Lithium-ion battery recycling
1. Cascade utilization and raw material recycling
Retired power lithium-ion batteries that are used in a tiered manner will be recycled after being used in a tiered manner; those that are directly recycled are those with too small a batch, no historical records, or those that fail safety monitoring, etc.
The pursuit of economic benefits is the driving force behind corporate and social behavior. In theory, tiered utilization, where the battery's usable value drops below maintenance costs before raw material recycling, maximizes battery value. However, in reality, early power lithium batteries suffered from poor traceability and inconsistent quality and models. Tiered utilization of early batteries carried significant risks, and mitigating these risks was costly. Therefore, it can be said that in the early stages of power lithium battery recycling, the primary destination for these batteries was likely raw material recovery.
2. Methods for extracting valuable metals from cathode materials
Current discussions about recycling power lithium-ion batteries do not actually cover the comprehensive recycling and reuse of all materials used in the battery. Important types of cathode materials include lithium cobalt oxide, lithium manganese oxide, ternary lithium batteries, and lithium iron phosphate batteries.
The cost of positive electrode materials accounts for more than one-third of the cost of a single battery cell. Since the negative electrode currently uses more carbon materials such as graphite, and lithium titanate Li4Ti5O12 and silicon-carbon negative electrode Si/C are less commonly used, the current battery recycling technology mainly focuses on the recycling of positive electrode materials.
There are three main categories of recycling methods for spent lithium-ion batteries: physical, chemical, and biological methods. Compared with other methods, hydrometallurgy is considered a more ideal recycling method due to its advantages such as low energy consumption, high recycling efficiency, and high product purity.
① Physical method
Physical methods utilize physicochemical reactions to treat lithium iron phosphate batteries. Common physicochemical treatment methods include crushing and flotation and mechanical grinding.
② Chemical method
Chemical methods are methods that use chemical reaction processes to process lithium-ion batteries, and are generally divided into two types: pyrometallurgical and hydrometallurgical methods.
③ Biological method
Biometallurgy is currently under research, utilizing the metabolic processes of microorganisms to selectively leach metals such as cobalt and lithium. Biometallurgy offers advantages such as low energy consumption, low cost, and the ability to reuse microorganisms, resulting in minimal pollution. However, cultivating these microorganisms requires stringent conditions, involves long cultivation times, and leads to low leaching efficiency, necessitating further process improvements.
The cathode material for lithium-ion batteries is lithium iron phosphate. This new material is not the traditional lithium-ion battery cathode materials such as LiCoO2, LiMn2O4, or LiNiMO2. Its safety performance and cycle life are unmatched by other materials, which are also the most important technical indicators of power lithium batteries. It achieves a 1C charge-discharge cycle life of 2000 cycles. A single cell will not burn or explode under an overcharge voltage of 30V. It will not explode even after puncture. Lithium iron phosphate cathode material makes it easier to use in parallel and series connections for high-capacity lithium-ion batteries.
Lithium iron phosphate batteries also have their disadvantages: for example, the tap density of lithium iron phosphate cathode material is relatively low, and the volume of lithium iron phosphate batteries of the same capacity is larger than that of lithium-ion batteries such as lithium cobalt oxide, so they do not have an advantage in the field of micro batteries.
Currently, the main entities involved in the recycling of power lithium-ion batteries are small recycling workshops, professional recycling companies, and government recycling centers. A recycling system primarily based on power lithium battery manufacturers or electric vehicle companies has not yet emerged.
