CN112467097A

CN112467097A - Negative electrode material, preparation method thereof, electrode and secondary battery

Info

Publication number: CN112467097A
Application number: CN202011191358.9A
Authority: CN
Inventors: 查道松; 王岑; 罗姝; 张和宝; 李喆; 骆亦琦
Original assignee: Amprius Nanjing Co ltd
Current assignee: Amprius Nanjing Co ltd
Priority date: 2020-10-30
Filing date: 2020-10-30
Publication date: 2021-03-09

Abstract

The present application provides an anode material for a secondary battery, comprising: silicon oxide compound particles containing lithium element and simple substance silicon nano particles; a carbon film layer coated on the surface of the silicon oxide particles; and the niobium-containing coating layer is coated on the surface of the silicon oxide compound particles with the carbon film layer and comprises a lithium niobate compound. The cathode material has high specific capacity, high coulombic efficiency, excellent rate capability and good cycling stability.

Description

Negative electrode material, preparation method thereof, electrode and secondary battery

Technical Field

The application relates to the field of batteries, in particular to a negative electrode material, a preparation method thereof, an electrode and a secondary battery.

Background

In recent years, as devices such as mobile terminals and electric vehicles become more and more popular and newer, secondary batteries as power supply sources thereof are also in demand for further development. Among the different types of secondary batteries, lithium ion secondary batteries are receiving attention and widely used in many fields due to their advantages of high voltage, low self-discharge rate, no memory effect, light weight, small size, and the like.

At present, graphite cathode materials with limited theoretical capacity are almost completely developed, and silicon-based cathode materials become research hotspots by virtue of the remarkable high capacity advantage and are gradually developed from laboratory to commercial application. Compared with simple substance silicon materials, the silicon oxide compound has relatively low theoretical capacity, but has obvious advantages in the aspects of expansion rate, cycling stability and the like, and is easier to realize large-scale application. However, when the silicon oxide material is first intercalated with lithium, a thick SEI film is often generated on the surface due to more side reactions with the electrolyte, and lithium is also consumed to generate substances such as lithium silicate and lithium oxide, and the consumed lithium cannot be removed again during discharge, so that the silicon oxide material generally faces the bottleneck of low first coulombic efficiency, and further improvement of the energy density of the battery is also limited. Meanwhile, although the expansion of the silicon-oxygen compound in the circulation process is obviously lower than that of the simple substance silicon cathode, the silicon-oxygen compound still generates particle fracture in the long-term circulation process and further consumes the electrolyte, so that the circulation retention rate still needs to be improved. In addition, the ionic and electronic conductivities of the silicon-oxygen compound are generally low, so that the lithium removal and lithium insertion reactions of the silicon-oxygen compound in the first charging and discharging process are not sufficient, and the problems of low coulombic efficiency, poor rate performance, poor cycle retention rate and the like of a battery in the subsequent cycle process are caused.

The statements in the background section merely represent techniques known to the public and are not intended to represent prior art in the field.

Disclosure of Invention

The present application provides an anode material for secondary batteries having high specific capacity, high coulombic efficiency, excellent rate capability and good cycling stability.

According to one aspect of the present application, an anode material for a secondary battery includes: silicon oxide compound particles containing lithium element and simple substance silicon nano particles; a carbon film layer coated on the surface of the silicon oxide particles; and the niobium-containing coating layer is coated on the surface of the silicon oxide compound particles with the carbon film layer and comprises a lithium niobate compound.

Further, the coating of the carbon film layer on the surface of the silicon-oxygen compound particles is a complete coating or a partial coating, and the coating layer containing niobium completely coats or partially coats the outer layer of the carbon film layer and the area of the surface of the silicon-oxygen compound particles which is not completely coated by the carbon film layer.

According to some embodiments of the present application, the form of lithium element present in the silica compound particles comprises a lithium silicate compound.

According to some embodiments of the present application, the lithium silicate compound comprises: li₂Si₂O₅、Li₂SiO₃、Li₈SiO₆、Li₆Si₂O₇And Li₄SiO₄One or more than two of them.

Preferably, the lithium silicate compound comprises Li₂Si₂O₅And/or Li₂SiO₃。

According to some embodiments of the present application, the elemental silicon nanoparticles have a median particle size of 0.2 to 20 nm.

Preferably, the median particle diameter of the simple substance silicon nanoparticles is 0.5-15 nm, and more preferably 1-10 nm.

According to some embodiments of the present application, the carbon film layer has a thickness of 0.001 to 5 μm.

Preferably, the thickness of the carbon film layer is 0.002-2 microns, and more preferably, the thickness is 0.005-1 micron.

According to some embodiments of the present application, the carbon film layer is 0.1 to 20 wt% of the negative electrode material.

Preferably, the mass ratio of the carbon film layer in the negative electrode material is 0.2-15 wt%, and more preferably 1-10 wt%.

According to some embodiments of the present application, the niobium-containing clad layer has a thickness of 0.001 to 3 μm.

Preferably, the thickness of the niobium-containing coating layer is 0.001 to 1 micrometer, and more preferably 0.001 to 0.5 micrometer.

In addition, the composite thickness of the carbon coating layer and the niobium coating layer is 0.002-8 microns, preferably, the composite thickness of the carbon coating layer and the niobium coating layer is 0.003-3 microns, and more preferably, the composite thickness is 0.006-1.5 microns.

According to some embodiments of the present application, the lithium niobate compound includes: LiNbO₂、LiNbO₃、Li₃NbO₈、Li₃NbO₄、Li₇NbO₁₆And Li₈Nb₂O₉One or more than two of them.

According to some embodiments of the present application, the content of the niobium element in the negative electrode material is 0.01 to 15 wt%.

Preferably, the content of niobium element in the negative electrode material is 0.02 to 10 wt%, and more preferably 0.05 to 5 wt%.

According to some embodiments of the present application, the niobium element in the anode material is concentrated in at least one of the niobium-containing coating layer, the carbon film layer, and the near-surface region of the silicon oxide compound particles.

According to some embodiments of the present application, a small amount of niobium may be doped into the silicon oxide particles during lithium doping after coating the niobium-containing precursor coating layer, but due to the process conditions, the doped and infiltrated niobium may only be doped into regions of the silicon oxide particles close to shallower surfaces, and the doping amount is relatively small.

According to some embodiments of the present application, the niobium element in the anode material is present in a form including: one or more of niobium oxide, niobium silicate-containing compound, and lithium-containing composite niobium oxide. Wherein the lithium-containing composite niobium oxide comprises lithium niobate.

According to some embodiments of the present application, the total content of lithium element in the negative electrode material is 0.01 to 30 wt%.

Preferably, the total content of lithium element in the negative electrode material is 0.05-20 wt%, and more preferably 0.1-15 wt%.

According to some embodiments of the present application, the total content of elemental silicon in the negative electrode material is 29.9 to 69.9 wt%.

Preferably, the total content of silicon element in the negative electrode material is 35-65 wt%, more preferably 39.9-59.9 wt%.

According to some embodiments of the present application, the negative electrode material has a median particle diameter of 0.5 to 20 μm.

Preferably, the median particle diameter of the negative electrode material is 1 to 18 micrometers, and more preferably 3 to 15 micrometers.

According to another aspect of the present application, there is also provided a method for preparing the anode material as described above, including: preparing silicon oxide particles; forming a carbon film layer, coating the carbon film layer on the surface of the silicon oxide compound particles, and crushing and screening to obtain silicon oxide compound particles with the carbon film layer; forming a niobium-containing precursor coating layer, coating a niobium-containing precursor on the surface of the silicon oxide compound particles with the carbon film layer to complete secondary coating, and performing screening treatment to form particles with the niobium-containing precursor coating layer; and lithium doping, namely performing lithium doping on the particles with the niobium-containing precursor coating to obtain the negative electrode material.

Further, the stoichiometric ratio of the silicon element and the oxygen element in the prepared silicon-oxygen compound particles is 1:0.6 to 1:1.5, preferably 1:0.8 to 1: 1.2.

Further, the forming the carbon film layer includes: and coating a carbon film layer on the surfaces of the silicon oxide particles by means of chemical vapor deposition.

Further, the forming the carbon film layer further includes: and coating a carbon film layer on the surfaces of the silicon oxide particles by coating a carbon precursor and then carrying out heat treatment carbonization in a non-oxidizing atmosphere. Wherein the carbon precursor comprises: polyacrylonitrile, epoxy resin, polyvinyl alcohol, polymethyl methacrylate, petroleum asphalt, coal tar pitch, aniline, pyrrole, thiophene, glucose, sucrose, polyacrylic acid, and polyvinylpyrrolidone.

Further, the temperature of the heat treatment carbonization is 550-1100 ℃, preferably 650-1050 ℃; the heating rate is 0.2-10 ℃/min, and the heat preservation time is 1-24 hours.

Additionally, the non-oxidizing atmosphere comprises: one or more of hydrogen, nitrogen, argon and helium.

Preferably, other metal elements with the weight percentage of 0.01-10 wt% can be doped during, before or after the process of coating the silicon oxide compound particles with carbon, wherein the other metal elements comprise one or more than two of Mg, Al, Cu, Mn, Ca and Zn. The step of doping other metal elements includes: uniformly mixing the silicon oxide particles with a doping substance; and carrying out heat treatment doping in a non-oxidizing atmosphere.

Further, the temperature of the heat treatment doping other metal elements is 600-1200 ℃, preferably 650-1050 ℃; the heating rate is 0.2-10 ℃/min, and the heat preservation time is 0.5-24 hours.

