Common Anode Materials for Lithium-Ion Batteries and Their Characteristics
In lithium-ion batteries, the role of the anode material is often underestimated. Many people focus more on how high the energy density of the cathode is, but in reality, the cycle life, safety, rate capability, and even the initial coulombic efficiency of a battery are all closely related to the anode material.
A wide variety of anode materials have been studied to date, including carbon materials, alloys and alloy oxides, transition-metal oxides, phosphides, nitrides, and Li₄Ti₅O₁₂. However, among these, graphite-based materials still dominate large-scale commercial applications.
I. Graphite-Based Anodes
Graphite has become the “workhorse” anode material for lithium-ion batteries mainly because of its layered crystal structure. Lithium ions can reversibly intercalate into and deintercalate from the graphite layers to form intercalation compounds such as LiC₆, resulting in good reversibility and excellent cycling stability.
1. Natural Graphite
Natural graphite features a high degree of graphitization, low cost, and a flat voltage plateau, making it one of the earliest anode materials used in lithium-ion batteries. High-quality flake graphite can reach purities of up to 99.9%, with a reversible capacity typically in the range of 300–350 mAh/g.
However, natural graphite also has several drawbacks:
Relatively low initial charge–discharge efficiency
More surface impurities and oxygen-containing functional groups
Cycling stability that is highly sensitive to processing conditions
As a result, natural graphite is almost always surface-modified in practical applications, such as by mild oxidation, reduction treatments, or coating with an amorphous carbon layer, to improve SEI film quality and extend cycle life.
2. Artificial Graphite
Compared with natural graphite, the main advantages of artificial graphite lie in its tunable structure, better consistency, and more controllable impurity levels. Most commercial artificial graphite is derived from petroleum coke or pitch through high-temperature graphitization.
Although artificial graphite is slightly more expensive, it offers superior overall performance, higher yield, and better safety. Therefore, it is widely used in consumer electronics, power tools, and some power battery applications.
II. MCMB Anodes
Mesocarbon microbeads (MCMB) are spherical graphitized carbon materials characterized by:
Regular particle morphology
High tap density
Excellent cycling consistency
MCMB typically delivers a reversible capacity of 300–320 mAh/g, with an initial coulombic efficiency exceeding 90%, and was once regarded as one of the most successful anode materials for lithium-ion batteries.
However, due to its complex preparation process, high energy consumption, and relatively high cost, the market share of MCMB has gradually declined as modified natural graphite and artificial graphite have matured.
III. Hard Carbon: A Promising Candidate for Energy Storage and Sodium-Ion Batteries
Hard carbon is an amorphous carbon material without an ordered layered structure. It contains a large number of micropores and defects, enabling multiple lithium storage mechanisms, including:
Lithium intercalation into graphite-like microcrystallites
Lithium storage in nanopores
Lithium adsorption at defect sites
As a result, hard carbon usually exhibits a relatively high reversible capacity, ranging from 400 to 1000 mAh/g. In addition, its raw materials are abundant and low-cost, giving it considerable potential in energy-storage batteries and emerging battery systems.
Nevertheless, hard carbon still faces challenges such as low initial coulombic efficiency and an uneven voltage profile. Its commercial application is therefore still progressing gradually.
IV. Alloy-Type Anodes
To break through the theoretical capacity limit of graphite (372 mAh/g), researchers have turned their attention to alloy-type anode materials, such as silicon, tin, and antimony.
Among them, silicon-based anodes are the most attractive:
A theoretical capacity as high as 4200 mAh/g
Abundant resources and strong cost-reduction potential
However, alloy-type materials undergo severe volume expansion during lithiation and delithiation (often exceeding 300%), which easily leads to particle pulverization and electrode failure. As a result, cycle life remains the biggest bottleneck.
Current mainstream solutions include:
Nanostructured materials
Silicon–carbon composite structures
Core–shell designs and buffering matrix architectures
These technologies have already been applied in some high-end batteries, but there is still a long way to go before they can fully replace graphite.
V. Li₄Ti₅O₁₂ “Zero-Strain” Anodes
Li₄Ti₅O₁₂ has a spinel structure and undergoes almost no volume change during lithium insertion and extraction, earning it the name “zero-strain” material. Its key characteristics include:
Extremely long cycle life
Excellent high-rate performance
High safety with no tendency to form lithium dendrites
However, its operating voltage is as high as 1.55 V (vs. Li/Li⁺), which significantly reduces the overall energy density of the full cell. Therefore, Li₄Ti₅O₁₂ is mainly used in applications that prioritize safety and high power, such as certain energy-storage systems and hybrid devices.
VI. Conclusion
From the current industrial perspective, graphite-based anodes remain the mainstream choice, silicon-based anodes represent a key future direction, Li₄Ti₅O₁₂ focuses on safety and long cycle life, and hard carbon as well as novel alloy materials are worthy of long-term attention.
Different application scenarios impose very different requirements on anode materials. Choosing the right anode system is often far more important than simply pursuing the highest possible capacity.
