High Capacity and Ultralong Lifespan Aqueous Lithium–Bromine Batteries Realized by Low-Cost Concentrated Electrolyte Coupled with Dependable Lithium Titanium Phosphate

Aqueous halogen batteries are gaining recognition for large-scale energy storage due to their high energy density, safety, environmental sustainability, and cost-effectiveness. However, the limited electrochemical stability window of aqueous electrolytes and the absence of desirable carbonaceous hosts that facilitate halogen redox reactions have hindered the advancement of halogen batteries. Here, a low-cost, high-concentration 26 m Li–B5–C15–O6 aqueous solution incorporating lithium bromide (LiBr), lithium chloride (LiCl), and lithium acetate (LiOAc) was developed for aqueous batteries, which demonstrated an expanded electrochemical stability window of ca. 2.5 V. In addition, the electrochemical performance of the electrolyte in various carbonaceous hosts (graphene, activated carbon, and nitrogen-doped activated carbon (NAc)) was systematically investigated. In-depth analysis using X-ray photoelectron spectroscopy and Raman spectroscopy revealed that the NAc host promoted the redox kinetics of active bromine species and improved the delivery capacity of the battery. Results revealed that the electrolyte in the NAc host achieved a discharge specific capacity exceeding 376 mA h g–1 while maintaining a capacity retention rate of up to 97% after 7800 cycles. When paired with hierarchically porous LTP@C/CNTs anode material, a LTP@C/CNTs-NAc full cell was constructed, which delivered a discharge specific capacity of 238.4 mA h g–1 and an average output voltage of 1.24 V. Moreover, it demonstrated a reversible specific capacity of 158.2 mA h g–1 with near-complete Coulombic efficiency over more than 10,000 cycles.