According to some embodiments of the present application, the forming a carbon film layer includes: and coating a carbon film layer on the surfaces of the silicon oxide compound particles, and then doping lithium.

Further, the forming a niobium-containing precursor clad layer comprises: coating the niobium-containing precursor on the surface of the carbon-coated silicon oxide compound particles.

Further, the niobium-containing precursor includes one or more of an oxide, a hydroxide, and a niobium salt of niobium. Preferably, the niobium-containing precursor includes one or more of niobium oxide, niobium hydroxide, niobium oxalate, ammonium niobium oxalate, niobium ethoxide, niobium isopropoxide, and niobium chloride.

Further, the forming of the niobium-containing precursor coating layer preferably includes coating the silicon oxide particles having the carbon film layer with the niobium-containing precursor in a liquid phase system.

According to some embodiments of the present application, the forming a niobium-containing precursor cladding layer may further comprise: and before the surfaces of the silicon oxide particles are coated with the niobium-containing precursor film layers, lithium doping is carried out on the silicon oxide particles with the carbon film layers.

Further optionally, the forming a niobium-containing precursor cladding layer may further include: and simultaneously doping lithium sources required in the subsequent lithium doping step into the niobium-containing precursor while coating the niobium-containing precursor film layer on the surface of the silicon oxide compound particles.

According to some embodiments of the present application, the lithium doping is performed by one or more methods selected from the group consisting of an electrochemical method, a liquid phase doping method, a thermal doping method, a high temperature mixing method, and a high energy mechanical method. Preferably, the lithium doping method is a liquid phase doping method and/or a thermal doping method.

According to yet another aspect of the present application, there is also provided an electrode comprising the anode material as described above.

According to another aspect of the present application, there is also provided a secondary battery including the electrode as described above.

According to some embodiments, the surface region of the silica compound particle forms a dense silicate-based compound with good water resistance. In addition, the compact silicate compound formed on the surface layer region of the silicon oxide compound particles can cooperate with the carbon film layer and the niobium-containing coating layer on the surface of the silicon oxide compound particles to improve the performance of the material in the charge-discharge cycle process. Furthermore, the carbon film layer can improve the conductivity of the cathode material, and the niobium-containing coating layer has high lithium ion conductivity and structural stability.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application. In the drawings:

fig. 1 is a schematic cross-sectional structure of an anode material according to an exemplary embodiment of the present application;

fig. 2 is a scanning electron micrograph of 20000 times of the negative electrode material according to an exemplary embodiment of the present application;

fig. 3 is an EDX element mapping diagram of an anode material according to an exemplary embodiment of the present application;

fig. 4 is a graph of full cell cycle performance of an anode material according to an exemplary embodiment of the present application;

fig. 5 is a flowchart of a method of preparing an anode material according to an exemplary embodiment of the present application.

Detailed Description

The following detailed description of the present application, taken in conjunction with the accompanying drawings and examples, is provided to enable the aspects of the present application and its advantages to be better understood. However, the specific embodiments and examples described below are for illustrative purposes only and are not limiting of the present application.

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The terms "including" and "having," and any variations thereof, in the description and claims of this application and the drawings described herein, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

As mentioned in the background section above, researchers have developed silicone materials by a number of means to address their application issues. In order to improve the conductivity of the silicon oxide material so as to obtain high capacity and better cycle retention rate, conductive materials such as a carbon film layer and the like can be coated on the surface of the silicon oxide material; in order to increase the first coulombic efficiency of the material, lithium may be previously intercalated into the silicon oxide material by various methods. However, due to the presence of lithium-containing compounds, such materials are generally more basic and less water resistant. Therefore, when such materials are applied to an aqueous homogenization process in actual battery production, problems such as slurry denaturation, poor coating quality, low yield, and the like are likely to occur.

In view of the above, the present application provides an anode material for a secondary battery.

The present application will be described with reference to specific examples.

Fig. 1 is a schematic cross-sectional structure diagram of an anode material according to an exemplary embodiment of the present application.

Referring to fig. 1, according to an exemplary embodiment, an anode material of a secondary battery includes silicon oxide compound particles 101, a carbon film layer 103, and a niobium-containing clad layer 105. Wherein, the silicon-oxygen compound particles 101 contain lithium element, the carbon film layer 103 is coated on the surface of the silicon-oxygen compound particles 101, the niobium-containing coating layer 105 is coated on the outer layer of the silicon-oxygen compound particles with the carbon film layer, and the niobium-containing coating layer 105 comprises lithium niobate compound, as shown in the scanning electron microscope photograph of fig. 2.

According to some embodiments, the carbon film layer and the niobium-containing coating layer in the negative electrode material disclosed by the application protect nano silicon in the silicon-oxygen compound particles from contacting with external water system slurry, so that the problem of active silicon loss caused by gas production reaction generated by contact of the nano silicon and water in a water system homogenizing process is effectively solved.

As shown in FIG. 1, according to an exemplary embodiment, the lithium silicate compound in the silicon oxide compound particles 101 includes Li₂Si₂O₅、Li₂SiO₃、Li₈SiO₆、Li₆Si₂O₇And Li₄SiO₄One or more than two of them. In some embodiments, the lithium silicate compound comprises Li₂Si₂O₅And/or Li₂SiO₃。

According to some embodiments, by pre-inserting lithium into the silicon oxide particles, the first coulombic efficiency and the cycle retention rate of the obtained material can be obviously improved compared with those of a traditional silicon oxide negative electrode material; by coating the lithium niobate compound with high lithium ion conductivity and structural stability on the surface of the particles, the volume effect of the silicon nanoparticles in the repeated charge and discharge process can be further relieved and inhibited, and the ionic conductivity of the obtained material can be remarkably improved, so that the cycle stability and the rate capability of the battery are improved.

As shown in FIG. 1, according to some embodiments, the silicon oxide particles 101 further include elemental silicon nanoparticles 102 having a median particle diameter of 0.2-20 nm. In the embodiment, the median particle diameter of the simple substance nano silicon is preferably 0.5 to 15 nm, and more preferably 1 to 10 nm.

According to some embodiments, the size of the elemental silicon nanoparticles is regulated and controlled within the interval, so that the obtained anode material can be ensured to have good cycle characteristics, and the first charge-discharge efficiency can be effectively improved.

Referring to fig. 1, according to some embodiments, the carbon film layer 103 has a thickness ranging from 0.001 to 5 μm and a mass ratio of 0.1 to 20 wt% in the anode material. In the present embodiment, the thickness of the carbon film layer is 0.002 to 2 microns, and more preferably, the thickness of the carbon film layer is 0.005 to 1 micron.

In addition, according to some embodiments, the mass ratio of the carbon film layer in the anode material is 0.2 to 15 wt%, and more preferably, the mass ratio is 1 to 10 wt%.

According to some embodiments, the carbon film layer may significantly enhance the electrical conductivity of the resulting material, while the further outer niobium-containing coating layer 105, in particular the lithium niobate coating layer, has high ion conductivity and high structural stability.

According to some embodiments, the niobium-containing cladding layer 105 has a thickness in a range of 0.001 to 3 micrometers. In this embodiment, the thickness of the niobium-containing coating layer is 0.001 to 1 micron, and more preferably 0.001 to 0.5 micron.

As shown in fig. 1, according to an exemplary embodiment, the carbon film layer 103 may be completely or partially coated on the surface of the silicon oxide particles 101, and the niobium-containing coating layer 105 may be completely or partially coated on the outer layer of the carbon film layer 103 and the area of the surface of the silicon oxide particles 101 that is not completely coated by the carbon film layer. For example, in the present embodiment, the carbon film layer 103 and the niobium-containing coating layer 105 may be a composite film layer, and the thickness of the composite film layer is in a range of 0.002 to 8 micrometers, preferably, the thickness of the composite film layer is in a range of 0.003 to 3 micrometers, and more preferably, the thickness of the composite film layer is in a range of 0.006 to 1.5 micrometers.

According to some embodiments, if the thickness of the coating layer is too thin or the mass ratio is insufficient, it is difficult to achieve the purposes of sufficiently improving the conductivity of the obtained material and forming a stable SEI film, and at the same time, it is difficult to achieve the effect of effectively relieving gas production from water system homogenate, thereby affecting the cycle stability and processability of the obtained material; if the coating layer is too thick or the mass ratio is too large, the capacity is reduced due to the increase of low-capacity components, and meanwhile, the increase of the thickness of the coating layer also increases the specific surface area of the material to a certain extent, so that the first coulombic efficiency of the material is influenced, and further the energy density of the battery is influenced.

Referring to fig. 1, according to an exemplary embodiment, a lithium niobate compound is included in the niobium-containing clad layer 105. In some embodiments, the lithium niobate compound comprises LiNbO₂、LiNbO₃、Li₃NbO₈、Li₃NbO₄、Li₇NbO₁₆And Li₈Nb₂O₉One or more than two of them.

According to an exemplary embodiment, the niobium element is concentrated in at least one region of the near-surface region of the niobium-containing coating layer 105, the carbon film layer 103, and the silicon oxide compound particles 101, as shown in fig. 3. According to some embodiments, the content of the niobium element in the anode material is in a range of 0.01 to 15 wt%. In addition, the content of the niobium element is preferably 0.02 to 10 wt%, more preferably 0.05 to 5 wt%. According to an exemplary embodiment, the niobium element may be present in the form of one or more of a niobium oxide, a niobium silicate-containing compound, and a lithium-containing composite niobium oxide. Specifically, the lithium-containing composite niobium oxide includes lithium niobate.

