Dual-engineered Ni-LiMn2O4 microsheets for sustainable lithium mining: Accelerated ion transport and robust electrochemical extraction in brine

Abstract

The surging demand for lithium in energy storage necessitates sustainable and efficient electrochemical lithium recovery from salt lakes. Herein, we develop Ni-doped LiMn₂O₄ microsheets (LNMO-MS) via a green bio-templated synthesis that integrates 2D morphology engineering and Ni-doping using chitosan biopolymer as a structural guide. This dual modulation addresses intrinsic limitations of conventional LiMn₂O₄. Ni doping induces [MnO₆] octahedral contraction to stabilize the framework and enhance Li⁺ selectivity (Mg²⁺/Li⁺ separation factor: 401.32 at Mg²⁺/Li⁺ = 200), while the 2D architecture shortens Li⁺ diffusion paths, enabling 10-fold faster ion kinetics and improved charge transfer. In capacitive deionization (CDI), the LNMO-MS achieves a record Li⁺ adsorption capacity (4.12 mmol g⁻¹), with low energy consumption (1.96 Wh moL⁻¹ Li⁺), outperforming conventional LiMn₂O₄ electrodes. Real-world validation using Qarhan Salt Lake brine demonstrates practical viability, producing concentrated LiCl solutions (1 g L⁻¹ Li, Mg²⁺/Li⁺=0.13) at 8.63 Wh·mol⁻¹ Li⁺, while maintaining 92 % capacity retention over 200 cycles. The strategy of bio-guided 2D structuring and Ni doping establishes an energy-efficient, durable platform for selective lithium extraction, offering a sustainable solution to bridge lithium supply–demand gaps with minimized environmental footprint.