(NH₄ )₂ V₇ O₁₆ 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 (NH₄ )₂ V₇ O₁₆ 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 (NH₄ )₂ V₇ O₁₆ ||Li₂ SO₄ ||LiMn₂ O₄ and (NH₄ )₂ V₇ O₁₆ ||Na₂ SO₄ ||LiMn₂ O₄ 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 (NH₄ )₂ V₇ O₁₆ ||Li₂ SO₄ ||LiMn₂ O₄ system, whereas no capacity attenuation is observed in the (NH₄ )₂ V₇ O₁₆ ||Na₂ SO₄ ||LiMn₂ O₄ system. The reaction mechanisms of the (NH₄ )₂ V₇ O₁₆ electrode and impedance variation of the two full cells were also researched. The excellent cycling stability suggests that layered (NH₄ )₂ V₇ O₁₆ can be a promising anode material for aqueous rechargeable lithium-ion batteries.