Stable cycling of lithium-sulfur batteries by optimizing the cycle condition
Stable cycling of lithium-sulfur batteries by optimizing the cycle condition
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DOI：
10.1016/j.electacta.2019.134948
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发表时间：
2019-12
影响因子：
6.6
通讯作者：
Chao Shen;P. Andrei;Jim P. Zheng
中科院分区：
文献类型：
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作者：
Chao Shen;P. Andrei;Jim P. Zheng
锂硫（Li-S）电池存在活性物质利用率低、循环寿命短等问题。本文设计了三种条件循环方法，即不对称循环、恒压（CV）放电循环和部分循环，以提高Li-S电池的循环性能。据发现，固体沉积过程中发生的较低的平台放电是实现高放电容量和循环保持的主要限制步骤，和阴极表面覆盖可以推迟通过施加最佳的放电/充电速率和CV放电循环。不对称循环使比容量约为1.5g。700 mAh g-1，比对称循环高30%，而应用CV放电循环能够完全保持ca的目标比容量。800 mAh g− 1超过50次循环。在放电/充电结束时具有低数量的相变步骤和降低的表面覆盖率的部分循环也增强了可循环性。这项工作为理解和改善锂硫电池的循环性能铺平了道路，而不增加电极设计的成本或改变电池的配置。
Lithium-sulfur (Li–S) batteries suffer from poor utilization of active material and short cycle life due to the complicated multi-step reaction mechanisms. Herein, three conditional cycling methods, i.e. asymmetrical cycling, constant voltage (CV) discharge cycling, and partial cycling are designed in order to increase the cyclability of Li–S batteries. It is found that the solid deposition process that takes place during the lower plateau of discharge is the major limiting step for achieving high discharge capacity and cycle retention, and the cathode surface coverage can be deferred by applying an optimal discharge/charge rate and CV discharge cycling. The asymmetrical cycling renders a specific capacity of ca. 700 mAh g−1after 200 cycles, 30% higher than that under symmetrical cycling, while applying a CV discharge cycling enables a full retention of target specific capacity of ca. 800 mAh g−1over 50 cycles. The partial cycling with a low number of phase transformation steps and reduced surface coverage at the end of discharge/charge also enhances cyclability. This work paves the way for understanding and improving the cycling performance of Li–S batteries without increasing the cost of electrode design or changing the configuration of the cell.