LITHIUM-DOPED SILICON OXIDE COMPOSITE ANODE MATERIAL WITH HIGH INITIAL COULOMBIC EFFICIENCY AND PREPARATION METHOD THEREOF

Abstract

A lithium-doped silicon oxide composite anode material with high initial Coulombic efficiency and a preparation method are provided, which relates to the field of anode materials for lithium batteries. The material includes nano-silicon, lithium silicate and a conductive carbon layer. A diffraction peak intensity of Li.sub.2Si.sub.2O.sub.5(111) with 2θ being 24.7±0.2° in an XRD pattern of the lithium-doped silicon oxide composite anode material is I1, a diffraction peak intensity of Li.sub.2SiO.sub.3(111) with 2θ being 26.8±0.3° in the XRD pattern is I2, and I1/I2<0.25. The material provided in the present invention has a specific phase composition ratio, thereby achieving the effect of high initial Coulombic efficiency and high specific capacity.

Claims

1. A lithium-doped silicon oxide composite anode material, comprising nano-silicon, lithium silicate and a conductive carbon layer, wherein a diffraction peak intensity of Li.sub.2Si.sub.2O.sub.5(111) with 26 being 24.7±0.2° in an XRD pattern of the lithium-doped silicon oxide composite anode material is I1, a diffraction peak intensity of Li.sub.2SiO.sub.3(111) with 2θ being 26.8±0.3° in the XRD pattern is I2, and I1/I2<0.25.

2. The lithium-doped silicon oxide composite anode material according to claim 1, wherein I1/I2<0.15.

3. The lithium-doped silicon oxide composite anode material according to claim 1, wherein I1/I2<0.05.

4. The lithium-doped silicon oxide composite anode material according to claim 1, wherein a diffraction peak area of Li.sub.2SiO.sub.3(111) with 2θ being 26.8±0.3° in an XRD pattern of the lithium-doped silicon oxide composite anode material is A1, and a diffraction peak area of Si(111) with 2θ being 28.4±0.3° in the XRD pattern is A2, and A2/A1≥1.0.

5. The lithium-doped silicon oxide composite anode material according to claim 4, wherein A2/A1≥1.3.

6. The lithium-doped silicon oxide composite anode material according to claim 1, wherein the lithium-doped silicon oxide composite anode material has a core-shell structure comprising a core and a shell, the core comprises the nano-silicon and the lithium silicate, the lithium silicate comprises either or both of Li.sub.2SiO.sub.3 and Li.sub.2Si.sub.2O.sub.5, and the shell comprises the conductive carbon layer distributed on a surface of the core.

7. The lithium-doped silicon oxide composite anode material according to claim 6, wherein the shell further comprises a water-resistant coating.

8. The lithium-doped silicon oxide composite anode material according to claim 1, wherein, with a total mass of the lithium-doped silicon oxide composite anode material being 100 wt %, a mass percentage of a carbon material is 0.5 wt % to 10 wt %.

9. The lithium-doped silicon oxide composite anode material according to claim 8, wherein the carbon material comprises a coated carbon in a silicon oxide SiO.sub.x and a coated carbon in a water-resistant coating, and a content of the coated carbon of the water-resistant coating is 0.5 wt % to 4 wt % of the lithium-doped silicon oxide composite anode material.

10. The lithium-doped silicon oxide composite anode material according to claim 1, wherein the nano-silicon is elemental silicon, and an average grain size of the nano-silicon is in a range of 3 nm to 20 nm.

11. The lithium-doped silicon oxide composite anode material according to claim 1, wherein a particle size D50 of the lithium-doped silicon oxide composite anode material is in a range of 2 μm to 15 μm, and a particle size D90 of the lithium-doped silicon oxide composite anode material is in a range of 5 μm to 25 μm.

12. The lithium-doped silicon oxide composite anode material according to claim 1, wherein an initial Coulombic efficiency at 0.8V cutoff potential of the lithium-doped silicon oxide composite anode material is greater than 84%.

13. The lithium-doped silicon oxide composite anode material according to claim 1, wherein a reversible specific capacity at 0.8V cutoff potential of the lithium-doped silicon oxide composite anode material is greater than 1300 mAh/g.

14. A preparation method of the lithium-doped silicon oxide composite anode material according to claim 1, comprising steps of: S1, mixing a silicon oxide SiO.sub.x, a lithium source with a Li.sub.2SiO.sub.3 nucleating agent by a solid-phase mixing mode to form a pre-lithiated precursor; S2, carrying out heat treatment on the pre-lithiated precursor under a vacuum or non-oxidizing atmosphere, and then depolymerizing and screening the pre-lithiated precursor to obtain a compound powder; and S3, carrying out impurity removal and modification on the compound powder formed in Step S2 to obtain a lithium-doped silicon oxide composite anode material.

15. The preparation method of the lithium-doped silicon oxide composite anode material according to claim 14, wherein, by mass fraction, 100 parts of the silicon oxide SiO.sub.x, 5 to 20 parts of the lithium source, and 0.02 to 1 part of the Li.sub.2SiO.sub.3 nucleating agent are included.

16. The preparation method of the lithium-doped silicon oxide composite anode material according to claim 14, wherein the Li.sub.2SiO.sub.3 nucleating agent comprises a rare earth metal oxide.

17. The preparation method of the lithium-doped silicon oxide composite anode material according to claim 14, wherein the Li.sub.2SiO.sub.3 nucleating agent comprises at least one of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide and yttrium oxide.

18. The preparation method of the lithium-doped silicon oxide composite anode material according to claim 14, wherein in the silicon oxide SiO.sub.x, 0.7≤x≤1.3.

