Internal and External Co‐Engineering of Stable Cathode Interface Improves Cycle Performance of Polymer Sodium Batteries

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Abstract
The development of polymer sodium batteries requires cathode materials with stable interfaces to avoid poor interfacial contact and interfacial side reactions during cycling. Here, a co‐engineering strategy is deployed to tailor the cathode internal structure and improve the cathode interface stability through bonding interactions. Internally, the effect of low‐cost Fe substitution in the obtained Na0.67Mn2/3Fe1/3O2 cathode material renders favorable effects in several aspects. First, the increased lattice constant facilitates Na+ intercalation and thereby lowers the diffusion barrier of Na+ ions. Second, it increases the electronic conductivity, thereby improving the reaction reversibility. Third, the MnO bond length is shortened, which alleviates the Jahn‐Taylor effect and improves structural stability. In addition to these internal effects, the FeOB bond interactions due to Fe substitution promote the decomposition of the tris(trimethylsilane)borate additive and the formation of a dense and uniform cathode electrolyte interface film, leading to improved cycling stability. Owing to the co‐engineering of both internal structure and surface modification, the polymer solid‐state sodium battery with a stable interface exhibits a specific capacity of 85.2 mAh g‐1 after 800 cycles at 1 C.
Funding Information
  • National Natural Science Foundation of China (22209199)
  • Ministry of Education - Singapore (AcRF Tier 2 (MOE‐T2EP50121‐0006))

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