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With the large-scale retirement of new energy vehicles, it is particularly important to recycle and reuse retired lithium-ion batteries (LIBs). However, the current improper handling of spent electrolytes will cause serious environmental problems. Here, we propose a novel, simple and easy-to-implement method to realize the high-value utilization of recovered electrolytes from retired LIBs. Comparing with the initial content of LiPF6 (1 mol L−1 in a mixed carbonate solvent system, and about 1 g in a 18650 type LIB) in fresh batteries, a maximum leaching efficiency of 29% could be realized during the full-component resource reclamation of retired LIBs, using the selective mixed leaching solvent system of dimethyl carbonate + CHClF2 (1 : 1, v/v ratio). Then the water and HF impurities are reduced from 80.90 ppm to 4.56 ppm and from 1312.91 ppm to 291.52 ppm by pre-treatment with hexamethyl disilazane (C6H19NSi2). Although the purified electrolyte does not meet the standards for re-use in LIBs, it can be used as a synthetic raw material for lithium salt additives. As a typical case, the LiPF6 salt in a leached electrolyte is recycled into a salt additive of lithium difluorodioxalate phosphate (LiDFBOP) under the preferred reaction conditions (75 °C, 27 h, with a molar ratio of 1 : 3 for LiPF6 : bis (trimethylsilicon)oxalate), realizing closed-loop recycling. The electrochemical results show that the electrochemical performances of the graphite/Li and LNCA/Li half cells are significantly improved with the addition of the as-prepared LiDFBOP additive. This research gives a large-scale synthesis route to realize high-value utilization of low-quality LiPF6, and helps establish a full-component resource reclamation process of retired LIBs. It not only improves environmental friendliness, but also realizes the high efficiency utilization of resources. [ABSTRACT FROM AUTHOR]

The widespread application of Li 4 Ti 5 O 12 (LTO) anode in lithium-ion batteries has been hindered by its relatively low energy density. In this study, we investigated the capacity enhancement mechanism of LTO anode through the incorporation of Na + cations in an Li + -based electrolyte (dual-cation electrolyte). LTO thin film electrodes were prepared as conductive additive-free and binder-free model electrodes. Electrochemical performance assessments revealed that the dual-cation electrolyte boosts the reversible capacity of the LTO thin film electrode, attributable to the additional pseudocapacitance and intercalation of Na + into the LTO lattice. Operando Raman spectroscopy validated the insertion of Li + /Na + cations into the LTO thin film electrode, and the cation migration kinetics were confirmed by ab initio molecular dynamic (AIMD) simulation and electrochemical impedance spectroscopy, which revealed that the incorporation of Na + reduces the activation energy of cation diffusion within the LTO lattice and improves the rate performance of LTO thin film electrodes in the dual-cation electrolyte. Furthermore, the interfacial charge transfer resistance in the dual-cation electrolyte, associated with ion de-solvation processes and traversal of the cations in the solid-electrolyte interphase (SEI) layer, are evaluated using the distribution of relaxation time, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Our approach of performance enhancement using dual-cation electrolytes can be extrapolated to other battery electrodes with sodium/lithium storage capabilities, presenting a novel avenue for the performance enhancement of lithium/sodium-ion batteries., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Layered ternary oxide LiNi x Mn y Co 1- x - y O 2 is a promising cathode candidate for high-energy lithium-ion batteries (LIBs). However, the capacity of LIBs is significantly restricted by several factors, including the repeated dissolution-regeneration of the interfacial film at high temperatures, the dissolution of transition metals, and the increase of impedance. Herein, a new precycling strategy in suitable voltage scope at room temperature is proposed to construct a uniform, thermally stable, and insoluble cathode-electrolyte interface (CEI), which helps to maintain stable cycling performances at high temperatures. Specifically, after 5 precycles in the range of 3.85-4.3 V at room temperature, a CEI layer containing numerous inorganic components and oligomers is formed on the surface of LiNi 0.6 Mn 0.2 Co 0.2 O 2 . Subsequently, the harmful side reactions are effectively suppressed, endowing the cell with an excellent capacity retention of 84.67% after 50 cycles at 0.5C and 55 °C, much higher than that of 65.61% under the conventional film-forming process conditions. This work emphasizes the crucial role of the precycling strategy in regulating the characteristics of CEI layer on the surface of cathode electrode, opening up a new avenue for the high-temperature application of positive electrodes of LIBs.