All-element recovery and regeneration of mixed LiNixCoyMn1-x-yO2/LiFePO4 cathode materials by synergistic redox processes.

Given the rising lithium-ion battery retirement trend, there is a pressing need for a sustainable, cost-effective, versatile, and industrially viable positive active powder reprocessing method. The current treatment methods require significant amounts of acids, reducing agents, and other additives, resulting in increased treatment expenses and detrimental environmental consequences. This paper proposes a synergistic redox strategy, based on thermodynamic calculations of potential self-promoting reactions in mixed LFP/NCM systems, for the recovery of spent LFP and NCM batteries without the need for additional agents in a milder acidic atmosphere. In this cooperative redox strategy, the spontaneous extraction and oxidation of Fe2+ to Fe3+ took place within the acidic solution atmosphere encapsulating LFP. Simultaneously, NCM underwent further reduction, yielding Ni2+ and Fe2+, thereby enabling the proficient dissolution and segregation of lithium and transition metal ions. The leaching rate of lithium, nickel, cobalt and manganese was close to 100% when the reaction was carried out at 20 °C for 40 min. The final raw material was reprepared into a battery with a capacity of 168.8 mA h g-1 at 1C, and the cycle retention rate was 76.78% after 300 cycles. Regenerating FPO into LFP cathode material achieves closed-loop recycling of all elements and generates 12% higher profits compared to separate processes. Our method proposes a zero-additive battery recycling process and successfully explains the intrinsic redox process.

Al-doping enables high stability of single-crystalline LiNi0.7Co0.1Mn0.2O2 lithium-ion cathodes at high voltage.

LiNi0.7Co0.1Mn0.2O2 (NCM) is a kind of promising cathode material for lithium ion batteries because of its high capacities. However, the further commercialization of this material has been seriously hindered by the unstable structure at a deep de-lithiation state. Herein, it is identified that this drawback can be diminished by Al-doping, which is inherently stable in the lattice framework to restrain the structural collapse of LiNi0.7Co0.1Mn0.2O2 at a high cut-off voltage (4.4 V). As expected, the Al-doped NCM (NCM-0.2Al) material obtains the highest reversible capacity and capacity retention (144.69 mA h g-1, 80.26%) after 90 cycles at 1C. The excellent performance demonstrates that Al-doping can effectively enhance the Li+-ion diffusion kinetic and structural stability of NCM, providing a feasible strategy for the further industrialization of Ni-rich materials.