Cathode material, method of manufacturing the same, and use, and lithium-ion battery including the same

Abstract

The present invention relates to a silicon-based negative electrode material, a method for manufacturing the same, and an application of the same in a lithium-ion battery, and also to a lithium-ion battery comprising the silicon-based negative electrode material. The negative electrode material of the present invention comprises a silicon-containing material and a phosphorus-containing coating layer on the surface of the silicon-containing material, wherein the phosphorus-containing coating layer comprises a polymer having polycyclic aromatic hydrocarbon structural segments. The negative electrode material of the present invention simultaneously provides improved initial Coulomb efficiency, reversible charge capacity, cycle charge capacity retention rate, and conductivity. When the negative electrode material of the present invention is used in a lithium-ion battery, the energy density of the battery can be improved.

Description

Technology Field

[0001] The present invention generally relates to the field of lithium-ion batteries. In particular, the present invention relates to a silicon-based negative electrode material comprising a phosphorus-containing coating layer, a method for manufacturing the same, and an application of the same in a lithium-ion battery, and also relates to a lithium-ion battery comprising the silicon-based negative electrode material. Background Technology

[0002] Recently, commercial demand for high-energy-density lithium-ion batteries has been increasing. Currently, the anode materials for commercial lithium-ion batteries are primarily carbon-containing materials. However, the theoretical specific capacity of carbon is only 372 mAh / g, which cannot meet the demand for high-energy-density lithium-ion batteries. Silicon, with a theoretical specific capacity of 4,200 mAh / g, is expected to become the most promising anode material for lithium-ion batteries. However, silicon has a different charge-discharge mechanism than graphite. Solid Electrolyte Interface (SEI) films can continuously form at the interface between Si and Li ions within the electrolyte during charging and discharging. The formation of irreversible SEI can consume a significant amount of Li ions from the electrolyte and cathode materials. Consequently, the initial cycle Coulombic efficiency (also known as ICE) of silicon-based anode materials is generally only 65–85%. Furthermore, the conductivity and lithium-ion diffusion rate of silicon are lower than those of graphite, which can limit silicon's performance under high-current and high-power conditions.

[0003] To address the aforementioned problems, methods to improve the performance of silicon-based anode materials through doping, nanosizing, surface modification, and prelithiation have been proposed. Among the disclosed processes, nanosizing, coating, and alloying are the focus of research and development for modifying silicon-based anode materials. Nanosizing can significantly improve the cycle stability of materials by reducing volume changes of silicon-based materials during charging and discharging. However, nano-sized silicon has a large specific surface area and is prone to aggregation. Consequently, nano-sized silicon cannot be evenly distributed within a porous matrix, leading to reduced cycle stability and material uniformity. Coating refers to applying a protective layer of a certain thickness to the surface of silicon-containing materials. This can not only mitigate the volume expansion of silicon but also suppress side reactions between the silicon-containing material and the electrolyte, thereby improving the material's initial Coulomb efficiency and cycle stability. Currently, commonly used coating methods include solid-state ball milling, spray coating, and liquid-state coating. However, it is difficult to accurately control the thickness and uniformity of the coatings obtained through these processes. Therefore, it is possible to reduce the reversible charge capacity and cycle stability at different current rates of the material to varying degrees while improving the cycle stability of the material. Alloying is a new modification process developed in recent years. Generally, silicon reacts with metal precursors such as aluminum, magnesium, and copper to form Si-Al, Si-Mg, and Si-Cu alloys. This can not only buffer volume expansion but also improve the conductivity of silicon-containing materials, thereby enhancing some electrical properties of cathode materials. However, silicon alloys also have some disadvantages that cannot meet current commercial demand, such as low reversible charge capacity and the sensitivity of some alloys to water and oxygen.Therefore, current manufacturing processes have difficulty completely resolving the defects of poor cycle stability, low initial Coulomb efficiency, and poor cycle stability at different current rates associated with silicon-based cathodes.

[0004] CN108172775A discloses a phosphorus-doped silicon-based anode material. An example thereof indicates that the phosphorus-doped silicon-based anode has a specific capacity of 610.1 mAh / g and an initial Coulomb efficiency of 91.7%. Since the manufacturing process of CN108172775A requires spray drying, the yield is low but the cost is high. CN101179126B discloses a doped silicon-based anode material for lithium-ion batteries. The initial Coulomb efficiency of the silicon-based anode material is improved by doping with at least one of boron, aluminum, gallium, antimony, and phosphorus. CN101179126B has a high cost because the manufacturing process requires high vacuum argon arc fusion welding, which requires high reaction temperatures (> 1000°C) and complex reactions (including fusion welding, low-temperature blowing, rapid cooling, planetary ball milling, and other operations). CN103400971A discloses a lithium silicate-doped silicon-carbon anode material. When silicon is added in an amount of 50% and Li2SiO3 in an amount of 35%, the specific capacity of the resulting material is 1156.2 mAh / g and the initial Coulomb efficiency is 88.2%.

[0005] As mentioned above, although there has been some progress in the modification of silicon-based anode materials, generally only a single performance characteristic can be improved rather than the overall electrical properties of silicon-based anode materials. However, when used in high-energy-density lithium-ion batteries, anode materials must simultaneously possess excellent reversible charge capacity, initial Coulomb efficiency, and cycle charge capacity retention rate, particularly excellent initial Coulomb efficiency and cycle charge capacity retention rate. Therefore, the development of silicon-based anode materials with improved initial Coulomb efficiency, reversible charge capacity, cycle charge capacity retention rate, and conductivity is still required. A simple method for manufacturing such silicon-based anode materials is also necessary.

[0006] In order to solve one or more of the above problems of the prior art, the present invention provides a silicon-based negative electrode material comprising a phosphorus-containing coating layer, a method for manufacturing said negative electrode material, an application of said negative electrode material in a lithium-ion battery, and a lithium-ion battery comprising said negative electrode material. The negative electrode material of the present invention has improved reversible charge capacity (also referred to as reversible charge specific capacity) and initial Coulomb efficiency, and is particularly suitable for lithium-ion batteries.

[0007] In one embodiment, the present invention relates to a cathode material comprising a silicon-containing material and a phosphorus-containing coating layer located on the surface of the silicon-containing material, wherein the phosphorus-containing coating layer comprises a polymer having polycyclic aromatic hydrocarbon structure segments.

[0008] In one embodiment, the present invention relates to a method for manufacturing a cathode material, wherein the cathode material comprises a silicon-containing material and a phosphorus-containing coating layer located on the surface of the silicon-containing material, wherein the phosphorus-containing coating layer comprises a polymer having a polycyclic aromatic hydrocarbon structure segment.

[0009] Here, the above method includes the following steps.

[0010] (1) a step of contacting a silicon-containing material, a phosphorus source, and a solvent at 30°C to 80°C to graft the phosphorus source onto the surface of the silicon-containing material; and

[0011] (2) By temperature-programmed calcination, a phosphorus source around a silicon-containing material is converted into a phosphorus-containing coating layer comprising a polymer having polycyclic aromatic hydrocarbon structural segments, wherein the temperature-programmed calcination comprises:

[0012] Heating to a first temperature of 400-500℃ at a first heating rate, and

[0013] Heating to a second temperature of 600-800℃ at a second heating rate, wherein the second heating rate is lower than the first heating rate, and

[0014] Maintains the second temperature.

[0015] In one embodiment, the present invention relates to a cathode material manufactured by the above method.

[0016] In one embodiment, the present invention relates to the use of the negative electrode material in a lithium-ion battery.

[0017] In one embodiment, the present invention relates to a lithium-ion battery comprising a cathode, a positive electrode, a separator, and an electrolyte, wherein the cathode material comprises the above-mentioned cathode material.

[0018] Specifically, the present invention may be embodied in the following items:

[0019] 1. Polymeric lithium salt. A negative electrode material for a battery comprising a phosphorus source and an active component, wherein the active component contains silicon elements.

[0020] 2. In the cathode material of Item 1, the polymeric lithium salt has a weight average molecular weight of 2,000-5,000,000, preferably 80,000-240,000;

[0021] Preferably, the molecular chain of the polymeric lithium salt comprises a -C(O)-OLi group;

[0022] Preferably, the polymeric lithium salt is at least one selected from the group consisting of lithium polyacrylate, lithium polymethacrylate, lithium polymalate, lithium polyfumarate, lithium carboxymethylcellulose, and lithium alginate.

