# Densely Carboxylated Graphene for Synthesis of High-Performing NASICON Cathodes for Na-Ion Batteries

## TL;DR

This paper introduces a new method using carboxylated graphene to improve the performance of sodium-ion battery cathodes.

## Contribution

A simple synthesis strategy using graphene acid as a multifunctional additive for high-performance NASICON cathodes.

## Key findings

- GA enables efficient V5+ reduction to V3+ and phase-pure NVP formation.
- NVP@GA cathodes achieve 85 wt% active material with excellent charge-transfer kinetics.
- Optimized cathodes show stable cycling and 65.4% capacity retention at high rates.

## Abstract

Sodium-ion batteries are emerging as a promising alternative to lithium-ion technology due to the abundance and low cost of sodium. Among the cathode candidates, Na3V2(PO4)3 (NVP) with a NASICON framework and its analogues offer a high operating voltage and excellent structural stability. However, their practical use is limited by poor electronic conductivity, a low active material fraction, and trade-offs in terms of morphology and tap density. Here, we report a simple synthesis strategy that employs densely carboxylated graphene, graphene acid (GA), as a multifunctional additive. GA acts simultaneously as a chelating agent, pH regulator, and in situ-formed carbon shell prior to calcination. GA allows the efficient reduction of V5+ to electrochemically active V3+, phase-pure NVP formation, and the growth of a thin, conformal carbon shell strongly anchored to NVP particles. The resulting electrodes contain 85 wt % active material while maintaining outstanding charge-transfer kinetics. The optimized NVP@GA cathode delivers an excellent rate performance up to 15 A gEM
–1 (151 C), retaining 65.4% of the theoretical capacity of NVP, and stable cycling. This approach provides a versatile route for tailoring NASICON cathodes and can be extended to other phosphate-based systems for high-power sodium-ion batteries.