Hydrothermal Selective Leaching of Lithium from LiCoO2 under CO2 Atmosphere | Takuya Okazaki

Lithium-ion batteries (LIBs) are widely used in electronic devices and electric vehicles due to their high energy density. Consequently, the growing accumulation of spent LIBs has created an urgent need to develop technologies that can efficiently and sustainably recover critical metals such as lithium and cobalt. In this study, a method for selectively leaching lithium from LiCoO₂, a cathode material for LIBs, under hydrothermal conditions with high pressure CO₂ was proposed. An autoclave was charged with water, LiCoO₂, and solid CO₂ at prescribed ratios. The sealed vessel was heated at 1.67 °C min⁻¹ to the target temperature, maintained, then cooled. The mixture was filtered, lithium and cobalt were determined by inductively coupled plasma-atomic emission spectrometry, and the solids characterized by X-ray diffraction. At 15 MPa, the lithium leaching rate increased with rising reaction temperature, reaching 74.3% at 250 °C. On the other hand, the leaching rate of cobalt was low, remaining below the limit of detection (0.8 mg/L) at temperatures above 200 °C. Therefore, selective leaching of lithium from LiCoO₂ to the liquid phase was achieved by the hydrothermal reaction in the presence of CO₂. XRD analysis indicated Co₃O₄ as the main product and CoOOH as a by-product.

Keywords: Lithium-ion batteries; LiCoO₂; hydrothermal leaching; CO₂

This presentation is part of the Power-to-X for a Sustainable Future Workshop 2025, taking place on 14–16 September 2025 at the Montien Hotel Surawong, Bangkok, Thailand. The Power-to-X initiative is supported by the Royal Academy of Engineering.