Self-Healing Phenomenon Observed During Capacity-Control Cycling of Freestanding Si-Based Composite Paper Anodes for Li-Ion Batteries.

Abstract

A different strategy of capacity-control cycling under fixed upper and lower capacity/voltage limits is used in an attempt to seek an extended cycle life for Si nanoparticle-multiwalled carbon nanotube (Si-MW) electrodes for Li-ion batteries. For cells using Si-MW 1:1 (w/w) electrodes in the electrolyte of ethylene carbonate-diethyl carbonate-fluoroethylene carbonate (EC-DEC-FEC, 45:45:10 w/w/w) tested at a current of 1 mA, stable 326 charge/discharge cycles at a designated capacity of 506 mA h g-1 are attained. The new cycling protocol allows for the observation of a self-healing phenomenon by studying the specific capacities and charge/discharge end voltages. Prolonged cycling under capacity control (500 mA h g-1) and the interesting pattern of variations in the discharge/charge end voltage are successfully reproduced under different electrode/electrolyte and current conditions: Si-MW 3:2 in the electrolyte of DEC-FEC (1:1 w/w) at 1 mA (490 cycles), Si-MW 3:2 in DEC-FEC at 0.5 mA (483 cycles), and Si-MW 1:1 in DEC-FEC at 0.5 mA (576 cycles), which can be explained by applying the proposed self-healing mechanism as well.