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 casing.
1. Cathode material
Cathode materials are lithium-containing transition metal oxides and phosphides such as LiCoO2 and LiFePO4, and conductive polymers such as polyacetylene, polyphenylene, polypyrrole, polythiophene, and active polysulfide compounds; lithium intercalation compound cathode materials are an important component of lithium-ion batteries.
The positive electrode material accounts for a large proportion in lithium-ion batteries (the mass ratio of positive to negative electrode materials is 3:1 to 4:1). Therefore, the performance of the positive electrode material will greatly affect the performance of the battery, and its cost will directly determine the cost of the battery.
2. Negative electrode material
Negative electrode materials include carbon materials, nitrides, silicon-based materials, tin-based materials, and novel alloys that can store large amounts of lithium. The biggest difference between lithium-ion batteries and rechargeable lithium batteries is that the former uses lithium intercalation compounds instead of metallic lithium as the negative electrode. Therefore, the research and development of lithium-ion batteries largely involves the research and development of lithium intercalation compounds for the negative electrode.
3. Electrolytes
Electrolytes are organic solutions, polymers, or inorganic solids of lithium salts. As an important component of batteries, electrolytes play a role in transporting ions and conducting current between the positive and negative electrodes. Selecting a suitable electrolyte is key to obtaining lithium-ion batteries with high energy density and power density, long cycle life, and good safety performance.
4. Adhesives
Adhesives are fluoropolymers, ethylene propylene rubber, carbon-based materials, silicone-based gels, radioactive cross-linked polymers, etc.; the main functions of adhesives are: to adhere active materials; to make active materials adhere to current collectors; to preserve and adhere active materials and make active materials adhere to current collectors during charging and discharging; to form a paste during production to facilitate coating; and to alleviate the volume expansion of carbon anodes when lithium is inserted.
5. Diaphragm material
The separator material is a porous polyolefin, polyamide nonwoven fabric, etc.; the role of the separator paper in a lithium-ion battery is to separate the positive and negative electrode materials. The quality of the separator paper directly affects the battery's safety performance and capacity.
6. Positive temperature coefficient terminal
Positive temperature coefficient (PTC) terminals are composite materials of conductive fillers and polymers; PTC terminals prevent excessive battery current. At normal temperatures, the resistance of a PTC terminal is very low, but when the temperature reaches around 120°C, the resistance suddenly increases, causing the current to drop rapidly. Once the temperature drops, the resistance of the PTC terminal decreases again, allowing for normal charging and discharging.
7. Negative electrode current collector material
The negative electrode current collector material is copper foil, copper mesh, stainless steel mesh, or other metal mesh; copper foil (10μm～20μm thick) is generally used as the negative electrode current collector material. As a non-ferrous metal foil material, copper foil is used as the negative electrode current collector in lithium batteries, and its main technical requirements are as follows: (1) thickness (8μm～12μm); (2) tensile strength (>30kg/mm2); (3) elongation (>5%).
8. Positive electrode current collector material: The positive electrode current collector material is aluminum foil, etc.; the positive electrode current collector material is generally aluminum foil (20μm thick).
9. Conductive Agents: Due to the low conductivity of active materials, conductive agents are generally added to accelerate electron transfer and effectively improve the migration rate of lithium ions in the electrode material. Commonly used conductive agents include graphite, carbon black, acetylene black, and colloidal carbon.
10. Battery casing: The battery casing is made of materials such as steel and aluminum.