19. The preparation method of the lithium-doped silicon oxide composite anode material according to claim 14, wherein the silicon oxide SiO.sub.x is uncoated with carbon.

20. The preparation method of the lithium-doped silicon oxide composite anode material according to claim 14, wherein the silicon oxide SiO.sub.x is coated with carbon by either of gas-phase coating and solid-phase coating, and a mass percentage of a coated carbon in the silicon oxide SiO.sub.x is 0.1% to 6%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings facilitate an understanding of the various embodiments of this invention. In such drawings:

[0044] FIG. 1 is an XRD pattern of the material prepared in Embodiment 1-2 according to the present invention;

[0045] FIG. 2 is an XRD pattern of the material prepared in Embodiment 2-3 according to the present invention;

[0046] FIG. 3 is a scanning electron microscope (SEM) photograph of the material prepared in Embodiment 2-3 according to the present invention;

[0047] FIG. 4 is an initial charge-discharge curve chart of the material prepared in Embodiment 2-3 according to the present invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

[0048] The embodiments of the invention are described below by specific concrete examples, and persons skilled in the art can easily understand other advantages and functions of the invention from the contents disclosed in this specification. The invention may also be implemented or applied in other specific embodiments, and the details in this specification may also be modified or changed based on different points of view and applications without deviating from the spirit of the invention.

[0049] In order to better understand the invention, the following embodiments of the invention are further explained, which are not limited here however.

[0050] As a first aspect, the present invention provides a lithium-doped silicon oxide composite anode material with high initial Coulombic efficiency, which includes nano-silicon, lithium silicate and a conductive carbon layer, and optionally, may include a water-resistant coating at the surface. The diffraction peak intensity of Li.sub.2Si.sub.2O.sub.5(111) with 2θ being 24.7±0.2° in an XRD (X-Ray Diffraction) pattern of the lithium-doped silicon oxide composite anode material is I1, the diffraction peak intensity of Li.sub.2SiO.sub.3(111) with 2θ being 26.8±0.3° in the XRD pattern is I2, and I1/I2<0.25.

[0051] Furthermore, for the lithium-doped silicon oxide composite anode material with high initial Coulombic efficiency, the diffraction peak area of Li.sub.2SiO.sub.3(111) with 2θ being 26.8±0.3° in the XRD pattern of the lithium-doped silicon oxide composite anode material is A1, and the diffraction peak area of Si(111) with 2θ being 28.4±0.3° in the XRD pattern is A2, and A2/A1≥1.0.

[0052] As a preferable embodiment of the present invention, the lithium-doped silicon oxide composite anode material has a core-shell structure including a core and a shell, the core includes the nano-silicon and the lithium silicate, the lithium silicate includes either or both of Li.sub.2SiO.sub.3 and Li.sub.2Si.sub.2O.sub.5, and the shell includes a conductive carbon layer and/or a water-resistant coating distributed on the surface of the core.

[0053] In an exemplary embodiment, the diffraction peak intensity of Li.sub.2Si.sub.2O.sub.5(111) with 2θ being 24.7±0.2° in the XRD pattern of the lithium-doped silicon oxide composite anode material is I1, the diffraction peak intensity of Li.sub.2SiO.sub.3(111) with 2θ being 26.8±0.3° in the XRD pattern is I2, and I1/I2<0.25.

[0054] Furthermore, the nano-silicon is elemental silicon, and an average grain size of the nano-silicon is in a range of 3 nm to 20 nm, preferably 3 nm to 10 nm, and more preferably 4 nm to 8 nm.

[0055] Furthermore, with the total mass of the lithium-doped silicon oxide composite anode material being 100 wt %, the mass percentage of the carbon material is 0.5 wt % to 10 wt %, such as 0.5 wt %, 1 wt %, 2 wt %, 2.5 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt % or 10 wt %, etc, and further preferably is 2 wt % to 6 wt %. Furthermore, the lithium-doped silicon oxide composite anode material with high initial Coulombic efficiency has a particle size D50 of 2 μm to 15 μm and a particle size D90 of 5 μm to 25 μm.

[0056] As a second aspect, the present invention provides a preparation method of the lithium-doped silicon oxide composite anode material with high initial Coulombic efficiency mentioned above, which should not be construed as a limitation of the technical solution of the invention however. The method includes the following steps: [0057] S1, mixing a silicon oxide SiO.sub.x, a lithium source with a Li.sub.2SiO.sub.3 nucleating agent by a solid-phase mixing mode to form a pre-lithiated precursor; [0058] S2, carrying out heat treatment on the pre-lithiated precursor under a vacuum or non-oxidizing atmosphere, and then depolymerizing and screening the pre-lithiated precursor to obtain a compound powder; and [0059] S3, carrying out impurity removal and modification on the compound powder formed in Step S2 to obtain an intermediate of a lithium-doped silicon oxide composite anode material; and [0060] S4, modifying the intermediate in Step S3 with a water-resistant coating to obtain a lithium-doped silicon oxide composite anode material.

[0061] Furthermore, in Step S1, by mass fraction, 100 parts of silicon oxide SiO.sub.x, 5 to 20 parts of lithium source, 0.02 to 1 part of Li.sub.2SiO.sub.3 nucleating agent are included.

[0062] Furthermore, in the silicon oxide SiO.sub.x, 0.7≤x≤1.3.

[0063] Furthermore, the silicon oxide SiO.sub.x may be coated or uncoated with carbon. The carbon coating method may be gas-phase coating or solid-phase coating, and a mass percentage of a coated carbon in the silicon oxide SiO.sub.x is 0 to 6%.

