Unlocking the multi-electron transfer reaction in NASICON-type cathode materials
Yuan Liu, Xiaohui Rong, Fei Xie, Yaxiang Lu, Junmei Zhao, Liquan Chen, Yong‐Sheng Hu
Abstract
Abstract The growing concern about scarcity and large-scale applications of lithium resources has attracted efforts to realize cost-effective phosphate-based cathode materials for next-generation Na-ion batteries (NIBs). In previous work, a series of materials (such as Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ), Na 3 VCr(PO 4 ) 3 , Na 4 VMn(PO 4 ) 3 , Na 3 MnTi(PO 4 ) 3 , Na 3 MnZr(PO 4 ) 3 , etc) with ∼120 mAh g −1 specific capacity and high operating potential has been proposed. However, the mass ratio of the total transition metal in the above compounds is only ∼22 wt%, which means that one-electron transfer for each transition metal shows a limited capacity (the mass ratio of Fe is 35.4 wt% in LiFePO 4 ). Therefore, a multi-electron transfer reaction is necessary to catch up to or go beyond the electrochemical performance of LiFePO 4 . This review summarizes the reported NASICON-type and other phosphate-based cathode materials. On the basis of the aforementioned experimental results, we pinpoint the multi-electron behavior of transition metals and shed light on designing rules for developing high-capacity cathodes in NIBs.