[0023] 3. In the cathode material of item 1 or 2, based on the total amount of the cathode material, the polymeric lithium salt is present in an amount of 1-15 wt%, the phosphorus source is present in an amount of 10-60 wt%, and the active component is present in an amount of 25-75 wt%;

[0024] Preferably, based on the total amount of the cathode material, the polymeric lithium salt is present in an amount of 3-15 weight%, the phosphorus source is present in an amount of 14-45 weight%, and the active component is present in an amount of 40-75 weight%.

[0025] 4. In a cathode material according to any one of items 1 to 3, the phosphorus source is connected to a silicon element through a chemical bond, preferably the chemical bond is P(O)-O-Si;

[0026] Preferably, the phosphorus source is polybasic phosphoric acid, and more preferably phytic acid;

[0027] Preferably, the above phosphorus source is coated on the surface of the silicon.

[0028] 5. In a cathode material according to any one of items 1 to 4, the cathode material further comprises a conductive agent;

[0029] Preferably, the conductive agent is at least one selected from the group consisting of carbon nanotubes, acetylene black, and conductive carbon black;

[0030] Preferably, the conductive agent is present in an amount of 1-10 weight percent based on the total amount of the cathode material.

[0031] 6. A method for manufacturing a negative electrode material for a battery, comprising the following steps:

[0032] (1) A step of mixing a silicon source, a phosphorus source, and a solvent;

[0033] (2) A step of drying the material obtained from the mixture of step (1);

[0034] (3) A step of mixing the solid material obtained by drying with a polymeric lithium salt.

[0035] 7. In the method of Item 6, the silicon source comprises silicon powder;

[0036] Preferably, the phosphorus source is polybasic phosphoric acid, preferably phytic acid;

[0037] Preferably, the solvent is an organic solvent, preferably at least one selected from the group consisting of toluene, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0038] 8. In the method of Item 6, the mixing of Step (1) includes the following:

[0039] After mixing the above phosphorus source with a solvent, add a silicon source;

[0040] Preferably, the weight ratio of the phosphorus source to the silicon source is 0.1-2:1, more preferably 0.5-1:1;

[0041] Preferably, the material obtained by mixing in step (1) has a solid content of 5-40 weight%.

[0042] 9. In the method of any one of items 6 to 8, in step (3), the weight ratio of the solid material obtained by drying to the polymeric lithium salt is 1: (0.03-0.15), preferably 1: (0.08-0.13);

[0043] Preferably, the polymeric lithium salt has a weight average molecular weight of 2,000-5,000,000, preferably 80,000-240,000;

[0044] Preferably, the molecular chain of the polymeric lithium salt comprises a -C(O)-OLi group;

[0045] Preferably, the polymeric lithium salt is at least one selected from the group consisting of lithium polyacrylate, lithium polymethacrylate, lithium polymalate, lithium polyfumarate, lithium carboxymethylcellulose, and lithium alginate;

[0046] Preferably, the mixing in step (3) is performed in the presence of water;

[0047] Preferably, the method further comprises introducing a conductive agent in step (3);

[0048] Preferably, the conductive agent is at least one selected from the group consisting of carbon nanotubes, acetylene black, and conductive carbon black;

[0049] Preferably, the weight ratio of the solid material obtained by drying to the conductive agent is 1: (0.01-0.12), preferably 1: (0.06-0.1).

[0050] 10. A negative electrode material for a battery manufactured by the method of any one of items 6 to 9.

[0051] 11. Use of a negative electrode material for a battery in a lithium-ion battery of any one of items 1 to 5 and 10.

[0052] 12. A lithium-ion battery comprising a negative electrode material, a positive electrode active material, a separator, and an electrolyte for a battery according to any one of items 1 to 5 and 10;

[0053] Preferably, the lithium-ion battery is a liquid lithium-ion battery, a semi-solid lithium-ion battery, or a solid lithium-ion battery.

[0054] The cathode material of the present invention may have the following advantages.

[0055] (1) The cathode material of the present invention has a phosphorus-containing coating layer. At a high temperature of temperature-programmed firing, some phosphorus elements diffuse into silicon to form occupation doping, which can improve the conductivity of the silicon-based cathode material.

[0056] (2) The phosphorus-containing coating layer of the present invention comprises a polymer having polycyclic aromatic hydrocarbon structural segments, which means that the phosphorus-containing coating layer has a dense structure. Meanwhile, the dense coating layer can resist volume expansion of the silicon-based anode material during charging and discharging, thereby ensuring the structural integrity and safety of the battery. On the other hand, the dense coating layer can more effectively block the channels of lithium ions approaching the silicon-based anode material, thereby reducing and preventing the formation of irreversible SEI, and thus mitigating and eliminating adverse effects on electrical performance (e.g., ICE, reversible charge capacity and cycle charge capacity retention rate).

[0057] (3) The phosphorus-containing coating layer of the present invention is obtained by high-temperature treatment. High-temperature treatment can remove at least some of the polar groups on the surface of the coating layer. Therefore, on the one hand, the cathode material of the present invention has a very small particle size, and the intermediate particle size may be on the nanometer side, but it does not aggregate well. Therefore, it has excellent storage stability and dispersibility. In addition, the cathode material of the present invention is more suitable for additional surface modification and has excellent processability. Brief explanation of the drawing

[0058] The accompanying drawings are incorporated to provide a further understanding of the invention and are part of this specification, which, together with the following detailed description, illustrate embodiments of the invention but do not limit its scope. In the drawings, FIG. 1 is a transmission electron microscope (TEM) diagram of an intermediate of a phosphorus-containing coating layer related to Comparative Example 1 and Examples 1-3; FIG. 2 shows the elemental distribution by line scanning of cathode material P1 obtained in Example 1; FIG. 3 shows the cathode material P1 obtained in Example 1 and the cathode material CP2 obtained in Comparative Example 2. 13 Representing the C-NMR spectrum; FIG. 4 shows the cathode material P1 obtained in Example 1. 29 Representing the Si-NMR spectrum; FIG. 5 shows the primary charge-discharge profile of a lithium-ion battery using the cathode material P1 of Example 1; FIG. 6 shows the profile of cycle stability at various current rates of a lithium-ion battery using the cathode material P1 of Example 1; FIG. 7 shows the cycle stability profile of a lithium-ion battery using the cathode material P1 of Example 1; FIG. 8 shows the profile of cycle stability at various current rates of a lithium-ion battery using the cathode material CP2 of Comparative Example 2; Figure 9 shows the cycle stability profile of a lithium-ion battery using the cathode material CP2 of Comparative Example 2. Specific details for implementing the invention

[0059] It should be understood that the endpoints of the ranges and any values ​​disclosed in this specification are not limited to exact ranges or values, but include values ​​close to such ranges or values. In value ranges, where such value ranges are specifically disclosed in this specification, one or more new value ranges may be provided by combining the endpoints of each range, the endpoints of each range with individual points, and the individual points.

[0060] Except for examples, all numerical values ​​of parameters in this specification should be understood to be modified by the term "approximately" in all cases, regardless of whether "approximately" actually exists before the numerical value.

[0061] In this specification, the central particle size (or D 50 ) refers to the particle size when the cumulative particle size distribution rate reaches 50%. The median particle size is often used to indicate the average particle size of a powder.

[0062] In one embodiment, the present invention relates to a cathode material comprising a silicon-containing material and a phosphorus-containing coating layer located on the surface of the silicon-containing material, wherein the phosphorus-containing coating layer comprises a polymer having polycyclic aromatic hydrocarbon structure segments.

[0063] In the cathode material of the present invention, the phosphorus-containing coating layer has a very thin thickness and high uniformity. Generally, the phosphorus-containing coating layer has a thickness of 2-6 nm.

[0064] The above silicon-containing material is silicon element, SiO x , where 0.6 < x < 1.5, and is at least one selected from the group consisting of silicon-containing alloys. Preferably, the silicon-containing material is a silicon element. The silicon element is usually used in the form of silicon powder. Preferably, the silicon powder has a median particle size of 0.05-10 μm.

[0065] The above silicon-containing material may be commercially available or manufactured by known methods.

