(NH 4 ) 2 V 7 O 16 Microbricks as a Novel Anode for Aqueous Lithium‐Ion Battery with Good Cyclability

Searching for novel anode materials to address the issues of poor cycle stability in the aqueous lithium‐ion battery system is highly desirable. In this work, ammonium vanadium bronze (NH 4 ) 2 V 7 O 16 with brick‐like morphology has been investigated as an anode material for aqueous lithium‐ion batteries and Li + /Na + hybrid ion batteries. The two novel full cell systems (NH 4 ) 2 V 7 O 16 ||Li 2 SO 4 ||LiMn 2 O 4 and (NH 4 ) 2 V 7 O 16 ||Na 2 SO 4 ||LiMn 2 O 4 both demonstrate good rate capability and excellent cycling performance. A capacity retention of 78.61 % after 500 cycles at 300 mA g −1 was demonstrated in the (NH 4 ) 2 V 7 O 16 ||Li 2 SO 4 ||LiMn 2 O 4 system, whereas no capacity attenuation is observed in the (NH 4 ) 2 V 7 O 16 ||Na 2 SO 4 ||LiMn 2 O 4 system. The reaction mechanisms of the (NH 4 ) 2 V 7 O 16 electrode and impedance variation of the two full cells were also researched. The excellent cycling stability suggests that layered (NH 4 ) 2 V 7 O 16 can be a promising anode material for aqueous rechargeable lithium‐ion batteries.