According to some embodiments, the total content of lithium in the negative electrode material provided by the present application is in a range of 0.01 to 30 wt%, preferably, the total content of lithium in the negative electrode material is between 0.05 to 20 wt%, and more preferably, between 0.1 to 15 wt%. According to an exemplary embodiment, if the lithium element content is too low, the first coulombic efficiency improvement for the material is insufficient; if the content of lithium element is too high, although the first coulombic efficiency can be significantly improved, the silicon nano-crystal grains are significantly increased and the alkalinity of the material is enhanced, which is not favorable for the circulation stability and the stability of the homogenate slurry.

According to an exemplary embodiment, the total content of elemental silicon in the anode material provided by the present application is in a range of 29.9 to 69.9 wt%, preferably, the total content of elemental silicon in the anode material is between 35 to 65 wt%, more preferably, between 39.9 to 59.9 wt%.

According to an exemplary embodiment, the negative electrode material has a median particle diameter of 0.5 to 20 micrometers, preferably 1 to 18 micrometers, and more preferably 3 to 15 micrometers.

According to some embodiments, if the particle size of the negative electrode material is too large, the particles are easy to crack and pulverize due to the stress generated by the volume effect in the later battery cycle process; if the particle size is too small, the coulombic efficiency of the battery is low due to large specific surface area of the particles, and during the circulation process, the SEI on the surfaces of the particles repeatedly generates and thickens to block lithium ion conduction, so that the electrochemical inactivation of the particles is caused, and the circulation performance of the battery is limited.

According to an exemplary embodiment, the negative electrode material provided herein has a median particle diameter that is a particle diameter corresponding to 50% by mass of particles smaller than the particle diameter on a particle diameter distribution curve of the total mass, i.e., D50.

Referring to fig. 5, in S501, silicon oxide particles are prepared.

According to some embodiments, the silica compound particles may be prepared by themselves or may be purchased for use directly. The specific process of preparation can be carried out by adopting the following steps: first, a mixture of metal silicon powder and silicon dioxide powder is heated at a temperature ranging from 900 to 1600 ℃ in an inert gas atmosphere or under reduced pressure, thereby generating silicon oxide gas. The molar ratio of the metal silicon powder to the silicon dioxide powder is set in the range of 0.8 to 1.3 in consideration of the presence of surface oxygen of the metal silicon powder and a trace amount of oxygen in the reaction furnace. Gas generated by the heating reaction of the raw materials is deposited on the adsorption plate. When the temperature in the reaction furnace is lowered to 100 ℃ or lower, the deposit is taken out, and pulverized and powdered by means of a ball mill, a jet mill or the like to obtain silicon oxide particles for use. Wherein the stoichiometric ratio of silicon element and oxygen element in the silicon-oxygen compound particles is 1: 0.6-1: 1.5, preferably 1: 0.8-1: 1.2.

According to some embodiments, if the silica ratio in the silica compound particles is too high, the volume effect during charge-discharge cycles is significant, resulting in a decrease in capacity retention; if the silicon-oxygen ratio is too low, the electron conductivity is reduced, and the content of active silicon is reduced, which leads to a reduction in capacity retention.

After the silica compound particles are prepared, the process proceeds to step S503.

In S503, according to an exemplary embodiment, a carbon film layer is formed, the carbon film layer is coated on the surface of the silicon oxide compound particles, and crushing and sieving processes are performed to obtain the carbon-coated silicon oxide compound particles.

According to an exemplary embodiment, the surface of the silicon oxide particles prepared in the previous step may be coated with a carbon film layer by means of chemical vapor deposition. According to some embodiments, the silicon oxide particles may be coated with a carbon film layer by first coating a carbon precursor and then performing heat treatment in a non-oxidizing atmosphere for carbonization.

According to some embodiments, the carbon source selected for the chemical vapor deposition in S503 includes one or more of methane, ethane, ethylene, acetylene, propylene, benzene, toluene, biphenyl, naphthalene, and styrene. In some embodiments, the processing temperature for chemical vapor deposition is 600-1100 ℃, preferably 700-1000 ℃, so as to prevent the silicon oxide particles from being disproportionated excessively when the vapor deposition temperature is too high, and to prevent the generated carbon film layer from having poor quality when the temperature is too low. According to some embodiments, the temperature rise rate is 0.5-10 ℃/min and the holding time is 1-24 hours.

According to an exemplary embodiment, in S503, if the carbon film layer is formed by first coating a carbon precursor, and then performing thermal treatment carbonization in a non-oxidizing atmosphere, the carbon precursor includes: polyacrylonitrile, epoxy resin, polyvinyl alcohol, petroleum asphalt, coal tar pitch, aniline, pyrrole, glucose, sucrose, polyacrylic acid, and polyvinylpyrrolidone.

According to some embodiments, the optional apparatus for coating the carbon precursor includes one or more of a mechanical fusion machine, a mechanical stirrer, a hydrothermal reaction kettle, a coating kettle, a VC mixer, a spray dryer, a sand mill, a high-speed dispersing machine, and the like.

According to some embodiments, the heat treatment carbonization process may be performed using one of a rotary kiln, a roller kiln, an electric oven, a pusher kiln, a tube furnace, or an atmosphere box furnace. According to an exemplary embodiment, the temperature of the heat treatment carbonization is 550-1100 ℃, preferably 650-1050 ℃, so as to prevent excessive disproportionation of the silicon-oxygen compound particles when the temperature is too high, and also prevent problems of incomplete carbonization or poor quality of the carbon film layer caused by too low temperature; the heating rate is 0.2-10 ℃/min, and the heat preservation time is 1-24 h.

According to an exemplary embodiment, the non-oxidizing atmosphere used for the heat treatment carbonization includes one or more of hydrogen, nitrogen, argon, and helium.

According to some embodiments, by coating the silicon oxide particles with the carbon film, the reduction of conductivity caused by doping, inserting and diffusing lithium in the subsequent stage can be effectively alleviated, and the reduction of conductivity can be helpful for isolating moisture and enhancing the water resistance of the material to some extent, so that the stability of the material in the water homogenate is improved.

In addition, according to some embodiments, the carbon-coated silicon oxide compound particles may be further doped with 0.01 to 10 wt% of other metal elements. In this embodiment, the other metal elements include one or two or more of Mg, Al, Cu, Mn, Ca, and Zn.

According to some embodiments, the silicon oxide particles are homogeneously mixed with the doping substance and subsequently doped by thermal treatment in a non-oxidizing atmosphere. According to an exemplary embodiment, the doping substance comprises a powder of an element or compound of a doping element, preferably a compound containing a doping element. For example, metal oxides, metal salts (including inorganic metal salts such as nitrates, nitrites, sulfates, sulfites, hydrogen sulfates, hydrogen phosphates, dihydrogen phosphates, and halogen salts, and organic metal salts such as acetates, oxalates, and citrates), and the like are used.

According to some embodiments, the temperature for doping the silicon oxide particles with other metal elements is 600 to 1200 ℃, preferably 650 to 1050 ℃, so as to prevent the silicon oxide particles from being excessively disproportionated when the temperature is too high or insufficiently doped when the temperature is too low. The heating rate is 0.2-10 ℃/min, and the heat preservation time is 0.5-24 h.

Further, according to an exemplary embodiment, the step of doping the silicon oxide compound particles with other metal elements may be performed before forming the carbon film layer in S503, after forming the carbon film layer in S503, or simultaneously with forming the carbon film layer in S503.

At least one of the following benefits can be produced by appropriate metal element doping of the silicon oxide compound particles: (a) the electronic conductivity of the silicon oxide particles can be improved, so that the rate capability of the material is improved; (b) the water resistance of the obtained cathode material is enhanced, the stability of the material in water system homogenate is improved, and a more stable and compact SEI film can be formed on the surface of the obtained material in the use process of the lithium ion secondary battery; (c) when the metal element doping step is performed before the carbon film layer is formed, a strong covalent bond can be formed between the doped metal element and the carbon film layer coated subsequently, and coupling between silicon oxide particles and the carbon film layer is improved, so that the conductivity of the material and the structural stability of the carbon film layer are effectively improved, and the effects of further improving the conductivity of the material and inhibiting the volume expansion of silicon nanoparticles are achieved.

After the carbon film layer is formed, the process proceeds to S505.

In S505, a niobium-containing precursor coating layer is formed, the niobium-containing precursor is coated on the surface of the carbon-coated silicon oxide particles, secondary coating is completed, and sieving treatment is performed to form particles having a niobium-containing precursor coating layer. According to some embodiments, the niobium precursor comprises one or more of an oxide, a hydroxide, and a niobium salt of niobium. Preferably, the niobium-containing precursor includes one or more of niobium oxide, niobium hydroxide, niobium oxalate, ammonium niobium oxalate, niobium ethoxide, niobium isopropoxide, and niobium chloride.

In accordance with some embodiments, in order to improve the uniformity and integrity of the coating of the niobium precursor on the surface of the carbon-coated silicon oxide particles while effectively controlling the coating amount of the niobium precursor, in some embodiments, it is preferable to coat the carbon-coated silicon oxide particles with the niobium-containing precursor in a liquid-phase system.

According to an exemplary embodiment, the solvent for coating the niobium-containing compound in the liquid phase system preferred in S505 includes one or a combination of two or more of water, methanol, ethanol, isopropanol, ethylene glycol, toluene, acetone, N-methylpyrrolidone, and the like.

