基于界面膜清洗的废旧锂离子电池石墨负极的再生修复

The regeneration of graphite anode from spent lithium-ion batteries by washing with a nitric acid/ethanol solution

    摘要
  • 摘要: 石墨因其良好的导电性、适合锂脱嵌的层状结构和良好的循环稳定性，成为目前商品化锂离子电池最主要的负极材料。随着越来越多的锂离子电池、特别是动力电池进入退役期，石墨负极材料的回收处理与循环再利用引起学术界和产业界的高度重视。本文对废旧锂离子电池拆解、极片分离和清洗进行研究，对拆解得到的石墨负极进行结构分析发现：锂离子电池经长时间循环后负极表面生成厚的固体电解质界面（SEI）层，增厚的SEI层增加了电池阻抗，同时降低了石墨负极表面的润湿性。将得到的废旧石墨负极浸泡在硝酸乙醇溶液中以清洗除去表面厚的SEI层和金属杂质从而恢复其电化学性能，同时保持了电极的原始初始形貌。最后，通过电化学测试发现，修复后的石墨负极在50 mA·g−1电流密度循环60圈无容量损失，而以磷酸铁锂作正极组装全电池在0.5 C下循环100圈容量保持率达到92%。对比已报道的废旧石墨回收方法，此法过程简单，无需将石墨从铜箔表面剥离，解决了现有回收方法存在的共性问题即回收工艺复杂，而且界面洗后石墨的电化学性能得到了显著提升，为废旧石墨负极回收提供了新的思路。

     

    Abstract: Graphite is one of the main components of lithium-ion batteries (LIBs) because of its good recycling performance and uniform layers suitable for lithium intercalation. This study focused on the separation of spent LIBs, the isolation of the anode and the washing of its surface to remove the solid electrolyte interphase that leads to an increase in the electrical resistance. The spent graphite was incubated in a nitric acid/ethanol solution which cleans the spent graphite anode while retaining its original morphology. The regenerated graphite anode has a better electrochemical performance when used in a new lithium-ion battery than does the spent graphite, with no capacity loss at a current density of 50 mA·g−1 for 60 cycles. A full battery using regenerated graphite as the anode and lithium iron phosphate as the cathode has a capacity retention of 92% at 0.5 C after 100 cycles. Our work provides a new strategy for regeneration of the anode graphite.

     

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