[0066] Preferably, the silicon-containing alloy is at least one selected from the group consisting of silicon-aluminum alloy, silicon-magnesium alloy, silicon-zirconium alloy, and silicon-boron alloy. The silicon content in the silicon-containing alloy is not particularly limited. It may be selected within a wide range. For example, based on the total amount of the silicon-containing alloy, silicon may be present in an amount of 10 to 50 weight percent. The method for manufacturing the silicon-containing alloy is not particularly limited. For example, a method for manufacturing a silicon-aluminum alloy provided herein comprises: 1) ball milling aluminum powder and silicon powder for 30 minutes under an inert protective atmosphere; and 2) treating the mixture obtained in the above step at 900°C for 10 hours.

[0067] In one variant, a polymer having a polycyclic aromatic hydrocarbon structural segment is prepared from a phosphorus source selected from the group consisting of organic polybasic phosphoric acids and their esters or salts, preferably phytic acid.

[0068] The polycyclic aromatic hydrocarbon structure segment of a polymer having a polycyclic aromatic hydrocarbon structure segment is 13 It is characterized by C-NMR. In one variant, a polymer having a polycyclic aromatic hydrocarbon structural segment 13 The C-NMR spectrum contains signals at 110 ppm–140 ppm, which indicates the presence of polycyclic aromatic hydrocarbon structural segments. 13 The message regarding the chemical shift of polycyclic aromatic hydrocarbons in C-NMR spectra is Harris, KJ, Reeve ZEM, et al. Electrochemical Changes in Lithium-Battery Electrodes Studied Using 7 Li NMR and Enhanced 131 C NMR of Graphene and Graphitic Carbons[J]. Chem. Mater. 2015, 27, 9, pp 3299-3305 is disclosed, which is incorporated by reference in its entirety into the present invention.

[0069] In one variant, phosphorus within a phosphorus-containing coating layer located on the surface of a silicon-containing material and silicon within the silicon-containing material are connected via chemical bonds, preferably P(O)-O-Si. By being connected via chemical bonds, the silicon-containing material can be connected more closely to the surrounding phosphorus-containing coating layer. The connection of phosphorus and silicon via P(O)-O-Si is 29 It can be characterized by Si-NMR spectra.

[0070] Optionally, the cathode material may further comprise a carbon layer on the surface of the phosphorus-containing coating layer. The carbon layer may form a housing for the cathode material, and the housing comprises a silicon-containing material and a phosphorus-containing coating layer located on the surface of the silicon-containing material. The carbon layer may have a porous structure. The pore size distribution of the porous structure is not particularly limited.

[0071] Optionally, the cathode material may further comprise a polymeric lithium salt, preferably a polymeric lithium salt having -C(O)-OLi groups in its molecular chain. The groups can be identified by total reflection Fourier transform absorption infrared spectroscopy.

[0072] Introducing a polymeric lithium salt as a cathode material can compensate for lithium loss within the cathode material during charging and discharging, thereby improving the reversible charge capacity and ICE of the cathode material.

[0073] The above polymeric lithium salt is preferably at least one selected from the group consisting of lithium polyacrylate, lithium polymethacrylate, lithium polymalate, lithium polyfumarate, lithium carboxymethylcellulose, and lithium alginate.

[0074] The molecular weight of the polymeric lithium salt is not particularly limited. It is possible to select it within a wide range. Preferably, the polymeric lithium salt may have a weight average molecular weight of 2,000 to 5,000,000, preferably 80,000 to 240,000.

[0075] The above polymeric lithium salts may be commercially available or manufactured by known methods. For example, lithium polyacrylate can be obtained by reacting polyacrylic acid with a lithium source (preferably lithium hydroxide) in the presence of a solvent (e.g., water). Lithium polymethacrylate can be obtained by reacting polymethacrylic acid with a lithium source (preferably lithium hydroxide) in the presence of a solvent (e.g., water). Lithium polymaleate can be obtained by reacting polymaleic acid with a lithium source (preferably lithium hydroxide) in the presence of a solvent (e.g., water). Lithium polyfumarate can be obtained by reacting polyfumaric acid with a lithium source (preferably lithium hydroxide) in the presence of a solvent (e.g., water). Lithium carboxymethylcellulose can be obtained by reacting carboxymethylcellulose and / or its salt (e.g., sodium salt) with a lithium source (preferably lithium hydroxide and / or lithium oxide) in the presence of a solvent (e.g., water). Lithium alginate can be obtained by reacting alginic acid and / or its salt (e.g., sodium salt) with a lithium source (preferably lithium hydroxide and / or lithium oxide) in the presence of a solvent (e.g., water). Specific reactions may be carried out according to general practice in the art and are not repeated here.

[0076] The polymeric lithium salt may be contained within a phosphorus-containing coating layer or within a carbon layer. Preferably, the polymeric lithium salt is contained within the carbon layer, and more preferably, at least some of the lithium ions of the polymeric lithium salt are intercalated within the porous carbon layer.

[0077] The content of the polymeric lithium salt in the cathode material is not particularly limited. It is also possible to select within a wide range. Preferably, based on the total amount of the cathode material, the polymeric lithium salt is present in an amount of 0-34 weight%, more preferably 10-30 weight%.

[0078] Optionally, the cathode material may further include graphite. Although the theoretical capacity of carbon is much lower than that of silicon, introducing graphite as a cathode material can compensate for the low conductivity of silicon, thereby significantly improving the cycle charge capacity retention rate. In addition, the use of graphite does not suffer from the volume expansion problem experienced by silicon cathode materials during charge and discharge.

[0079] Optionally, the cathode material may further comprise a conductive agent. The conductive agent is preferably at least one selected from the group consisting of carbon nanotubes, acetylene black, and conductive carbon black. Carbon nanotubes, acetylene black, and conductive carbon black may be commercially available in a sense generally understood by a person skilled in the art.

[0080] Preferably, based on the total amount of the cathode material, the conductive agent is present in an amount of 1-10 weight%, more preferably 1-6 weight%.

[0081] The cathode material of the present invention may be in the form of particles. When graphite is not introduced into the cathode material, the cathode material has a small central particle size (D 50 It has a particle size distribution that is generally 0.1-20 microns. Preferably, the cathode material is in the form of nanoparticles. Nanosizing the cathode material can further improve overall electrical properties. When graphite is introduced as a cathode material, the cathode material may have an increased particle size. For example, when graphite is included, the median particle size of the cathode material may be 1-25 microns.

[0082] In one embodiment, the present invention relates to a method for manufacturing a cathode material, wherein the cathode material comprises a silicon-containing material and a phosphorus-containing coating layer located on the surface of the silicon-containing material, wherein the phosphorus-containing coating layer comprises a polymer having a polycyclic aromatic hydrocarbon structure segment, and the method comprises the following steps:

[0083] (1) a step of contacting a silicon-containing material, a phosphorus source, and a solvent at 30°C to 80°C to graft the phosphorus source onto the surface of the silicon-containing material; and

[0084] (2) By temperature-programmed calcination, a phosphorus source around a silicon-containing material is converted into a phosphorus-containing coating layer comprising a polymer having polycyclic aromatic hydrocarbon structural segments, wherein the temperature-programmed calcination comprises:

[0085] Heating to a first temperature of 400-500℃ at a first heating rate, and

[0086] Heating to a second temperature of 600-800℃ at a second heating rate, wherein the second heating rate is lower than the first heating rate, and

[0087] Maintains the second temperature.

[0088] The above phosphorus source may be any phosphorus-containing precursor that can be converted into a polymer having a polycyclic aromatic hydrocarbon structural segment, for example, by polycondensation. A preferred phosphorus source is selected from the group consisting of organic polybasic phosphoric acids and their esters or salts, and preferably from phytic acid.

[0089] In step (1), the mass ratio of the phosphorus source to the silicon-containing material is 0.1-2:1, preferably 0.5-1:1. Any value within this range, for example, 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, can be selected.

[0090] The solvent used in step (1) may be an organic solvent commonly used in the art, preferably at least one selected from the group consisting of toluene, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. The solvent may be present in an amount such that the material obtained in step (1) has a solid content of 5-40 weight%, preferably 5-30 weight%.

[0091] Step (1) can be performed by first mixing the phosphorus source with a solvent, then adding the silicon-containing material, heating to a temperature of 30-80°C, and maintaining for 0.5-4 hours; or by first mixing the silicon-containing material with a solvent, then adding the phosphorus source, heating to a temperature of 30-80°C, and maintaining for 0.5-4 hours. Preferably, the phosphorus source and the solvent are mixed first, then the silicon-containing material is added, the mixture is heated to 30-80°C, and maintained for 1-4 hours.

