With the wide usage of Li-ion batteries (LIBs) in portable electronics, electric vehicles, and grid storage, recycling and reusing LIBs have attracted wide attention. However, due to the low added value and rigorous separation steps, recycling and recovering graphite anode materials are discarded. Although some direct physical recycling processes have been reported, all of them are limited by rigorous separation steps and lab scales. In this paper, a scalable recycling process for graphite anode materials from spent LIBs by a hydrometallurgical process without separation steps is reported. After the leaching process, graphite was separated by filtration as a residue with impurities. Then, all residual cathode materials, other metal impurities, most binding materials, and aluminum oxide were removed after releaching and fusion steps. Finally, high-quality graphite powder was obtained, and the recycled graphite exhibits a comparable discharge capacity of 377.3 mAh/g at 0.1 C.
Amorphous Li 0.35 La 0.55 TiO 3 (LLTO) shows great promise as solid electrolyte material in all-solid-state Li-ion batteries (ASSLiB). Amorphous LLTO thin films with high stability were successfully synthesized by sol-gel process in our previous work. The ionic conductivity can reach up to 1.88*10 −5 S cm −1 at 30 °C. In order to further increase the ionic conductivity to meet the requirements of ASSLiB, cation doping is applied in this study. Specifically, Strontium (Sr) is introduced as dopant and the ionic conductivity reaches 8.38 × 10 −5 S cm −1 at 30 °C with 5% of Sr doping, which is about one order of magnitude higher than that of undoped LLTO. It is also confirmed that amorphous LLSTO is stable in direct contact with Lithium and with stability window up to 10 V. Furthermore, the relationship between the structure change along with Sr ratio and ionic conductivity is identified. This could be critical for further study of solid electrolyte materials.
From portable electronics to electric vehicles, lithium-ion batteries have been deeply integrated into our daily life and industrial fields for a few decades. The booming field of battery manufacturing could lead to shortages in resources and massive accumulation of battery waste, hindering sustainable development. Therefore, hydrometallurgy-based approaches have been widely used in industrial recycling to recover cathode materials due to their high efficiency and throughput. Impurities have always been a great challenge for hydrometallurgical recycling, introducing challenges to maintain the consistency of product quality because of potential unintended effects caused by impurities. Herein, after comprehensive investigation, we first report the impacts of phosphate impurity on a recycled LiNi 0.6 Co 0.2 Mn 0.2 O 2 ("NCM622") cathode via a hydrometallurgy method. We demonstrate that a passivation layer of Li 3 PO 4 is formed at grain boundaries during sintering, which significantly raises the activation barrier and hinders lithium diffusion. In addition, the distinct degradation of cathode electrochemical properties is observed from poor particle morphology and high cation mixing as a result of phosphate impurity. Cathode powders with 1 at. % phosphate impurity retain a capacity of 146 mAh/g after 100 cycles at 0.33C, 6% less than that of a virgin cathode. Furthermore, cathodes with higher phosphate concentrations perform even worse in electrochemical tests. Therefore, phosphate impurities are detrimental to the hydrometallurgical recycling of NCM cathode materials and need to be excluded from the recycling process.
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