[0064] Furthermore, organic carbon source gases used in the gas-phase coating may include at least one of methane, ethylene, acetylene, benzene, toluene, xylene, styrene and phenol.

[0065] Furthermore, the method of gas-phase coating includes the following steps: placing the silicon oxide in a rotary furnace, introducing a protective atmosphere into the rotary furnace, heating to 600° C. to 1000° C., introducing an organic carbon source gas, holding the temperature for 0.5 h to 8 h, and then cooling to obtain a carbon-coated silicon oxide.

[0066] Furthermore, the carbon source in the solid-phase coating includes at least one of asphalt, polyethylene powder, saccharides, and organic acid.

[0067] Furthermore, the solid-phase coating includes the following steps: mixing the silicon oxide and a carbon source in a mixer at a speed of 300 rpm to 1500 rpm for 0.5 h to 4 h to obtain a carbon source-containing mixture, then placing the carbon source-containing mixture in a carbonization furnace for carbonization at a temperature of 600° C. to 1000° C. for 2 h to 8 h, and then cooling and discharging to obtain the carbon-coated silicon oxide composite material.

[0068] Furthermore, the lithium sources include at least one of lithium hydride, lithium alkylide, lithium metal, lithium aluminum hydride, lithium amide, lithium nitride, lithium carbide, lithium silicide and lithium borohydride.

[0069] Furthermore, the Li.sub.2SiO.sub.3 nucleating agent includes at least one rare earth metal oxide.

[0070] Furthermore, the rare earth metal oxide may be selected from 15 lanthanide oxides with atomic numbers of 57 to 71 in the periodic table, and 17 oxides of scandium and yttrium with chemical properties similar to the lanthanide elements, and further preferably includes at least one of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide and yttrium oxide.

[0071] Furthermore, a mixing time is 0.5 h to 10 h, a tool clearance width is 0.01 cm to 0.5 cm, and the mixer has a speed of 800 rpm to 2500 rpm.

[0072] Furthermore, the heat treatment in Step S2 is carried out at temperature of 550° C. to 900° C., for example, 550° C., 600° C., 650° C., 700° C., 750° C., 800° C., 850° C. or 900° C., and the treatment time is 2 h to 8 h. Preferably, the temperature of the heat treatment is 600° C. to 800° C., and the treatment time is 2 h to 5 h.

[0073] Furthermore, the heat treatment is carried out in a non-oxidizing atmosphere, such as in an inert gas atmosphere preferably. The inert gas includes at least one of helium and argon.

[0074] Furthermore, the powder material has a particle size D50 of 2 μm to 15 μm, a particle size D90 of 5 μm to 25 μm, and preferably, the particle size D50 is 3 μm to 10 μm, and the particle size D90 is 9 μm to 15 μm.

[0075] Furthermore, the impurity removal and modification in Step S3 is washing, and the composite powder prepared in Step S2 is soaked in solution A to remove active lithium from the surface of the lithium-containing silicide particles. The solution A may include one of alcohol, weak alkalis, weak acid and water, or a mixture of water and at least one of alcohol, weak alkalis and weak acid.

[0076] Furthermore, after the composite powder is soaked in the solution A, solid-liquid separation is carried out by centrifugation, extraction filtration or pressure filtration.

[0077] Furthermore, the solid obtained after solid-liquid separation is dried. A drying atmosphere may be air, a vacuum atmosphere or a non-oxidizing atmosphere. A drying temperature is 40° C. to 150° C., preferably 40° C. to 100° C. A drying time is 6 h to 48 h, and preferably 6 h to 24 h.

[0078] Furthermore, the water-resistant coating in Step S4 may be a hydrophobic polymer or a water-resistant inorganic substance, and preferably is a carbon coating. The carbon coating is coated on the surface of the core by either gas-phase coating or solid-phase coating, and preferably by gas-phase coating. The water-resistant coating is accounted for 0.5% to 4% of the mass of the composite anode material.

[0079] Furthermore, when the water-resistant coating is a carbon coating by gas-phase coating, the organic carbon source gases used in the gas-phase coating may include at least one of methane, ethylene, acetylene, benzene, toluene, xylene, styrene and phenol. The method of the gas-phase coating includes the following steps: placing the silicon oxide in a rotary furnace, introducing a protective atmosphere into the rotary furnace, heating to 600° C. to 1000° C., introducing an organic carbon source gas, holding the temperature for 0.5 h to 8 h, and then cooling to obtain a lithium-doped silicon oxide composite anode material with high initial Coulombic efficiency with a water-resistant coating.

[0080] As a third aspect, the present invention provides a lithium-ion battery including a lithium-doped silicon oxide composite anode material with high initial Coulombic efficiency according to the first aspect.

Comparative Example 1—Lithium-Doped Silicon Oxide Composite Anode Material (A2/A1≥0.0, I1/I2>0.25)

[0081] S1, 100 parts by mass fraction of silicon oxide powder SiO.sub.0.7 that was uncoated with carbon and had a particle size D50 of 4.8 μm and a particle size D90 of 8.0 μm, and 20 parts by mass fraction of lithium amide were weighed, and subjected to VC mixing at a mixing speed of 600 rpm for a mixing time of 2 h, and a pre-lithiated precursor was obtained after mixing.

[0082] S2, the pre-lithiated precursor was placed in a box furnace and heat treated at a temperature of 550° C. for a holding time of 4 h, under an argon atmosphere. The material was cooled, and then depolymerized and screened to obtain a composite powder.