[0092] Through step (1), the phosphorus source is uniformly grafted onto the surface of the silicon-containing material to form an intermediate of a phosphorus-containing coating layer. The inventors discovered that if step (1) is performed at a temperature higher than room temperature (i.e., 30-80°C) unintentionally, the phosphorus-containing coating layer has a reduced thickness with high uniformity. Generally, the intermediate of the phosphorus-containing coating layer may have a thickness of 3-15 nm, preferably 4-10 nm.

[0093] The temperature-programmed firing of step (2) may include heating to a first temperature of 450-500°C, e.g., 480°C, at a first heating rate of 1-10°C / min, preferably 1-5°C / min, then heating to a temperature of 600-650°C, e.g., 620°C, at a second heating rate of 1-5°C / min, preferably 1-3°C / min; and maintaining at the second temperature for 1-8 hours, preferably 2-4 hours.

[0094] Temperature-programmed calcination at high temperatures is advantageous for converting a phosphorus source into a coating layer comprising a polymer having polycyclic aromatic hydrocarbon structural segments. At the same time, this high-temperature operation also promotes the doping of phosphorus into silicon and removes at least some of the polar groups on the surface of the coating layer (e.g., by removing phosphate groups). Without being limited to specific theories, phosphorus-doped silicon can improve the conductivity of silicon-based anode materials. Polymers having polycyclic aromatic hydrocarbon structural segments can impart a dense structure to the phosphorus-containing coating layer. Accordingly, it can resist volume expansion of the silicon-based anode material during charging and discharging, thereby ensuring the structural integrity and safety of the battery. At the same time, the dense coating layer can more effectively block the channels of lithium ions approaching the silicon-based anode material, thus reducing and preventing the formation of irreversible SEI, and consequently mitigating and eliminating adverse effects on electrical performance. In addition, at least a portion of the polar groups on the surface of the coating layer are also removed by high-temperature processing, so the obtained cathode material has excellent storage stability, dispersibility, and processability.

[0095] In one embodiment, the present invention relates to a cathode material manufactured by the above method.

[0096] In one embodiment, the present invention relates to the use of the anode material in a lithium-ion battery. Compared to a conventional pure graphite anode material, the anode material contains silicon with a higher theoretical capacity, thereby significantly improving the reversible charge capacity. Therefore, when the anode material is used in a lithium-ion battery, the energy density of the lithium-ion battery can be improved.

[0097] In one embodiment, the present invention relates to a lithium-ion battery comprising the cathode material, the anode, the separator, and the electrolyte.

[0098] A lithium-ion battery according to an embodiment of the present invention has a structure well known to those skilled in the art. Generally, the separator is disposed between the positive electrode and the negative electrode. Additionally, the positive electrode contains a positive electrode material. The chemical composition of the positive electrode material is not particularly limited. It may be a lithium-based positive electrode material commonly used in the art.

[0099] The above separator may be various separators commonly used in lithium-ion batteries, for example, polypropylene microporous membrane, polyethylene mat, glass fiber, or ultra-thin glass fiber paper.

[0100] The above electrolyte may be various conventional electrolytes, for example, water-insoluble electrolytes. A water-insoluble electrolyte is a solution formed from an electrolyte lithium salt in a water-insoluble solvent. A lithium salt suitable for forming a water-insoluble electrolyte may be at least one selected from the group consisting of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), and lithium hexafluorosilicate (LiSiF6). A suitable water-insoluble solvent may be selected from the group consisting of linear esters, cyclic esters, and mixtures thereof. The linear ester may be at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), and dipropyl carbonate (DPC). The above cyclic ester may be at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0101] Examples

[0102] The structure and advantages of the present invention are evident from the following examples. The examples are intended to illustrate the invention and are not intended to limit the invention in any way.

[0103] Test method

[0104] 1. Check materials

[0105] 1.1 Transmission Electron Microscope (TEM) Image

[0106] The morphology of the sample is determined by a transmission electron microscope. Specifically, the transmission electron microscope used was the JEM-2100 transmission electron microscope from Japan Electronics Co., Ltd., and the test conditions included an acceleration voltage of 160 KV. After placing the sample on a copper support, it was inserted into the electron microscope for observation. A magnification of 800,000 was used for observation.

[0107] 1.2 Elemental Distribution from Line Scanning

[0108] The elements of the coating layer are identified using a spherical aberration transmission electron microscope. Specifically, the transmission electron microscope used is the Titan Cubed Themis G2 300 transmission electron microscope from FEI, USA. Test conditions include an acceleration voltage of 300 kV, a HAADF detector for signal acquisition, and a reception angle of 52-200 mrad. The sample is placed on an ultrathin carbon film for observation, and the chemical composition of the sample is analyzed using an X-ray energy spectrometer (Aztec X-max 100TLE) mounted on the electron microscope.

[0109] 1.3 Carbon Nuclear Magnetic Resonance ( 13 C-NMR spectrum

[0110] The microstructure of the material is determined using a JNMR-500 solid-state nuclear magnetic resonance spectrometer from Japan Electronics Co., Ltd. Test conditions include an 8 mm zirconia rotor and a rotational speed of 5,000–6,000. 13The resonance frequency of C is 125.72 MHz, and tetramethylsilane is used as the standard for chemical shift. A test method of high-power decoupling and cross-polarization is adopted, and the number of scans is 5000.

[0111] 1.4 Silicon Nuclear Magnetic Resonance ( 29 Si-NMR spectrum

[0112] The microstructure of the material is determined using a JNMR-500 solid-state nuclear magnetic resonance spectrometer from Japan Electronics Co., Ltd. Test conditions include an 8 mm zirconia rotor and a rotational speed of 5,000–6,000. 29 The resonance frequency of Si is 79.49 MHz, and tetramethylsilane is used as the standard for chemical shift. High-power decoupling and cross-polarization test methods are adopted, and the number of scans is 5000.

[0113] 2. Electrical properties of materials

[0114] The manufactured cathode material is assembled into a lithium-ion battery sample. The electrochemical characteristics of the obtained lithium-ion battery sample are tested using a Wuhan blue battery test system (CT2001B). Test conditions include a voltage range of 0.05V to 2V. Each cathode material is assembled into 10 samples in the form of coin cells. The battery performance of the samples is detected at the same voltage and current. The average value is taken as the measurement.

[0115] 2.1 Primary Charge / Discharge Profile

[0116] At a voltage range of 0.05V-2V and a current rate of 0.1C, the assembled lithium-ion battery sample undergoes primary charge-discharge, and a primary charge-discharge profile is obtained. The battery test system (CT2001B) provides the primary discharge capacity and primary charge capacity of the tested battery. The primary discharge capacity is the specific capacity of the negative electrode material, and the primary charge capacity is the reversible charge specific capacity of the negative electrode material. The initial Coulomb efficiency (also referred to as "ICE") can be calculated as follows.

[0117] ICE = Reversible charge capacity of cathode material / Capacity of cathode material.

[0118] 2.2 Cycle Stability Test

[0119] At a current rate of 0.2C, the assembled lithium-ion battery sample is charged and discharged for a selected number of cycles, such as 20, 50, or 100 cycles. The reversible charge capacity of the sample is measured during each cycle. The cycle charge capacity retention rate for each cycle is calculated as follows: Cycle Charge Capacity Retention Rate = Reversible Charge Capacity of Selected Cycles / Reversible Charge Capacity at Initial Charge × 100%

[0120] The cycle stability profile is displayed with the number of cycles on the X-axis and the cycle charge capacity retention rate on the Y-axis.

[0121] 2.3 Cycle Stability at Various Current Rates

[0122] The sample undergoes five charge and discharge cycles at current rates of 1 / 3C, 1 / 2C, 1C, 2C, 3C, and 5C, respectively. The reversible charge capacity of the sample in each cycle is measured. The cycle charge capacity retention rate for each cycle is calculated as described above.

[0123] The cycle stability profile at various current rates is displayed with the number of cycles on the X-axis and the cycle charge capacity retention rate on the Y-axis.

[0124] Generally, at the same current rate, the cycle charge capacity retention rate of a cathode material is positively correlated with its conductivity. In other words, a cathode material with good conductivity can have a higher cycle charge capacity retention rate at the same rate. Therefore, it is possible to use cycle stability at different current rates to indicate the conductivity of the cathode material.

