Lithium iron phosphate (LFP) cathode material has been extensively employed in energy storage and electric vehicle applications. However, the conventional solid-state synthesis method for LFP suffers from limitations in reducing anti-site defects and optimizing Li+ migration efficiency along one-dimensional channels. As a result, it exhibits subpar electrochemical performance at high current and low temperature, which hampers its further development. In this work, a micro-nano-scaled high performance LFP cathode material was successfully synthesized using hydrothermal method, offering superior cost-effectiveness and environmental sustainability. The experiment achieved zero pollutant discharge by recycling waste liquid containing lithium. Additionally, in-situ nitrogen-doped carbon coating was applied to the LFP during the hydrothermal process. This approach not only enhanced the material's conductivity but also restrained the growth of LFP crystal cell volume, particularly along the b-axis direction of crystallization. Moreover, the synthesis of low-defect LFP with wider Li + transport channel has significantly enhanced the efficiency of Li+ extraction/insertion of the material, thereby addressing the issue of poor electrochemical performance of LFP at high-rate and low-temperature. Various electrochemical characterization methods have also confirmed that LFP synthesized from recycled lithium waste liquid exhibits significant advantages than commercial LFP, especially in terms of high-current and low-temperatures charge-discharge performance. This novel strategy provides a theoretical foundation for the industrial-scale production of LFP using low-cost hydrothermal methods.
Direct regeneration of spent lithium-ion batteries has received wide attention owing to its potential for resource reuse and environmental benefits. The repair effect of direct regeneration methods undergoing heterogeneous repair process is usually inferior, while homogenous repair process plays a vital role to achieve satisfactory repair results. However, the practical applications of current homogeneous repair methods are challenged by the complex operations and relatively high costs owing to the requirement of additional heating or pressurization. Herein, this work proposes a simple strategy to achieve homogeneous repair of spent cathode materials under relatively mild conditions by uniformly precoating lithium source at room temperature and atmospheric pressure. Followed by annealing, highly degraded LiNi 0.83 Co 0.12 Mn 0.05 O 2 with severe Li deficiency and irreversible phase transition is repaired to have an initial capacity of 181.6 mAh g -1 and capacity retention of 80.7% after 150 cycles at 0.5 C. The lithium source used in this strategy is from the spent lithium anode. Moreover, this strategy is suitable for the direct regeneration of various layer oxide cathode materials with different failure degrees. This work provides both theoretical guidance and practical examples for the straightforward, effective, and universally applicable direct regeneration methods.
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