CN-122025589-A - Silicon-carbon composite anode material protected by interface lithium-conducting layer and preparation method thereof

CN122025589ACN 122025589 ACN122025589 ACN 122025589ACN-122025589-A

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a silicon-carbon composite anode material protected by an interface lithium-conducting layer and a preparation method thereof. The silicon-carbon composite anode material comprises a silicon-carbon inner core and an interface lithium-conducting sublayer, wherein the inner core is composed of a porous carbon substrate and nano silicon, and the interface lithium-conducting sublayer contains a lithium-conducting compound. According to the invention, the continuous interface lithium-conducting layer is constructed on the surface of the silicon carbon in situ, so that the interfacial lithium-ion transmission dynamics of the silicon carbon material interface is obviously improved, meanwhile, the interfacial layer can be used as a rigid mechanical protection layer, the mechanical stability of the interface lithium-conducting sublayer is maintained, and the volume expansion of the silicon carbon is restrained, so that the multiplying power performance and the cycle stability of a lithium ion battery using the silicon carbon material are obviously improved, and meanwhile, the interface lithium-conducting layer is beneficial to avoiding the direct contact of the silicon carbon and a solid electrolyte, avoiding side reaction, and improving the cycle stability of the solid battery using the material.

Inventors

ZHAO YUMING
LI GE
XU DIXIN
CHEN HONGXIN
HE XIANG
YUE FENGSHU

Assignees

安徽壹金新能源科技有限公司
山西富佶新能源材料科技有限公司
江西壹金新能源科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260211

Claims (10)

1. The silicon-carbon composite anode material protected by the interface lithium-conducting layer is characterized by comprising a silicon-carbon inner core and an interface lithium-conducting layer on the surface of the silicon-carbon inner core, wherein a lithium-conducting compound in the interface lithium-conducting layer is one or a combination of more than two of Li 2 SiO 3 、Li 2 Si 2 O 5 、Li 8 SiO 6 、Li 4 SiO 4 、Li 6 Si 2 O 7 、Li 2 Si 5 O 11 , and the thickness of the interface lithium-conducting layer is 20-80 nm.
2. The silicon-carbon composite anode material protected by the interface lithium-conducting layer according to claim 1, wherein the thickness of the interface lithium-conducting layer is 30nm-50nm.
3. The interface lithium-conducting layer protected silicon-carbon composite anode material of claim 1, wherein the XRD profile of the silicon-carbon composite anode material has characteristic peaks at 2Θ = 18.8 ± 0.1 °, 24.6 ± 0.1 °, 27.0 ± 0.1 °, 33.0 ± 0.1 °, 43.2 ± 0.1 ° in addition to the characteristic peaks of silicon occurring in the 2Θ = 15-40 ° and 40-60 ° intervals.
4. A method for preparing the silicon-carbon composite anode material protected by the interface lithium-conducting layer as claimed in any one of claims 1 to 3, which is characterized by comprising the following steps: (S1) carrying out heat treatment on a silicon-carbon inner core material with an elemental silicon layer on the surface under a carbon-containing passivation gas atmosphere to carry out passivation, wherein obvious peaks appear in dQ/dV curves of the first lithium removal voltage-capacity of the silicon-carbon inner core material with the elemental silicon layer on the surface at positions of 0.3+/-0.05V and 0.45+/-0.05V, and 1.9 is more than or equal to alpha >0.64, and alpha is 0.45+/-0.05V position peak intensity/0.3+/-0.05V position peak intensity; (S2) oxidizing the passivated material in an oxygen-containing atmosphere; and (S3) carrying out lithiation treatment on the material subjected to the oxidation treatment to obtain the silicon-carbon composite anode material protected by the interface lithium-conducting layer.
5. The method according to claim 4, wherein in the step (S1), the silicon-carbon core material having the elemental silicon layer on the surface satisfies that 1.375. Gtoreq.α. Gtoreq.0.898, preferably 1.156. Gtoreq.α. Gtoreq.0.89.
6. The method according to claim 4, wherein in the step (S1), the silicon-carbon core material having the elemental silicon layer on the surface is obtained by silicon deposition of a porous carbon substrate in a mixed gas of a silane gas and a carrier gas; Further, the silane is at least one selected from monosilane, disilane, silicon tetrachloride, trichlorosilane, dichlorosilane and monochlorosilane, the silane deposition temperature is 400-700 ℃, preferably 460-650 ℃, the silane flow rate is preferably 1-10L/min, the carrier gas flow rate is 2-5 times of the silane flow rate, more preferably the porous carbon substrate is at least one selected from coconut shell-based porous carbon, bamboo-based porous carbon, coal-based porous carbon, petroleum coke-based porous carbon and synthetic resin-based porous carbon, further preferably the porous carbon substrate has a specific surface area of 1300-2900 m 2 /g, a pore volume of 0.4-1.5 cm 3 /g, a particle size of 2-2300-m 2 /g, a pore volume of 0.7-1.1-cm 3 /g, and a particle size of 5-2300-15 μm.
7. The method according to claim 4, wherein in the step (S1), the passivation gas containing carbon is at least one selected from the group consisting of C1-4 alkane, C2-4 alkene and C2-4 alkyne, and preferably the passivation temperature is 500-700 ℃ and the passivation time is 3-8 hours.
8. The process according to claim 4, wherein in the step (S2), the oxygen-containing atmosphere is oxygen or air, the oxidation temperature is 100-500 ℃, the oxidation time is 1-5 hours, preferably 200-300 ℃, and the oxidation time is 1-3 hours, and further, the oxygen content in the oxidized material is 2.4-20.6wt%, preferably 4.1-15.2wt%, more preferably 4.1-7.5wt%.
9. The method according to claim 4, wherein in the step (S3), the lithiation treatment is a liquid phase treatment or a solid phase treatment: (a) The liquid phase treatment is to immerse the oxidized material in an aromatic lithium compound solution, react for 10-30h at 20-50 ℃, remove the solvent, heat-preserving at 400-800 ℃ for 5-15h, cool to obtain, preferably, the aromatic lithium is a complex formed by the reaction of an aromatic compound and metallic lithium, the aromatic compound is at least one of benzene, biphenyl, dimethylbiphenyl, naphthalene, anthracene and Phil, the aromatic lithium compound solution is an aromatic compound, the organic solvent is obtained by the reaction of metallic lithium according to the proportion of 2-5g:50-100mL:50-100mg, and the solvent of the aromatic lithium compound solution is at least one of tetrahydrofuran, dioxane, n-hexane, benzene and toluene; (b) The solid phase treatment is to mix the oxidized material with an inorganic lithiation reagent, and heat-preserving the mixture at 400-800 ℃ for 5-15h under the inert atmosphere condition, and cooling the mixture to obtain the solid phase treatment, wherein the inorganic lithiation reagent is preferably at least one selected from lithium hydride, lithium metal, lithium hydroxide and lithium carbonate, and the mass ratio of the oxidized material to the inorganic lithiation reagent is 0.1-5:100.
10. A lithium ion battery, wherein the negative electrode comprises the silicon-carbon composite negative electrode material protected by the interface lithium-conducting layer according to any one of claims 1 to 3 or the silicon-carbon composite negative electrode material protected by the interface lithium-conducting layer prepared by the preparation method according to any one of claims 4 to 9.

