The rapid expansion of lithium-ion batteries has increased the demand for sustainable lithium resources. Salt lakes and brines are attractive sources for large-scale lithium recovery; however, high concentrations of competing ions, particularly Mg²⁺, make selective Li⁺ recovery challenging. In a study published in ENG. Chem. Eng. , researchers at Taiyuan University of Science and Technology and collaborators report a zirconium-modified LiMn₂O₄ film electrode that addresses these challenges through enhanced structural stability and electrochemical kinetics.
The LZMO materials with zirconium doping levels from 0.01 to 0.04 were synthesized via a high-temperature solid-state reaction and fabricated into film electrodes. XRD analysis confirmed successful zirconium incorporation, with a weak ZrO₂-related peak at 30.2 degrees and a shift of the (111) and (311) diffraction peaks toward smaller angles, indicating lattice expansion. TEM revealed an expanded lattice spacing from 0.251 nanometres for pristine LMO to 0.257 nanometres for LZMO-0.03, consistent with the larger ionic radius of Zr⁴⁺. XPS showed that the Mn⁴⁺ to Mn³⁺ ratio increased from 1.02 for LMO to 1.04 for LZMO-0.03, attributed to charge compensation. After ten cycles, the Mn⁴⁺ to Mn³⁺ ratio of LMO increased to 1.12, while LZMO-0.03 only reached 1.08, confirming suppressed manganese dissolution.
Electrochemical characterization showed that LZMO-0.03 exhibited significantly larger CV peak currents and areas than LMO, indicating higher Li⁺ intercalation capacity. EIS revealed a 21.2 % reduction in charge-transfer resistance. The discharge capacity of LZMO-0.03 reached 131.37 mAh·g⁻¹, an 11.94 % improvement over pristine LMO which achieved 117.36 mAh·g⁻¹. The Li⁺ diffusion coefficient of LZMO-0.03 was 8.41 × 10⁻¹¹ cm²·s⁻¹, one order of magnitude higher than that of LMO at 7.29 × 10⁻¹² cm²·s⁻¹. After 500 CV cycles, LZMO-0.03 retained 90.24 % of its initial capacity, compared to only 81.55 % for LMO.
DFT calculations revealed that zirconium doping enhanced Mn–O p–d hybridization, downshifted Mn 3d peaks, and mitigated Jahn–Teller distortion, collectively improving structural stability and cycling performance.
In real brine from Qarhan Salt Lake with a Li⁺ concentration of 329.88 mg·L⁻¹ and Mg²⁺ concentration of 131,952 mg·L⁻¹, the LZMO-0.03 electrode achieved a Li⁺ intercalation capacity of 22.16 mg·g⁻¹ under optimized constant current-constant voltage mode at 1.0 mA·cm⁻² and 1.0 V. The separation factors were 685.43 for Li/Mg, 86.31 for Li/Na, 32.54 for Li/K, and 24.17 for Li/Ca, demonstrating excellent selectivity. Energy consumption was as low as 3.61 Wh·mol⁻¹. After 20 consecutive cycles, the Li⁺ intercalation capacity remained stable with 87.6 % retention, and the deintercalation efficiency reached 84.6 %. Manganese dissolution in LZMO-0.03 was only 0.38 %, compared to 0.85 % for LMO, representing a reduction of 51.8 %.
This work demonstrates that targeted zirconium doping simultaneously enhances the structural stability and electrochemical kinetics of LiMn₂O₄ through synergistic lattice and electronic modulation, providing an effective strategy for designing high-performance electroactive materials for selective lithium extraction.
ENGINEERING Chemical Engineering
Experimental study
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