Sodium
batteries are attractive alternatives to the rapidly emerging
large-scale intermittent renewable energy storage devices due to their
low production cost and abundant sodium resources. The electrochemical
performances of sodium batteries are highly dependent on the compatibility
and interface resistances between electrode materials and electrolytes.
Herein, we develop a simple method to modify a glass fiber (GF) separator
by interfacial ionization and in situ introduction of a sodium source
into the separator for a sodium metal battery. Polyionic liquid/ionic
liquid gels were synthesized to incorporate into modified GF separators
to prepare supported ionic liquid gel membranes (SILGMs) as dual separators
and electrolytes for sodium batteries. The sodium-ion transference
number of ionogel electrolytes incorporated on the support with and
without modification was measured. The electrochemical performance
characteristics of the battery with and without GF modification were
evaluated by cyclic voltammetry, galvanostatic charge–discharge
tests, and cycling stability as well as the galvanostatic intermittent
titration technique (GITT). It was found that the specific capacity
of the sodium metal battery increased by more than 20% after modification
at a relatively high current density. Surprisingly, the specific discharge
capacity of the assembled sodium metal battery can reach 112 mAh·g–1 at 0.1 C, fairly close to the theoretical capacity
of cathode materials. The specific capacity retention of the battery
with the modified GF separator was up to 99% after 100 cycles at 1.0
C. This work presents a novel method for separator modification to
alter the interface compatibility between electrode materials and
electrolytes for sodium metal batteries and provides a new insight
to improve battery performance.