Boosting Li-Ion Storage Capability of Self-Standing Ni-Doped LiMn₂O₄ Nanowall Arrays as Superior Cathodes for High-Performance Flexible Aqueous Rechargeable Li-Ions Batteries

To meet the increasing desire for a means of powering wearable and portable devices, the development of high-performance flexible aqueous rechargeable lithium-ion batteries (FARLIBs) would be greatly desirable. The design of binder-free cathode materials with 3D architectures is the key to develop FARLIBs. Herein, self-standing 3D Ni-doped LiMn₂O₄ (NLMO) nanosheets are successfully prepared assembled by nanowall arrays (NWAs) directly grown on carbon cloth (CC) as the cathode for LIBs, which is performed to slow down the dissolution of Mn and the Jahn–Teller effect of LiMn₂O₄ during the reaction process. The as-prepared NLMO NWAs/CC electrode delivers a high capacity of 113.27 mAh g⁻¹ at a current density of 1 A g⁻¹, and can also have a capacity retention rate of 81% after 500 cycles at 10 A g⁻¹, both higher than that of pure LiMn₂O₄. The results of density functional theory simulation demonstrate that the Ni-doped LiMn₂O₄ can significantly decrease the bandgap and Li ions diffusion barriers. A quasi-solid-state FARLIB is successfully constructed by using NLMO NWAs/CC as the positive electrode and rugby-shaped NaTi₂(PO₄)₃/CC as the negative electrode, exhibiting remarkable electrochemical performance and flexibility. These results offer a new opportunity for developing high-performance FARLIB.