[0083] S3, the composite powder prepared in Step S2 was washed by a washing solvent of deionized water, with a mass ratio of the water and the composite power being 3:1, at a stirring speed of 300 rpm for a stirring time of 2 h. And then solid-liquid separation was carried out by suction filtration to obtain a wet mud material with a certain moisture content, and then the wet mud material was placed into a vacuum drying oven for drying at 80° C. for a drying time of 12 h, to obtain an intermediate of lithium-doped silicon oxide composite anode material.

[0084] S4, the intermediate prepared in Step S3 was coated with carbon by chemical vapor deposition, and then was placed in a CVD rotary furnace, with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 800° C. for 0.5 h. The material was then cooled and discharged, depolymerized, and screened for 400 meshes, to obtain a lithium-doped silicon oxide composite anode material, wherein the carbon content of the composite anode material was 0.5%.

Comparative Example 2—Lithium-Doped Silicon Oxide Composite Anode Material (A2/A1≥1.0, I1/I2>0.25)

[0085] Raw material preparation: silicon oxide powder SiO.sub.0.89 with a particle size D50 of 2.5 μm and a particle size D90 of 5.0 μm was coated with carbon by chemical vapor deposition. The powder SiO.sub.0.89 was placed in a CVD rotary furnace with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 850° C. for 3.0 h. The material was then cooled and discharged to obtain a carbon-coated silicon oxide materia, wherein the carbon-coated amount was 4%.

[0086] S1, 100 parts by mass fraction of silicon oxide material prepared by the mentioned-above method and 12.5 parts by mass fraction of lithium hydride were weighed, and subjected to VC mixing at a mixing speed of 400 rpm for a mixing time of 3 h, and a pre-lithiated precursor was obtained after mixing.

[0087] S2, the pre-lithiated precursor was placed in a box furnace and heat treated at a temperature of 680° C. for a holding time of 8 h, under a nitrogen atmosphere. The material was cooled, and then depolymerized and screened to obtain a composite powder.

[0088] S3, the composite powder prepared in Step S2 was washed by a washing solvent of deionized water, with a mass ratio of the water and the composite power being 6:1, at a stirring speed of 500 rpm for a stirring time of 2 h. And then solid-liquid separation was carried out by press filtration, after that, the material was washed with anhydrous ethanol for 3 times to obtain a wet mud material with a certain moisture content, and then the wet mud material was placed in an air blast drying oven for drying at 80° C., for a drying time of 16 h, to obtain an intermediate of lithium-doped silicon oxide composite anode material.

[0089] S4, the intermediate prepared in Step S3 was coated with carbon by chemical vapor deposition, and then was placed in a CVD rotary furnace, with ethylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 850° C. for 1 h. The material was cooled and discharged, depolymerized, and screened for 400 meshes, to obtain a lithium-doped silicon oxide composite anode material, wherein the carbon content of the composite anode material was 6%.

Comparative Example 3—Lithium-Doped Silicon Oxide Composite Anode Material (A2/A1≥1.0, I1/I2>0.25)

[0090] Raw material preparation: silicon oxide powder SiO.sub.0.95 with a particle size D50 of 10.0 μm and a particle size D90 of 25.0 μm was coated with carbon by chemical vapor deposition. The powder SiO.sub.0.95 was placed in a CVD rotary furnace with methane as the carbon source and nitrogen as the protective atmosphere, and deposited at 1000° C. for 2.0 h. The material was then cooled and discharged to obtain a carbon-coated silicon oxide material, wherein the carbon-coated amount was 3%.

[0091] S1, 100 parts by mass fraction of silicon oxide material prepared by the mentioned-above method and 5 parts by mass fraction of lithium nitride were weighed, and subjected to VC mixing at a mixing speed of 400 rpm for a mixing time of 3 h, and a pre-lithiated precursor was obtained after mixing.

[0092] S2, the pre-lithiated precursor was placed in a box furnace and heat treated at a temperature of 900° C. for a holding time of 3 h, under an argon atmosphere. The material was cooled, and then depolymerized and screened to obtain a composite powder.

[0093] S3, the composite powder prepared in Step S2 was washed by a washing solvent of deionized water, with a mass ratio of the water and the composite power being 3:1, at a stirring speed of 500 rpm for a stirring time of 2 h. And then solid-liquid separation was carried out by press filtration, after that, the material was washed with anhydrous ethanol for 3 times to obtain a wet mud material with a certain moisture content, and then the wet mud material was placed in an air blast drying oven for drying at 80° C., for a drying time of 16 h, to obtain an intermediate of lithium-doped silicon oxide composite anode material.

[0094] S4, the intermediate prepared in Step S3 was coated with carbon by chemical vapor deposition, and then was placed in a CVD rotary furnace, with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 800° C. for 1 h. The material was cooled and discharged, depolymerized, and screened for 400 meshes, to obtain a lithium-doped silicon oxide composite anode material, wherein the carbon content of the composite anode material was 4.5%.

Comparative Example 4—Lithium-Doped Silicon Oxide Composite Anode Material (A2/A1≥1.0, I1/I2>0.25)

[0095] Raw material preparation: silicon oxide powder SiO.sub.1.3 with a particle size D50 of 6.0 μm and a particle size D90 of 10.0 μm was coated with carbon by chemical vapor deposition. The powder SiO.sub.1.3 and asphalt at a mass percentage of 100:10 were weighed, and subjected to VC mixing at a mixing speed of 500 rpm for a mixing time of 3 h. The material was placed to a roller kiln for carbonization after uniform mixing, at a carbonization temperature of 900° C. for a holding time of 5 h. The material was then cooled and discharged to obtain a carbon-coated silicon oxide material, wherein the carbon-coated amount was 6%.

