Intrinsic Barrier to Electrochemically Decompose Li2CO3 and LiOH

详细信息    查看全文

• 作者：Chen Ling ; Ruigang Zhang ; Kensuke Takechi ; Fuminori Mizuno
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：November 20, 2014
• 年：2014
• 卷：118
• 期：46
• 页码：26591-26598
• 全文大小：405K
• ISSN：1932-7455

文摘

It is widely acknowledged that Li₂CO₃ and LiOH as side-products in the operation of a Li鈥揳ir cell should be completely removed in the cycling to avoid cumulative negative effect on the cycling performance. However, the understanding of their electrochemical decomposition is limited. We report a mechanistic analysis of the intrinsic barrier to electrochemically decompose Li₂CO₃ and LiOH. Our first-principles study reveals that the decomposition is rate-limited by the electrochemical extraction of Li⁺, whereas the chemical release of anions is barrierless once the applied voltage overcomes the energy penalty to generate a Li-deficient surface. The voltage necessary for the decomposition of Li₂CO₃ is predicted to be in the range of 4.38鈥?.61 V, whereas for LiOH it is in the range of 4.67鈥?.02 V. The maximum charge efficiency to decompose Li₂CO₃ and LiOH in the operation of a Li鈥揳ir cell is estimated to be 66% and 61%, respectively. The high intrinsic barrier originates from the energy cost of oxidizing redox-inert anions for the charge neutrality when lithium is extracted. Therefore, one strategy for lowering the barrier is incorporating redox-active species as a charge mediator to compensate the electron loss during the decomposition.