Flexible sodium-ion battery anodes using indium sulfide-based nanohybrid paper electrodes

Abstract

Flexible nanohybrid paper electrode (termed as C-I) consisting of multi-walled carbon nanotubes (MWCNTs) and indium sulfide (In2S3) nanoplates is formed via a simple vacuum-assisted assembly and used as an anode for sodium-ion batteries (SIBs). In2S3 nanoplates which are well distributed on and bound to the MWCNTs provide a high Na storage capacity of the nanohybrid electrode as high as 410 mAh g(-1) at a specific current of 50 mA g(-1) over 100 charge/discharge cycles and similar to 97% of rate-retention capability over the specific currents of 50 mA g(-1) to 1 A g(-1) for at least 50 charge/discharge cycles. Particularly, when In2S3 in the form of nanoplates was added to MWCNTs, the electrochemical performances are considerable as compared to those of bulk In2S3 or MWCNTs film electrodes. This highlights the importance of nanohybrid approach in overcoming the intrinsic complication of In2S3, i.e., the agglomeration of In2S3 into bulk form during assembly, followed by annealing. For C-I nanohybrid electrode, capacitive contribution (similar to 95%) rather than insertion contribution (similar to 5%) is predominant during charge/discharge process. The nanohybrid paper electrode is robust and thus retains capacity even under repeated mechanical deformation (flat-bent-flat cycles), demonstrating the potential of the electrode being used for flexible and wearable energy storage.