Multi-ion Strategy toward Highly Durable Calcium/Sodium-Sulfur Hybrid Battery.

Nonlithium (Li) metal-sulfur batteries are a viable technology for large-scale energy storage due to their relative high energy densities and low cost. However, their practical application is still hindered by the insufficient reversibility and/or limited cycling stability. Herein, we report a high-performance calcium/sodium-sulfur (Ca/Na-S) hybrid battery enabled by a multi-ion chemistry. The introduction of Na ions in the electrolyte greatly boosts the conversion of Ca polysulfides, which has been verified by theoretical calculation and experimental investigation. Meanwhile, the presence of Ca ions constructs a protective electrostatic shield around the initial protrusions on the Na metal anode without prereduction, thus efficiently suppressing the Na dendrite growth. The as-developed Ca/Na-S cell exhibited a high reversible capacity of 947 mAh g ^-1 at 0.1 C with long cycle life, clearly demonstrating the feasibility of this multi-ion strategy for developing low-cost non-Li metal-sulfur batteries.