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Electron microscopy (EM), specifically in situ, is a powerful analytical and characterisation technique that is widely used to study electrode materials for battery applications.

A mixed metal compound from separation and processing of spent batteries is demonstrated to be feasible as a “second-life” anode.

Sodium-ion battery (NIB) technology has drawn increased attention for stationary storage applications owing to its potential in facilitating the transition to a world powered by renewables, mainly due to sodium’s vast elemental abundance, lower costs, and suitable redox potential. Nevertheless, it is still a challenge to realize practical NIBs due to the lack of low-cost and high-performance electrode materials with sufficient power densities, cycling stability, and long life. This work examines the potential of sustainable hard carbons synthesized from the thermal transformation of readily available macadamia nutshell biomass to achieve NIBs with high specific and areal capacities. A comprehensive characterization of the hard carbons is performed to understand their structural and morphological attributes. The carbons synthesized at 1100 °C demonstrated excellent long-term cycling performance and specific capacities as high as 220 mAh/g at a current density of 10 mA/g. Furthermore, the areal capacity of 0.85 mAh/cm2 was obtained at 20 mA/g, even at low mass loadings of 4.5 mg/cm2. Based on these findings, the hard carbons prepared in this work are likely to be a promising candidate for the negative electrode in practical Na-ion batteries for grid-level energy storage.

The current electrolyte compositions makes it hard to achieve a high energy density lithium-ion battery based on LiCoO 2 chemistry due to the destabilization of the LiCoO 2 crystal structure beyond 4.2 V vs Li/Li + leading to oxygen evolution and electrolyte decomposition. Therefore, electrolyte developments may hold promise for improved performance, for example, if some of the advantageous properties of ionic liquids can be introduced into a carbonate electrolyte system. Here, we report the use of a hybrid electrolyte (HE) system with a LiCoO 2 cathode and have observed an excellent electrochemical performance when cycled to 4.4 V vs Li/Li + . This extended potential range produces higher capacity via greater ion insertion/extraction and better structural stability. A discharge capacity of 161 mAh/g (0.7 lithium extraction) was observed in the HE as compared to 128 mAh/g in conventional electrolyte, after 60 cycles. The charge−discharge studies at extended potentials also indicate better capacity retention in the HE as compared to the conventional electrolyte (LP30). Investigations to confirm the origin of such behavior establish that surface film formation is protecting or delaying the phase transition for LiCoO 2 at extended potentials. In situ XRD studies suggest that the electrolyte combination helps to delay the potential for monoclinic phase formation in LiCoO 2 , and ex situ XRD studies suggest less structural degradation takes place in the HE than the conventional electrolyte at the end of 60 cycles. Therefore, we believe that the future tailoring of the HE will provide a significant step toward high energy density lithium batteries.