TEMPO-modified PEO-based oxygen electrode enabling long-term cyclability for quasi-solid-state lithium-oxygen batteries

In terms of stability and safety, quasi-solid-state lithium-oxygen batteries (QSSLOBs) outperform traditional liquid LOBs. However, using redox mediators (RMs) in QSSLOBs requires unique strategy to inhibit the shuttle effect of RMs. In this work, a PEO-based oxygen electrode with anchored 4-OH-TEMPO (4-hydroxy-2,2,6,6tetramethyl-piperidinyloxy) RM (referred to as TEMPO-PEO) is developed via hydrogen-bonding interaction for QSSLOBs. The TEMPO-PEO oxygen electrode can perform both significant mediation function and oxygen reduction reaction (ORR) activity. The QSSLOB using TEMPO-PEO electrode achieves a low discharge/charge voltage gap of 0.9 V and a high Coulombic efficiency of 96.8 %, which is significantly superior to the counterparts using TEMPO solution (TEMPO cell) or unanchored TEMPO (TEMPO+PEO cell). On this basis, the TEMPO-PEO cell achieves an unprecedented cycle performance for 320 cycles under the limited capacity of 300 mAh g- 1 , overwhelmingly outperforming the counterpart cells that only deliver 63 cycles (TEMPO cell) and 119 cycles (TEMPO+PEO cell), respectively. After cycling, the TEMPO RM can still be well retained on TEMPO-PEO oxygen electrode and no significant side product is formed on the after-cycled Li anode of TEMPO-PEO cell, explicitly demonstrating a strong and consistent anchoring effect on suppressing the shuttling of RM species.