Polyanion‐type sodium (Na) vanadium phosphate in the form of Na3V2(PO4)3 has demonstrated reasonably high capacity, good rate capability, and excellent cyclability. Two of three Na ions per formula can be deintercalated at a potential 3.4 V versus Na+/Na with oxidation of V3+/4+. In the reversible process, two Na ions intercalate back resulting in a discharge capacity of 117.6 mAh g−1. Further intercalation is possible but at a low potential of 1.4 V versus Na+/Na accompanied by vanadium reduction V3+/2+, leading to a capacity of 60 mAh g−1. Due to its marvelous electrochemical performance, it has attracted a lot of attention since its discovery in the 1990s. To develop truly useable polyanion‐type vanadium phosphate, better understanding of its crystal configuration, sodium ions' transportation, and electronic structure is essential. Therefore, this review only focuses on the inside of crystal configuration and electronic structure of polyanion‐type vanadium phosphate, Na3V2(PO4)3, since there are a few good reviews on various processing technologies.

To enhance the compatibility between the polymer‐based electrolytes and electrodes, and promote the interfacial ion conduction, a novel approach to engineer the interfaces between all‐solid‐state composite polymer electrolyte and electrodes using thin layers of ferroelectrics is introduced. The well‐designed and ferroelectric‐engineered composite polymer electrolyte demonstrates an attractive ionic conductivity of 7.9 × 10–5 S cm–1 at room temperature. Furthermore, the ferroelectric engineering is able to effectively suppress the growth of solid electrolyte interphase (SEI) at the interface between polymer electrolytes and Na metal electrodes, and it can also enhance the ion diffusion across the electrolyte‐ferroelectric‐cathode/anode interfaces. Notably, an extraordinarily high discharge capacity of 160.3 mAh g–1, with 97.4% in retention, is achieved in the ferroelectric‐engineered all‐solid‐state Na metal cell after 165 cycles at room temperature. Moreover, outstanding stability is demonstrated that a high discharge capacity retention of 86.0% is achieved over 180 full charge/discharge cycles, even though the cell has been aged for 2 months. This work provides new insights in enhancing the long‐cyclability and stability of solid‐state rechargeable batteries.

No abstract

The demand for electrical energy storage (EES) is ever increasing in order to develop better batteries. NASICON-structured Na ion conductor represents a class of solid electrolytes, which is of great interest due to its superior ionic conductivity and stable structures. They are widely employed in all-solid-state ion batteries, all-solid-state air batteries, and hybrid batteries. In this review, their structure, composition, properties, and applications for next generation energy storage are reviewed.

LiFePO4/graphene nanocomposite was successfully synthesized by rheological phase method and its electrochemical properties as the cathode materials for lithium ion batteries were measured. As the iron source in the synthesis, FeOOH nanorods anchored on graphene were first synthesized. The FeOOH nanorods precursors and the final LiFePO4/graphene nanocomposite products were characterized by XRD, SEM, and TEM. While the FeOOH precursors were nanorods with 5–10 nm in diameter and 10–50 nm in length, the LiFePO4were nanoparticles with 20–100 nm in size. Compared with the electrochemical properties of LiFePO4particles without graphene nanosheets, it is clear that the graphene nanosheets can improve the performances of LiFePO4as the cathode material for lithium ion batteries. The as-synthesized LiFePO4/graphene nanocomposite showed high capacities and good cyclabilities. When measured at room temperature and at the rate of 0.1C(1C = 170 mA g−1), the composite showed a discharge capacity of 156 mA h g−1in the first cycle and a capacity retention of 96% after 15 cycles. The improved performances of the composite are believed to be the result of the three-dimensional conducting network formed by the flexible and planar graphene nanosheets.