Quasi‐Solid Sulfur Conversion for Energetic All‐Solid‐State Na−S Battery

Abstract

AbstractThe high theoretical energy density (1274 Wh kg−1) and high safety enable the all‐solid‐state Na−S batteries with great promise for stationary energy storage system. However, the uncontrollable solid–liquid‐solid multiphase conversion and its associated sluggish polysulfides redox kinetics pose a great challenge in tunning the sulfur speciation pathway for practical Na−S electrochemistry. Herein, we propose a new design methodology for matrix featuring separated bi‐catalytic sites that control the multi‐step polysulfide transformation in tandem and direct quasi‐solid reversible sulfur conversion during battery cycling. It is revealed that the N, P heteroatom hotspots are more favorable for catalyzing the long‐chain polysulfides reduction, while PtNi nanocrystals manipulate the direct and full Na2S4 to Na2S low‐kinetic conversion during discharging. The electrodeposited Na2S on strongly coupled PtNi and N, P‐codoped carbon host is extremely electroreactive and can be readily recovered back to S8 without passivation of active species during battery recharging, which delivers a true tandem electrocatalytic quasi‐solid sulfur conversion mechanism. Accordingly, stable cycling of the all‐solid‐state soft‐package Na−S pouch cells with an attractive specific capacity of 876 mAh gS−1 and a high energy of 608 Wh kgcathode−1 (172 Wh kg−1, based on the total mass of cathode and anode) at 60 °C are demonstrated.