[0125] 3. Reagents

[0126] Lithium polyacrylate was prepared. Specifically, 10 g of polyacrylic acid with a weight-average molecular weight of 240,000 was added to 40 g of deionized water to prepare a polyacrylic acid solution with a concentration of 20 mass%. 3.4 g of lithium hydroxide was added to the polyacrylic acid solution. The mixture was heated to 40°C under stirring until all solids were dissolved, and then dried at 100°C for 4 hours to obtain lithium polyacrylate.

[0127] Other reagents are commercially available.

[0128] Example 1

[0129] A solution was formed by mixing 8.425 g of N,N-dimethylformamide and 0.225 g of phytic acid. Silicon powder (D 50 0.45 g (120 nm) was added to the solution. The mixture was heated to 40°C under stirring and maintained for 50 minutes. The obtained material was sampled for transmission electron microscopy (TEM) testing, and TEM images were obtained. The results are shown in Figure 1 (b). Data measured by TEM indicates the formation of an intermediate phosphorus-containing coating layer with a thickness of 4 nm around silicon. Additionally, since silicon is a crystalline material, it had lattice stripes. In contrast, because the intermediate phosphorus-containing coating layer is an organic material, it had an amorphous structure. These exhibit different structures in the TEM images. Therefore, by distinguishing the lattice stripes and the amorphous structural texture in the TEM images, the boundary of the phosphorus-containing coating layer intermediate was drawn, as shown by the curve in Figure 1 (b). The thickness of the phosphorus-containing coating layer intermediate was basically uniform and consistent with the data provided by TEM.

[0130] The obtained material was heated to 480°C at a first heating rate of 5°C / min, then heated to 620°C at a second heating rate of 2°C / min, and maintained at 620°C for 3 hours.

[0131] After cooling to room temperature, the product was obtained and named cathode material P1.

[0132] As described above, the cathode material P1 was sampled for a line scanning test to obtain its elemental distribution. The results are shown in Fig. 2. As shown in Fig. 2, as scanning outward from the core, the silicon content gradually decreased, and the phosphorus content showed a peak in the range of 15-18.7 nm. This indicates the formation of a phosphorus-containing coating layer with a thickness of 3.7 nm on the silicon surface.

[0133] In addition, as mentioned above, the sample was subjected to carbon nuclear magnetic resonance testing, and its 13 A C-NMR spectrum was obtained. The results are shown in the upper graph of Fig. 3. As shown in the upper graph of Fig. 3, there are signals in the 110-140 ppm region, and peaks at 138 ppm and 119 ppm, which indicates the presence of polycyclic aromatic hydrocarbon structural segments within the phosphorus-containing coating layer located on the surface of silicon.

[0134] In addition, as mentioned above, the sample was subjected to silicon NMR testing, and its 29 A Si-NMR spectrum was obtained. The results are shown in Figure 4. As shown in Figure 4, there are P(O)-O-Si bonds in the cathode material P1, which indicates that phosphorus and silicon are connected through P(O)-O-Si bonds.

[0135] A lithium-ion battery sample for testing the electrical characteristics of the above-mentioned cathode material was prepared according to the following. 1 g of the obtained cathode material P1 was used to form a slurry. The slurry was uniformly coated onto a copper foil collector and dried at 120°C for 10 hours to obtain a cathode N1 containing cathode material P1. A CR2016 coin cell was assembled using cathode N1, a metallic lithium sheet as the anode, a 1 mol / L LiPF6 solution as the electrolyte (a mixture of vinyl carbonate and diethyl carbonate mixed in a volume ratio of 3:7 was used as the solvent), and a polypropylene microporous membrane as the separator.

[0136] The coin cell was tested for battery performance as described above, and the electrical performance of the negative electrode material P1 obtained in Example 1 was determined.

[0137] Figure 5 is the primary charge-discharge profile of a coin cell based on the cathode material P1 of Example 1. As can be seen in Figure 5, the cathode material P1 of Example 1 has a primary discharge capacity (specific capacity) of 3858 mAh / g and a primary charge capacity (reversible charge specific capacity) of 3442 mAh / g, and its initial Coulomb efficiency (ICE) is indicated to be 89.2%.

[0138] Figure 6 is a profile of the cycle stability of a coin cell based on the cathode material P1 of Example 1 at various current rates. As can be seen in Figure 6, the cathode material P1 of Example 1 had cycle charge capacity retention rates of 100%, 92%, 81%, 63%, 37%, and 6% at current rates of 1 / 3C, 1 / 2C, 1C, 2C, 3C, and 5C, respectively.

[0139] Figure 7 is a profile of the cycle stability of a coin cell based on the cathode material P1 of Example 1. As shown in the figure, the cathode material P1 of Example 1 has a cycle charge capacity retention rate of 86.7% after 100 charge-discharge cycles at a current rate of 0.2 C.

[0140] Example 2

[0141] A solution was formed by mixing 8.425 g of N,N-dimethylformamide and 0.225 g of phytic acid. Silicon powder (D 50 0.45 g (120 nm) was added to the solution. The mixture was heated to 60°C under stirring and maintained for 90 minutes. The obtained material was sampled for transmission electron microscopy testing, and its TEM image was obtained. The results are shown in Fig. 1(c). Data measured by transmission electron microscopy indicates the formation of an intermediate phosphorus-containing coating layer with a thickness of 10 nm around silicon. In addition, by distinguishing the lattice stripes and amorphous structural texture in the TEM image as described above, the boundary line of the phosphorus-containing coating layer intermediate was drawn, as shown by the curve in Fig. 1(c). The thickness of the phosphorus-containing coating layer intermediate was basically uniform and consistent with the data provided by transmission electron microscopy.

[0142] The obtained material was heated to 500°C at a first heating rate of 8°C / min, then heated to 650°C at a second heating rate of 3°C / min, and maintained at 650°C for 2 hours.

[0143] After cooling to room temperature, the product was obtained and named cathode material P2.

[0144] As described above, the cathode material P2 was sampled for line scanning to obtain its elemental distribution, which was similar to that of FIG. 2. The sample was similar to the upper graph of FIG. 3. 13 It had a C-NMR spectrum. The sample was similar to Fig. 4. 29 It had a Si-NMR spectrum. Therefore, cathode material P2 has a morphology similar to that of cathode material P1.

[0145] Except for replacing cathode material P1 with cathode material P2, the preparation of a lithium-ion battery sample for testing the electrical characteristics of the cathode material outlined in Example 1 was repeated. As a result of the test, the reversible charge capacity of cathode material P2 in Example 2 was 3208 mAh / g, and the ICE was 87.8%. The cathode material P2 in Example 2 had a cycle charge capacity retention rate of 87.4% after 100 charge-discharge cycles at a current rate of 0.2 C.

[0146] Example 3

[0147] A solution was formed by mixing 8.425 g of N,N-dimethylformamide and 0.225 g of phytic acid. Silicon powder (D 50 0.45 g (120 nm) was added to the solution. The mixture was heated to 70°C under stirring and maintained for 90 minutes. The obtained material was sampled for transmission electron microscopy testing, and its TEM image was obtained. The results are shown in Figure 1 (d). Data measured by transmission electron microscopy indicates the formation of an intermediate phosphorus-containing coating layer with a thickness of 12 nm around silicon. In addition, by distinguishing the lattice stripes and amorphous structural texture in the TEM image as described above, the boundary line of the phosphorus-containing coating layer intermediate was drawn, as shown by the curve in Figure 1 (d). The thickness of the phosphorus-containing coating layer intermediate was basically uniform and consistent with the data provided by transmission electron microscopy.

[0148] The obtained material was heated to 450°C at a first heating rate of 10°C / min, then heated to 600°C at a second heating rate of 3°C / min, and maintained at 600°C for 4 hours.

[0149] After cooling to room temperature, the product was obtained and named cathode material P3.

[0150] As described above, the cathode material P3 was sampled for line scanning to obtain its elemental distribution, which was similar to that of FIG. 2. The sample was similar to the upper graph of FIG. 3. 13 It had a C-NMR spectrum. The sample was similar to Fig. 4. 29 It had a Si-NMR spectrum. Therefore, cathode material P3 has a morphology similar to that of cathode material P1.

[0151] Except for replacing cathode material P1 with cathode material P3, the preparation of a lithium-ion battery sample for testing the electrical characteristics of the cathode material outlined in Example 1 was repeated. As a result of the test, the reversible charge capacity of cathode material P3 in Example 3 was 3119 mAh / g, and the ICE was 87.5%. The cathode material P3 in Example 3 had a cycle charge capacity retention rate of 87.9% after 100 charge-discharge cycles at a current rate of 0.2 C.

