Greener aqueous magnesium/fluorinated graphite primary batteries with mixed cation water-in-salt electrolytes

Fluorinated graphite (CF x ) is one of the most important cathode materials used in lithium primary (non-rechargeable) batteries due to its high theoretical energy density . While prior studies have predominantly focused on organic electrolyte systems, the exploration of high-capacity CF x cathode material in aqueous environments presents a compelling opportunity for greener energy storage solutions . Here, we report for the first time a high-performance hybrid aqueous CF x primary battery that employs metallic magnesium (Mg) as the anode in conjunction with a mixed cation acetate-based water-in-salt electrolyte. Our findings indicate that the optimized electrolyte effectively influences the fluorination products, thereby significantly enhancing the performance of the hybrid aqueous Mg/CF x primary battery . Specifically, this battery achieves a remarkable discharge specific capacity of 883 mAh g −1 at a 0.1C rate, maintaining a voltage platform of approximately 1.1 V and exhibiting over 89.7 % capacity retention at a 1C rate. Additionally, the pouch-type Mg/CF x battery demonstrates a commendable specific capacity of 780 mAh g −1 and a notable energy density of 814 Wh kg −1 at a 0.05C rate. This work provides a viable strategy to advance the practical application of high-capacity CF x primary batteries in aqueous electrolytes .