According to some embodiments, in S505, the niobium-containing precursor film layer is coated on the surface of the silicon oxide particles, and simultaneously the lithium source required in the subsequent lithium doping step is blended in the niobium-containing precursor.

After the niobium-containing precursor coating layer is formed, the process proceeds to S507.

In S507, according to an exemplary embodiment, lithium doping is performed, and lithium doping is performed on the particles coated with the niobium-containing precursor, resulting in a negative electrode material.

According to some embodiments, the lithium doping method includes one or more of an electrochemical method, a liquid phase doping method, a thermal doping method, a high temperature milling method, and a high energy mechanical method. Preferably, a liquid phase doping method and a thermal doping method are included.

According to some embodiments, when lithium doping is performed using a liquid phase doping method in S507, specifically, a metallic lithium source, particles to be doped with lithium, and an electron transfer catalyst are added to an ethereal solvent, sufficiently mixed under an anhydrous and high-purity inert atmosphere, and continuously reacted until the metallic lithium source in the solution completely disappears. And then, collecting the obtained product and carrying out heating treatment in anhydrous and high-purity inert atmosphere to obtain the cathode material. Under the action of an electron transfer catalyst, a metallic lithium source can be dissolved in an ether solvent to form a lithium complex with a lower reduction potential, and the obtained lithium complex can react with particles to be doped with lithium and dope the lithium into the structure of the lithium complex. The subsequent heat treatment process can stabilize the highly active lithium in the product, thereby obtaining a stable lithium-doped material. The metal lithium source comprises one or more than two of lithium particles, lithium wires, lithium powder, lithium foil or lithium sheets; the particles to be doped with lithium include the material obtained in step S505. The electron transfer catalyst comprises one or more of naphthalene, anthracene, phenanthrene, pyrene, picene, triphenylene, biphenyl, dimethyl biphenyl, triphenyl and derivatives thereof; the ether solvent comprises one or more of diethyl ether, methyl tert-butyl ether, ethylene glycol dimethyl ether, tetrahydrofuran, dioxane and diethylene glycol dimethyl ether; the high purity inert atmosphere is provided by at least one of argon, helium, and neon. The temperature of the heat treatment may be 400 to 850 ℃, preferably 450 to 750 ℃.

According to some embodiments, when lithium doping is performed using a thermal doping method, the particles coated with the niobium-containing precursor obtained in step S505 are uniformly mixed with a lithium source powder, and subjected to a heating treatment in a high-purity non-oxidizing atmosphere, to obtain a negative electrode material. The lithium source comprises one or more of metallic lithium, lithium hydroxide, lithium carbonate, lithium chloride, lithium acetate, lithium ethoxide, lithium oxalate and lithium hydride. The mixing equipment comprises one of a high-speed dispersion machine, a high-speed stirring mill, a ball mill, a cone mixer, a spiral mixer, a stirring mixer or a VC mixer. The non-oxidizing atmosphere comprises one or more of hydrogen, nitrogen, argon and helium. The equipment used for the heating treatment is one of a rotary furnace, a roller kiln, a pushed slab kiln, a tubular furnace or an atmosphere box furnace. The temperature of the heating treatment is 450-800 ℃, and preferably 500-750 ℃; the heating rate is 0.2-10 ℃/min, preferably 0.2-5 ℃/min; the heat preservation time is 0.5-24 h, preferably 1-12 h.

According to an exemplary embodiment, the silicon oxide particles may be lithium-doped before step S505, and the lithium doping process is performed after the silicon oxide particles form a carbon film layer. Alternatively, according to some embodiments, the lithium doping process to the silicon oxide particles may also be performed simultaneously with S507.

According to some embodiments, the present application further provides a secondary battery anode made of the above anode material and a corresponding secondary battery.

The characterization method comprises the following steps:

1. component detection: the anode materials prepared in the respective examples and comparative examples were characterized by the following equipment. The particle size distribution of the obtained cathode material was tested by a Dandongbott BetterSize 2000 laser particle sizer. And observing the surface morphology of the obtained cathode material by using a Hitachi SU8010 scanning electron microscope. And characterizing the element distribution of the obtained cathode material by using an energy dispersion X-ray spectrometer. The components and the crystal structure of the obtained cathode material are tested by a Rigaku miniFlex600 powder X-ray diffractometer. The elemental composition of the obtained cathode material was tested using an Agilent5100 inductively coupled plasma mass spectrometer.

2. Gas production monitoring: 30g of each of the slurry slurries of examples and comparative examples were stored at a constant temperature of 60 ℃ and the gas evolution starting time was monitored. In view of the fact that the slurry temperature is usually 20-40 ℃ in the actual production water homogenization process, the conditions adopted for evaluating the slurry stability in the application are obviously severer. If the slurry can ensure that no gas is generated within 24 hours under the evaluation method, the cathode material contained in the slurry has stronger water-resistant stability and can be suitable for large-scale water system homogenate production.

3. Half-cell evaluation: and (3) sequentially stacking the negative pole piece, the diaphragm, the lithium piece and the stainless steel gasket which all contain the negative pole material in each embodiment and comparative example, dropwise adding 200 mu L of electrolyte, and sealing to prepare the CR2016 type half cell. The capacity and the discharge efficiency of the half-cell are tested by adopting CT2001A type equipment of Wuhan blue-electron Limited company, wherein the lithium removal cut-off potential is 0.8V, and finally the first reversible lithium removal specific capacity and the first charge-discharge efficiency of the half-cell containing the obtained cathode material are tested.

4. Full cell evaluation: the negative electrode sheet of the negative electrode material prepared in each example and comparative example was cut, vacuum-baked, wound together with the paired positive electrode sheet and separator, and loaded into an aluminum plastic case of a corresponding size, and a certain amount of electrolyte was injected, degassed, sealed, and formed to obtain a lithium ion full cell of about 3.2 Ah. A battery tester of New Wille electronics Limited, Shenzhen, is used for testing the capacity and the average voltage of the full battery under 0.2C and 2C, and the capacity retention rate data is obtained after 500 charge-discharge cycles under the multiplying power of 0.7C.

The present application is further illustrated by the following specific examples.

Example 1

2000g of silicon oxide particles having a median particle diameter of 8 μm and a silicon-oxygen atom ratio of 1:1 were weighed and placed in a CVD furnace, and high-purity argon gas was introduced into the furnace at a gas velocity of 500ccm throughout the subsequent process. Firstly, heating the system to 900 ℃ at the speed of 5 ℃/min, keeping the temperature for 60min, then introducing acetylene into the furnace at the gas speed of 300ccm for 60min for coating the carbon film layer, then keeping the temperature at 900 ℃ for 1 hour, and then cooling to room temperature to obtain silicon oxide particles with the carbon film layer for subsequent operation.

500g of the above silicon oxide particles having a carbon film layer were weighed and uniformly dispersed in 1000ml of ethanol through a high-speed dispersion plate with a mass ratio of 30:1 with niobium oxide having a median particle diameter of about 1 μm. The dispersion obtained is then dried after continuous stirring to a viscous consistency at 150 ℃ and coarsely broken and subsequently screened through a 500-mesh screen for further processing.

Crushing the lithium hydride coarse powder in a drying room with the humidity of less than 10 percent by using a planetary ball mill and sieving the crushed lithium hydride coarse powder by using a 500-mesh sieve to obtain lithium hydride fine powder for later use. And (3) uniformly mixing the material obtained in the last step and lithium hydride fine powder in a VC mixer for 30min according to the mass ratio of 9:1, and then transferring the mixture into a tube furnace. And then raising the temperature to 700 ℃ at the speed of 2 ℃/min under the atmosphere of high-purity argon, keeping the temperature for 8 hours, naturally cooling, and sieving by a 500-mesh sieve to obtain the final cathode material.

And (3) homogenizing the obtained negative electrode material, natural graphite, a conductive additive, a thickening agent and a binder under a water system condition according to a mass ratio of 10:87:0.5:1: 1.5. And (3) taking part of the slurry to perform water resistance and stability tests, coating the rest of the slurry on copper foil, and then drying and rolling to obtain the negative pole piece containing the negative pole material.

The median particle size of the obtained anode material is detected to be about 8.5 μm, and the obtained anode material contains about 45 wt% of silicon element, about 43 wt% of oxygen element, about 3 wt% of carbon element, about 7 wt% of lithium element and about 2 wt% of niobium element; the size of the silicon nano-crystalline grains dispersed in the interior of the obtained anode material was about 5.5nm by fitting through X-ray diffraction analysis.

About 30g of the above homogenate was stored at a constant temperature of 60 ℃ and the gas evolution time was monitored. The results show that the resulting slurry starts to gas slowly after 12 hours.

The half-cell evaluation results of the anode material obtained in example 1 were: the first reversible lithium removal specific capacity is 438mAh/g, and the first charge-discharge efficiency is 89.6%.

The full-cell evaluation results of the anode material obtained in example 1 were: the volume energy density at 0.2C and 2C multiplying power is 764Wh/L and 723Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 82.6%.

Example 2

The silicon oxide particles were coated with a carbon film layer by the same CVD process as in example 1, and then passed through a 500-mesh screen for standby. Uniformly mixing the silicon oxide particles with the carbon film layer obtained in the last step and lithium hydride fine powder in a VC mixer for 30min according to the mass ratio of 10:1, transferring the mixture into a tube furnace, raising the temperature to 750 ℃ at a speed of 3 ℃/min under the atmosphere of high-purity argon, keeping the temperature for 6 h, naturally cooling, and screening the mixture through a 500-mesh screen for subsequent operation.

