Toward the efficient direct regeneration of spent cathode materials through the effect of residual sodium ions analysis.

Recycling spent lithium-ion batteries is an important means for promoting sustainability within the energy industry. In this study, the effects of residual sodium on the regeneration process and the performance of spent LiNi0.5Co0.2Mn0.3O2 were explored. An appropriate amount of residual sodium was found to improve the properties of the regenerated material, with the best cycle performance and rate performance at a residual sodium of 3 mol %. The first-cycle and 100-cycle discharge capacities were 136.4 mA h g-1 and 120 mA h g-1, respectively, with a capacity retention rate of 87.98% after 100 cycles at a rate of 1 C. The electrochemical performance of the regenerated cathode materials was improved because sodium occupied the lithium sites in the crystal structure, providing a channel for lithium deintercalation. These results indicate that the residual sodium ions should be monitored in appropriate quantities to improve the efficiency of recycling spent lithium-ion batteries.

Solid Carbon Spheres with Interconnected Open Pore Channels Enabling High-Efficient Polysulfide Conversion for High-Rate Lithium-Sulfur Batteries.

Hollow carbon spheres or core-sheath porous carbon spheres have been widely used in the S cathode of lithium-sulfur batteries. However, the sphere shells or the pore walls may block the free transport of active species to a certain extent and may have a negative influence on the effective accommodation of elemental sulfur. Herein, solid but porous carbon spheres (PNCS) with large porosity and high specific surface area are developed, which enable high sulfur loading and ample cathode/electrolyte contact area, and the interconnected open pore channels significantly shorten the ion/electron transport pathways. Together with high-conducting nitrogen-doped graphene (NG), facilitated polysulfide conversion kinetics is realized in the as-assembled Li-S batteries, which deliver a high initial discharge capacity of 1445 mAh g-1 at 0.2 C, excellent rate capability of 872 mAh g-1 at 4 C, and low capacity decay of 0.047% per cycle for 500 cycles at 1 C. Even under high sulfur loading of 5.5 mg cm-2 and low electrolyte/sulfur (E/S) ratio of 5 µL mg-1, the Li-S batteries still display high specific capacities of 896 mAh g-1 and 4.96 mAh cm-2. The real application of PNCS/NG is also demonstrated by the corresponding Li-S pouch cells showing high discharging capacity and stable open circuit voltage. This work exhibits the promising application of the solid carbon spheres as the S host for effectively addressing the polysulfide shuttle and propelling the development of high-performance Li-S batteries.