[0096] S1, 100 parts by mass fraction of silicon oxide material prepared by the mentioned-above method and 10.8 parts by mass fraction of lithium alkylide were weighed, and subjected to VC mixing at a mixing speed of 600 rpm for a mixing time of 2 h, and a pre-lithiated precursor was obtained after mixing.

[0097] S2, the pre-lithiated precursor was placed in a box furnace and heat treated at a temperature of 800° C. for a holding time of 5 h, under a nitrogen atmosphere. The material was cooled, and then depolymerized and screened to obtain a composite powder.

[0098] S3, the composite powder prepared in Step S2 was washed by a washing solvent of deionized water, with a mass ratio of the water and the composite power being 6:1, at a stirring speed of 500 rpm for a stirring time of 2 h. And then solid-liquid separation was carried out by press filtration, to obtain a wet mud material with a certain moisture content, and then the wet mud material was placed in an air blast drying oven for drying at 80° C., for a drying time of 16 h, to obtain an intermediate of lithium-doped silicon oxide composite anode material.

[0099] S4, the intermediate prepared in Step S3 was coated with carbon by chemical vapor deposition, and then was placed in a CVD rotary furnace, with ethylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 850° C. for 2 h. The material was cooled and discharged, depolymerized, and screened for 400 meshes, to obtain a lithium-doped silicon oxide composite anode material, wherein the carbon content of the composite anode material was 10%.

[0100] The specific process parameters of the lithium-doped silicon oxide composite anode materials prepared in Comparative examples 1-4 are shown in Table 1.

TABLE-US-00001 TABLE 1 Specific process parameters in Comparative examples 1-4 Carbon Carbon coating coating Treatment O/Si in of silicon method temperature Heat silicon oxide of silicon Lithium in S2 treatment oxide (wt %) oxide source (° C.) atmosphere Comparative 0.7 0 None Lithium 550 Ar example 1 amide Comparative 0.89 4 Gas-phase Lithium 680 N.sub.2 example 2 coating hydride Comparative 0.95 3 Gas-phase Lithium 900 Ar example 3 coating nitride Comparative 1.3 6 Solid-phase Lithium 800 N.sub.2 example 4 coating alkylide

[0101] The dosing parameters of the lithium-doped silicon oxide composite anode materials prepared in Comparative examples 1-4 are shown in Table 2.

TABLE-US-00002 TABLE 2 Dosing parameters in Comparative examples 1-4 Parts by mass fraction Parts by mass fraction of silicon oxide of lithium source Comparative 100 20.0 example 1 Comparative 100 12.5 example 2 Comparative 100 5.0 example 3 Comparative 100 10.8 example 4

[0102] The following embodiments adopt the same processing steps and parameters as the corresponding Comparative example. The difference is that, the present embodiments additionally adds Li.sub.2SiO.sub.3 nucleating agent when mixing, and the addition method and the addition amount of the nucleating agent are shown in Table 3.

TABLE-US-00003 TABLE 3 Addition method and addition amount of nucleating agent in Embodiments 1 to 4 Referenced comparative Addition method and addition amount of example Li.sub.2SiO.sub.3 nucleating agent Embodiment Comparative 0.15 wt % lanthanum oxide 1-1 example 1 Embodiment Comparative 1.0 wt % praseodymium oxide 1-2 example 1 Embodiment Comparative 0.02 wt % neodymium oxide 1-3 example 1 Embodiment Comparative 0.15 wt % neodymium oxide and 0.15 wt % 2-1 example 2 lanthanum oxide Embodiment Comparative 0.22 wt % cerium oxide 2-2 example 2 Embodiment Comparative 0.10 wt % yttrium oxide, 0.10 wt % 2-3 example 12 neodymium oxide and 0.20 wt % lanthanum oxide Embodiment Comparative 0.20 wt % yttrium oxide 3-1 example 3 Embodiment Comparative 0.10 wt % praseodymium oxide 3-2 example3 Embodiment Comparative 0.20 wt % neodymium oxide 3-3 example 3 Embodiment Comparative 0.10 wt % cerium oxide and 0.25 wt % 4-1 example 4 scandium oxide Embodiment Comparative 0.35 wt % scandium oxide 4-2 example 4 Embodiment Comparative 0.30 wt % praseodymium oxide and 4-3 example 4 0.35 wt % neodymium oxide

Comparative Example 5—Lithium-Doped Silicon Oxide Composite Anode Material (A2/A1<1.0, I1/I2≥0.25)

[0103] Raw material preparation: silicon oxide powder SiO.sub.1.1 with a particle size D50 of 2.5 μm and a particle size D90 of 5.0 μm was coated with carbon by chemical vapor deposition. The powder SiO.sub.1.1 was placed in a CVD rotary furnace with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 850° C. for 3.0 h. The material was then cooled and discharged to obtain a carbon-coated silicon oxide material, wherein the carbon-coated amount was 4%.

[0104] S1, 100 parts by mass fraction of silicon oxide material prepared by the mentioned-above method and 12 parts by mass fraction of lithium hydride were weighed, and subjected to VC mixing at a mixing speed of 400 rpm for a mixing time of 3 h, and a pre-lithiated precursor was obtained after mixing.

[0105] S2, the pre-lithiated precursor was placed in a box furnace and heat treated at a temperature of 500° C. for a holding time of 8 h, under a nitrogen atmosphere. The material was cooled, and then depolymerized and screened to obtain a composite powder.

