Ultrastable Na-TiS2 battery enabled by in situ construction of gel polymer electrolyte

Sodium (Na) metal batteries are low-cost, high-capacity alternatives for lithium-ion batteries. However, the safety concerns brought by the metallic Na hinder the development of Na metal batteries. Herein, we in situ construct a gel polymer electrolyte (GPE) under mild condition for Na-TiS2 battery to diminish the safety hazard. The room-temperature ionic conductivity of the GPE reaches 3.66 × 10−4 S cm−1. The transference number of Na+ is 0.66 and the excellent stability with Na metal anode is achieved. The in situ formed GPE can minimize the side reactions between Na metal anode and the electrolyte, and simultaneously the lower fluidity can hinder the shuttle effect of pulverized TiS2 cathode during cycling, significantly improving the cycling performance. The Na|Na symmetric cell shows stable cycling over 1300 h at 1.0 mA cm−2. The Na|TiS2 cell illustrates an ultralong cycle life of more than 6100 h at 50 mA g−1 with the reversible capacity of 371 mAh g−1. The cell can also be cycled 1000 times with the reversible capacity of 321 mAh g−1 at 200 mA g−1. We believe the work can inspire the development of the high-safety, low-cost, and long-cycle-life sodium batteries as energy storage systems.