500g of the material obtained in the previous step was weighed and uniformly dispersed with niobium oxide having a median particle size of about 1 μm in 1000ml of isopropanol at a mass ratio of 30:1 by means of a high-speed dispersion plate. The dispersion obtained is then dried after continuous stirring to a viscous consistency at 150 ℃ and coarsely broken and subsequently screened through a 500-mesh screen for further processing.

Crushing the coarse lithium oxalate powder in a drying room with the humidity of less than 10 percent by using a planetary ball mill, and sieving the crushed coarse lithium oxalate powder by using a 500-mesh sieve to obtain fine lithium oxalate powder for later use. Uniformly mixing the material obtained in the last step and lithium oxalate fine powder in a VC mixer for 30min according to the mass ratio of 80:1, transferring the mixture into a tube furnace, then heating to 700 ℃ at the speed of 2 ℃/min under the atmosphere of high-purity argon, keeping the temperature for 6 h, naturally cooling, and then sieving through a 500-mesh sieve to obtain the final cathode material.

Similarly, the preparation method of the negative electrode plate in embodiment 1 is not repeated.

The median particle size of the resulting negative electrode material was found to be about 8.5 μm. The obtained anode material contained about 44 wt% of silicon element, about 43 wt% of oxygen element, about 3 wt% of carbon element, about 8 wt% of lithium element, and about 2 wt% of niobium element. The size of the silicon nano-crystal grains dispersed in the obtained anode material is about 6.5nm through the fitting of X-ray diffraction analysis.

The gas production monitoring result of the homogenate slurry shows that the obtained slurry starts to produce gas slowly after 18 hours.

The half-cell evaluation results of the anode material obtained in example 2 were: the first reversible lithium removal specific capacity is 436mAh/g, and the first charge-discharge efficiency is 89.3%.

The full-cell evaluation results of the negative electrode material obtained in example 2 were: the volume energy density at 0.2C and 2C multiplying power is 761Wh/L and 722Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 83.4%.

Example 3

2000g of silicon oxide particles with a median particle size of 7 μm and a silicon-oxygen atom ratio of 1:1 were weighed and uniformly mixed with petroleum asphalt in a mass ratio of 15:1 by a heated VC mixer to coat the petroleum asphalt. And transferring the obtained product into a box type furnace, heating to 1000 ℃ at a speed of 5 ℃/min under the atmosphere of high-purity nitrogen, and keeping for 2h, wherein the product is used for realizing in-situ carbonization of the asphalt coating film layer on the surface of the silicon oxide compound particles. After the treatment, the resulting material was crushed and sieved through a 500 mesh screen for subsequent operations.

0.13mol of niobium ammonium oxalate is completely dissolved in 2000mL of mixed solvent of ethanol and water for standby, and 1000g of silicon oxide compound particles with the carbon film layer obtained in the previous step are weighed and uniformly dispersed in the niobium ammonium oxalate solution through a high-speed dispersion disc. The dispersion obtained is subsequently dried and coarsely broken after continuous stirring to a viscous consistency under heating and subsequently screened through a 500-mesh screen for further processing.

The material obtained in the previous step was uniformly mixed with lithium hydride fine powder in a mass ratio of 9:1 in a VC mixer for 30 minutes by a method similar to that of example 1, and then transferred to a tube furnace. And then raising the temperature to 700 ℃ at the speed of 2 ℃/min under the atmosphere of high-purity argon, keeping the temperature for 8 hours, naturally cooling, and sieving by a 500-mesh sieve to obtain the final cathode material.

The obtained anode material was found to have a median particle size of about 10 μm, and to contain about 45 wt% of silicon, about 43 wt% of oxygen, about 3 wt% of carbon, about 8 wt% of lithium, and about 1 wt% of niobium. The silicon nanocrystal particle size of the dispersed silicon inside the obtained anode material is about 6nm by fitting through X-ray diffraction analysis.

The gas production monitoring result of the homogenate slurry shows that the slurry begins to produce gas slowly after 30 hours.

The half-cell evaluation results of the anode material obtained in example 3 were: the first reversible lithium removal specific capacity is 439mAh/g, and the first charge-discharge efficiency is 90.1%.

The full-cell evaluation results of the anode material obtained in example 3 were: the volume energy density at 0.2C and 2C multiplying power is 765Wh/L and 736Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 86.1%. Fig. 4 is a graph of cycle performance of the full cell containing the negative active material prepared in example 3.

Example 4

The silicon oxide particles were coated with a carbon film layer by the same CVD process as in example 1, and then passed through a 500-mesh screen for subsequent operations. Under the protection of a high-purity argon atmosphere, uniformly mixing the carbon-coated silicon oxide compound particles obtained in the last step and the metal lithium particles in a tetrahydrofuran solution dissolved with naphthalene according to the mass ratio of 11:1, and continuously stirring at 70 ℃. And (3) when the lithium particles floating on the liquid surface completely disappear, continuously keeping the temperature of 70 ℃ for reaction for 30min, and naturally cooling to room temperature. And then under the protection of a high-purity argon atmosphere, evaporating and drying the solvent, transferring the obtained particles into a tubular furnace, raising the temperature to 700 ℃ at a speed of 2 ℃/min under the protection of the high-purity argon atmosphere, keeping the temperature for 3 hours, naturally cooling, and then screening the obtained material through a 500-mesh screen for subsequent operation.

0.13mol of niobium ethoxide, 0.075mol of lithium carbonate and 0.05mol of citric acid were completely dissolved in 2000mL of ethanol for use. Subsequently, 1000g of the material obtained in the previous step was weighed out and dispersed in the above solution by mechanical stirring with continuous stirring. The resulting dispersion was stirred continuously under heating until viscous, dried and coarsely crushed, and then passed through a 500 mesh screen for further processing.

And transferring the material obtained in the last step into a tubular furnace, then raising the temperature to 700 ℃ at the speed of 2 ℃/min under the atmosphere of high-purity argon, keeping the temperature for 6 hours, naturally cooling, and then sieving by a 500-mesh sieve to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 8.5 μm. The obtained anode material contained about 46 wt% of silicon element, about 44 wt% of oxygen element, about 3 wt% of carbon element, about 6 wt% of lithium element, and about 1 wt% of niobium element. The silicon nano-crystalline grain size dispersed inside the obtained anode material was about 5nm by fitting through X-ray diffraction analysis.

The gas production monitoring result of the homogenate slurry shows that the obtained slurry starts to produce gas slowly after 42 hours.

The half-cell evaluation results of the anode material obtained in example 4 were: the first reversible lithium removal specific capacity is 436mAh/g, and the first charge-discharge efficiency is 90.1%.

The full-cell evaluation results of the anode material obtained in example 4 were: the volume energy density at 0.2C and 2C multiplying power is 764Wh/L and 730Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 85.8%.

Example 5

2000g of silicone compound particles having a median particle diameter of 7 μm and a silicone-oxygen atomic ratio of 1:1 were weighed and then uniformly mixed with petroleum asphalt in a mass ratio of 15:1 by means of a heated VC mixer for coating the petroleum asphalt. And transferring the obtained product into a box type furnace, heating to 900 ℃ at a speed of 5 ℃/min under the atmosphere of high-purity nitrogen, and keeping for 3h, wherein the product is used for realizing in-situ carbonization of the petroleum asphalt coating film layer on the surface of the silicon oxide compound particles. After the treatment, the resulting material was crushed and sieved through a 500 mesh screen for subsequent operations.

Under the protection of a high-purity argon atmosphere, uniformly mixing the carbon-coated silicon oxide compound particles obtained in the last step and the metal lithium particles in a methyl tert-butyl ether solution dissolved with naphthalene according to the mass ratio of 10:1, and continuously stirring at 70 ℃. And (3) when the lithium particles floating on the liquid surface completely disappear, continuously keeping the temperature of 70 ℃ for reaction for 30min, and naturally cooling to room temperature. And then under the protection of a high-purity argon atmosphere, evaporating and drying the solvent, transferring the obtained particles into a tubular furnace, raising the temperature to 650 ℃ at the speed of 2 ℃/min under the protection of the high-purity argon atmosphere, keeping the temperature for 4 hours, naturally cooling, and then screening the obtained material through a 500-mesh screen for subsequent operation.

0.13mol of ammonium niobium oxalate and 0.15mol of lithium acetate were completely dissolved in 2000mL of a mixed solvent of ethanol and water for use. 1000g of the material obtained in the previous step were weighed and dispersed in the above-mentioned ammonium niobium oxalate-lithium acetate solution by mechanical stirring. The dispersion obtained is subsequently dried and coarsely broken after continuous stirring to a viscous consistency under heating and subsequently screened through a 500-mesh screen for further processing.

And transferring the material obtained in the last step into a tubular furnace, then heating to 650 ℃ at a speed of 3 ℃/min under the atmosphere of high-purity argon, keeping for 8 hours, naturally cooling, and sieving by a 500-mesh sieve to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 10 μm. The obtained anode material contained about 45 wt% of silicon element, about 43 wt% of oxygen element, about 3 wt% of carbon element, about 8 wt% of lithium element, and about 1 wt% of niobium element. The size of the silicon nano-crystalline grains dispersed in the interior of the obtained anode material was about 4.5nm by fitting through X-ray diffraction analysis.

The gas production monitoring result of the homogenate slurry shows that the obtained slurry starts to produce gas slowly after 36 hours.

