Upcycling of LiFePO4 to high-performance LiMnxFe1−xPO4: activating the Mn redox platform for stable energy storage

Abstract

Driven by the demand for greener and cost-effective solutions for lithium-ion battery recycling, direct regeneration of cathode materials from spent batteries has gained significant attention. To address the growing requirements for higher operating voltage and energy density in energy storage systems, LiMn_xFe_1−xPO₄ (LMFP) has emerged as a promising cathode material for next-generation batteries due to its superior electrochemical performance compared to conventional LiFePO₄ (LFP). Herein, we propose a novel upcycling strategy that transforms LFP into high-performance LMFP through a facile high-temperature solid-state synthesis method. The regenerated LMFP cathode exhibits reduced particle size, well-defined crystallinity, and exceptional electrochemical properties, delivering a specific capacity of 144.7 mAh g⁻¹ at 0.5C, a rate capability of 120.5 mAh g⁻¹ at 5.0C, and 91.1% capacity retention after 500 cycles at 1.0C. The underlying phase transformation and Mn activation mechanisms during high-temperature calcination were systematically investigated, revealing critical insights into the structural evolution from LFP to LMFP. This work provides fundamental insights into the design of efficient upcycling strategies for transitioning low-voltage cathodes to advanced high-energy-density materials, offering both environmental and technological benefits for sustainable energy storage.