Search

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]

Optimizing the properties of solid electrolyte interphase (SEI) layers on graphite electrodes is a crucial method for influencing the performance of cells. However, most studies ignore any potential synergistic effects of the reduction and oxidation products of electrolytes and only focus on their individual properties. In this study, we have formatted the pure reduction and oxidation products of lithium difluorobis(oxalato) phosphate (LiDFBOP) on highly oriented pyrolytic graphite (HOPG) and lithiation HOPG surfaces and proved that there is rigid and high viscoelasticity, respectively. Accordingly, a cracked reduction product forming layer is built at a high discharge current. During the following charging process, a low current is used to oxidize LiDFBOP, generating oxidation products that strongly attach to the crack inside. Finally, a multifunctional SEI layer with a gomphosis-like structure is constructed, which prevents lithium dendrite degradation, improves the stability of the interphase layer, and significantly increases the capacity retention of graphite half cells (from 50.2% to 96.7% at 0.5C after 200 cycles). This research opens up new possibilities for logically controlling the SEI production process and clarifies the high-power LIB design strategy. [ABSTRACT FROM AUTHOR]

The high price of lithium salts hinders the sustainable development of high concentration electrolytes, while the poor electrochemical performance limits the large-scale application of low concentration electrolytes. Herein, the electrochemical performance of a low concentration electrolyte is improved via dual interfacial modification of the fluoroethylene carbonate (FEC) solvent and the lithium difluoro(oxalato)borate (LiODFB) additive. LiODFB is preferentially oxidized via a ring-opening path to generate a lithium fluoride (LiF)-rich inner layer on the surface of a ferrous lithium phosphate cathode, and then a large amount of C–F polycarbonate oligomers is generated in the outer layer via a reaction between LiODFB and FEC. LiF has a large bandgap and a low lithium ion (Li+) diffusion barrier, and the electronegative C–F groups provide the lithiophilic sites to reduce the interaction between Li+ and solvents, resulting in a repulsive force towards the C＝O dipole of the carbonate ester solvent to improve the oxidation stability of the electrolyte. The clever design of the multi-layer cathode electrolyte interphase suppresses the excessive decomposition of the electrolyte, improves the diffusion of Li+, and enables much-improved cycling stability of the cathodes. This work gives a fruitful insight into the key role of cathode electrolyte interphase components in Li+ diffusion and improves the performance of low-concentration electrolytes. [ABSTRACT FROM AUTHOR]

The application of activated carbon is greatly limited by its low energy density. Here, the angelica herb residue–based activated carbon (AHRAC) materials modified by loading NiO and MnO2 were prepared via a hydrothermal reaction, respectively. The results of structure measurements and electrochemical tests reveal that NiO is more beneficial for improving the specific capacitance (about 678.2 F g−1) and energy density (about 30 Wh kg−1) of AHRAC owing to its unique flower-like morphology and abundant porosity. In addition, combining the density functional theory calculation (DFT), differential pulse voltammetry (DPV), and diffusion coefficient calculation, the difference between AHRAC@NiO and AHRAC@MnO2 was analyzed, which may be ascribed to the larger pseudo-capacitance contribution, bigger diffusion coefficient, and higher adsorption behavior for OH−. In this work, not only a porous carbon with a high specific surface area was prepared, but also the biomass waste was reused. [ABSTRACT FROM AUTHOR]

The low‐concentration electrolyte possesses the benefits of desirable wettability, low viscosity, and low cost. However, the mechanism of its poor electrochemical performance is not clear. Herein, the properties of interfacial films on the surface of LiFePO4 (LFP) cathode material formed by electrolytes with different concentrations are compared by interfacial component analysis. It is shown that moderate content of lithium fluoride increases the length of Li+–ethylene carbonate bond from 1.676 to 1.824 Å through lithium bond and then decreases the desolvation activity energy of Li+ ion, which effectively promotes the desolvation process of Li+ ion at the interface of LFP/electrolyte, and finally ensures the perfect performance of the battery. That is, the fundamental cause for the undesirable electrochemical performances of the low‐concentration electrolyte is the low content of LiF components in the interface film rather than the low ionic conductivity of the electrolyte itself. This indicates the direction of optimizing the electrochemical performance of low‐concentration electrolytes. [ABSTRACT FROM AUTHOR]