UC San Diego

Rechargeable Li-SO2 batteries offer low-cost, high-energy density benefits and can leverage manufacturing processes for the existing primary version at a commercial scale. However, they have so far only been demonstrated in an open-system with continuous gas supply, preventing practical application. Here, the utilization and reversibility of SO2 along with the lithium stability are addressed, all essential for long-life, high-energy batteries. The study discovers that high SO2 utilization is achievable only from SO2 dissolved in electrolytes between the lithium anode and carbon cathode. This results from a unique osmosis phenomenon where SO2 consumption increases salt concentration, driving the influx of organic solvents rather than SO2 from outside the current path. This insight leads to configure a bobbin-cell with all electrolytes between the electrodes, realizing nearly 70% of SO2 utilization, > 12x greater than in conventional coin cells. To improve reaction rate and SO2 reversibility, triphenylamine is employed to the electrolyte, creating an electron-rich environment that alleviates the disproportionation of discharge products. Incorporating this additive into a bobbin-cell with a lithium protective layer yields a cell with a projected energy density exceeding 183.2 Wh kg-1. The work highlights the potential of Li-SO2 batteries as affordable, sustainable energy storage options.