Lithium ion battery full decoding: principles, materials, and classification

1. Working principle of lithium battery

The working principle of lithium-ion batteries is a delicate and complex process that involves the internal structure and chemical reactions of the battery.

 Lithium ion batteries mainly consist of four key components: positive electrode material, negative electrode material, electrolyte, and separator.

 Positive and negative electrode materials are collectively referred to as electrode materials, which are crucial for the performance and cost of batteries.

Positive electrode material: usually composed of transition metal oxides containing lithium, 

such as lithium cobalt oxide (LiCoO ₂), lithium nickel manganese cobalt oxide (NMC), or lithium iron phosphate (LiFePO ₄).

Negative electrode material: mainly made of carbon materials, such as graphite. 

In recent years, new materials such as graphene have also been explored for use as negative electrode materials.

Electrolyte: It is an organic solvent containing lithium salts used for transporting lithium ions.

Diaphragm: It is a microporous membrane used to separate positive and negative electrodes, prevent short circuits, and allow lithium ions to pass freely.

When the battery is charged, lithium ions are deintercalated from the positive electrode (delithiation process), move through the electrolyte to the negative electrode, 

and intercalate in the negative electrode (lithiation process). At the same time, electrons flow from the positive pole to the negative pole through an external circuit. 

During the discharge process, the flow direction of lithium ions and electrons is opposite.

2. Classification of lithium batteries

The classification of lithium-ion batteries is mainly based on the different positive electrode materials. 

The mainstream positive electrode materials on the market currently include ternary lithium, lithium manganese oxide, lithium iron phosphate, and lithium titanate.

Ternary lithium battery

Positive electrode material: Nickel cobalt manganese (NMC) is used as the positive electrode material, combining the advantages of lithium cobalt oxide and lithium manganese oxide, 

with high energy density and good cycling performance.

Application: Widely used in the field of new energy vehicles. 

The 18650 single cell battery is a typical representative of this type of battery, with standardized dimensions for easy production and assembly.

Lithium manganese oxide battery

Positive electrode material: Lithium manganese oxide (LiMn ₂ O ₄) without cobalt is used as the positive electrode material, which has a lower cost.

Characteristics: Suitable for producing large and medium-sized battery cells, with good low-temperature performance but poor high-temperature stability, easy swelling, and rapid capacity decay.

Lithium iron phosphate battery

Positive electrode material: Lithium iron phosphate (LiFePO ₄) is used as the positive electrode material, which has high stability, safety, and environmental friendliness.

Advantages: Excellent performance at high temperatures and low risk of fire. But its theoretical capacity is limited and its room temperature conductivity is low.

Lithium titanate battery

Negative electrode material: Lithium titanate (LiTi ₂ (PO ₄) ∝) is used as the negative electrode material,

 often in combination with positive electrode materials such as lithium manganese oxide, 

ternary materials, or lithium iron phosphate.

Features: High lithium ion diffusion coefficient, support for rapid charging and discharging, long cycle life, strong thermal stability. 

But the energy density is low and the cost is high.

Each type of lithium-ion battery has its unique advantages and limitations, and the choice of battery depends on the specific application scenario and performance requirements. 

With the advancement of technology, it is expected that more high-performance and low-cost lithium-ion batteries will emerge in the future to meet the growing market demand.