[0106] S3, the composite powder prepared in Step S2 was washed by a washing solvent of deionized water, with a mass ratio of the water and the composite power being 6:1, at a stirring speed of 500 rpm, for a stirring time of 2 h. And then solid-liquid separation was carried out by press filtration, after that, the material was washed with anhydrous ethanol for 3 times to obtain a wet mud material with a certain moisture content, and then the wet mud material was placed in an air blast drying oven for drying at 80° C., for a drying time of 16 h, to obtain an intermediate of lithium-doped silicon oxide composite anode material.

[0107] S4, the intermediate prepared in Step S3 was coated with carbon by chemical vapor deposition, and then was placed in a CVD rotary furnace, with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 700° C. for 0.5 h. The material was cooled and discharged, depolymerized, and screened for 400 meshes, to obtain a lithium-doped silicon oxide composite anode material, wherein the carbon content of the composite anode material was 4.5%.

Comparative Example 6—Lithium-Doped Silicon Oxide Composite Anode Material (A2/A1<1.0, I1/I2≥0.25)

[0108] Raw material preparation: silicon oxide powder SiO.sub.1.0 with a particle size D50 of 2.5 μm and a particle size D90 of 5.0 μm was coated with carbon by chemical vapor deposition. The powder SiO.sub.1.1 was placed in a CVD rotary furnace with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 850° C. for 1.5 h. The material was then cooled and discharged to obtain a carbon-coated silicon oxide material, wherein the carbon-coated amount was 3%.

[0109] S1, 100 parts by mass fraction of silicon oxide material prepared by the mentioned-above method and 10 parts by mass fraction of lithium amide were weighed, and subjected to VC mixing at a mixing speed of 400 rpm for a mixing time of 3 h, and a pre-lithiated precursor was obtained after mixing.

[0110] S2, the pre-lithiated precursor was placed in a box furnace and heat treated at a temperature of 420° C. for a holding time of 16 h, under a nitrogen atmosphere. The material was cooled, and then depolymerized and screened to obtain a composite powder.

[0111] S3, the composite powder prepared in Step S2 was washed by a washing solvent of deionized water, with a mass ratio of the water and the composite power being 6:1, at a stirring speed of 500 rpm, for a stirring time of 2 h. And then solid-liquid separation was carried out by press filtration, after that, the material was washed with anhydrous ethanol for 3 times to obtain a wet mud material with a certain moisture content, and then the wet mud material was placed in an air blast drying oven for drying at 80° C., for a drying time of 16 h, to obtain an intermediate of lithium-doped silicon oxide composite anode material.

[0112] S4, the intermediate prepared in Step S3 was coated with carbon by chemical vapor deposition, and then was placed in a CVD rotary furnace, with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 650° C. for 1 h. The material was cooled and discharged, depolymerized, and screened for 400 meshes, to obtain a lithium-doped silicon oxide composite anode material, wherein the carbon content of the composite anode material was 3.5%.

Comparative Example 7—Lithium-Doped Silicon Oxide Composite Anode Material (A2/A1<1.0, I1/I2<0.25)

[0113] Raw material preparation: silicon oxide powder SiO.sub.1.1 with a particle size D50 of 2.5 μm and a particle size D90 of 5.0 μm was coated with carbon by chemical vapor deposition. The powder SiO.sub.1.1 was placed in a CVD rotary furnace with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 850° C. for 3.0 h. The material was then cooled and discharged to obtain a carbon-coated silicon oxide material, wherein the carbon-coated amount was 4%.

[0114] S1, 100 parts by mass fraction of carbon-coated silicon oxide material prepared by the mentioned-above method and 12 parts by mass fraction of lithium hydride were weighed, and yttrium oxide, neodymium oxide and lanthanum oxide respectively accounted for 0.10%, 0.10% and 0.20% of the total mass of the material were added, the all were subjected to VC mixing at a mixing speed of 400 rpm for a mixing time of 3 h, and a pre-lithiated precursor was obtained after mixing.

[0115] S2, the pre-lithiated precursor was placed in a box furnace and heat treated at a temperature of 500° C. for a holding time of 8 h, under a nitrogen atmosphere. The material was cooled, and then depolymerized and screened to obtain a composite powder.

[0116] S3, the composite powder prepared in Step S2 was washed by a washing solvent of deionized water, with a mass ratio of the water and the composite power being 6:1, at a stirring speed of 500 rpm, for a stirring time of 2 h. And then solid-liquid separation was carried out by press filtration, after that, the material was washed with anhydrous ethanol for 3 times to obtain a wet mud material with a certain moisture content, and then the wet mud material was placed in an air blast drying oven for drying at 80° C., for a drying time of 16 h, to obtain an intermediate of lithium-doped silicon oxide composite anode material.

[0117] S4, the intermediate prepared in Step S3 was coated with carbon by chemical vapor deposition, and then was placed in a CVD rotary furnace, with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 700° C. for 0.5 h. The material was cooled and discharged, depolymerized, and screened for 400 meshes, to obtain a lithium-doped silicon oxide composite anode material, wherein the carbon content of the composite anode material was 4.5%.

Comparative Example 8—Lithium-Doped Silicon Oxide Composite Anode Material (A2/A1<1.0, I1/I2<0.25)

[0118] Raw material preparation: silicon oxide powder SiO.sub.1.0 with a particle size D50 of 2.5 μm and a particle size D90 of 5.0 μm was coated with carbon by chemical vapor deposition. The powder SiO.sub.1.0 was placed in a CVD rotary furnace with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 850° C. for 1.5 h. The material was then cooled and discharged to obtain a carbon-coated silicon oxide material, wherein the carbon-coated amount was 3%.

