Compound, preparation method therefore, and use in lithium ion secondary battery

Patent metadata

Field	Value
Publication number	US-11929484-B2
Application number	US-201816476471-A
Country	US
Kind code	B2
Filing date	Feb 27, 2018
Priority date	Mar 6, 2017
Publication date	Mar 12, 2024
Grant date	Mar 12, 2024

Abstract

Disclosed in the present application is a compound, comprising nano silicon, a lithium-containing compound and a carbon coating, or comprising nano silicon, silicon oxide, a lithium-containing compound, and a carbon coating. The method comprises: (1) solid-phase mixing of carbon coated silicon oxide with a lithium source; and (2) preforming heat-treatment of the pre-lithium precursor obtained in step (1) in a vacuum or non-oxidising atmosphere to obtain a compound. The method is simple, and has low equipment requirements and low costs; the obtained compound has a stable structure and the structure and properties do not deteriorate during long-term storage, a battery made of cathode material containing said compound exhibits high delithiation capacity, high initial coulombic efficiency, and good recycling properties, the charging capacity is over 1920 mAh/g, the discharging capacity is over 1768 mAh/g, and the initial capacity is over 90.2%.

First claim

What is claimed is:

1. A composite, which is a Si—O—C—Li composite comprising nano-silicon, a silicon-oxygen-lithium compound selected from the group consisting of Li2SiO3, Li4SiO4, Li2Si2O5, Li2Si3O7 and combinations thereof, silicon oxide and a carbon coating,
wherein the silicon-oxygen-lithium compound is partially crystalline, the nano-silicon is dispersed in the silicon-oxygen-lithium compound to form fusion particles of the nano-silicon and the silicon-oxygen-lithium compound without clear interface between the nano-silicon and the silicon-oxygen-lithium compound, and the fusion particles are uniformly dispersed in the silicon oxide to form a composite particle wherein all directions of the fusion particles are surrounded by the silicon oxide matrix, forming a sea-island structure with the fusion particles as islands and with the silicon oxide as the sea, with the carbon coating coated on the surface of the composite particles;
wherein the nano-silicon and the silicon-oxygen-lithium compound are produced by in-situ redox growth.

2. The composite according to claim 1 , wherein the silicon oxide has a chemical composition of SiOx, in which 0<x<2.

3. The composite according to claim 1 , wherein the nano-silicon is grown from in-situ reduction of a carbon-coated silicon oxide, and the carbon-coated silicon oxide comprises a silicon oxide and a carbon coating coated on the surface of the silicon oxide.

4. The composite according to claim 1 , wherein the carbon coating comprises a carbon matrix and carbon nanotubes and/or graphene sheets embedded in the carbon matrix, and the carbon matrix is obtained by cracking an organic carbon source via carbonization treatment.

5. The composite according to claim 1 , wherein based on 100 wt % of the total mass of the composite, the carbon coating has a mass percent of 0.1-50 wt %.

