Anode materials

The anode (negative electrode) is another critical component of a rechargeable lithium-ion battery.

The performance of a battery depends not only on the type of material used for the anode, but also on its structure.

Among the various materials studied for anodes, graphite and silicon are the most commonly used in lithium-ion batteries today.

Graphite

Graphite is widely used as the anode in commercial lithium-ion batteries due to its widespread availability, high electronic conductivity, low cost, and appropriate structure for lithium-ion insertion.

Graphite is a form of carbon with a layered structure. These layers are made up of carbon atoms bonded together in a pattern called graphene. The ideal crystalline structure of graphene is a hexagonal grid.

_{Graphene. AlexanderAlUS; CC BY-SA 3.0}

When a lithium-ion battery charges, lithium ions move into the graphite layers and attach to the carbon atoms, forming a compound known as LiC₆. This process allows the battery to store energy.

Graphite can store up to 372 milliamp-hours per gram (mAh/g) of energy, making it an excellent candidate for use in lithium-ion batteries.

Silicon

Another potential anode material for lithium-ion batteries is silicon (Si), due to its high theoretical specific capacity of 4200 milliamp-hours per gram, which is about 11 times greater than the 372 mAh/g offered by graphite.

_{© Getty Images}

Silicon is also abundant, being the second most common element in Earth’s crust, and operates at low potential (<0.4 volt (V) vs. Li/Li⁺), making it an environmentally friendly option (Xu et al., 2020).

However, using silicon as an anode in lithium-ion batteries can pose significant problems. Silicon anodes usually experience significant volume changes (300–400%) during lithium ion insertion into and extraction from silicon structure. These dramatic volume changes can cause the anode material to crack and eventually lead to battery failure.

In addition, silicon has poor electrical conductivity (∼10^–5 S cm^–1) and slow ion diffusion kinetics (∼10^–14 cm² s^–1), which further complicate its use in practical applications (Franco Gonzalez et al., 2017).

These issues make it difficult to implement silicon anodes in commercial lithium-ion batteries. Therefore, more research is needed to develop practical solutions to fully realise their potential (Sun et al., 2022).

Research and share

There are other materials that can be used as anodes in lithium-ion batteries as well. Research some other anode materials and their properties, and share what you’ve found about one of them in the comments below.

References

Franco Gonzalez, A., Yang, N.-H., & Liu, R.-S. (2017). Silicon anode design for lithium-ion batteries: progress and perspectives. The Journal of Physical Chemistry C, 121(50), 27775-27787.

Sun, L., Liu, Y., Shao, R., Wu, J., Jiang, R., & Jin, Z. (2022). Recent progress and future perspective on practical silicon anode-based lithium ion batteries. Energy Storage Materials, 46, 482-502.

Xu, C., Wang, B., Luo, H., Jing, P., Zhang, X., Wang, Q., Zhang, Y., & Wu, H. (2020). Embedding silicon in pinecone‐derived porous carbon as a high‐performance anode for lithium‐ion batteries. ChemElectroChem, 7(13), 2889-2895.