Nitrogen-doped carbon-coated silicon composite material and preparation method thereof

Abstract

The invention discloses a nitrogen-doped carbon-coated silicon composite material and a preparation method thereof, and belongs to the field of lithium ion batteries. The nitrogen-doped carbon-coated silicon composite material comprises a silicon lithium-storage material which exists in the composite material as a main active substance, and organic pyrolytic nitrogen-doped carbon with certain lithium storage capacity and good electrical conductivity as a coating layer, wherein the content of silicon in the composite material is 30%-90%; and the preparation method comprises preparation and carbon-coating technologies of a composite material precursor. In addition, with cheap silicon dioxide as a silicon source, and the silicon dioxide is transformed into a silicon material with the lithium storage activity through a metal magnesiothermic reduction process. Compared with the prior art, the preparation method of the nitrogen-doped carbon-coated silicon composite material is short in flow, easy to operate and simple in synthetic process; large-scale production is easy to realize; and the prepared nitrogen-doped carbon-coated silicon composite material has excellent electrochemical property when taken as a lithium ion battery anode material, and has a potential application prospect in the fields of portable mobile devices and electric cars.

Description

Technical field: [0001] The invention relates to the field of negative electrode materials for lithium ion batteries, in particular to a nitrogen-doped carbon-coated silicon composite material and a preparation method thereof. Background technique: [0002] At present, the negative electrodes of commercial lithium-ion batteries mainly use graphite-like carbon materials as active materials, but their theoretical capacity is low, only 372mAh / g, and it is gradually difficult to meet people's needs for lithium-ion batteries with high capacity and high energy density. . [0003] In recent years, various high-capacity negative electrode materials for lithium-ion batteries have been gradually developed, among which silicon negative electrode materials are due to their very high theoretical capacity (4200mAh / g, Li 22 Si 5 ) has become a hot spot for researchers. However, the silicon negative electrode is accompanied by a huge volume change (about 300%) during the charge-discharge...

AI Technical Summary

Problems solved by technology

Nanoization mainly includes methods such as preparing nano-silicon powder (such as Chinese patent CN104332613A), silicon nanowires (such as Chinese patent CN103515604A) and silicon thin films (such as Chinese patent CN102637852A). Attenuation problem, but the synthesis process it adopts is complex, time-consuming and labor-intensive, which is not conducive to large-scale preparation

Silicon compounding is mainly to prepare silicon-carbon composite materials, such as Chinese patent (CN102623682A) and Chinese patent (CN103928662A). The existing preparation method is difficult to obtain uniformly coated silicon-carbon composite materials by simply physically mixing solid materials, which affects the composite material. The cycle performance of the material, and the limited conductivity of the pure pyrolytic carbon layer also limits the charge and discharge performance of the composite material at high current density

Images