6. A preparation method of a composite, wherein the composite is a Si—O—C—Li composite comprising nano-silicon, a silicon-oxygen-lithium compound selected from the group consisting of Li2SiO3, Li4SiO4, Li2Si2O5, Li2Si3O7 and combinations thereof, silicon oxide and a carbon coating:
wherein the silicon-oxygen-lithium compound is partially crystalline, the nano-silicon is dispersed in the silicon-oxygen-lithium compound to form fusion particles of the nano-silicon and the silicon-oxygen-lithium compound without clear interface between the nano-silicon and the silicon-oxygen-lithium compound, and the fusion particles are uniformly dispersed in the silicon oxide to form a composite particle wherein all directions of the fusion particles are surrounded by the silicon oxide matrix, forming a sea-island structure with the fusion particles as islands and with the silicon oxide as the sea, with the carbon coating coated on the surface of the composite particles; and
wherein the nano-silicon and the silicon-oxygen-lithium compound are produced by in-situ redox growth;
the preparation method comprises the following steps:
(1) blending a carbon-coated silicon oxide and a lithium source by solid-phase mixing mode to implement primary treatment to form a pre-lithium precursor; wherein the lithium source undergoes a redox reaction with the silicon oxide in the interior of the carbon coating, and in-situ redox growth results in nano-silicon and a silicon-oxygen-lithium compound, and there is no clear interface between the nano-silicon and the silicon-oxygen- lithium compound; wherein the solid-phase mixing mode comprises any one selected from the group consisting of ball milling, VC mixing, fusion, mixing, kneading, dispersion, or a combination of at least two selected therefrom, and the solid-phase mixing mode is performed in vacuum condition;
(2) heat-treating the pre-lithium precursor in vacuum or a non-oxidizing atmosphere to implement structural adjustment and secondary treatment to form the Si—O—C—Li composite according to any of claim 1 , wherein the lithium source infiltrates into the interior of the carbon-coated silicon oxide to react in situ with the silicon oxide to produce nano-silicon and the Si—O—C—Li composite, wherein the temperature of the heat-treating is 160-1000° C., and the time for the heat-treating is 2-12 h;
(3) subjecting the composite to surface treatment to compound the residual lithium or silicon-oxygen-lithium compound on the surface to the interior to obtain a surface- treated composite; the manner of compounding the residual lithium or the silicon-oxygen- lithium compound is any one selected from the group consisting of coating, cladding, film plating, spraying, and a combination of at least two selected therefrom; the manner of impurity removal is any one selected from the group consisting of washing, impregnation, and a combination of at least two selected therefrom, the washing or impregnation is carried out using an impurity removing solution.

7. The method according to claim 6 , further comprising step ( 3 ) of subjecting the composite to surface treatment after the heat treatment of step ( 2 ) to obtain a surface-treated composite.

8. The method according to claim 6 , wherein the lithium source in step ( 1 ) is any one selected from the group consisting of lithium-containing compound with strong alkalinity, lithium-containing compound with reducibility, elemental lithium, and a combination of at least two selected therefrom.

9. The method according to claim 6 , wherein the carbon-coated silicon oxide in step ( 1 ) comprises a silicon oxide and a carbon coating coated on the surface of the silicon oxide.

10. The method according to claim 9 , wherein the carbon coating comprises a carbon matrix and carbon nanotubes and/or graphene sheets embedded in the carbon matrix, and the carbon matrix is obtained by cracking an organic carbon source via carbonization treatment.

11. The method according to claim 10 , wherein the temperature of the carbonization treatment is 500-1300° C.;
the time for the carbonization treatment is 1-10 h.

12. The method according to claim 6 , wherein in the carbon-coated silicon oxide in step ( 1 ), the mass ratio of the silicon oxide to the carbon coating is 100:(2-15);
the mass ratio of the carbon-coated silicon oxide to the lithium source in step ( 1 ) is 1:(0.01-0.3).

13. The method according to claim 6 , wherein the solid-phase mixing mode in step ( 1 ) comprises any one selected from the group consisting of ball milling, VC mixing, fusion, mixing, kneading, dispersion, and a combination of at least two selected therefrom;
the time for the blending in step ( 1 ) is 2-12 h.

14. The method according to claim 6 , wherein the non-oxidizing atmosphere in step ( 2 ) comprises any one selected from the group consisting of hydrogen atmosphere, nitrogen atmosphere, helium atmosphere, neon atmosphere, argon atmosphere, krypton atmosphere, xenon atmosphere, and a combination of at least two selected therefrom;
the temperature of the heat-treating in step ( 2 ) is 160-1000° C.;
the time for the heat-treating in step ( 2 ) is 2-12 h.

15. The method according to claim 6 , wherein the manner of the surface treatment in step ( 3 ) comprises any one selected from the group consisting of impurity removal, cladding, surface functional group alteration, coating, film plating, spraying, and a combination of at least two selected therefrom.

16. A lithium-ion secondary battery comprising the composite according to claim 1 .

Assignees

• Btr New Mat Group Co Ltd

Inventors

• Pang Chunlei
• Qu Lijuan
• Ren Jianguo
• Yue Min

Classifications

• H01M4/131 Primary

  Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title

• C01B33/025

  with carbon or a solid carbonaceous material, i.e. carbo-thermal process · CPC title

• C01B33/12

  Silica; Hydrates thereof, e.g. lepidoic silicic acid · CPC title

• H01M4/364

  as mixtures · CPC title

• H01M4/366 Primary

  as layered products · CPC title