A lithium-ion battery consists of the following components: positive electrode, negative electrode, electrolyte, electrolyte salt, adhesive, separator, positive electrode lead, negative electrode lead, center terminal, insulating material, safety valve, positive temperature coefficient terminal (PTC terminal), negative electrode current collector, positive electrode current collector, conductive agent, and battery case.
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Positive electrode material:
Positive electrode materials are lithium-containing transition metal oxides and phosphides, such as LiCoO2 and LiFePO4, as well as conductive polymers like polyacetylene, polystyrene, polythiophene, polypyrrole, and active polythioether compounds, among others. Lithium-intercalating compound positive electrode materials are vital components of lithium-ion batteries.
Positive electrode materials make up a significant portion in lithium-ion batteries, with the mass ratio of positive to negative electrode materials typically ranging from 3:1 to 4:1. Therefore, the performance of positive electrode materials greatly affects the battery’s overall performance, and their cost directly impacts the battery’s overall cost.
Negative electrode materials:
Negative electrode materials are typically carbon-based materials, nitrides, silicon-based materials, tin-based materials, new alloys, and more. The main difference between lithium-ion batteries and secondary lithium batteries is that the former use lithium intercalation compounds as the negative electrode material instead of metallic lithium. Therefore, research and development of lithium-ion batteries largely revolve around the study of negative electrode intercalation compounds.
Electrolyte:
The electrolyte is an organic solution, a polymer, or an inorganic solid containing lithium salts. It plays a crucial role in the battery by facilitating ion transport and conducting electrical current between the positive and negative electrodes. Selecting the appropriate electrolyte is key to achieving high energy density, high power density, long cycle life, and good safety performance in lithium-ion batteries.
Adhesive materials:
Adhesive materials for lithium-ion batteries can include fluorinated polymers, ethylene-propylene rubber, carbon-based materials, silicone-based gels, and radiation-crosslinked polymers. These adhesives primarily serve the purpose of adhering active materials, allowing active materials to bond with the current collector, and facilitating coating in a slurry form during production. They can also help mitigate the expansion of the carbon negative electrode as it intercalates lithium during charge and discharge processes.
Separator material:
Separator materials for lithium-ion batteries can include porous polyolefins, polyamide non-woven fabrics, and more. The role of the separator in a lithium-ion battery is to physically separate the positive and negative electrode materials while allowing the transport of lithium ions. The quality of the separator significantly affects the battery’s safety performance and capacity.
Positive Temperature Coefficient (PTC) terminal
A Positive Temperature Coefficient (PTC) terminal, also known as a PTC thermistor, is a composite material made of conductive fillers and polymers. PTC terminals are used to prevent excessive current in a battery. At normal temperatures, PTC terminals have low resistance. However, when the temperature reaches around 120°C, their resistance suddenly increases, causing the current to drop rapidly. When the temperature decreases, the resistance of the PTC terminal returns to normal, allowing for regular charge and discharge operations.
Negative electrode current collector:
Negative electrode current collector materials include copper foil, copper mesh, stainless steel mesh, and other metal meshes. Typically, copper foil (10μm-20μm thick) is used as a negative electrode current collector material in lithium-ion batteries. There are three key technical specifications for copper foil used in the negative electrode current collector: (1) Thickness (8μm-12μm); (2) Tensile strength (>30kg/mm²); (3) Elongation (>5%).
Positive electrode current collector
Positive electrode current collector materials include aluminum foil, and typically, aluminum foil (20μm thick) is used as a positive electrode current collector material.
Conductive Agent:
Due to the low electrical conductivity of active materials, conductive agents, such as graphite, carbon black, acetylene black, and colloidal carbon, are commonly added to accelerate electron transfer and enhance the migration rate of lithium ions within the electrode material.
Battery Case:
The battery casing is typically made of materials like steel or aluminum.
