Electrolyte design or functional development is very effective at promoting the performance of sodium-ion batteries, which are attractive for electrochemical energy storage devices due to abundant sodium resources and low cost. The roadmap of the sodium ion batteries based on electrolyte materials was drawn firstly and shows that the electrolyte type decides the electrochemical window and energy density.

Considering the natural abundance and low cost of sodium resources, sodium-ion batteries (SIBs) have received much attention for large-scale electrochemical energy storage. However, smart structure design strategies and good mechanistic understanding are required to enable advanced SIBs with high energy density. In recent years, the exploration of advanced cathode, anode and electrolyte materials, as well as advanced diagnostics have been extensively carried out. This review mainly focuses on the challenging problems for the attractive battery materials (i.e. cathode, anode and This article is protected by copyright. All rights reserved. 3 electrolytes) and summarizes the latest strategies to improve their electrochemical performance as well as presenting recent progress in operando diagnostics to disclose the physics behind the electrochemical performance, and to provide guidance and approaches to design and synthesize advanced battery materials. Outlook and perspectives on the future research to build better SIBs are also provided.

Many industrial catalysts are composed of metal particles supported on metal oxides (MMO). It is known that the catalytic activity of MMO materials is governed by metal and metal oxide interactions (MMOI), but how to optimize MMO systems via manipulation of MMOI remains unclear, due primarily to the ambiguous nature of MMOI. Herein, we develop a Pt/NbO/C system with tunable structural and electronic properties via a modified arc plasma deposition method. We unravel the nature of MMOI by characterizing this system under reactive conditions utilizing combined electrochemical, microscopy, and in situ spectroscopy. We show that Pt interacts with the Nb in unsaturated NbO owing to the oxygen deficiency in the MMO interface, whereas Pt interacts with the O in nearly saturated NbO, and further interacts with Nb when the oxygen atoms penetrate into the Pt cluster at elevated potentials. While the Pt-Nb interactions do not benefit the inherent activity of Pt toward oxygen reduction reaction (ORR), the Pt-O interactions improve the ORR activity by shortening the Pt-Pt bond distance. Pt donates electrons to NbO in both Pt-Nb and Pt-O cases. The resultant electron eficiency stabilizes low-coordinated Pt sites, hereby stabilizing small Pt particles. This determines the two characteristic features of MMO systems: dispersion of small metal particles and high catalytic durability. These findings contribute to our understandings of MMO catalytic systems.

Hierarchically structured carbon coated SnO2 nanoparticles well-anchored on the surface of a CNT (C-SnO2/CNT) material were synthesized by a facile hydrothermal process and subsequent carbonization. The as-obtained C-SnO2/CNT hybrid, when applied as an anode material for lithium ion batteries (LIBs), showed a high reversible capacity up to 1572 mA h g(-1) at 200 mA g(-1) with a superior rate capability (685 mA h g(-1) at 4000 mA g(-1)). Even after 100 charge/discharge cycles at 1000 mA g(-1), a specific capacity of 1100 mA h g(-1) can still be maintained. Such impressive electrochemical performance can be mainly attributed to the hierarchical sandwiched structure and strong synergistic effects of the ultrafine SnO2 nanoparticles and the carbon coating, and thus presents this material a promising anode material for LIBs.

O3-Type layered oxides are widely studied as cathodes for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, their rate capability and durability are limited by tortuous Na+ diffusion channels and complicated phase evolution during Na+ extraction/insertion. Here we report our findings in unravelling the mechanism for dramatically enhancing the stability and rate capability of O3-NaNi0.5Mn0.5–x Sb x O2 (NaNMS) by substitutional Sb doping, which can alter the coordination environment and chemical bonds of the transition metal (TM) ions in the structure, resulting in a more stable structure with wider Na+ transport channels. Furthermore, NaNMS nanoparticles are obtained by surface energy regulation during grain growth. The synergistic effect of Sb doping and nanostructuring greatly reduces the ionic migration energy barrier while increasing the reversibility of the structural evolution during repeated Na+ extraction/insertion. An optimized NaNMS-1 electrode delivers a reversible capacity of 212.3 mAh g–1 at 0.2 C and 74.5 mAh g–1 at 50 C with minimal capacity loss after 100 cycles at a low temperature of −20 °C. Such electrochemical performance is superior to most of the reported layered oxide cathodes used in rechargeable SIBs.