Instantaneous formation of SiOx nanocomposite for high capacity lithium ion batteries by enhanced disproportionation reaction during plasma spray physical vapor deposition

Tohru Tashiro,Masashi Dougakiuchi,Makoto Kambara

doi:10.1080/14686996.2016.1240574

Abstract

Nanocomposite SiOx particles have been produced by a single step plasma spray physical vapor deposition (PS-PVD) through rapid condensation of SiO vapors and the subsequent disproportionation reaction. Core-shell nanoparticles, in which 15 nm crystalline Si is embedded within the amorphous SiOx matrix, form under typical PS-PVD conditions, while 10 nm amorphous particles are formed when processed with an increased degree of non-equilibrium effect. Addition of CH4 promotes reduction in the oxygen content x of SiO x , and thereby increases the Si volume in a nanocomposite particle. As a result, core-shell nanoparticles with x = 0.46 as anode exhibit increased initial efficiency and the capacity of lithium ion batteries while maintaining cyclability. Furthermore, it is revealed that the disproportionation reaction of SiO is promoted in nanosized particles attaining increased Si diffusivity by two orders of magnitude compared to that in bulk, which facilitates instantaneous composite nanoparticle formation during PS-PVD.

Highlights

Silicon is a strong candidate for anodes in high density lithium ion batteries (LIB) owing to its 10-fold higher theoretical gravimetric and volumetric capacities than those of the conventional carbonous material
Various structures have been reported to be effective in maintaining high cycle capacity:[1,2,3,4,5,6,7,8,9,10] decreasing the size of the material improves the capacity at longer cycles,[1,2,3] and in particular sizes smaller than 150 nm are reported to be free from fracturing
With large non-equilibrium effect by rapid gas quenching, together with CH4 addition, Amorphous Si (a-Si) core structure is expected to form by low temperature disproportionation reaction in smaller SiO nanoparticles (SiO-NP) with reduced oxygen content

Summary

Introduction

Silicon is a strong candidate for anodes in high density lithium ion batteries (LIB) owing to its 10-fold higher theoretical gravimetric and volumetric capacities than those of the conventional carbonous material. Coating the silicon materials with carbonous materials works to improve the cyclability, possibly due to more stable SEI formation.[5,6] Composites including porous and nanotube structures are effective in accommodating the Si dilation during lithiation and maintaining the contacts between particles and current collector after delithiation.[7,8,9,10] Another approach is to use SiO as active material.[11,12,13,14,15,16,17,18,19,20,21] Using the characteristic disproportionation reaction of SiO, nanosized Si can be dispersed within a SiO2 matrix that is expected to reinforce the Si crystalline precipitates and attain stable. With large non-equilibrium effect by rapid gas quenching, together with CH4 addition, a-Si core structure is expected to form by low temperature disproportionation reaction in smaller SiO-NP with reduced oxygen content. We report the advantages and uniqueness of PS-PVD SiO-NP as anode for an increase in the capacity and cyclability of LIB, and the fundamental path of composite formation during PS-PVD with particular emphasis on the enhanced disproportionation reaction in nanosized particles

Experimental details

Results and discussion

SiO nanoparticle growth

Disproportionation reaction in a nanoparticle

Conclusions