Lithium-ion battery performance enhanced by the combination of Si thin flake anodes and binary ionic liquid systems

Kei Hosoya,Akihito Imanishi,Tetsuya Tsuda,Takayuki Doi,Susumu Kuwabata,Minoru Inaba,Masakazu Haruta,Toshiki Kamidaira

doi:10.1039/d0ma00296h

Abstract

An appropriate combination of Si anodes and binary bis(fluorosulfonyl)amide-based ionic liquid electrolytes significantly improves Li-ion battery performances.

Highlights

Bis((fluorosulfonyl)amide) anion ([FSA]À)-based ionic liquid (IL) electrolytes have been widely used for Si anode lithium ion batteries (LIBs), as [FSA]À contributes to the formation of a favorable solid electrolyte interface (SEI) layer onto the Si anode.[13,14,15,16]
Similar experiments were carried out using the 50.0–50.0 mol% [C2mim][FSA]–Li[TFSA] electrolyte, but a reversible lithiation reaction was not observed due to the unstable SEI layer formed on the Si anode, as reported by Ishikawa et al.[13] in a previous paper
In the 83.3–16.7 mol% [C2mim][FSA]– Li[TFSA] electrolyte, a large capacity drop appeared at 1/3C, whereas most of the capacity was maintained in the two binary IL electrolytes containing Li[FSA] even at 1C

Summary

Introduction

Ionic liquids (ILs), which are liquid salts at room temperature, have great potential as advanced electrolytes for LIBs because of their various unique properties including wide electrochemical window, negligible vapor pressures, nonflammability, and good thermal stability.[11,12] In particular, bis((fluorosulfonyl)amide) anion ([FSA]À)-based IL electrolytes have been widely used for Si anode LIBs, as [FSA]À contributes to the formation of a favorable SEI layer onto the Si anode.[13,14,15,16] there is insufficient information on. CR2032type coin full cells were constructed by stacking the Si composite anode, a polyolefin separator (Nippon Sheet Glass Co., Ltd (Japan)), and a LiCoO2 composite cathode with an Al foil current collector (3.0 mA h cmÀ2, Hohsen (Japan)) in an Ar-filled glove box An operando SEM observation of the binder-free Si anodes was performed using a two-electrode type full cell with a mesh-type anode, a LiCoO2 composite cathode with an Al foil current collector (3.0 mA h cmÀ2, Hohsen (Japan)), and glass microfiber filter separators (GF/A, Whatman (UK)) with IL electrolytes (Fig. 1d). The electrochemical experimental conditions were controlled with a potentiostat/galvanostat (VersaSTAT 4, Princeton Applied Research (USA))

Results and discussion

Conclusions

Conflicts of interest