How To Improve Capacity and Cycling Stability for Next Generation Li-O2 Batteries: Approach with a Solid Electrolyte and Elevated Redox Mediator Concentrations
How To Improve Capacity and Cycling Stability for Next Generation Li-O2 Batteries: Approach with a Solid Electrolyte and Elevated Redox Mediator Concentrations
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DOI：
10.1021/acsami.5b10979
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发表时间：
2016-03-30
影响因子：
9.5
通讯作者：
Janek, Juergen
中科院分区：
文献类型：
--
作者：
Bergner, Benjamin J.;Busche, Marlin R.;Janek, Juergen
非质子锂氧电池(Li-O-2)由于具有极高的比能量，被认为是未来潜在的储能材料。然而，它们的实际应用仍然受到高充电过电压和有害副反应的阻碍。最近，溶解在电解液中的氧化还原介质的使用成为一种很有前途的工具，可以在中等电压下充电。通过将高氧化还原介质浓度与固体电解液(SE)相结合，提出了这一概念，并显著提高了Li-O-2电池的容量和循环稳定性。高氧化还原介质浓度的使用通过将氧化还原介质的氧化和还原包含在电荷循环中，显著增加了放电容量。高效率的循环是通过用固体电解液保护锂阳极来实现的，这完全阻止了阳极上不利于氧化物种的失活。令人惊讶的是，SE还在很大程度上抑制了碳电极上的有害副反应，并能够在较长时间内完全稳定地充电到4.0V以下。研究表明，阳极和阴极通过液体电解液进行有害的交流，从而在碳电极上引起降解反应。因此，用SE分离正负极被认为是实现稳定的Li-O-2电池的关键一步，与集中式氧化还原介体电解液相结合。
Because of their exceptionally high specific energy, aprotic lithium oxygen (Li-O-2) batteries are considered as potential future energy stores. Their practical application is, however, still hindered by the high charging overvoltages and detrimental side reactions. Recently, the use of redox mediators dissolved in the electrolyte emerged as a promising tool to enable charging at moderate voltages. The presented work advances this concept and distinctly improves capacity and cycling stability of Li-O-2 batteries by combining high redox mediator concentrations with a solid electrolyte (SE). The use of high redox mediator concentrations significantly increases the discharge capacity by including the oxidation and reduction of the redox mediator into charge cycling. Highly efficient cycling is achieved by protecting the lithium anode with a solid electrolyte, which completely inhibits unfavored deactivation of oxidized species at the anode. Surprisingly, the SE also suppresses detrimental side reactions at the carbon electrode to a large extent and enables stable charging completely below 4.0 V over a prolonged period. It is demonstrated that anode and cathode communicate deleteriously via the liquid electrolyte, which induces degradation reactions at the carbon electrode. The separation of cathode and anode with a SE is therefore considered as a key step toward stable Li-O-2 batteries, in conjunction with a concentrated redox mediator electrolyte.