The development of low-cost and long-lasting all-climate cathode materials for the sodium ion battery has been one of the key issues for the success of large-scale energy storage. One option is the utilization of earth-abundant elements such as iron. Here, we synthesize a NASICON-type tuneable Na₄Fe₃(PO₄)₂(P₂O₇)/C nanocomposite which shows both excellent rate performance and outstanding cycling stability over more than 4400 cycles. Its air stability and all-climate properties are investigated, and its potential as the sodium host in full cells has been studied. A remarkably low volume change of 4.0% is observed. Its high sodium diffusion coefficient has been measured and analysed via first-principles calculations, and its three-dimensional sodium ion diffusion pathways are identified. Our results indicate that this low-cost and environmentally friendly Na₄Fe₃(PO₄)₂(P₂O₇)/C nanocomposite could be a competitive candidate material for sodium ion batteries.

The energy storage system (ESS) revolution has led to next-generation personal electronics, electric vehicles/hybrid electric vehicles, and stationary storage. With the rapid application of advanced ESSs, the uses of ESSs are becoming broader, not only in normal conditions, but also under extreme conditions (high/low-temperatures, high stretching/compression conditions, etc.), bringing new challenges in the energy storage field. To break the electrochemical constraints of ESSs under normal conditions, it is urgent to explore new approaches/concepts to address the critical challenges for ESSs working under extreme conditions via mechanistic understanding of new electrochemical reactions and phenomena in diverse scenarios. In this review, we first summarize the key scientific points (such as electrochemical thermodynamics and kinetics, and mechanical design) for electrochemical ESSs under extreme conditions, along with the scientific directions to maintain satisfactory performance. Then, we have covered the main obstacles to the utilization of existing ESSs under extreme conditions, and summarized the corresponding solutions to overcome them, as well as effective strategies to improve their electrochemical performance. Finally, we highlight existing critical barriers and the corresponding strategies needed for advancing ESSs under extreme conditions.

The electrochemical performance of layered P2-type Na _2/3 Ni _1/3 Mn _2/3 O ₂ is highly related to the cut-off voltage and the electrolyte used.