[0119] S1, 100 parts by mass fraction of carbon-coated silicon oxide material prepared by the mentioned-above method and 10 parts by mass fraction of lithium amide were weighed, and yttrium oxide, neodymium oxide and lanthanum oxide respectively accounted for 0.10%, 0.30% and 0.30% of the total mass of the material were added, the all were subjected to VC mixing at a mixing speed of 400 rpm for a mixing time of 3 h, and a pre-lithiated precursor was obtained after mixing.

[0120] S2, the pre-lithiated precursor was placed in a box furnace and heat treated at a temperature of 420° C. for a holding time of 16 h, under a nitrogen atmosphere. The material was cooled, and then depolymerized and screened to obtain a composite powder.

[0121] S3, the composite powder prepared in Step S2 was washed by a washing solvent of deionized water, with a mass ratio of the water and the composite power being 6:1, at a stirring speed of 500 rpm, for a stirring time of 2 h. And then solid-liquid separation was carried out by press filtration, after that, the material was washed with anhydrous ethanol for 3 times to obtain a wet mud material with a certain moisture content, and then the wet mud material was placed in an air blast drying oven for drying at 80° C., for a drying time of 16 h, to obtain an intermediate of lithium-doped silicon oxide composite anode material.

[0122] S4, the intermediate prepared in Step S3 was coated with carbon by chemical vapor deposition, and then was placed in a CVD rotary furnace, with acetylene as the carbon source and nitrogen as the protective atmosphere, and deposited at 650° C. for 1 h. The material was cooled and discharged, depolymerized, and screened for 400 meshes, to obtain a lithium-doped silicon oxide composite anode material, wherein the carbon content of the composite anode material was 3.5%.

[0123] Product Testing

[0124] Test Methods

[0125] 1. Crystal structure characterization: the crystal structure of the lithium-doped silicon oxide composite anode material prepared in the Embodiments and the Comparative examples was characterized. A powder diffractometer Xpert3 Powder of PANalytical in Netherlands was used for XRD tests, the test voltage was 40 KV, the test current was 40 mA, the scanning range was 10° to 90°, the scanning step was 0.008°, and the time of each step of scanning was 12 s.

[0126] The average grain size of Si in the material was characterized by an X-ray diffractometer, scanning was carried out within 10° to 90° of 2θ, then fitting was carried out within 26° to 30° of 2θ to obtain a half-peak width of a Si(111) peak, and finally, the average grain size of Si grains was calculated according to the Scherrer formula.

[0127] The diffraction peak area of Li.sub.2SiO.sub.3(111) with 2θ of 26.8±0.3° in an XRD pattern was A1, the diffraction peak area of Si(111) with 2θ of 28.4±0.3° in the XRD pattern was A2, and the ratio of A2 to A1 was calculated.

[0128] The peak area is calculated by fitting the XRD results with Jade 5.0, and the steps follow: [0129] S1, setting the 2theta in a range of 26° to 30°; [0130] S2, smoothing once, selecting a background (selecting the third option “Cubic spline” in Background function and Point Sampling), and clicking the button Apply; [0131] S3, fitting the diffraction peak of Li.sub.2SiO.sub.3(111) (2theta=26.8±0.3°) and the diffraction peak of Si(111) (2theta=28.4±0.3°), and the calculated peak areas are denoted as A1 and A2, respectively. [0132] S4, calculating a peak area ratio A2/A1.

[0133] The diffraction peak intensity of Li.sub.2Si.sub.2O.sub.5(111) with 2θ of 24.7±0.2° in the XRD pattern is I1, the diffraction peak intensity of Li.sub.2SiO.sub.3(111) with 2θ of 26.8±0.3° in the XRD pattern is I2, and the ratio I1/I2 is calculated.

[0134] The peak intensity is calculated by analyzing the XRD results with Jade 5.0, and the steps follow: [0135] S1, setting the 2theta in a range of 23° to 30°; [0136] S2, smoothing once, selecting a background (selecting the third option “Cubic spline” in Background function and Point Sampling), clicking the button Apply, then clicking the button Remove; [0137] S3, automatically marking peaks; [0138] S4, recording the diffraction peak intensity of Li.sub.2Si.sub.2O.sub.5(111) (2theta=24.7±0.2°) and the diffraction peak intensity of Li.sub.2SiO.sub.3(111) (2theta=26.8±0.3°) as I1 and I2, respectively; [0139] S5, calculating a peak intensity ratio I1/I2.

[0140] 2. Test of the first charge-discharge performance of button batteries: the lithium-doped silicon oxide composite anode materials prepared in the embodiments and the comparative examples were used as active substances to be mixed with a binder, namely an aqueous dispersion of an acrylonitrile multipolymer (LA132, solid content 15%), and a conductive agent (Super-P) according to a mass ratio of 70:10:20, a proper amount of water was added to be used as a solvent to prepare paste, and the paste was smeared on a copper foil, dried in vacuum and rolled to prepare anodes; with lithium metal as a counter electrode, CR2032 button batteries were assembled in a glove box filled with an inert gas with polypropylene microporous membranes as membranes, by means of 1 mol/L of an electrolyte which was a LiPF.sub.6 three-component mixed solvent mixed according to EC:DMC:EMC=1:1:1(v/v). The charge-discharge performance of the button batteries was tested by means of a battery test system of LANHE. Specifically, under a normal temperature, the button batteries were discharged by lithium intercalation to 0.01 V at a constant current of 0.1 C, then further discharged by lithium intercalation to 0.005 V at a constant current of 0.02 C, and finally charged by lithium deintercalation to 1.5 V at a constant current of 0.1 C. An initial Coulombic efficiency at 0.8 V and 1.5 V was respectively calculated by taking a ratio of the charging capacity at 0.8 V and 1.5 V of the discharging capacity.

