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Sodium-ion batteries (SIBs) are in the spotlight because of their potential use in large-scale energy storage devices due to the abundance and low cost of sodium-based materials. There are many SIB cathode materials under investigation but only a few candidate materials such as carbon, oxides and alloys were proposed as anodes. Among these anode materials, hard carbon shows promising performances with low operating potential and relatively high specific capacity. Unfortunately, its low initial coulombic efficiency and high cost limit its commercial applications. In this study, low-cost maple tree-biomass-derived hard carbon is tested as the anode for sodium-ion batteries. The capacity of hard carbon prepared at 1400 °C (HC-1400) reaches 337 mAh/g at 0.1 C. The initial coulombic efficiency is up to 88.03% in Sodium trifluoromethanesulfonimide (NaTFSI)/Ethylene carbonate (EC): Diethyl carbonate (DEC) electrolyte. The capacity was maintained at 92.3% after 100 cycles at 0.5 C rates. The in situ X-ray diffraction (XRD) analysis showed that no peak shift occurred during charge/discharge, supporting a finding of no sodium ion intercalates in the nano-graphite layer. Its low cost, high capacity and high coulombic efficiency indicate that hard carbon is a promising anode material for sodium-ion batteries.

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The electrochemical performance of Al-doped and un-doped Li1+xNi0.6Co0.2Mn0.2O2 (NCM) cathodes was evaluated at a high cut-off voltage up to 4.6 V (vs Li/Li+) using 1 Ah pouch-type full cells and coin-type half cells. The batteries employing Al-doped NCM exhibited lower internal resistance, higher C-rate capability, and better low-temperature performance. In situ X-ray diffraction revealed that the Al-doped cathode followed a one-phase reaction route, which is attributed to enhanced Li+ diffusion due to Al doping and the relatively small and porous secondary particles. The existence of the pristine phase in undoped NCM throughout the cycling is explained by the slow diffusion of lithium in and out of the large and dense particles, leading to phase separation caused by regions with different lithium concentrations. Analysis using time-of-flight secondary ion mass spectrometry combined with a focused ion-beam scanning electron microscopy confirmed that the Li-ion distribution of undoped NCM was less homogeneous than that of the doped NCM.

A Li4Ti5O12 (LTO) anode material was coated with a Li-rich PTCLi4 organic molecule using a spray-dryer technique to increase the Li-ion transfer at the electrode–electrolyte interface enabling battery cycling at sub-zero temperatures.