In a study published in Advanced Energy Materials, a research team led by Prof. ZHANG Yunxia from Institute of Solid State Physics,Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS) developed a solid-phase sintering strategy to enable direct conversion of the degraded LiCoO₂ (D-LCO) into the cathode materials with high energy density.

With the impending influx of retired lithium-ion batteries, it is critical to investigate effective regeneration and upcycling strategies in order to alleviate resource scarcity, mitigate environmental contamination, and meet the demand for high-energy-density cathode materials.

In this research, a facile, non-constructive, one-stone-for-three-birds solid-phase sintering strategy is proposed to regenerate the degraded LiCoO₂ (D-LCO) cathode and even upgrade its stability at high voltages.

"It's like hitting three birds with one stone," said Prof. ZHANG, referring to the simultaneous integration of lithium supplement, Li₂SO₄ coating, and Mn doping into Co sites, along with N and S doping into Li-O slabs using a one-pot solid-phase sintering approach.

The upcycled cathode not only yielded high discharge specific capacity of 188.2 mAh/g at 0.2 C, but also delivered superior cycling performance with 92.5% of capacity retention after 100 cycles at 0.5 C and excellent rate capability at a high cutoff voltage of 4.5 V, superior to the freshly commercial counterpart. Evidently, various spent LCO cathode materials from various manufacturers or with varying Li/Co molar ratios could be effectively upgraded into high-performance lithium-ion batteries, highlighting the universality and feasibility of the developed one-stone-for-three-birds solid-phase sintering method.

"Our study provided meaningful guidance for the upcycling of D-LCO into high-energy-density batteries with long-term cycling stability," said Dr. ZHANG, corresponding author of the study, "it may also be extended to upgrade other degraded cathode materials into high-performance lithium-ion batteries."

Figure 1. Schematic illustration for the upcycling procedure of D-LCO cathodes. (Image by LIU Zhenzhen)