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A new green recycling process (named as direct regeneration process) of cathode material mixture from scrapped LiFePO4 batteries is designed for the first time. Through this direct regeneration process, high purity cathode material mixture (LiFePO4 + acetylene black), anode material mixture (graphite + acetylene black) and other by-products (shell, Al foil, Cu foil and electrolyte solvent, etc.) are recycled from scrapped LiFePO4 batteries with high yield. Subsequently, recycled cathode material mixture without acid leaching is further directly regenerated with Li2CO3. Direct regeneration procedure of recycled cathode material mixture from 600 to 800 °C is investigated in detail. Cathode material mixture regenerated at 650 °C display excellent physical, chemical and electrochemical performances, which meet the reuse requirement for middle-end Li-ion batteries. The results indicate the green direct regeneration process with low-cost and high added-value is feasible.

According to the tetrahedral phase diagram of LiNiO2–LiCoO2–LiMnO2–Li2MnO3, a series of Li1.2(Ni0.2Mn0.6)x(Co0.4Mn0.4)y(Ni0.4Mn0.4)1−x−yO2 (0 ≤ x + y ≤ 1) have been designed to explore new Li-rich solid solution cathode materials. The effects of Li1.2Ni0.2Mn0.6O2, Li1.2Co0.4Mn0.4O2 and Li1.2Ni0.4Mn0.4O2 content in solid solutions on structure and electrochemical properties are investigated. Micro-sized spherical or ellipsoidal precursors are first prepared via a carbonate co-precipitation route. After calcination with lithium sources, all samples are indexed to a typical layered structure with an Rm space group as detected by X-ray diffraction (XRD). It is found that the introduction of Co can improve the tap density. However, these Co referred samples reveal lower discharge specific capacities and inferior cycle life. For these Co-free materials with high Ni content, for instance Li1.2Ni0.3Mn0.5O2, although low capacity is observed in the initial cycle, a large capacity of above 250 mA h g−1 is achieved after about 10 cycles. Importantly, the activated Li1.2Ni0.3Mn0.5O2 material still delivers a high capacity of over 230 mA h g−1 after 70 cycles, displaying superior cycle stability. These results may be instructive in designing and exploring high performance cathode materials for advanced LIBs.

A new Li-rich positive-electrode Li1.13(Ni0.26Co0.09Mn0.52)O2 is successfully achieved via a dual ammonia and oxalate chelating agent co-precipitation route for the first time, which delivers a high volumetric energy density of over 2100 W h L−1, superior cycle life and stable high median-voltage. The dual or multiple chelating agent method gives a new insight towards high energy density for Li-rich materials with outstanding electrochemical performances for advanced lithium-ion batteries.

A green recycling process was designed and used to recycle spent LiCoO2 batteries, and the recycled LiCoO2 was regenerated after the solid state synthesis with Li2CO3. XRD results showed that the layered structure of LiCoO2 was repaired after regeneration. The physical and chemical properties (XRD, morphology, tap density, average particle size, specific surface areas and pH value) and electrochemical properties (discharge capacity, attenuation rate of capacity, plateau retention at 3.6 V and attenuation rate of plateau) of LiCoO2 after regeneration were tested in detail and compared with commercial LiCoO2. The test data show that the regenerated LiCoO2 at 900 °C can meet the commercial requirements for reuse.