separation includes at least one of filtration and centrifugation.

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

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

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

15. A battery characterized by comprising the negative electrode material described in claim 1.

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