[0152] Comparative Example 1

[0153] A solution was formed by mixing 8.425 g of N,N-dimethylformamide and 0.225 g of phytic acid. Silicon powder (D 50 0.45 g (= 120 nm) was added to the solution. The mixture was maintained at room temperature for 50 minutes under stirring. The obtained material was sampled for transmission electron microscopy testing, and TEM images were obtained. The results are shown in Fig. 1 (a). Data measured by transmission electron microscopy indicated the formation of a larger and non-uniform phosphorus-containing coating layer intermediate around silicon, with a thickness of 20 nm in some parts and 90 nm in others. Additionally, by distinguishing the lattice stripes and amorphous structural texture in the TEM images as described above, the boundary of the phosphorus-containing coating layer intermediate was drawn, as indicated by the curve in Fig. 1 (a). The thickness of the phosphorus-containing coating layer intermediate was non-uniform and consistent with the data provided by transmission electron microscopy.

[0154] The obtained material was heated to 480°C at a first heating rate of 5°C / min, then heated to 620°C at a second heating rate of 2°C / min, and maintained at 620°C for 3 hours.

[0155] After cooling to room temperature, the product was obtained and named cathode material CP1.

[0156] The above-mentioned cathode material CP1 was sampled, and as described above, its 13 A C-NMR spectrum was obtained, which was similar to the upper graph in Fig. 3. This indicates the presence of a polymer having polycyclic aromatic hydrocarbon structural segments in the phosphorus-containing coating layer of the cathode material CP1.

[0157] Except for replacing cathode material P1 with cathode material CP1, the preparation of a lithium-ion battery sample for testing the electrical characteristics of the cathode material outlined in Example 1 was repeated. As a result of the test, the reversible charge capacity of cathode material CP1 of Comparative Example 1 was 2820 mAh / g, and the ICE was 84.3%. The cathode material CP1 of Comparative Example 1 had a cycle charge capacity retention rate of 65.9% after 100 charge-discharge cycles at a current rate of 0.2 C.

[0158] Comparative Example 2

[0159] A solution was formed by mixing 8.425 g of N,N-dimethylformamide and 0.225 g of phytic acid. Silicon powder (D 50 0.45g (= 120nm) was added to the solution. The mixture was heated to 40℃ under stirring and maintained for 6 hours.

[0160] After cooling to room temperature, the product was obtained and named cathode material CP2.

[0161] The above-mentioned cathode material CP2 was sampled, and as described above, its 13Tests were performed to obtain C-NMR spectra. The results are shown in the lower graph of Fig. 3. As shown in the lower graph of Fig. 3, while there was no signal in the 110–140 ppm region, two broad peaks were present at 70–80 ppm, which indicates that phytic acid 13 It is interpreted by the C-NMR signal. This indicates that phytic acid has not undergone polycondensation and lacks polycyclic aromatic hydrocarbon structural segments. of phytic acid 13 The C-NMR spectrum can be found in JR Zhou, JW Erdman Jr. Phytic acid in health and disease [J]. Critical Reviews in Food Science and Nutrition, 1995, 35(6):495-508, which is incorporated herein by reference in its entirety. The preparation of lithium-ion battery samples for testing the electrical properties of the cathode materials outlined in Example 1 was repeated, except that cathode material P1 was replaced with cathode material CP2. As a result of the test, the reversible charge capacity of cathode material CP2 of Comparative Example 2 was 2621 mAh / g, and the ICE was 80.6%.

[0162] FIG. 8 is a cycle stability profile of a coin cell at different current rates based on the cathode material CP2 of Comparative Example 2. The cathode material CP2 of Comparative Example 2 has cycle charge capacity retention rates of 70%, 60%, 20%, 5%, 3%, and 1% at current rates of 1 / 3C, 1 / 2C, 1C, 2C, 3C, and 5C, respectively.

[0163] Comparing Fig. 6 and Fig. 8, it was found that when subjected to charge-discharge cycles at the same current rate, the cathode material P1 of Example 1 exhibited a superior charge capacity retention rate compared to the cathode material of Comparative Example 2. This indicates that the cathode material P1 of Example 1 has superior conductivity compared to the cathode material of Comparative Example 2.

[0164] Figure 9 is a cycle stability profile of a coin cell based on the cathode material CP2 of Comparative Example 2. As shown in Figure 9, the cathode material CP2 of Comparative Example 2 had a cycle charge capacity retention rate of less than 18.9% after 100 charge-discharge cycles at a current rate of 0.2C.

[0165] Example 4

[0166] The cathode material P1 of Example 1 was blended with graphite in a mass ratio of 10:1 to obtain cathode material P4. The cathode material P4 was sampled using a transmission electron microscope as described above and tested. The test results indicated that graphite was distributed on the outer surface.

[0167] Except for replacing cathode material P1 with cathode material P4, the preparation of a lithium-ion battery sample for testing the electrical characteristics of the cathode material outlined in Example 1 was repeated. As a result of the test, the reversible charge capacity of cathode material P4 in Example 4 was 552 mAh / g, and the ICE was 88.5%. The cathode material P4 in Example 4 had a cycle charge capacity retention rate of 89.2% after 100 charge-discharge cycles at a current rate of 0.2 C.

[0168] Example 5

[0169] The cathode material P1 of Example 1 was blended with lithium polyacrylate in a mass ratio of 10:1 to obtain cathode material P5.

[0170] Except for replacing cathode material P1 with cathode material P5, the preparation of a lithium-ion battery sample for testing the electrical characteristics of the cathode material outlined in Example 1 was repeated. As a result of the test, the reversible charge capacity of cathode material P5 in Example 5 was 3289 mAh / g, and the ICE was 90.5%. The cathode material P5 in Example 5 had a cycle charge capacity retention rate of 85.5% after 100 charge-discharge cycles at a current rate of 0.2 C.

[0171] Example 6

[0172] 1 g of cathode material P1 of Example 1 and 0.12 g of petroleum pitch were added together to 10 g of N,N-dimethylformamide and ultrasonically stirred for 40 minutes. The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours. Pitch-coated cathode material P1 was obtained. This was heated in a tubular furnace to 800°C at a rate of 5°C / min, maintained under a nitrogen atmosphere for 30 minutes, and then naturally cooled to room temperature. A cathode material P1 equipped with a carbon housing was obtained. 0.125 g of lithium polyacrylate and cathode material P1 equipped with a carbon housing were added to 3 mL of deionized water and stirred at room temperature for 12 hours. Subsequently, the obtained slurry was placed in a freeze-vacuum drying oven with a cold trap temperature of -80℃ and a cavity vacuum of 100Pa and dried for 12 hours. Lithium ions were inserted into the carbon housing of cathode material P1 equipped with a carbon housing to obtain cathode material P6.

[0173] Except for replacing cathode material P1 with cathode material P6, the preparation of a lithium-ion battery sample for testing the electrical characteristics of the cathode material outlined in Example 1 was repeated. As a result of the test, the reversible charge capacity of cathode material P6 in Example 6 was 3552 mAh / g, and the ICE was 91.3%. The cathode material P6 in Example 6 had a cycle charge capacity retention rate of 90.4% after 100 charge-discharge cycles at a current rate of 0.2 C.

[0174] Example 7

[0175] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0176] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0177] According to the TEM image of the phosphorus-containing silicon powder above, the surface of the nano silicon powder is coated with a phosphorus-containing material to form a “core-shell” structure.

[0178] According to the X-ray photoelectron spectrum of phosphorus-containing silicon powder, phosphorus and silicon elements are bonded through P(O)-O-Si. This chemical bonding ensures that the coating layer is stable and unaffected by the external environment. Therefore, the material can exhibit excellent electrical properties.

[0179] 3) 10 g of polyacrylic acid with a weight-average molecular weight of 240,000 was added to 40 g of deionized water to prepare a polyacrylic acid solution with a concentration of 20 mass%. 3.4 g of lithium hydroxide was added to the polyacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polyacrylate.

[0180] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.55 g of lithium polyacrylate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-1. The content of each component of the lithium-containing cathode material S-1 is shown in Table 1.

[0181] According to the total internal reflection Fourier transform absorption infrared spectra of polyacrylic acid and lithium polyacrylate obtained in Step 3), before reacting with lithium hydroxide, polyacrylic acid at 1700 cm⁻¹ -1 It had a C=O vibrational peak. After lithiation, peak blue was at 1580 cm⁻¹. -1It moves to, which indicates that C(O)-OH was changed to C(O)-OLi after the reaction.

