# Study on sodium ion supplementation performance of CNT-coated sodium oxalate in sodium ion batteries

## TL;DR

Researchers improved sodium-ion battery performance by coating sodium oxalate with carbon nanotubes, boosting capacity and cycle life.

## Contribution

A novel CNT-coated sodium oxalate material is introduced for enhanced sodium compensation in sodium-ion batteries.

## Key findings

- CNT-10@Na2C2O4 achieved a sodium compensation capacity of 392.65 mAh g−1.
- Full cells with CNT-10@Na2C2O4 retained 38.35 mAh g−1 after 100 cycles.
- CNT coating reduced decomposition voltage to 3.82 V.

## Abstract

Low initial coulombic efficiency of hard carbon anodes and irreversible sodium loss during cycling in sodium-ion batteries (SIBs) lead to reduced specific capacity and shortened cycle life. Introducing sodium supplementation can effectively enhance the specific capacity and cycle life of SIBs. Na2C2O4 was selected as the sodium compensation agent owing to its high theoretical capacity, excellent chemical stability, and environmental friendliness. To improve conductivity and reduce decomposition voltage of Na2C2O4, carbon nanotubes (CNTs) were employed for coating. The optimized 10% CNT-coated sodium oxalate (CNT-10@Na2C2O4) exhibited a reduced initial decomposition voltage of 3.82 V (vs. Na+/Na) and delivered an irreversible (sodium compensation) capacity of 392.65 mAh g−1. NNFMO-CN||HC full cells were assembled using NaNi1/3Fe1/3Mn1/3O2 cathode containing 10% CNT-10@Na2C2O4 and hard carbon anode, demonstrating a discharge retention capacity of 38.35 mAh g−1 after 100 cycles, higher than the retained capacity of only 15.16 mAh g−1 of the NNFMO||Na cell without CNT-10@Na2C2O4. These results indicate that CNT-10@Na2C2O4 significantly improves the specific capacity and cycling performance of SIBs.

•Efficiently synthesized CNT-10@Na2C2O4 with sodium compensation capacity of 392.11 mAh g−1•CNT-10@Na2C2O4 improves cycle performance of battery (retains 38.35 mAh g−1 after 100 cycles)•Provides a candidate for sodium compensation material of sodium-ion batteries

Efficiently synthesized CNT-10@Na2C2O4 with sodium compensation capacity of 392.11 mAh g−1

CNT-10@Na2C2O4 improves cycle performance of battery (retains 38.35 mAh g−1 after 100 cycles)

Provides a candidate for sodium compensation material of sodium-ion batteries

Electrochemistry; Applied sciences; Energy storage