Engineering LDH-Derived LiCoMnO4 Spinel/MXene Heterostructures via a Dual-Tuning Strategy for Efficient Lithium Extraction from Low-Grade Brines

Electrochemical lithium extraction from low-grade salt lake brines is a sustainable approach to reliable and cost-efficient lithium supply, yet it is hindered by sluggish diffusion kinetics and the severe interference from competing Mg 2+ ions. This study proposes a “dual-tuned” strategy to engineer a high-performance electrode by simultaneously optimizing the intrinsic crystal architecture and the extrinsic conductive network. First, nanosized LiCoMnO 4 (LCMO) spinels (∼100 nm) were synthesized via a topotactic transformation from ultrathin Co-Mn-layered double hydroxide (LDH) precursors, effectively shortening ion diffusion paths. Second, these nano-spinels were integrated with Ti 3 C 2 T x MXene nanosheets to construct a 3D conductive framework that accelerates electron transport. The optimized 50%LCMO/MXene electrode achieved a superior lithium adsorption capacity of 188.55 mg g –1 (4.45 mmol g –1 ) and remarkable stability (87.6% retention over 200 cycles). Mechanistic investigations via ex - situ XPS and DFT revealed a distinct adsorption pathway: Li + undergoes bulk intercalation driven by reversible lattice volume evolution, while Mg 2+ is restricted to surface accumulation. Moreover, DFT analysis reveals that the Mn environment remains remarkably rigid. This local electronic rigidity minimizes the Jahn-Teller effect and Mn dissolution, providing a fundamental structural explanation for the electrode’s enhanced durability. A dual-tuned LCMO@MXene heterostructure is synthesized via topotactic transformation for selective lithium recovery. The material exhibits a divergent adsorption pathway where bulk lithium intercalation is facilitated by a lower kinetic barrier, while structural stability is maintained through the local electronic rigidity of the Mn 3d orbitals, effectively suppressing Jahn-Teller distortion and Mn dissolution. • Nanosized spinel LiCoMnO 4 was derived from Co-Mn-LDH via topotactic transformation. • Dual-tuned LCMO@MXene electrodes for faster electrochemical lithium extraction. • Superior lithium extraction capacity of 188.55 mg g –1 with high energy efficiency. • Excellent stability (87.6% retention over 200 cycles) due to suppressed Jahn-Teller effect. • DFT and ex-situ analysis reveal relationship between redox and electronic rigidity.