[0182] 5) 1 g of the slurry of the lithium-containing cathode material S-1 obtained in step 4) was uniformly coated onto a copper foil collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-1.

[0183] A CR2016 coin cell was assembled using the electrode sheet obtained in Step 5), a metallic lithium sheet as the anode and cathode, respectively, a 1 mol / L LiPF6 solution as the electrolyte (wherein a mixture of vinyl carbonate and diethyl carbonate mixed in a volume ratio of 3:7 was used as the solvent), and a polypropylene microporous film as the separator. The electrical characteristics of the lithium-containing cathode material S-1 of the example were determined using the cell.

[0184] A primary charge-discharge profile of a coin cell based on lithium-containing cathode material S-1 was obtained (under conditions of a test voltage of 0.05-3V and a current of 50mA). As a result of the test, the reversible charge capacity of the lithium-containing cathode material S-1 was 3000mAh / g and the ICE was 86.9%.

[0185] Example 8

[0186] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0187] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0188] The TEM image and X-ray photoelectron spectrum of the above phosphorus-containing silicon powder were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0189] 3) 10 g of polyacrylic acid with a weight-average molecular weight of 2,000,000 was added to 90 g of deionized water to prepare a polyacrylic acid solution with a concentration of 10 mass%. 3.4 g of lithium hydroxide was added to the polyacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polyacrylate.

[0190] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.52 g of lithium polyacrylate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-2. The content of each component of the lithium-containing cathode material S-2 is shown in Table 1.

[0191] 5) 1 g of the slurry of the lithium-containing cathode material S-2 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-2.

[0192] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-2. As a result of the test, the reversible charge capacity of lithium-containing anode material S-2 was 2720 mAh / g and the ICE was 85.2%.

[0193] Example 9

[0194] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0195] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0196] The TEM image and X-ray photoelectron spectrum of the above phosphorus-containing silicon powder were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0197] 3) 10 g of polyacrylic acid with a weight-average molecular weight of 100,000 was added to 40 g of deionized water to prepare a polyacrylic acid solution with a concentration of 20 mass%. 3.4 g of lithium hydroxide was added to the polyacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polyacrylate.

[0198] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.46 g of lithium polyacrylate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-3. The content of each component of the lithium-containing cathode material S-3 is shown in Table 1.

[0199] 5) 1.5 g of the slurry of the lithium-containing cathode material S-3 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-3.

[0200] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-3. As a result of the test, the reversible charge capacity of lithium-containing anode material S-3 was 2978 mAh / g and the ICE was 86.1%.

[0201] Example 10

[0202] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0203] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0204] The TEM image and X-ray photoelectron spectrum of the above phosphorus-containing silicon powder were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0205] 3) 10 g of polyacrylic acid with a weight-average molecular weight of 200,000 was added to 40 g of deionized water to prepare a polyacrylic acid solution with a concentration of 20 mass%. 1.2 g of lithium hydroxide was added to the polyacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polyacrylate.

[0206] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.42 g of lithium polyacrylate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-4. The content of each component of the lithium-containing cathode material S-4 is shown in Table 1.

[0207] 5) 1.5 g of the slurry of the lithium-containing cathode material S-4 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-4.

[0208] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-4. As a result of the test, the reversible charge capacity of lithium-containing anode material S-4 was 2650 mAh / g and the ICE was 83.1%.

[0209] Example 11

[0210] 1) Silicon monooxide powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0211] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon monooxide powder.

[0212] The TEM image and X-ray photoelectron spectrum of the phosphorus-containing silicon monooxide powder above were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0213] 3) 10 g of polyacrylic acid with a weight-average molecular weight of 200,000 was added to 40 g of deionized water to prepare a polyacrylic acid solution with a concentration of 20 mass%. 0.35 g of lithium hydroxide was added to the polyacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polyacrylate.

[0214] 4) 4 g of phosphorus-containing silicon monooxide powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.34 g of lithium polyacrylate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-5. The content of each component of the lithium-containing cathode material S-5 is shown in Table 1.

[0215] 5) 1.2 g of the slurry of the lithium-containing cathode material S-5 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-5.

[0216] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-5. As a result of the test, the reversible charge capacity of lithium-containing anode material S-5 was 1650 mAh / g and the ICE was 73.5%.

[0217] Example 12

[0218] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0219] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0220] The TEM image and X-ray photoelectron spectrum of the above phosphorus-containing silicon powder were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0221] 3) 10 g of polyacrylic acid with a weight-average molecular weight of 200,000 was added to 40 g of deionized water to prepare a polyacrylic acid solution with a concentration of 20 mass%. 2 g of lithium oxide was added to the polyacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polyacrylate.

[0222] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.27 g of lithium polyacrylate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-6. The content of each component of the lithium-containing cathode material S-6 is shown in Table 1.

[0223] 5) 1.2 g of the slurry of the lithium-containing cathode material S-6 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-6.

[0224] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-6. As a result of the test, the reversible charge capacity of lithium-containing anode material S-6 was 3120 mAh / g and the ICE was 87.2%.

[0225] Example 13

[0226] 1) Silicon monooxide powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0227] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon monooxide powder.

[0228] The TEM image and X-ray photoelectron spectrum of the phosphorus-containing silicon monooxide powder above were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0229] 3) 10 g of polyacrylic acid with a weight-average molecular weight of 200,000 was added to 40 g of deionized water to prepare a polyacrylic acid solution with a concentration of 20 mass%. 0.3 g of lithium oxide was added to the polyacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polyacrylate.

[0230] 4) 4 g of phosphorus-containing silicon monooxide powder and 0.05 g of conductive carbon black were added sequentially to a slurry containing 0.21 g of lithium polyacrylate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-7. The content of each component of the lithium-containing cathode material S-7 is shown in Table 1.

[0231] 5) 1.2 g of the slurry of the lithium-containing cathode material S-7 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-7.

[0232] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-7. As a result of the test, the reversible charge capacity of lithium-containing anode material S-7 was 1810 mAh / g and the ICE was 80.1%.

[0233] Example 14

[0234] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0235] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0236] The TEM image and X-ray photoelectron spectrum of the above phosphorus-containing silicon powder were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0237] 3) 10 g of polyacrylic acid with a weight-average molecular weight of 200,000 was added to 40 g of deionized water to prepare a polyacrylic acid solution with a concentration of 20 mass%. 4.5 g of lithium carbide was added to the polyacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polyacrylate.

[0238] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.18 g of lithium polyacrylate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-8. The content of each component of the lithium-containing cathode material S-8 is shown in Table 1.

[0239] 5) 1 g of the slurry of the lithium-containing cathode material S-8 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-8.

[0240] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-8. As a result of the test, the reversible charge capacity of lithium-containing anode material S-8 was 2950 mAh / g and the ICE was 86.1%.

[0241] Example 15

[0242] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0243] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0244] The TEM image and X-ray photoelectron spectrum of the above phosphorus-containing silicon powder were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0245] 3) 10 g of alginate with a weight-average molecular weight of 120,000 was added to 40 g of deionized water to prepare an alginate solution with a concentration of 20 mass%. 3.2 g of lithium hydroxide was added to the alginate solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium alginate.

[0246] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.15 g of lithium alginate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-9. The content of each component of the lithium-containing cathode material S-9 is shown in Table 1.

[0247] 5) 1 g of the slurry of the lithium-containing cathode material S-9 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-9.

[0248] The battery assembly and electrical performance test of Example 7 were repeated, except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-9. As a result of the test, the reversible charge capacity of lithium-containing anode material S-9 was 2760 mAh / g and the ICE was 83.5%.

[0249] Example 16

[0250] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0251] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0252] The TEM image and X-ray photoelectron spectrum of the above phosphorus-containing silicon powder were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0253] 3) 10 g of carboxymethyl cellulose with a weight-average molecular weight of 10,000 was added to 40 g of deionized water to prepare a carboxymethyl cellulose solution with a concentration of 20 mass%. 2.5 g of lithium hydroxide was added to the carboxymethyl cellulose solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium carboxymethyl cellulose.

[0254] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.13 g of lithium carboxymethyl cellulose. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-10. The content of each component of the lithium-containing cathode material S-10 is shown in Table 1.

[0255] 5) 1.5 g of the slurry of the lithium-containing cathode material S-10 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-10.

