As a core component of lithium-ion batteries, the negative electrode material typically needs to meet the following conditions for application:
① The lithium-ion intercalation potential is low and stable to ensure a high output voltage;
② It allows for a greater number of reversible lithium insertion/extraction operations, resulting in higher specific capacity;
③ The structure is relatively stable during charging and discharging, and it has a long cycle life;
④ High electronic conductivity, ionic conductivity, and low charge transfer resistance ensure low voltage polarization and good rate performance;
⑤ It can form a stable solid electrolyte film with the electrolyte, ensuring high coulombic efficiency;
⑥ The preparation process is simple, easy to industrialize, and inexpensive;
⑦ Environmentally friendly; the material processing and actual use will not cause serious pollution to the environment.
⑧ Abundant resources, etc.
For over 30 years, although new lithium-ion battery anode materials have been continuously reported, very few have actually achieved commercial application. This is primarily because few materials can simultaneously meet the aforementioned conditions. For example, while materials such as metal oxides, sulfides, and nitrides, which operate on a conversion reaction mechanism, possess high specific capacity, they suffer from high plateau potentials, severe polarization, large volume changes during lithium-ion intercalation, difficulty in forming a stable SEI, and high costs, preventing their practical application.
Graphite has been widely used precisely because it effectively balances the aforementioned conditions. Furthermore, although Li4Ti5O12 has low capacity and a high lithium-ion intercalation potential, its structure remains stable during charge and discharge, allowing for high-rate charge and discharge, thus it also has some applications in power lithium-ion batteries and large-scale energy storage.
The processing of negative electrode materials is only one part of the entire battery manufacturing process. The establishment of standards helps battery companies to judge the quality of materials. In addition, materials are inevitably affected by factors such as people, machines, materials, environment, and testing conditions during processing and transportation. Only by standardizing their various physicochemical properties can their reliability be truly ensured.
Generally speaking, the key technical indicators of anode materials include: crystal structure, particle size distribution, tap density, specific surface area, pH, water content, main element content, impurity element content, first discharge specific capacity, and first charge-discharge efficiency.
