Encapsulation of Na4MnV(PO4)3 in robust dual-carbon framework rendering high-energy, durable sodium storage

Abstract

Na4MnV(PO4)3 (NMVP) is a green, cheap, and high-energy cathode material for sodium-ion batteries. However, the low electrical conductivity severely limits its sodium storage performance. Herein, we report the spray-drying synthesis of robust and highly conductive reduced graphene oxide/amorphous carbon framework encapsulated NMVP (NMVP@rGO/AC) composite microspheres. The unique dual-carbon encapsulation architecture enables the NMVP@rGO/AC a high specific capacity (100 mAh g−1 at 100 mA g−1) with durable cyclability (capacity retention of 77.5% for 500 cycles). In situ XRD measurements reveal the reversible extraction/insertion of Na+ via unique solid-solution and two-phase reactions during de-sodiation/sodiation processes. This work provides a versatile platform for the construction of rGO/AC dual-carbon encapsulated active materials for electrochemical energy storage.