Recently, Professor Li Li's team at Northeastern University School of Metallurgy has made significant progress in the research of recycling and reuse of cathode materials of used lithium-ion batteries. The related research results have been published in Acta Materialia, the top international journal in the field of metals, under the title of “Direct regeneration of spent LiCoO2 cathodes with Ca2+-assisted molten salt strategy”. NEU is the first completion unit, and Professor Li Li is the corresponding author.
The team proposed a simple trace calcium-assisted molten salt strategy for direct regeneration of degraded LiCoO2. The regeneration kinetics of degraded LiCoO2 was optimized by introducing a trace amount of cheap Ca2+ into the molten salt environment to promote the generation of ordered structures and uniform stable interfaces, and at the same time, the uniform embedding of Ca2+ in some of the lithium vacancies was achieved, which enhanced the structural stability of the regenerated LiCoO2 in the process of the electrochemical reaction, accelerated the reaction kinetics, and obtained a high multiplicity and a long cycling stability performance.
The research results have achieved efficient recycling and reuse of degraded cathode materials from used lithium-ion batteries, which not only effectively reduces the supply-side pressure of valuable metals and promotes the sustainable development of the economy, but also avoids the possibility of environmental pollution by the leakage of heavy metals or organic electrolytes. Currently, recycling methods can be categorized into three main groups: traditional pyrometallurgy, hydrometallurgy and direct regeneration. The high energy consumption, strong pollution and complex processes of traditional pyrometallurgy and hydrometallurgy have led to significant limitations in their application in environmental and economic scenarios. In contrast, direct regeneration, which does not destroy the original structure and directly replenishes the lost elements with in-situ repair of the damaged structure, is seen as a more attractive alternative. The exploration of a direct regeneration method for degraded LiCoO2 cathode materials is based on the advantages of its huge market retention, wide application fields, relatively stable atomic structure, and excellent electrochemical properties. Realizing the direct regeneration of degraded LiCoO2 could provide a boost to the development of current consumer electronics market. The presence of Ca2+ not only optimizes the regeneration kinetics of regenerated LiCoO2 in molten salt environments, but also maximizes the structural stability, multiplicative performance under high currents, and cycling stability performance of regenerated LiCoO2 by uniformly embedding it into the lithium vacancies. This work not only provides new insights into the direct regeneration of degraded LiCoO2 cathode materials, but also provides a new means for a viable solution for recycling waste batteries in the future. In the process of research, the Analysis and Testing Center of NEU provided important support for data collection and characterization.
