Hard Carbon Anodes in Sodium-ion

Optimization of hard carbon anodes in Sodium-ion Batteries

Giar Alsofi, Carl Reynolds, Emma Kendrick

School of Metallurgy and Materials, University of Birmingham, Elms Rd, Birmingham B15 2SE


  • Describes recent attempts to design structured electrodes by incorporating different kinds of conductive additives and binders to combat the volumetric changes during cell charging and discharging.
  • Results with different formulations and production techniques of Sodium-ion half cells are presented.
  • High internal resistance was the major problem so far. The optimization of the formulation and cell procedure for hard carbon anodes, successfully resulted in the reduction of the internal resistance.
sodium ion spider diagram


  • Emerging battery technology – promising cost, safety, sustainability, and performance advantages over current commercialised lithium-ion batteries1,2.
  • Advantages:
    • widely available
    • inexpensive raw materials
    • rapidly scalable technology
    • meeting global demand for carbon-neutral energy storage solutions3,4.
  • Adding metals would increase the overall energy density, but results in volumetric changes leading to failure.


  • Firstly, the electrode slurry was made with a ratio of 92:5:1:2 (Hard Carbon:Conductive additives:Binders) and tested with a Hegman gauge to determine the particle sizes.
  • The electrode slurry was coated on a foil
  • The electrodes were then used to make Swagelok Sodium-half cells (as shown below) and tested afterwards.
swagelok sodium half-cell


The progress so far can be divided into the following 3 sections:

1. Optimization of formulation

  • 1st step a suitable procedure was identified to ensure a uniform mixture of the slurry with no agglomerates to optimize the resulting electrode performance.
sodium ion results

2. Cell building optimization

  • 2nd step involved refining the cell making including changes in the thickness of the metal piece that was used in the half-cell to reduce the internal resistance resulting in an increase in cell conductivity.

3. Green Binders

  • Final step included the investigation of finding the best suitable binder for the electrode.
sodium ion hard carbon anode cycling


  • Large agglomerates were formed in mixed, and the mixing procedure was optimized to overcome this.
sodium ion agglomeration size
  • While cycling the cells, some internal resistance which decreased the conductivity of the cell and hence the overall performance of the half-cell was observed.
  • Steps to reduce internal resistance:
    1. Reduction in binder content
    2. Reduction in metal thickness
sodium ion internal resistance

Impact / Next Steps

  • The next step is to incorporate metals.
  • Find a suitable mixing formulation to achieved a well dispersed mixture with no agglomerates.
  • Optimize the cell performance.
  • Investigate possible metal-composites.
  • Adding of structural integrity to the system.


  1. Hou, H., Qiu, X., Wei, W., Zhang, Y. & Ji, X. Carbon Anode Materials for Advanced Sodium-Ion Batteries. Adv. Energy Mater. 7, 1–30 (2017).
  2. Kim, H. et al. Recent Progress and Perspective in Electrode Materials for K-Ion Batteries. Adv. Energy Mater. 8, 1–19 (2018).
  3. Saurel, D. et al. From Charge Storage Mechanism to Performance: A Roadmap toward High Specific Energy Sodium-Ion Batteries through Carbon Anode Optimization. Adv. Energy Mater. 8, 1–33 (2018).
  4. Zhang, W. et al. Graphitic Nanocarbon with Engineered Defects for High-Performance Potassium-Ion Battery Anodes. Adv. Funct. Mater. 29, (2019).
optimization of hard carbon for sodium ion - poster

Researcher Bio

Giar Alsofi is a PhD researcher at The University of Birmingham. Interested in anodes of Sodium-ion Batteries, aspiring to understand the volumetric expansions and capacity fading of anodes.

Note: This poster has been published here with the kind permission of the University of Birmingham. All images and content are copyright of the University of Birmingham and cannot be reproduced without permission.

The Faraday Institution

Nextrode – Electrode Manufacturing

Nextrode focuses principally on manufacturing research into how to engineer a new generation of battery electrode structures. Novel developments in electrode structuring will be drawn from basic science understanding of the current slurry casting manufacture of Li-ion electrodes along with predictive modelling to suggest how control of electrode microstructure can deliver improved energy storage characteristics. Nextrode will support UK manufacturers and supply chain companies, draw on cutting edge scientific and technological knowledge to produce increased cell performance, add value in electrode processing, and improve safety and sustainability.

NMC 9.5.5 for Li Ion Batteries

NMC 9.5.5 for Li Ion Batteries

A poster from the same research team at the University of Birmingham.

  • The synthesis and optimisation of Ni-rich cathode materials are of interest as they have a higher energy density and limit the cobalt content However, higher Ni content is detrimental to the bulk and surface stability of material, resulting in structural breakdown and rapid capacity fade.
  • Previous studies indicate use of additives can act to stabilise the 003 lattice space, thus improving battery performance.
  • Optimised manufacturing methods can reduce the economic and environmental impact of this process.

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