Amorphous titanium oxide passivated lithium titanium phosphate electrode for high stable aqueous lithium ion batteries with oxygen tolerance

Abstract Undesirable side reactions at interface usually ruin the electrode stability and lead to serious self-discharge or decrease the coulombic efficiency. An ionic permeable and electronic insulating amorphous TiO 2 passivation could be deposited on the carbon encapsulated LiTi 2 (PO 4 ) 3 electrode through sol-gel method, which drastically enhance the aqueous electrode stability and oxygen tolerance in wide potential window by kinetically suppressing the side reactions at new formed interface. Raman depth profile and SEM have confirmed this surface coating, while nanoelectronic conductivity analysis reveal the TiO 2 layer is electronically insulate. The capacity retention of the TiO 2 passivated carbon encapsulated LiTi 2 (PO 4 ) 3 /LiNO 3 /LiMn 2 O 4 coin cell for 2000 cycles is 66% assembled in ambient air, which is higher than 55% for the one without TiO 2 coating. Electrochemical investigation suggests the TiO 2 layer is Li + ionic conductive, which suppressed the surface water reduction or oxygen reduction reaction. As an interestingly result, the cell stability improvement also benefited from the less degradation of the LiMn 2 O 4 counter electrode. This comprehensive understanding of the electrode passivation using an ionic conductive layer can be potentially applied in other electrochemical devices.