[0256] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-10. As a result of the test, the reversible charge capacity of lithium-containing anode material S-10 was 2632 mAh / g and the ICE was 81.4%.

[0257] Example 17

[0258] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0259] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0260] The TEM image and X-ray photoelectron spectrum of the above phosphorus-containing silicon powder were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0261] 3) 10 g of polymethacrylic acid with a weight-average molecular weight of 240,000 was added to 40 g of deionized water to prepare a polymethacrylic acid solution with a concentration of 20 mass%. 2.5 g of lithium hydroxide was added to the polymethacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polymethacrylate.

[0262] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.13 g of lithium polymethacrylate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-11. The content of each component of the lithium-containing cathode material S-11 is shown in Table 1.

[0263] 5) 1.5 g of the slurry of the lithium-containing cathode material S-11 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-11.

[0264] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-11. As a result of the test, the reversible charge capacity of lithium-containing anode material S-11 was 2753 mAh / g and the ICE was 83.6%.

[0265] Example 18

[0266] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0267] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0268] The TEM image and X-ray photoelectron spectrum of the above phosphorus-containing silicon powder were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0269] 3) 10 g of polymaleic acid with a weight-average molecular weight of 80,000 was added to 40 g of deionized water to prepare a polymaleic acid solution with a concentration of 20 mass%. 2.5 g of lithium hydroxide was added to the polymethacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polymaleate.

[0270] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.13 g of lithium polymalate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-12. The content of each component of the lithium-containing cathode material S-12 is shown in Table 1.

[0271] 5) 1.5 g of the slurry of the lithium-containing cathode material S-12 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-12.

[0272] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-12. As a result of the test, the reversible charge capacity of lithium-containing anode material S-12 was 2695 mAh / g and the ICE was 82.1%.

[0273] Example 19

[0274] 1) Silicon powder (D 50 0.45 g (= 120 nm) was added. The mixture was stirred for 40 minutes.

[0275] 2) The slurry obtained after stirring was transferred to a 50 mL centrifuge tube and centrifuged at 5,000 rpm for 5 minutes. The solid at the bottom was collected and dried at 100°C for 4 hours to obtain phosphorus-containing silicon powder.

[0276] The TEM image and X-ray photoelectron spectrum of the above phosphorus-containing silicon powder were similar to those of the phosphorus-containing silicon powder of Example 7, respectively.

[0277] 3) 10 g of polyfumaric acid with a weight-average molecular weight of 120,000 was added to 40 g of deionized water to prepare a polyfumaric acid solution with a concentration of 20 mass%. 2.5 g of lithium hydroxide was added to the polyfumaric acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polyfumarate.

[0278] 4) 4 g of phosphorus-containing silicon powder and 0.25 g of conductive carbon black were added sequentially to a slurry containing 0.13 g of lithium polyfumarate. The mixture was stirred for 2 hours to obtain a slurry of lithium-containing cathode material S-13. The content of each component of the lithium-containing cathode material S-13 is shown in Table 1.

[0279] 5) 1.5 g of the slurry of the lithium-containing cathode material S-13 obtained in step 4) was uniformly coated onto a copper foil current collector and dried at 120°C for 10 hours to obtain an electrode sheet of the lithium-containing cathode material S-13.

[0280] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing anode material S-1 was replaced with the electrode sheet of lithium-containing anode material S-13. As a result of the test, the reversible charge capacity of lithium-containing anode material S-13 was 2710 mAh / g and the ICE was 82.5%.

[0281] Comparative example a

[0282] Cathode material D-1 was prepared by repeating Example 7, except that 3.4 g of lithium hydroxide was not added in Step 3). The content of each component of cathode material D-1 is shown in Table 1.

[0283] The battery assembly and electrical performance test of Example 7 were repeated, except that the electrode sheet of lithium-containing cathode material S-1 was replaced with cathode material D-1.

[0284] The primary charge-discharge profile of a coin cell based on cathode material D-1 was obtained. The reversible charge capacity of cathode material D-1 was 908 mAh / g, and the ICE was 38.9%.

[0285] Comparative Example b

[0286] Example 7 was repeated except that a phosphorus source was not included in the manufacture of the cathode material.

[0287] In particular, 10 g of polyacrylic acid with a weight-average molecular weight of 240,000 was added to 40 g of deionized water to prepare a polyacrylic acid solution with a concentration of 20 mass%. 3.4 g of lithium hydroxide was added to the polyacrylic acid solution. The mixture was heated and stirred at 40°C until all solids were dissolved to obtain a slurry containing lithium polyacrylate.

[0288] Silicon powder (D) in a slurry containing 0.55g of lithium polyacrylate 50 4g of (= 120nm) and 0.25g of conductive carbon black were added sequentially. The mixture was stirred for 2 hours to obtain a slurry of cathode material D-2. The content of each component of the lithium-containing cathode material D-2 is shown in Table 1.

[0289] 1 g of a slurry of cathode material D-2 was uniformly coated onto a copper foil current collector, and dried at 120°C for 10 hours to obtain an electrode sheet of cathode material D-2.

[0290] The battery assembly and electrical performance test of Example 7 were repeated except that the electrode sheet of lithium-containing cathode material S-1 was replaced with the electrode sheet of cathode material D-2. As a result of the test, the reversible charge capacity of cathode material D-2 was 1650 mAh / g and the ICE was 83.5%.

[0291] [Table 1]

[0292]

[0293] From the above examples and results, it can be seen that, compared to the cathode material of the comparative example, the cathode material according to the embodiment of the present invention has improved reversible charge capacity, initial Coulomb efficiency, and cycle charge capacity retention rate, in particular, an improved cycle charge capacity retention rate over a long period.

[0294] Preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Various simple variations, including combining various technical features in other suitable ways within the technical scope of the present invention, may be made to the embodiments of the present invention. Such simple variations and combinations should also be considered as disclosed herein and as being within the scope of protection of the present invention.

Claims

Claim 1 A cathode material comprising a silicon-containing material and a phosphorus-containing coating layer located on the surface of the silicon-containing material, wherein the phosphorus-containing coating layer comprises a polymer having a polycyclic aromatic hydrocarbon structure segment, the cathode material further comprises a carbon layer on the surface of the phosphorus-containing coating layer, wherein the carbon layer is a porous carbon layer, and the cathode material further comprises a polymeric lithium salt, wherein the polymeric lithium salt is inserted within the porous carbon layer. Claim 2 In claim 1, the silicon-containing material is a silicon element, SiO x A cathode material selected from the group consisting of (0.6 < x < 1.5) and silicon-containing alloys. Claim 3 In paragraph 2, the silicon-containing material is a cathode material that is a silicon element. Claim 4 In paragraph 3, the above silicon element is a cathode material in the form of silicon powder with a central particle size of 0.05-10 μm. Claim 5 In claim 1, the polymer having the polycyclic aromatic hydrocarbon structure segment 13 A C-NMR spectrum containing signals at 110 ppm–140 ppm; and / or a cathode material in which phosphorus in the phosphorus-containing coating layer and silicon in the silicon-containing material are connected through P(O)-O-Si bonds. Claim 6 In claim 1, the polymeric lithium salt is at least one selected from the group consisting of lithium polyacrylate, lithium polymethacrylate, lithium polymalate, lithium polyfumarate, lithium carboxymethylcellulose, and lithium alginate; or the polymeric lithium salt has a weight average molecular weight of 2,000 to 5,000,000, a cathode material. Claim 7 In claim 1, the cathode material, wherein the polymeric lithium salt is present in an amount of 0-34 weight% based on the total amount of the cathode material. Claim 8 In claim 1, the cathode material further comprises graphite; or the cathode material further comprises a conductive agent. Claim 9 In claim 8, the cathode material is at least one selected from the group consisting of carbon nanotubes, acetylene black, and conductive carbon black. Claim 10 In claim 9, the cathode material is present in an amount of 1-10 weight% based on the total amount of the cathode material. Claim 11 In claim 1, the cathode material is a cathode material having a central particle size of 0.1-20 microns. Claim 12 A lithium-ion battery comprising a cathode, an anode, a separator, and an electrolyte, comprising a cathode material according to any one of claims 1 to 11. Claim 13 delete Claim 14 delete Claim 15 delete Claim 16 delete Claim 17 delete Claim 18 delete Claim 19 delete Claim 20 delete Claim 21 delete Claim 22 delete Claim 23 delete Claim 24 delete Claim 25 delete Claim 26 delete

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