Nano-silicon composite material and preparation method thereof, electrode material, and battery
In fields related to battery cathode material technologies, a nano-silicon composite material and a preparation method thereof, an electrode material, and a battery are provided to resolve large volume expansion of a cathode material of a battery and a serious side reaction with an electrolyte. The nano-silicon composite material includes a core, a first coating layer, and a second coating layer. The core includes a nano-silicon crystal. The first coating layer covers a surface of the core. The first coating layer is of a porous structure. A material of the first coating layer includes bisilicate and silicon oxide in a deoxidized state. The second coating layer covers a surface of the first coating layer. A material of the second coating layer includes silicon dioxide in a deoxidized state.
1 . A nano-silicon composite material comprising:
a core comprising a nano-silicon crystal;
a first coating layer covering a surface of the core, wherein the first coating layer has a porous structure, and a material of the first coating layer comprises bisilicate and silicon oxide in the deoxidized state; and
a second coating layer covering a surface of the first coating layer, wherein a material of the second coating layer comprises silicon dioxide in the deoxidized state.
2 . The nano-silicon composite material according to claim 1 , wherein a particle size of the nano-silicon composite material is 10 nm to 150 nm.
3 . The nano-silicon composite material according to claim 1 , wherein a particle size of the core is 10 nm to 130 nm.
4 . The nano-silicon composite material according to claim 1 , wherein a thickness of the first coating layer is 0.1 nm to 10 nm.
5 . The nano-silicon composite material according to claim 1 , wherein a thickness of the second coating layer is 0.1 nm to 10 nm.
6 . The nano-silicon composite material according to claim 1 , wherein a proportion of mass of the nano-silicon crystal to mass of the nano-silicon composite material is 70% to 85%.
7 . The nano-silicon composite material according to claim 1 , wherein a proportion a of mass of the bisilicate to mass of the nano-silicon composite material meets 0%<a≤7.5%.
8 . The nano-silicon composite material according to claim 1 , wherein a proportion b of mass of the silicon oxide to mass of the nano-silicon composite material meets 0%<b≤7.5%.
9 . The nano-silicon composite material according to claim 1 , wherein a proportion c of mass of the silicon dioxide to mass of the nano-silicon composite material meets 0%<c≤15%.
10 . The nano-silicon composite material according to claim 1 , wherein the bisilicate comprises lithium metasilicate.
11 . An electrode material comprising: a mixture of the nano-silicon composite material according to claim 1 , graphite, and carbon.
12 . The electrode material according to claim 11 , wherein a proportion of mass of the nano-silicon composite material to mass of the electrode material is 3% to 60%.
13 . A battery, comprising: an electrochemical cell, a corresponding connecting accessory, and a circuit, wherein the electrochemical cell comprises an anode, a cathode, an electrolyte, and a separator, and the cathode comprises the electrode material according to claim 11 .
14 . The nano-silicon composite material according to claim 1 , wherein the first coating layer forms a buffer when the core expands or shrinks to alleviate internal stress of the core.
15 . The nano-silicon composite material according to claim 1 , wherein:
a chemical formula of the silicon oxide in the deoxidized state is SiO 1-m , where 0<m<1; and
a chemical formula of the silicon dioxide in the deoxidized state is SiO n , where 1<n<2.
16 . A preparation method of a nano-silicon composite material, the preparation method comprising:
performing processing on silicon oxide and a metal source to obtain a mixture of nano-silicon, bisilicate, and silicon oxide in the deoxidized state; and
performing acid cleaning on and grinding the mixture of the nano-silicon, the bisilicate, and the silicon oxide in the deoxidized state to obtain the nano-silicon composite material, wherein the nano-silicon composite material comprises a core, a first coating layer covers a surface of the core, and a second coating layer covers a surface of the first coating layer, the core comprises a nano-silicon crystal, the first coating layer has a porous structure, a material of the first coating layer comprises bisilicate and the silicon oxide in the deoxidized state, and a material of the second coating layer comprises silicon dioxide in the deoxidized state.
17 . The preparation method of the nano-silicon composite material according to claim 16 , wherein the performing of the processing on the silicon oxide and the metal source comprises:
evenly mixing the silicon oxide and the metal source in a solid state at a first preset ratio, or introducing the metal source in a vapor state into the silicon oxide at a second preset ratio, and performing roasting in a furnace in an inert atmosphere or a reducing atmosphere.
18 . The preparation method of the nano-silicon composite material according to claim 17 , wherein a temperature of the furnace for performing the roasting is 300° C. to 900° C.
19 . The preparation method of the nano-silicon composite material according to claim 17 , wherein the first preset ratio is a molar ratio that is of a metal element in the metal source to a silicon element in the silicon oxide and that is 0.1 to 1.0, and the second preset ratio is the molar ratio that is of the metal element in the metal source to the silicon element in the silicon oxide and that is 0.1 to 1.0.
20 . The preparation method of the nano-silicon composite material according to claim 17 , wherein the metal source comprises a lithium source, and the lithium source comprises metal lithium or a lithium salt.
21 . The preparation method of a nano-silicon composite material according to claim 16 , wherein the metal source is an organic solvent containing a metal ion; and
the performing of the processing on the silicon oxide and the metal source comprises:
mixing, at a preset ratio, the silicon oxide and the organic solvent containing the metal ion, and reacting in an inert atmosphere or a reducing atmosphere, wherein a reaction temperature is less than 200° C.; and
cleaning and drying a reaction product.
22 . The preparation method of the nano-silicon composite material according to claim 21 , wherein the organic solvent containing the metal ion comprises an organic solvent containing a lithium ion.