Recovery of valuable metals from spent lithium-ion batteries through biomass pyrolysis gas-induced reduction

Highly efficient selective extraction of Li from spent LiNixCoyMnzO2 assisted with activated pyrite in a subcritical water system

As the strategic importance of Li in the energy sector increases, selective Li extraction technology from spent lithium-ion batteries (LIBs) is attracting increasing attention. Current Li extraction processes typically suffer from lengthy procedures, high costs, and low efficiency. To improve the efficiency of Li extraction, a novel approach to achieve efficient Li recovery is proposed in this study, namely, reacting pyrite (FeS2) with LiNixCoyMnzO2 (NCM) powder in a subcritical water reduction (SWR) system. The reducing solvent environment created by the enhanced reaction of FeS2 with subcritical water converts the high-valent metals in NCM to a low-valent state, causing the collapse of the stable laminar structure and allowing Li+ to be released smoothly. After dual activation through mechanochemical and roasting processes, more than 99 % of Li is preferentially extracted under optimal conditions. Furthermore, Li+ in solution is converted into highly pure Li2CO3, while other metallic elements remain in the residue. Using inexpensive FeS2 for efficient Li extraction without adding additional chemical reagents is a promising approach for recovering spent LIBs.

Revealing the delithiation process of spent LiMn2O4 and LiNi0.6Co0.2Mn0.2O2 batteries during the biomass-assisted gasthermal and carbothermal reduction

The utilization of biomass-assisted pyrolysis in the recycling of spent lithium-ion batteries has emerged as a promising and reliable process. This article furnishes theoretical underpinnings and analytical insights into this method, showcasing sawdust pyrolysis reduction as an efficient means to recycle spent LiMn2O4 and LiNi0.6Co0.2Mn0.2O2 batteries. Through advanced thermogravimetry-gas chromatography-mass spectrometry analysis complemented by traditional thermodynamic demonstration, the synergistic effects of biomass pyrolysis reduction are elucidated, with minor autodecomposition and major carbothermal and gasthermal reduction pathways identified. The controlled manipulation of transition metals has demonstrated the capability to modulate surface pyrolysis gas catalytic reactions and facilitate the preparation of composite materials with diverse morphologies. Optimization of process conditions has culminated in recovery efficiency exceeding 99.0 % for LiMn2O4 and 99.5 % for LiNi0.6Co0.2Mn0.2O2. Economic and environmental analyses underscore the advantages of biomass reduction and recycling for these two types of spent LIBs: low energy consumption, environmental compatibility, and high economic viability.

Crystal phase and nanoscale size regulation utilizing the in-situ catalytic pyrolysis of bamboo sawdust in the recycling of spent lithium batteries

Current Li-ion battery (LIB) recycling methods exhibit the disadvantages of low metal recovery efficiencies and high levels of pollution and energy consumption. Here, products generated via the in-situ catalytic pyrolysis of bamboo sawdust (BS) were utilized to regulate the crystal phase and nanoscale size of the NCM cathode to enhance the selective Li extraction and leaching efficiencies of other valuable metals from spent LIBs. The catalytic effect of the NCM cathode significantly promoted the release of gases from BS pyrolysis. These gases (H2, CO, and CH4) finally transformed the crystal phase of the NCM cathode from LiNixCoyMnzO2 into (Ni-Co/MnO/Li2CO3)/C. The size of the spent NCM cathode material was reduced approximately 31.7-fold (from 4.1 μm to 129.2 nm) after roasting. This could be ascribed to the in-situ catalytic decomposition of aromatic compounds generated via the primary pyrolysis of BS into C and H2 on the surface of the cathode material, resulting in the formation of the nanoscale composite (Ni-Co/MnO/Li2CO3)/C. This process enabled the targeted control of the crystal phase and nanoscale size of the material. Water leaching studies revealed a remarkable selective Li extraction efficiency of 99.27 %, and sulfuric acid leaching experiments with a concentration of 2 M revealed high extraction efficiencies of 99.15 % (Ni), 93.87 % (Co), and 99.46 % (Mn). Finally, a novel mechanism involving synergistic thermo-reduction and carbon modification for crystal phase regulation and nanoscale control was proposed. This study provides a novel concept for use in enhancing the recycling of valuable metals from spent LIBs utilizing biomass waste and practices the concept of "treating waste with waste".

Recycling of spent lithium-ion batteries for a sustainable future: recent advancements

Lithium-ion batteries (LIBs) are widely used as power storage systems in electronic devices and electric vehicles (EVs). Recycling of spent LIBs is of utmost importance from various perspectives including recovery of valuable metals (mostly Co and Li) and mitigation of environmental pollution. Recycling methods such as direct recycling, pyrometallurgy, hydrometallurgy, bio-hydrometallurgy (bioleaching) and electrometallurgy are generally used to resynthesise LIBs. These methods have their own benefits and drawbacks. This manuscript provides a critical review of recent advances in the recycling of spent LIBs, including the development of recycling processes, identification of the products obtained from recycling, and the effects of recycling methods on environmental burdens. Insights into chemical reactions, thermodynamics, kinetics, and the influence of operating parameters of each recycling technology are provided. The sustainability of recycling technologies (e.g., life cycle assessment and life cycle cost analysis) is critically evaluated. Finally, the existing challenges and future prospects are presented for further development of sustainable, highly efficient, and environmentally benign recycling of spent LIBs to contribute to the circular economy.

Balancing the Components of Biomass and the Reactivity of Pyrolysis Gas: Biomass-Assisted Recycling of Spent LiCoO2 Batteries

Waste biomass is one of the promising feedstocks to supply syngas that can be used as fuels, chemicals, reductants, etc. However, the relationship between the component of biomass and the constituent of pyrolysis gas remains unclear. Here, we study the pyrolysis behaviors of various biomasses and reveal the relationship between the biomass components and gas compositions. Further, different pyrolysis gases are applied for the reduction of spent lithium cobalt oxide (LiCoO2) below 500 °C. The pyrolysis gas with a higher concentration of CO has a higher reductivity to convert LiCoO2 to CoO and Li2CO3 with a conversion rate close to 100% in 1 h at 500 °C. The biomass rich in cellulose and with a lower content of lignin tends to produce pyrolysis gas with a high concentration of CO, which comes from the deliberate breakdown of carboxyl, carbonyl, ether, and ester linkages. Moreover, LiCoO2 exerts catalytic functions over the deoxygenation and enhancement of oxygenates and single-ring aromatics. Overall, this paper offers a tailored approach to regulating biomass pyrolysis gases, enabling highly efficient battery recycling and syngas production.