Graphite. Doing the Real Work in Lithium Batteries
Yes, ≈ 95 % of anode active material in today's lithium-ion batteries is graphite. Graphite is not just present in lithium-ion batteries—it is integral, forming the overwhelming majority of the anode and representing over half of the battery’s mineral mass.
1.High Lithium-Ion Intercalation Capacity
The theoretical lithium intercalation capacity of graphite is 372 mAh/g, and in practical applications, it can reach 330–370 mAh/g, significantly higher than other carbon-based materials. This characteristic allows it to store a large number of lithium ions, meeting the high energy density requirements of batteries. Compared to silicon-based anodes, graphite has a lower capacity, but it offers superior cycling stability and cost advantages.
2.Graphite is Safe in LIBs
- Stable Intercalation Voltage
Graphite operates at a low but stable voltage (~0.1–0.2 V vs. Li⁺/Li), minimizing lithium plating risk during charge/discharge cycles—an issue that can lead to short circuits or fires.
- Solid Electrolyte Interphase (SEI) Formation
During initial cycling, a passivation layer (SEI) forms on graphite, which stabilizes further reactions with the electrolyte and prevents degradation. This SEI is well-studied and predictable.
- Minimal Volume Expansion
Graphite expands only about 10% upon full lithiation (formation of LiC₆), compared to 300%+ for silicon. Lower expansion means reduced mechanical stress and safer long-term cycling.
3.Unique Layered Structure
Graphene’s unique layered structure allows lithium ions to intercalate easily between layers, with a low diffusion barrier (~0.3–0.5 eV). Its large surface area (~2630 m²/g) provides abundant active sites, enhancing lithium-ion transport. Structural features like layer number, defects, and doping (e.g., N, B, S) can further improve conductivity and diffusion. Its flexibility also helps buffer volume changes during cycling, improving battery stability.
4.Cost Advantage of Graphite
Graphite offers a significant cost advantage compared to alternative anode materials. It is abundant, easy to process, and commercially mature, resulting in low raw material and production costs. Additionally, graphite’s long cycle life and low degradation rate reduce the total cost of ownership for lithium-ion batteries over time. These factors make graphite the most cost-effective and widely adopted anode material in current commercial battery systems.
5. SEI Compatibility of Graphite
Graphite forms a stable and uniform SEI layer during initial cycling, which effectively prevents further electrolyte decomposition and ensures reversible lithium-ion intercalation. Its minimal volume change keeps the SEI intact over long cycles, enhancing battery life and safety. Compared to silicon, graphite shows much better SEI stability and electrolyte compatibility, making it ideal for commercial use.
As the dominant anode material in lithium-ion batteries, graphite continues to set the benchmark for performance, safety, and cost-efficiency. While next-generation materials like silicon and lithium metal are gaining attention, graphite remains the most reliable and scalable solution for today’s energy storage demands.