The half-cell evaluation results of the anode material obtained in example 5 were: the first reversible lithium removal specific capacity is 442mAh/g, and the first charge-discharge efficiency is 90.2%.

The full-cell evaluation results of the anode material obtained in example 5 were: the volume energy density at 0.2C and 2C multiplying power is 767Wh/L and 738Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 85.4%.

Example 6

1000g of silicon oxide compound particles with the median particle diameter of 7 mu m and the silicon-oxygen atom ratio of 1:1, magnesium acetate tetrahydrate, glucose and polyvinylpyrrolidone are weighed and uniformly dispersed in 2000ml of isopropanol/water mixed solvent through a high-speed dispersion disc according to the mass ratio of 10:1:0.5:0.1, wherein the volume ratio of isopropanol to water is 5: 1. The dispersion obtained is stirred continuously at 150 ℃ until it is viscous, dried and coarsely crushed and transferred into a tube furnace. And then heating to 900 ℃ at the speed of 3 ℃/min under the atmosphere of high-purity nitrogen, keeping for 3 hours, and realizing magnesium element doping and glucose carbonization film forming and coating on the surface of the material. After the treatment, the resulting material was crushed and sieved through a 500 mesh screen for subsequent operations.

0.13mol of niobium ethoxide, 0.075mol of lithium carbonate and 0.05mol of citric acid were dissolved in 2000mL of ethanol for use. Subsequently, 1000g of the magnesium-doped silica compound particles having a carbon film layer obtained in the previous step were weighed and dispersed in the above solution by mechanical stirring with continuous stirring. Subsequently, the resulting dispersion was continuously stirred under heating to be viscous, dried and coarsely crushed, and then passed through a 500-mesh screen for subsequent operations.

The material obtained in the previous step was uniformly mixed with lithium hydride fine powder in a mass ratio of 11:1 in a VC mixer for 30 minutes by a method similar to that of example 1, and then transferred to a tube furnace. And then, heating to 650 ℃ at the speed of 2 ℃/min under the atmosphere of high-purity argon, keeping for 8 hours, naturally cooling, and sieving by a 500-mesh sieve to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 11.5 μm. The obtained anode material contained about 45 wt% of silicon, about 43 wt% of oxygen, about 3 wt% of carbon, about 7 wt% of lithium, about 1 wt% of niobium, and about 1 wt% of magnesium. The silicon nano-crystalline grain size dispersed inside the obtained anode material was about 5nm by fitting through X-ray diffraction analysis.

The half-cell evaluation results of the anode material obtained in example 6 were: the first reversible lithium removal specific capacity is 443mAh/g, and the first charge-discharge efficiency is 89.1%.

The full-cell evaluation results of the negative electrode material obtained in example 6 were: the volume energy density at 0.2C and 2C multiplying power is 761Wh/L and 729Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 85.6%.

Example 7

2000g of silicon oxide particles having a median particle diameter of 7 μm and a silicon-oxygen atom ratio of 1:1 were weighed out and uniformly dispersed in 3000ml of deionized water through a high-speed dispersion plate with aluminum nitrate nonahydrate, sucrose and polyvinylpyrrolidone in a mass ratio of 10:2:1:0.1, followed by spray-drying. Wherein the inlet air temperature of spray drying is 150 ℃, the outlet temperature is 105 ℃, the rotating speed of the rotary atomizing nozzle is 350Hz, and the feeding speed is 100 g/min. And transferring the obtained product into a box furnace, and then heating to 900 ℃ at a speed of 5 ℃/min under the atmosphere of high-purity nitrogen for 3 hours for realizing aluminum element doping and sucrose carbonization film-forming coating on the surface of the material. After the treatment, the resulting material was crushed and sieved through a 500 mesh screen for subsequent operations.

0.13mol of niobium ammonium oxalate is completely dissolved in 2000mL of mixed solvent of ethanol and water for standby, 1000g of aluminum-doped silicon oxide compound particles with a carbon film layer obtained in the previous step are weighed, and the aluminum-doped silicon oxide compound particles are dispersed in the niobium ammonium oxalate solution through a high-speed dispersion disc. Subsequently, the resulting dispersion was continuously stirred under heating to be viscous, dried and coarsely crushed, and then passed through a 500-mesh screen for subsequent operations.

The material obtained in the previous step was uniformly mixed with lithium hydride fine powder in a mass ratio of 8:1 in a VC mixer for 30 minutes by a method similar to that of example 1, and then transferred to a tube furnace. And then, heating to 750 ℃ at the speed of 1 ℃/min under the atmosphere of high-purity argon, keeping for 6 hours, naturally cooling, and screening by a 500-mesh screen to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 10.5 μm. The obtained anode material contained about 44 wt% of silicon element, about 42 wt% of oxygen element, about 3 wt% of carbon element, about 9 wt% of lithium element, about 1 wt% of niobium element, and about 1 wt% of aluminum element. The silicon nanocrystal particle size of the dispersed silicon inside the obtained anode material is about 7nm by fitting through X-ray diffraction analysis.

The gas production monitoring result of the homogenate slurry shows that the obtained slurry starts to produce gas slowly after 84 hours.

The half-cell evaluation results of the anode material obtained in example 7 were: the first reversible lithium removal specific capacity is 432mAh/g, and the first charge-discharge efficiency is 90.6%.

The full-cell evaluation results of the negative electrode material obtained in example 7 were: the volume energy density at 0.2C and 2C multiplying power is 769Wh/L and 733Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 84.9%.

Example 8

The silicon oxide particles were coated with a carbon film layer by the same process as in example 5, and then passed through a 500-mesh screen for subsequent operations. 1500g of the carbon-coated silicon oxide particles obtained in the previous step were weighed out and uniformly dispersed in 3000ml of deionized water through a high-speed dispersion plate with aluminum nitrate nonahydrate, manganese acetate tetrahydrate, sucrose and polyvinylpyrrolidone in a mass ratio of 10:1:0.3:1:0.1, followed by spray drying. The operation scheme and specific parameters of the spray drying were the same as in example 7. And transferring the obtained product into a box furnace, and then heating to 850 ℃ at a speed of 5 ℃/min under the atmosphere of high-purity nitrogen for 4 hours for realizing the doping of aluminum and manganese elements and the carbonization of sucrose to form a film and coating the film on the surface of the material. After the treatment, the resulting material was crushed and sieved through a 500 mesh screen for subsequent operations.

0.13mol of ammonium niobium oxalate and 0.05mol of citric acid are dissolved in 2000mL of mixed solvent of ethanol and water for standby. Subsequently, 1000g of the particles of the Al-Mn doped Si compound with the carbon film layer obtained in the previous step were weighed, dispersed in the above solution by mechanical stirring and stirred continuously at 80 ℃ for 2 hours. The heating temperature is then raised, and the dispersion obtained is dried and coarsely crushed after being stirred continuously to a viscous state under heating and then screened through a 500-mesh screen for further processing.

The material obtained in the previous step was uniformly mixed with lithium hydride fine powder in a mass ratio of 8:1 in a VC mixer for 30 minutes by a method similar to that of example 1, and then transferred to a tube furnace. And then raising the temperature to 750 ℃ at a speed of 1 ℃/min under the atmosphere of high-purity argon, keeping for 6 hours, naturally cooling, and sieving by a 500-mesh sieve to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 10.5 μm. The obtained anode material contained about 43 wt% of silicon, about 43 wt% of oxygen, about 3 wt% of carbon, about 9 wt% of lithium, about 1 wt% of niobium, about 0.5 wt% of aluminum, and about 0.5 wt% of manganese. The silicon nanocrystal particle size of the dispersed silicon inside the obtained anode material is about 7nm by fitting through X-ray diffraction analysis.

The gas production monitoring result of the homogenate slurry shows that the slurry begins to produce gas slowly after 60 hours.

The half-cell evaluation results of the anode material obtained in example 8 were: the first reversible lithium removal specific capacity is 431mAh/g, and the first charge-discharge efficiency is 90.2%.

The full-cell evaluation results of the negative electrode material obtained in example 8 were: the volume energy density at 0.2C and 2C multiplying power is 768Wh/L and 731Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 84.1%.

Example 9

The silicon oxide particles were coated with a carbon film layer by the same CVD process as in example 1, and then passed through a 500-mesh screen for subsequent operations. 1500g of the carbon-coated silicon oxide particles obtained in the previous step were weighed out and uniformly dispersed in 3000ml of deionized water with aluminum nitrate nonahydrate, copper acetate monohydrate, sucrose and polyvinylpyrrolidone in a mass ratio of 10:1:0.3:1:0.1, followed by spray drying. The operation scheme and specific parameters of the spray drying were the same as in example 6. And transferring the obtained product into a box furnace, and then heating to 850 ℃ at 3 ℃/min under the atmosphere of high-purity nitrogen for 4 hours for doping aluminum elements and copper elements and carbonizing sucrose to form a film and coating the film on the surface of the material. After the treatment, the resulting material was crushed and sieved through a 500 mesh screen for subsequent operations.

0.13mol niobium oxalate is fully dispersed in 2000mL of mixed solvent of ethanol and water for standby, 1000g of aluminum-copper doped silica compound particles with the carbon film layer obtained in the previous step are weighed and uniformly dispersed in the niobium oxalate dispersion liquid through a high-speed dispersion disc. Subsequently, the resulting dispersion was continuously stirred under heating to be viscous, dried and coarsely crushed, and then passed through a 500-mesh screen for subsequent operations.

