Poly(vinylene carbonate)-Based Composite Polymer Electrolyte with Enhanced Interfacial Stability To Realize High-Performance Room-Temperature Solid-State Sodium Batteries

Abstract

Solid-state rechargeable batteries using polymer electrolytes have been considered, which can avoid safety issues and enhance energy density. However, commercial application of the polymer electrolyte solid-state battery is still significantly limited by the low room-temperature ionic conductivity, poor mechanical properties, and weak interfacial compatibility between the electrolyte and electrode, especially for the room-temperature solid-state rechargeable battery. In this work, a poly(vinylene carbonate)-based composite polymer electrolyte (PVC-CPE) is reported for the first time to realize room-temperature solid-state sodium batteries with high performances. This in situ solidified PVC-CPE possesses superior ionic conductivity (0.12 mS cm^-1 at 25 °C), high Na⁺ transference number (t_Na⁺ = 0.60), as well as enhanced electrode/electrolyte interfacial stability. Notably, the composite cathode NaNi_1/3Fe_1/3Mn_1/3O₂ (c-NFM) is designed through the in situ growth of the polymer electrolyte inside the electrode to decrease interfacial resistance and facilitate effective ion transport in electrode/electrolyte interfaces. It is demonstrated that the solid-state c-NFM/PVC-CPE/Na battery assembled by a one-step in situ solidification method exhibits remarkably enhanced cell performances at room temperature compared with a reference NFM/PVC-CPE/Na assembled through a conventional ex situ method. The battery presents a high initial specific capacity of 104.2 mA h g^-1 at 0.2 C with a capacity retention of 86.8% over 250 cycles and ∼80.2 mA h g^-1 at 1 C. This study suggests that PVC-CPE is a very promising electrolyte for solid-state sodium batteries. This study also suggests a new method to design high-performance polymer electrolytes for other solid-state rechargeable batteries to realize high safety and considerable electrochemical performance at room temperature.

Keywords: composite polymer electrolyte; high ionic conductivity; in situ solidification; interfacial stability; poly(vinylene carbonate); solid-state sodium batteries.