Description

Silicon-carbon composite anode material protected by interface lithium-conducting layer and preparation method thereof Technical Field The invention belongs to the technical field of lithium batteries, and particularly relates to a silicon-carbon composite anode material protected by an interface lithium-conducting layer and a preparation method thereof. Background The rapid development of consumer electronics and new energy automobile markets continually places higher demands on the energy density and power density of lithium ion batteries. The silicon-based negative electrode has very high theoretical specific capacity, and the use of the silicon-based negative electrode to replace or partially replace the traditional graphite negative electrode can remarkably improve the energy density of the lithium ion battery. The current commercial silicon-based negative electrode mainly comprises ground silicon carbon, a silicon oxygen negative electrode and vapor deposition silicon carbon, wherein the vapor deposition silicon carbon is prepared by in-situ vapor phase chemical deposition of silane into a porous carbon substrate at high temperature, the porous carbon substrate has good conductivity, and meanwhile, the porous property of the porous carbon substrate provides a reserved space for the expansion of silicon after lithium intercalation, so that the vapor deposition silicon carbon has the characteristics of high capacity, high first efficiency, low expansion and the like, and is one of the current very important commercial silicon-based negative electrode materials. The vapor deposition silicon-carbon material has low expansion and good cycle stability, but a large number of interfaces exist in the vapor deposition silicon-carbon material, so that the transmission capacity of lithium ions is limited, the quick charge performance of the material is general, and the requirements of certain quick charge application scenes are difficult to meet. It is difficult to substantially enhance its lithium ion transport capacity by conventional interface modification techniques, such as carbon coating and the like. CN120015783a discloses a silicon carbon material comprising a silicon carbon core and a lithium silicate coating layer coated on the silicon carbon core, the silicon carbon core comprising porous carbon and silicon particles, the silicon particles being deposited on the porous carbon. CN118020167a discloses a silicon-carbon negative electrode material, which comprises a porous carbon substrate, nano silicon crystal grains at least partially positioned in pore channels of the porous carbon substrate, and a carbon coating layer positioned on at least part of the surface of the porous carbon substrate or the nano silicon crystal grains, wherein a lithium silicate outer layer is also arranged on at least part of the surface of the Li xSiy coating layer, and optionally, the material of the lithium silicate outer layer comprises one or more of Li 2SiO3、Li4SiO4 and Li 2Si2O5. CN116799164a discloses a silicon-based negative electrode material, which comprises micrometer silicon particles and a silicon oxide layer, wherein the outer surface of the micrometer silicon particles is coated with a plurality of silicon oxide layers, the oxygen content of the silicon oxide layers is gradually reduced from an outer layer to an inner layer, carbon materials are uniformly distributed in the silicon oxide layer at the outermost layer in the silicon oxide layers, or the outer surface of the silicon oxide layer at the outermost layer in the silicon oxide layers is coated with a carbon material layer. The silicon oxide layer also contains a lithium compound, and the lithium content in the lithium compound is distributed in a gradient manner from the outer layer to the inner layer in the multi-layer silicon oxide layer. The lithium compound includes any one or a combination of several of Li 2Si2O5、Li2SiO3 and Li 4SiO4. The prior art discloses coating a silicon-carbon material with lithium silicate, but the interface bonding between silicon and carbon phases is weak, and there are problems of large silicon particle size, uneven dispersion, and the like. These problems result in a longer diffusion path of lithium ions during lithiation and delithiation, thereby impeding diffusion of lithium ions at high current density and causing serious polarization at high-rate charge and discharge. The rate performance is still poor. Although the porous carbon framework can provide efficient channels for electron transport, the discontinuous distribution and porosity of nanoscale silicon makes it difficult to establish stable li+ transport channels, resulting in poor li+ diffusion capability and limited rapid charge performance. Conventional interface modification techniques such as carbon coating have difficulty in enhancing li+ transport capacity at the interface. The poor Li + transport capability at the CVD-Si/C interface is also a key factor l