The material obtained in the previous step was uniformly mixed with lithium hydride fine powder in a mass ratio of 12:1 in a VC mixer for 30 minutes by a method similar to that of example 1, and then transferred to a tube furnace. And then raising the temperature to 700 ℃ at the speed of 2 ℃/min under the atmosphere of high-purity argon, keeping the temperature for 8 hours, naturally cooling, and sieving by a 500-mesh sieve to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 11.5 μm. The obtained anode material contained about 45 wt% of silicon element, about 44 wt% of oxygen element, about 3 wt% of carbon element, about 6 wt% of lithium element, about 1 wt% of niobium element, about 0.5 wt% of aluminum element, and about 0.5 wt% of copper element. The silicon nanocrystal particle size of the dispersed silicon inside the obtained anode material is about 7nm by fitting through X-ray diffraction analysis.

The half-cell evaluation results of the anode material obtained in example 9 were: the first reversible lithium removal specific capacity is 441mAh/g, and the first charge-discharge efficiency is 88.7%.

The full-cell evaluation results of the negative electrode material obtained in example 9 were: the volume energy density at 0.2C and 2C multiplying power is 754Wh/L and 722Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 85.9%.

Example 10

The silicon oxide particles were coated with a carbon film layer by the same process as in example 3, and then passed through a 500-mesh screen for subsequent operations. 0.026mol of niobium ammonium oxalate was completely dissolved in 2000mL of a mixed solvent of ethanol and water for standby, and 1000g of the silicon oxide particles having a carbon film layer obtained in the previous step were weighed and dispersed in the above niobium ammonium oxalate solution by a high-speed dispersion plate. Subsequently, the resulting dispersion was continuously stirred under heating to be viscous, dried and coarsely crushed, and then passed through a 500-mesh screen for subsequent operations.

The material obtained in the previous step and lithium hydride fine powder were uniformly mixed in a VC mixer at a mass ratio of 9:1 for 30 minutes by the same method as in example 3, and then transferred to a tube furnace. And then raising the temperature to 700 ℃ at the speed of 2 ℃/min under the atmosphere of high-purity argon, keeping the temperature for 8 hours, naturally cooling, and sieving by a 500-mesh sieve to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 9.5 μm. The obtained anode material contained about 45 wt% of silicon element, about 43 wt% of oxygen element, about 3 wt% of carbon element, about 8 wt% of lithium element, and about 0.2 wt% of niobium element. The silicon nanocrystal particle size of the dispersed silicon inside the obtained anode material is about 6nm by fitting through X-ray diffraction analysis.

The gas production monitoring result of the homogenate slurry shows that the obtained slurry starts to produce gas slowly after 12 hours.

The half-cell evaluation results of the anode material obtained in example 10 were: the first reversible lithium removal specific capacity is 437mAh/g, and the first charge-discharge efficiency is 90.1%.

The full-cell evaluation results of the anode material obtained in example 10 were: the volume energy density at 0.2C and 2C multiplying power is 764Wh/L and 726Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 83.2%.

Comparative example 1

1000g of silicon oxide particles with the median particle size of 8 mu m and the silicon-oxygen atom ratio of 1:1 are weighed and placed in a CVD furnace, the temperature is raised to 900 ℃ at the speed of 5 ℃/min under the atmosphere of high-purity argon, the temperature is kept for 3h, and then the temperature is reduced to room temperature, and the disproportionated silicon oxide particles are obtained for subsequent operation.

Subsequently, by a method similar to example 1, the disproportionated silicon oxide particles obtained in the previous step were uniformly mixed with lithium hydride fine powder in a VC mixer at a mass ratio of 9:1 for 30 minutes and then transferred to a tube furnace. And then raising the temperature to 750 ℃ at a speed of 3 ℃/min under the atmosphere of high-purity argon, keeping for 6 hours, naturally cooling, and sieving with a 500-mesh sieve to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 8 μm. The obtained negative electrode material contained about 47 wt% of silicon element, about 45 wt% of oxygen element, and about 8 wt% of lithium element. The silicon nanocrystal particle size of the dispersed silicon inside the obtained anode material is about 7nm by fitting through X-ray diffraction analysis.

The gas production monitoring result of the homogenate slurry shows that the obtained slurry starts to produce gas rapidly within 10 minutes.

The half-cell evaluation results of the anode material obtained in comparative example 1 were: the first reversible lithium removal specific capacity is 422mAh/g, and the first charge-discharge efficiency is 87.9%.

The full-cell evaluation results of the anode material obtained in comparative example 1 were: the volume energy density at 0.2C and 2C multiplying power is 745Wh/L and 566Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 39.7%.

Comparative example 2

The preparation flow was similar to that of example 3, except that after the silicon oxide particles were coated with the carbon film layer and passed through a 500-mesh screen by the same process as in example 3, the niobium-containing precursor was not coated, but the silicon oxide particles coated with the carbon film layer obtained in the previous step and the lithium hydride fine powder were uniformly mixed in a VC mixer at a mass ratio of 9:1 for 30 minutes and then transferred to a tube furnace directly by the same method as in example 3. And then raising the temperature to 700 ℃ at the speed of 2 ℃/min under the atmosphere of high-purity argon, keeping the temperature for 8 hours, naturally cooling, and sieving by a 500-mesh sieve to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 9 μm. The obtained negative electrode material contained about 45 wt% of silicon element, about 44 wt% of oxygen element, about 3 wt% of carbon element, and about 8 wt% of lithium element. The silicon nanocrystal particle size of the dispersed silicon inside the obtained anode material is about 6nm by fitting through X-ray diffraction analysis.

The gas production monitoring result of the homogenate slurry shows that the slurry begins to produce gas slowly after 6 hours.

The half-cell evaluation results of the anode material obtained in comparative example 2 were: the first reversible lithium removal specific capacity is 438mAh/g, and the first charge-discharge efficiency is 89.6%.

The full-cell evaluation results of the negative electrode material obtained in comparative example 2 were: the volume energy density at 0.2C and 2C multiplying power is 762Wh/L and 713Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 81.2%.

Comparative example 3

The preparation procedure is similar to example 4, with the difference that during the treatment in the CVD furnace, no acetylene is passed for coating the carbon film layer, but only the silicon oxide particles are treated for 3h under a high-purity argon atmosphere at 900C to give disproportionated silicon oxide particles. Subsequently, the disproportionated silica compound particles obtained in the previous step and the metallic lithium particles were reacted in a tetrahydrofuran solution dissolved with naphthalene under a high purity argon atmosphere by the same method parameters as in example 5. And then under the protection of a high-purity argon atmosphere, transferring the particles obtained after the solvent is evaporated and dried into a tubular furnace, raising the temperature to 700 ℃ at the speed of 2 ℃/min under the protection of the high-purity argon atmosphere, keeping the temperature for 3 hours, naturally cooling, and then screening the obtained material through a 500-mesh screen for subsequent operation.

The process flow and parameters for obtaining the final cathode material by performing niobium-containing precursor cladding and subsequent heat treatment lithium doping on the material obtained in the previous step are the same as those in embodiment 4, and are not described again.

The median particle size of the resulting negative electrode material was found to be about 8.5 μm. The obtained anode material contained about 48 wt% of silicon element, about 45 wt% of oxygen element, about 6 wt% of lithium element, and about 1 wt% of niobium element. The silicon nano-crystalline grain size dispersed inside the obtained anode material was about 5nm by fitting through X-ray diffraction analysis.

The gas production monitoring result of the homogenate slurry shows that the gas production of the obtained slurry starts in less than 4 hours.

The half-cell evaluation results of the anode material obtained in comparative example 3 were: the first reversible lithium removal specific capacity is 435mAh/g, and the first charge-discharge efficiency is 89.5%.

The full-cell evaluation results of the anode material obtained in comparative example 3 were: the volume energy density at 0.2C and 2C multiplying power is 759Wh/L and 681Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 72.9%.

Comparative example 4

The production flow was similar to that of example 5 except that after coating the silicon oxide particles with a carbon film layer and passing through a 500-mesh screen by the same procedure as in example 5, the obtained carbon-coated silicon oxide particles were not lithium-doped in a liquid phase system, but 1000g of the obtained carbon-coated silicon oxide particles were directly dispersed in 2000mL of a mixed solvent of ethanol and water in which 0.13mol of ammonium niobium oxalate and 0.15mol of lithium acetate were dissolved, by the same method as in example 5. Subsequently, the resulting dispersion was continuously stirred under heating to be viscous, dried and coarsely crushed, and then passed through a 500-mesh screen for subsequent operations.

And then, transferring the material obtained in the last step into a tubular furnace, raising the temperature to 650 ℃ at a speed of 2 ℃/min under the atmosphere of high-purity argon, keeping the temperature for 8 hours, naturally cooling, and screening by using a 500-mesh screen to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 10 μm. The obtained anode material contained about 49 wt% of silicon element, about 46 wt% of oxygen element, about 3 wt% of carbon element, about 0.5 wt% of lithium element, and about 1 wt% of niobium element. The size of the silicon nano-crystal grains dispersed in the obtained anode material is about 1.5nm through the fitting of X-ray diffraction analysis. The results show that the resulting slurry did not start to outgas after more than 120 hours.

The half-cell evaluation results of the anode material obtained in comparative example 4 were: the first reversible lithium removal specific capacity is 447mAh/g, and the first charge-discharge efficiency is 84.3%.

The full-cell evaluation results of the anode material obtained in comparative example 4 were: the volume energy density at 0.2C and 2C multiplying power is 726Wh/L and 705Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 87.1%.

