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

Abstract

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 Na 3 V 2 (PO 4 ) 2 shows a high discharge capacity of 104 mAh g −1 and a high capacity retention of 96.3% after 100 cycles at 1C.

Stabilized Solid–Solid Interface for Solid-State Sodium Batteries Using Gradient Ion-Electron Conductive Phases Modified Sodium Metal Anode

“…Up to now, many attempts have been made to create intimate interfacial contact between Na anode and NZSP electrolyte, such as introducing a sodiophilic modification layer, ,− decomposing surface impurities, , and ultrasonic welding. , These approaches have made significant progress in enhancing the interface of Na anode with NZSP electrolyte (interfacial impedance <10 Ω cm 2 ), but the symmetric cells can only be operated at lower current densities (0.05–0.3 mA cm –2 ) for shorter periods (400–1500 h). The main reason for this is that such methods of enhancing the Na|electrolyte interface contact can only improve the transport of Na across the solid Na|NZSP interface but cannot accelerate the migration rate of Na from bulk to interface, which will cause the voids and pores to be formed again at the interface during the speedy Na stripping operation.…”