Carbon‐Coated Na₃V₂(PO₄)₃ Supported on Multiwalled Carbon Nanotubes for Half‐/Full‐Cell Sodium‐Ion Batteries

Abstract

Na‐ion superionic conductor (NASICON)‐based Na3V2(PO4)3 is regarded as a potential cathode for sodium‐ion batteries, due to the excellent thermal stability and large ion diffusion channel. Herein, multiwalled carbon nanotube–pierced Na3V2(PO4)3 (NVP@C/MWCNT) is synthesized through a simple sol–gel approach. Tested as a cathode for sodium‐ion half batteries, the as‐prepared electrode displays an excellent reversible capacity (111.6 mA h g−1 at 1 C) and superior rate capability (63.2 mA h g−1 at 80 C). Furthermore, in situ X‐ray diffraction (XRD) patterns of NVP@C/MWCNTs indicate the apparent two‐phase (de‐)sodiation process. In contrast, the ortho‐disodium salts of tetrahydroxyquinone (o‐Na2C6H2O6) are prepared as an anode, which demonstrates a reversible discharge capacity of 156.8 mA h g−1 at 0.1 C and enhanced high‐rate performance (72.1 mA h g−1 at 20 C) for sodium–organic half batteries. When evaluated as a Na‐ion full cell, a NVP@C/MWCNT || o‐Na2C6H2O6 full cell shows outstanding rate capability (33.3 mA h g−1 at 1.0 A g−1). Such impressive electrochemical behavior is related to the addition of multiwalled carbon nanotubes. This not only enhances electronic conductivity of NVP, but also inhibits the growth of grains, which shortens the Na+ diffusion length and increases the contact space between electrode/electrolyte.

Polyanion Sodium Vanadium Phosphate for Next Generation of Sodium‐Ion Batteries—A Review

“…Carbon coating through high temperature treatment of the sol-gel-processed electrode is another facial way. [49,96,[147][148][149][150][151][152][153] As carbon sources, block copolymer such as poly(ethylene glycol) and poly(propylene glycol) is used together with P and Na precursors. [49] The gel is usually dried below 100 °C followed by further drying at an elevate temperature of 300 °C where the block copolymer is still in its polymer form.…”

Optimization of Electrochemical Presodiation Parameters of Na‐Ion Full Cells for Stable Solid–Electrolyte Interface Formation: Hard Carbon Rods from Waste Firefighter Suits

“…Three different methodological approaches to pretreatment are described in the literature, namely, the chemical process, electrochemical procedure, and Na/electrode direct‐contact technique. [ 20 ] While the chemical methods have some problems to obtain pure sodium–carbon bonding without impurity phases, [ 34 ] the direct contact method has a metallic coating problem on the surface of the anode which should be optimized. [ 35 ] The last method is an electrochemical procedure which is a technique of galvanostatic/potenstiostatic electrochemical presodiation on anodes with a piece of sodium metal by a half‐cell structure.…”