Authors: Le Yang, Yahui Hao, Jiande Lin, Ke Li, Siheng Luo, Jie Lei, Yanhong Han, Ruming Yuan, Guokun Liu, Bin Ren, Jiajia Chen
Published: 2021-12-06
Source: Full article
AbstractA highly soluble Li5BW12O40 cluster delivers 2 e− redox reaction with fast electron transfer rates (2.5 × 10−2 cm s−1) and high diffusion coefficients (≈2.08 × 10−6 cm2 s−1) at mild pH ranging from 3 to 8. In‐operando aqueous‐flowing Raman spectroscopy and density functional theory calculations reveal that Raman shift changing of {BW12} clusters is due to the bond length changing between W‐Ob‐W and W‐Oc‐W at different redox states. The structure changing and redox chemistry of Li5BW12O40 are highly reversible, which makes the Li5BW12O40 cluster versatile to construct all‐anion aqueous redox flow batteries (RFBs). The cation‐exchange Nafion membrane will also repel the cross permeability of the anion redox couples. Consequently, by coupling with Li3K[Fe(CN)6] catholyte, the aqueous RFB can be operated at pH 8 with a capacity retention up to 95% and an average Coulombic efficiency more than 99.79% over 300 cycles within 0 to 1.2 V. Meanwhile, Li5BW12O40 cluster can also be paired with LiI catholyte to form aqueous RFBs at pH 7 and pH 3, the capacity retention of 94% and 90% can be realized over 300 cycles within 0 to 1.3 V.