Comparative example 5

The preparation procedure was similar to that of example 2, and the silicon oxide particles were coated with a carbon film layer by the same procedure as in example 2. Subsequently, the silicon oxide compound particles having the carbon film layer obtained in the previous step and the lithium hydride fine powder were uniformly mixed in a mass ratio of 10:1 by the same process as in example 2 and heat-treated at 750 ℃ for 6 hours under a high purity argon atmosphere to achieve lithium doping. Subsequently, the niobium-containing precursor cladding was performed again by the same process as in example 2. The difference is that the obtained material coated by the niobium-containing precursor is not subjected to the step of heating the mixed lithium oxalate fine powder, but is directly applied to the subsequent step of manufacturing the battery by homogenate coating.

The median particle size of the resulting negative electrode material was found to be about 8.5 μm. The obtained anode material contained about 45 wt% of silicon element, about 43 wt% of oxygen element, about 3 wt% of carbon element, about 8 wt% of lithium element, and about 1 wt% of niobium element. The size of the silicon nano-crystal grains dispersed in the obtained anode material is about 6.5nm through the fitting of X-ray diffraction analysis. The results show that the resulting slurry started to evolve gas already after 12 hours.

The half-cell evaluation results of the anode material obtained in comparative example 5 were: the first reversible lithium removal specific capacity is 437mAh/g, and the first charge-discharge efficiency is 89%.

The full-cell evaluation results of the negative electrode material obtained in comparative example 5 were: the volume energy density at 0.2C and 2C multiplying power is 756Wh/L and 718Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 81.5%.

Comparative example 6

1000g of silicon oxide particles having a median particle diameter of 7 μm and a silicon-oxygen atom ratio of 1:1, 0.26mol of niobium oxalate, 100g of sucrose and 10g of polyvinylpyrrolidone were weighed out and uniformly dispersed in 3000ml of deionized water by a high-speed dispersion plate, followed by spray-drying treatment. The operation scheme and specific parameters of the spray drying were the same as in example 7. And transferring the obtained product into a box furnace, and then heating to 950 ℃ at the speed of 3 ℃/min under the atmosphere of high-purity nitrogen for 3 hours for doping the niobium element and carbonizing the sucrose to form a film and coating the film on the surface of the material. After the treatment, the resulting material was crushed and sieved through a 500 mesh screen for subsequent operations.

The material obtained in the previous step was uniformly mixed with lithium hydride fine powder in a mass ratio of 9:1 in a VC mixer for 30 minutes by a method similar to that of example 1, and then transferred to a tube furnace. And then raising the temperature to 750 ℃ at the speed of 2 ℃/min under the atmosphere of high-purity argon, keeping for 6 hours, naturally cooling, and sieving by a 500-mesh sieve to obtain the final cathode material.

The median particle size of the resulting negative electrode material was found to be about 10 μm. The obtained anode material contained about 44 wt% of silicon element, about 43 wt% of oxygen element, about 3 wt% of carbon element, about 8 wt% of lithium element, and about 2 wt% of niobium element. The silicon nanocrystal particle size of the dispersed silicon inside the obtained anode material is about 7nm by fitting through X-ray diffraction analysis.

The half-cell evaluation results of the anode material obtained in comparative example 6 were: the first reversible lithium removal specific capacity is 433mAh/g, and the first charge-discharge efficiency is 89.6%.

The full-cell evaluation results of the negative electrode material obtained in comparative example 6 were: the volume energy density at 0.2C and 2C multiplying power is 761Wh/L and 708Wh/L respectively, and the capacity retention rate after 500 charge-discharge cycles is 82.5%.

According to some embodiments, the negative electrode material constructed in the application can fully protect nano silicon contained in silicon oxide compound particles from contacting with external water system slurry, so that the problem of active silicon loss caused by gas production reaction generated by contact of the nano silicon and water in a water system homogenizing process is effectively solved; the compact silicate compound formed on the surface area of the silicon oxide compound particles has good water resistance, and meanwhile, the composite film layer with good coating on the outer layer can also effectively avoid direct contact between the internal silicon nanoparticles and water-based slurry, so that the negative influence of the silicon nanoparticles on the slurry is reduced; in addition, the structure constructed in the application can effectively control the alkalinity rise of the aqueous slurry, simultaneously cannot influence the rheological property and the stability of the slurry, and effectively avoids the quality problems of pole pieces, such as pole piece pinholes, pits, uneven surface density, poor adhesion and the like caused by slurry gas generation and slurry rheological property and stability deterioration in the coating process.

According to some embodiments, when the negative electrode material constructed in the application is applied to a lithium ion secondary battery, a compact silicate compound formed in the surface region of silicon oxide compound particles can generate a synergistic effect with the composite film layer coated on the surface of the silicon oxide compound particles, and silicon nanoparticles in the material are completely isolated from the external electrolyte, so that the side reaction between the silicon oxide compound and the electrolyte is effectively reduced, a more stable SEI film can be formed on the surface of the material, and the coulombic efficiency and the capacity stability of the material in the charge-discharge cycle process are remarkably improved.

According to some embodiments, the carbon film layer coated on the surface of the negative electrode material can significantly improve the conductivity of the obtained material, and the niobium-containing coating layer of the outer layer, especially the lithium niobate-containing coating layer, has high lithium ion conductivity and structural stability. Therefore, the composite film layer effectively combines the advantages of the two coating layers, not only can further relieve and inhibit the volume effect of the silicon nanoparticles in the repeated charge and discharge process, but also can remarkably improve the electronic conductivity and the ionic conductivity of the obtained cathode material, thereby obviously improving the cycle stability and the rate capability of the battery.

According to some embodiments, unlike silicon particles obtained by conventional bulk material crushing, the silicon nanoparticles formed by disproportionation reactions in the silicon oxide particles in the present application are significantly smaller in size, which can significantly mitigate the volume effect generated during repeated lithium deintercalation. In addition, the silicon nanoparticles are uniformly dispersed and fixed in the silicon oxide matrix, so that the expansion of the silicon nanoparticles can be effectively inhibited and buffered, and the expansion acceleration and local failure of active silicon caused by gradual fusion of the silicon nanoparticles into particles with larger sizes in the charging and discharging processes can be effectively prevented.

According to some embodiments, in order to further alleviate the volume expansion effect of the silicon oxide material and effectively promote the first coulombic efficiency, the silicon oxide particles are subjected to lithium intercalation. The concentration of lithium element is gradually reduced from the surface layer of the silicon-oxygen compound particles to the inner core region, and the lithium element, partial oxygen element and silicon element form a lithium silicate compound after entering the silicon-oxygen compound, so that the oxygen elements can not continuously form compounds such as lithium silicate or lithium oxide and the like in the lithium intercalation process of the negative electrode, the irreversible loss of lithium ions during the first charge and discharge is effectively reduced, and the first coulombic efficiency is improved. In addition, the lithium pre-inserted into the silicon oxide particles enables the silicon oxide particles to have less lithium to be inserted under the same lithium removal capacity, so that the silicon oxide particles have lower particle expansion rate and lower pole piece expansion rate and battery expansion rate, and the structure stability of a negative electrode material, a pole piece and a battery is facilitated.

It is apparent that the above examples and comparative examples are only examples for clearly illustrating the present application and do not limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of this invention may be made without departing from the spirit or scope of the invention.

Claims

1. An anode material for a secondary battery, characterized by comprising:

silicon oxide compound particles containing lithium element and simple substance silicon nano particles;

a carbon film layer coated on the surface of the silicon oxide particles;

a coating layer containing niobium coating the surface of the silicon oxide compound particles with the carbon film layer,

and the niobium-containing coating layer comprises a lithium niobate compound.

2. The anode material of claim 1, wherein the lithium element in the silica compound particles is present in a form comprising a lithium silicate compound.

3. The anode material of claim 2, wherein the lithium silicate compound comprises:

Li₂Si₂O₅、Li₂SiO₃、Li₈SiO₆、Li₆Si₂O₇and Li₄SiO₄One or more than two of them.

4. The negative electrode material of claim 1, wherein the niobium-containing coating layer has a thickness of 0.001 to 3 micrometers, preferably 0.001 to 1 micrometer, and more preferably 0.001 to 0.5 micrometer.

5. The anode material according to claim 1, characterized in that the lithium niobate compound comprises:

LiNbO₂、LiNbO₃、Li₃NbO₈、Li₃NbO₄、Li₇NbO₁₆and Li₈Nb₂O₉One or more than two of them.

6. The negative electrode material of claim 1, wherein the niobium is contained in an amount of 0.01 to 15 wt%, preferably 0.02 to 10 wt%, and more preferably 0.05 to 5 wt%.

7. The anode material according to claim 1, wherein the niobium element in the anode material is enriched in:

the niobium-containing coating layer, the carbon film layer, and the silicon oxide compound particles are formed in at least one region of the near-surface region.

8. A method for preparing an anode material, comprising:

preparing silicon oxide particles;

forming a carbon film layer, coating the carbon film layer on the surface of the silicon oxide compound particles, and crushing and screening to obtain silicon oxide compound particles with the carbon film layer;

forming a niobium-containing precursor coating layer, coating a niobium-containing precursor on the surface of the silicon oxide compound particles with the carbon film layer to complete secondary coating, and performing screening treatment to form particles with the niobium-containing precursor coating layer;

and lithium doping, namely performing lithium doping on the particles with the niobium-containing precursor coating to obtain the negative electrode material.

9. An electrode comprising the negative electrode material according to any one of claims 1 to 7.

10. A secondary battery comprising the electrode according to claim 9.