Research progress of key materials and engineering exploration for Na-ion batteries

Under the background of “Carbon Peaking and Carbon Neutrality”, Na-ion batteries (NIBs) have attracted much attention due to their advantages such as low cost, high safety, and excellent performance. Low-cost NIBs are beneficial supplements to Li-ion batteries and will show their special advantages in the field of energy storage. Nowadays, NIBs are at a critical point from laboratory exploration to industrialization promotion. Since 2011, the NIBs research group of the Institute of Physics, Chinese Academy of Sciences has been committed to the research and development of low-cost, high-safety and high-performance NIBs technologies. It has obtained more than 40 patents of core materials, and some patents have been authorized from the United States, Japan and the European Union. It is the first time in the world to propose Cu-based oxide cathode materials and low-cost anthracite-based anode materials with independent intellectual properties. In 2017, relying on the core patented technology, the first high-tech enterprise focusing on the development and manufacture of NIBs—HaiNa Battery Technology Co. Ltd. was established. Then, the world’s first example application of 100 kW h and 1 MW h NIBs energy storage systems was put forward. This paper firstly focuses on the series of progress in the layered oxide cathode materials made by the research group for NIBs, mainly including: (1) Cost-effective Cu-Fe-Mn layered cathode materials, (2) high-capacity lattice oxygen redox layered oxide cathodes, and (3) stable phase transition layered cathode materials (high entropy and high sodium content P2-type cathodes), and poly-anion compound phosphate cathode materials. In terms of anodes, a series of hard carbon anodes using different biomass materials with excellent sodium storage performance were synthesized, as well as the high-performance soft carbon anode materials based on anthracite and pitch. A long-cycle stable titanium-based oxide anode material was designed. In terms of electrolytes, high-salt-concentration aqueous electrolytes and low-salt-concentration inaqueous electrolytes were designed. In addition, NASICON (Na super ionic conductor) type solid electrolytes and polymer solid electrolytes were modified on purpose. For the mechanism investigation of electrode materials, this paper explores in detail the phase formation mechanism of layered cathode materials, the ordered/disordered arrangement of layered oxides, the sodium storage mechanism of titanium-based oxides, the design methods of new tunnel-type materials, the sodium storage mechanism of amorphous carbon materials, and the sodium storage mechanism of organic anode materials. Finally, in terms of the industrialization exploration of NIBs, the process in the industrialization exploration and example application of NIBs for our group was introduced. The future development directions of NIBs were put forward in order to promote the sustainable development and accelerate the commercial application of NIBs.