A kind of lithium ion battery, used silicon carbon negative electrode material and preparation method thereof

Abstract

The invention relates to a lithium ion battery, a used silicon carbon negative electrode material and a preparation method thereof. The silicon carbon negative electrode material is prepared by: kneading and mixing a slurry containing nano silicon powder or nano silicon monoxide powder with micron-sized graphite powder and coal tar maltha, conducting coking and crushing, and then performing surface chemical vapor deposition treatment. According to the invention, nano silicon / silicon monoxide particles are dispersed and fixed in graphite particles with asphaltic carbon, and then vapor depositcarbon is utilized to protect barish silicon particle surfaces, the prepared silicon carbon negative electrode material has obviously improved specific capacity, has a high capacity retention ratio inthe battery cycling process, has strong adaptability to an electrolyte solution, the battery has excellent comprehensive performance, and has wide application prospect.

Description

technical field [0001] The invention belongs to the field of lithium battery materials, relates to the fields of electrochemistry and carbon-carbon composite materials, and in particular relates to a lithium ion battery, a silicon-carbon negative electrode material used and a preparation method thereof. Background technique [0002] Lithium-ion batteries have excellent performance in terms of high energy density, high working voltage, small size, light weight, no pollution, fast charging and discharging, and long cycle life, so they have received great attention and been widely used in recent years. Lithium-ion batteries use carbon materials as negative electrodes and lithium-containing compounds as positive electrodes; for negative electrode materials, although the actual delithiation capacity of graphite-based negative electrode materials in half-cells is as high as 365mAh / g (theoretically, the reversible storage capacity of graphite Lithium capacity can reach 372mAh / g), b...

AI Technical Summary

Problems solved by technology

Lithium-ion batteries use carbon materials as negative electrodes and lithium-containing compounds as positive electrodes; for negative electrode materials, although the actual delithiation capacity of graphite-based negative electrode materials in half-cells is as high as 365mAh / g (theoretically, the reversible storage capacity of graphite Lithium capacity can reach 372mAh / g), but it still cannot meet the demand of high energy density battery. Taking 18650 lithium battery as an example, the graphite negative electrode can no longer meet the energy density requirements of batteries above 3.0Ah. To meet market requirements, a new type of lithium battery must be developed. Anode materials with high energy density and long cycle life

[0003] In order to improve the specific capacity of negative electrode materials and improve the charge-discharge performance, researchers began to study non-carbon-based negative electrode materials. The study found that the theoretical capacity of silicon is much higher than that of graphite, and its capacity can reach 4200mAh / g. The theoretical capacity of silicon oxide 2043mAh / g, the delithiation potential platform is about 0.45V; however, silicon-based materials also have obvious electrical performance defects, mainly because silicon-based materials will produce 100% to 300% volume shrinkage and expansion in the process of lithium deintercalation, resulting in The battery cycle performance is poor and it is difficult to use it alone

Researchers have turned to the development of silicon-carbon anode materials in order to increase the capacity of lithium-ion batteries and solve the problem of silicon contacting the electrolyte due to volume expansion and contraction during charging and discharging, and constantly forming new interfaces, thus affecting the battery cycle. longevity problem

[0004] In recent years, some people have used slurry to disperse nano-silicon-based materials or co-dispersed nano-silicon-based and nano-conductive agent materials, and then coated or impregnated with pitch, and then carbonized silicon-carbon anode material preparation technology has appeared, which has improved to varying degrees. The cycle performance of silicon carbon negative electrode materials, but because it adopts the process of carbonization after coating or impregnating with pitch (hydrocarbons), it is essentially coating or impregnating silicon-containing materials with hydrocarbons first, and then carbonizing at above 700 °C , the hydrogen element is detached, and the remaining carbon element forms a carbon layer on the surface of the silicon material, and such a carbon layer is not dense and uniform enough to effectively limit the contact between the silicon particles and the electrolyte, nor can it effectively limit the silicon particles. Inflated, so its product performance is far from meeting people's expectations

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