Improved stability of nano-Sn electrode with high-quality nano-SEI formation for lithium ion battery

By KwangSup Eom and Jaehan Jung and Jung Tae Lee and Valentin Lair and Tapesh Joshi and Seung Woo Lee and Zhiqun Lin and Thomas F. Fuller
Published in Nano Energy NULL 2015

Abstract

Sn materials offer high theoretical capacities in lithium ion batteries, but they must have good cycling stability and high rate-capability in order to be commercialized. Complex and costly material treatments of Sn have been effective in reducing capacity fade, but conventionally produced bare Sn is desired for reducing cost. One simple method is to form a high-quality solid electrolyte interphase (SEI) on Sn particles with low resistance and high passivation. Fluoroethylene carbonate (FEC) added to the electrolyte forms a protective and less-resistant \SEI\ on Sn particles during the in-situ electrochemical \SEI\ formation cycle. \FEC\ is a good oxidizing agent that removes highly oxidized carbon compounds and makes a \SEI\ thinner during an oxidation process (delithiation) of \SEI\ formation cycle. The high-quality \SEI\ greatly improves the rate-capability and capacity of nano-sized bare Sn electrodes without any treatments: minimal capacity fade (0.014% cycle?1) at 320 mA h g?1 (1.3 C) for 150 cycles. The mitigating effect of \FEC\ on capacity fade is not seen with electrodes fabricated from micro-scale (0.1~0.2 ?m) Sn. The long lithium-ion diffusion path makes these micro-sized materials susceptible to decrepitation during repeated volume changes.

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