Xiangyu Zhao

Abstract:

Rechargeable batteries are receiving particular attention in diverse areas of portable electronic devices, electric vehicles (EV) and other energy storage systems. We previously reported the proof-of-principle of a new concept of rechargeable batteries based on chloride shuttle, i.e., chloride ion batteries. The concept has the advantage of a broad variety of potential electrochemical couples with high theoretical energy density up to values of 2500 Wh/L, which is close to the theoretical energy density of the Li/S battery. Moreover, chloride ion batteries can be built from abundant material resources and have environmentally friendly features. These attributes could make the chloride ion battery a potential alternative in the field of rechargeable batteries. A key challenge is to suppress the dissolution of cathode materials mainly composed of transition metal chlorides, which are Lewis acid and can react with a Lewis base containing chloride ion in the electrolyte, resulting in the formation of soluble complex ions. One approach is to use metal oxychlorides as cathode materials. For the FeOCl cathode (FeOCl/Li), a discharge capacity of 158 mAh g-1 was measured in the first cycle and a stable discharge capacity of 60 mAh g-1 in after 30 cycles. These results suggest that metal oxychlorides are promising cathode materials for chloride ion batteries. A key advantage of chloride ion batteries is the use of abundant materials such as Mg, La, Ca and Na as anode materials. We found that Mg is promising as anode material based on our new results. For instance, the BiOCl cathode (BiOCl/Mg) showed a discharge capacity of 70 mAh g-1, i.e., 68% of theoretical capacity at the second cycle. The electrochemical performance of metal oxychloride/Mg systems was investigated including single electron or multi-electron cathode. Moreover, a new approach was tested using multi-electron vanadium oxychloride cathode and Mg/MgCl2 composite anode.