[0141] Other battery performance tests are carried out according to the general testing methods of the industry. The results are shown in Table 4, Table 5 and Table 6, respectively.

TABLE-US-00004 TABLE 4 Indicator and battery performance of lithium-doped silicon oxide composite anode materials prepared in Comparative examples 1-4 Initial Grain Coulombic size of Carbon Capacity efficiency silicon content at 0.8V at I1/12 A2/A1 (nm) (%) (mAh/g) 0.8V (%) Comparative 0.25 1.78 3 0.5 1310 81.0 example 1 Comparative 0.42 1.80 6 6.0 1300 81.5 example 2 Comparative 1.00 1.74 20 4.5 1320 78.4 example 3 Comparative 0.65 1.94 9 10.0 1308 81.2 example 4

TABLE-US-00005 TABLE 5 Indicator and battery performance of lithium-doped silicon oxide composite anode materials with high initial Coulombic efficiency prepared in each embodiment Initial Referenced Capacity at Coulombic comparative 0.8 V efficiency at example I1/I2 A2/A1 (mAh/g) 0.8 V (%) Embodiment Comparative 0.03 1.27 1320 84.0 1-1 example 1 Embodiment Comparative 0.13 1.63 1325 84.5 1-2 example 1 Embodiment Comparative 0.02 1.38 1333 85.5 1-3 example 1 Embodiment Comparative 0.05 1.29 1330 84.1 2-1 example 2 Embodiment Comparative 0.24 1.65 1340 87.0 2-2 example 2 Embodiment Comparative 0.01 1.49 1334 86.0 2-3 example 2 Embodiment Comparative 0.12 1.26 1327 84.3 3-1 example 3 Embodiment Comparative 0.03 1.35 1321 84.5 3-2 example 3 Embodiment Comparative 0.07 1.44 1328 84.2 3-3 example 3 Embodiment Comparative 0.22 1.71 1330 85.3 4-1 example 4 Embodiment Comparative 0.15 1.57 1336 85.5 4-2 example 4 Embodiment Comparative 0.05 1.33 1337 86.2 4-3 example 4

TABLE-US-00006 TABLE 6 Indicator and battery performance of lithium-doped silicon oxide composite anode materials prepared in Comparative examples 5-8 Initial Grain Coulombic size of Carbon Capacity efficiency silicon content at 0.8V at I1/12 A2/A1 (nm) (%) (mAh/g) 0.8V (%) Comparative 0.27 0.71 4.1 4.5 1296 79.8 example 5 Comparative 0.87 0.89 3.5 3.5 1287 79.5 example 6 Comparative 0.15 0.83 4.0 4.5 1307 81.9 example 7 Comparative 0.24 0.91 3.4 3.5 1318 81.4 example 8

[0142] In Table 4, Groups 1 to 4 refer to the data of the product obtained in Comparative examples 1 to 4 respectively. In Table 5, Groups 1 to 3 refer to the data of the product obtained in Embodiment 1, Groups 4 to 6 refer to the data of the product obtained in Embodiment 2, Groups 7 to 9 refer to the data of the product obtained in Embodiment 3, and Groups 10 to 12 refer to the data of the product obtained in Embodiment 4. In Table 6, Groups 1 to 4 refer to the data of the product obtained in Comparative examples 5 to 8, respectively.

[0143] According to the records in Tables 4 to 6, comparing the Comparative example 1 with Embodiments 1-1 to 1-3, it's seen that, the composite anode material in the embodiments has decreased A2/A1 ratio, significant reduced I1/I2 ratio, increased capacity at 0.8V, and as well as improved initial Coulombic efficiency; comparing the Comparative example 2 with Embodiments 2-1 to 2-3, it's seen that, the composite anode material in the embodiments has increased capacity at 0.8 V, and as well as improved initial Coulombic efficiency; comparing the Comparative example 3 with Embodiments 3-1 to 3-3, it's seen that, the composite anode material in the embodiments has increased capacity at 0.8 V, and as well as improved initial Coulombic efficiency; and comparing the Comparative example 4 with Embodiments 4-1 to 4-3, it's seen that, the Embodiments 4-1 to 4-3 including an oxide nucleation agent with single or composite component can significantly increase the capacity and the initial Coulombic efficiency in material battery performance. From Comparative examples 5 and 8, it's seen that, the capacity and the initial Coulombic efficiency of the material battery performance are lower than those of the material provided by the present invention, when the composition of the composite anode material is beyond the scope of the invention, such as A2/A1<1.0, I1/I2<0.25; and the foregoing capacity and initial Coulombic efficiency are further weakened when A2/A1<1.0, I1/I2≥0.25.

[0144] A lithium-doped silicon oxide composite anode material with a specific parameter range (I1/I2<0.25, A2/A1≥1.0) is prepared in the present invention according to specific preparation process steps and parameters, thus a composite anode with higher initial Coulombic efficiency can be obtained, which has a promoting effect on the application of such materials in high energy density lithium-ion batteries.

[0145] Several preferable specific implementation modes and embodiments of the present invention are described in detail above, However, the present invention is not limited to the above-mentioned implementation modes and embodiments and embodiments. Within the scope of knowledge possessed by a person skilled in the art, various modifications or changes can be made without departing from the concept of the present invention.