Insight into the Evolution of Voids at the NASICON/Na Interface and Suppressing Void Accumulation by a Semiliquid Wetting Strategy

NASICON-based solid-state batteries have attracted much attention due to their high safety and high energy density. However, the unstable interface contact usually leads to sodium dendrite formation and cell failure during cycling. Deep insights into the evolution of the NASICON/Na interface are conducive to designing a morphologically stable interface. Herein, for the first time, we develop an asymmetric stripping/plating method to investigate the evolution process of the NASICON/Na interface via a facile two-electrode cell. It is revealed that the “initial voltage drop” phenomenon is closely related to the rapid lateral growth of the Na film on the NASICON electrolyte, which will result in void accumulation, interface contact loss, dendrite growth, and ultimate cell failure. Inspired by this failure mechanism, we developed a semiliquid wetting agent (sodium biphenyl/C composite, NBPC) to construct a continuous Na+ transport pathway at the NASICON/Na interface. The symmetric cell modified with NBPC shows excellent cycling stability at 0.2 mA cm–2. The solid-state battery paired with Na3V2(PO4)2 shows a high discharge capacity of 104 mAh g–1 and a high capacity retention of 96.3% after 100 cycles at 1C.