Lithium ion battery silicon oxide and carbon composite negative pole material and preparation method thereof

Abstract

The invention discloses a lithium ion battery silicon oxide and carbon composite negative pole material and a preparation method thereof. The technical purposes are improvement of first Coulomb effect, capacity and circulating properties and reduction of cost. According to the lithium ion battery silicon oxide and carbon composite negative pole material, a graphite-based silicon oxide composite material serves as a body, the body is wrapped with a pyrolytic carbon wrapping layer of an organic carbon source, and amorphous carbon in the graphite-based silicon oxide composite material is bonded with a silicon oxide and graphite with a nanoporous structure by means of Van der Waals force. The preparation method includes the steps of nano-silica sol preparation, ultrasonic dispersion, primary sintering, wrapping and secondary sintering. Compared with the prior art, stress generated by size change of the silicon oxide during high lithium intercalation and deintercalation is effectively reduced, and interfacial potential energy between materials is effectively reduced, so that the material has high specific capacity, and is suitable for high-rate charge and discharge, simple in preparation method, easy to control, low in cost and suitable for large-scale industrial production.

Description

technical field [0001] The invention relates to a novel energy material and a preparation method thereof, in particular to a lithium-ion battery composite negative electrode material and a preparation method thereof. Background technique [0002] Lithium-ion batteries commercialized in the prior art mainly use graphite-like carbon materials as negative electrode active materials, but the specific capacity of carbon materials is low, and the theoretical capacity is 372mAh / g. The energy density of the battery system composed of positive electrode materials is generally below 150Wh / Kg; at the same time, the lithium intercalation potential of graphite is close to the lithium deposition potential, and low-temperature charging or high-rate charging and discharging are easy to decompose lithium, causing safety problems. Therefore, the graphite-based anode materials in the prior art have been difficult to meet the requirements for the miniaturization of electronic equipment and the ...

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Problems solved by technology

[0005] In the prior art, the research on silicon oxide-based composite materials is mainly obtained by physically mixing and covering silicon oxide, silicon, graphite or organic carbon sources. Since agglomeration and inhomogeneity are prone to occur during the dispersion process, the prepared The particle size distribution of the silica-based composite material is not uniform, which affects the first-time efficiency and cycle stability of the negative active material.

At the same time, commercial silicon and silicon oxide are directly used as raw materials, the raw materials are expensive, and the preparation cost is relatively high.

For example, CN103441250A discloses a lithium-ion secondary battery, a negative electrode material for the secondary battery, and a preparation method. The negative electrode material is a composite particle comprising silicon nanoparticles and conductive metal particles that can be dispersed in silicon oxide. Although the capacity can reach about 600mAh / g, the initial efficiency is less than 70%

CN103022446A discloses a lithium-ion battery silicon oxide / carbon negative electrode material and a preparation method thereof, a three-layer composite material with a core-shell structure, adopting graphite material as the core, porous silicon oxide as the middle layer, and organic pyrolytic carbon as The outermost cladding layer has good cycle performance and specific capacity, and the first Coulombic efficiency can reach 88%. However, the preparation process is complicated, the cost is high, the composite structure is difficult to control, and it is difficult to realize large-scale industrial production.

CN102208634A discloses a porous silicon / carbon composite material and a preparation method thereof, using ethyl orthosilicate, silicon tetrachloride, methyl silicone oil, and sodium silicide as raw materials to prepare porous silica, and then porous silica It is reduced to porous silicon, then coated with an organic carbon source, and then heat-treated in an inert atmosphere to prepare a porous silicon / carbon composite material. The first reversible capacity of the composite material can reach about 1245mAh / g, but the prepared composite material Large silicon particles lead to obvious volume expansion effect of the composite material, rapid capacity cycling decay, and the preparation process of this method is complicated

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