In Situ Forming Na─Sn Alloy/Na₂S Interface Layer for Ultrastable Solid State Sodium Batteries

Abstract

The poor interfacial compatibility between sodium superionic conductor (NASICON) electrolyte and metallic sodium anode will lead to severe dendrite penetration, impeding the application of NASICON electrolytes for solid state sodium batteries. Herein, a homogeneous SnS2 coating layer is sputtered on the surface of Na3.4Zn0.1Zr1.9Si2.2P0.8O12 electrolyte to in situ construct a kinetically stable Na─Sn alloy/Na2S interlayer, possessing superior Na affinity, low diffusion barrier, and electronic insulating character to suppress dendrite growth, which is confirmed by experiments and density‐functional theory calculations. Benefiting from the Na─Sn alloy/Na2S interphase, the critical current density of Na3.4Zn0.1Zr1.9Si2.2P0.8O12 increases from 2.4 to 9.4 mA cm−2. In addition, the obtained Na3V2(PO4)3/Na3.4Zn0.1Zr1.9Si2.2P0.8O12@SnS2/Na solid state batteries exhibit a high initial reversible discharge capacity of 115.1 mAh g−1 at 0.1 °C with an initial Coulombic efficiency of 93.6%, and a capacity retention rate of 88.1% after 1000 cycles at 1 C.

High-Strength, Thin, and Lightweight Solid Polymer Electrolyte for Superior All-Solid-State Sodium Metal Batteries

“…However, traditional sodium metal batteries (SMBs) generally use highly flammable organic liquid electrolytes, which may lead to catastrophic battery accidents such as fire and explosions. − Furthermore, SMBs for practical applications are always hampered by the notorious dendrite growth that can penetrate the separator and cause battery short circuits . The most promising solution to these problems is using a solid-state electrolyte instead of a liquid electrolyte, which can offer greater safety. − …”