How to recycle lithium-ion batteries?
In practical applications, the core technologies of recycling are mainly divided into two categories: fire method and wet method. The fire method is a process of extracting or separating non-ferrous metals from battery materials by heating under high temperature conditions according to the physical properties (melting point, vapor pressure) of different metals. Wet method is a recovery process that utilizes acid, alkali or organic solvent to leaching valuable metal components in batteries. The recycling process can be roughly divided into three steps: pretreatment of batteries, separation of active materials and current collectors, and recovery and reuse of valuable metals.
Pretreatment of waste lithium-ion batteries
1. Discharge
Used lithium-ion batteries have residual power in them. To prevent accidents during battery removal, discharge the battery before removing it. The treatment methods include physical discharge method and chemical discharge method. The physical discharge method mainly uses low-temperature forced discharge. This method is suitable for small batch production. Umicore and Toxco companies in the United States use liquid nitrogen to pretreat the battery at low temperature, and safely break the battery at a temperature of -198 ℃. However, this method Higher requirements for equipment. The chemical discharge method mainly uses electrolysis to discharge.
2, dismantling, breaking
In the laboratory, due to the small size of the battery, most of the batteries are disassembled and separated manually. In actual production, the method of mechanical crushing is often used to disassemble the battery. One method of mechanical crushing is the wet method. The wet method uses various acid and alkaline solutions as the transfer medium to transfer metal ions from the electrode material to the leaching solution, and then through ion exchange, precipitation, adsorption and other means, the metal ions are removed from the solution in the form of salts, oxides, etc. extracted. The wet recycling technology is relatively complex, but the recovery rate of valuable metals is relatively high. It is currently the main technology for processing waste nickel-hydrogen batteries and lithium-ion batteries. Some scientists have tried to soak the battery in dilute alkaline water and then pulverize it. This method can reduce the production of HF, but cannot effectively recover the fluorine-containing electrolyte, which is easy to cause secondary pollution. Another method is the dry method. Dry method mainly includes mechanical sorting method and high temperature pyrolysis method (or high temperature metallurgy method).
Recycling and utilization of waste lithium-ion batteries
(1) In the process of dismantling and crushing waste lithium-ion batteries, the separation effect is still not ideal. Therefore, the safe and effective disassembly and crushing of waste lithium-ion batteries is a prerequisite for the recycling of waste batteries.
(2) At present, in the research process of valuable metals of waste lithium-ion batteries, the recovery process of valuable metals is mainly based on wet method. This method uses chemical substances such as acid and alkali, which will produce harmful waste gas and waste liquid, which will cause certain harm to people and the environment. Therefore, secondary pollution in the process is also an important problem to be solved.
(3) In the process of recovering valuable metals from waste lithium-ion batteries, most of them focus on the recovery of valuable metals in cathode materials. Neglect the negative electrode and electrolyte. In particular, the electrolyte is mostly composed of high-concentration organic solvents, electrolyte lithium salts, additives and other raw materials. These substances are toxic and pollute the environment. Therefore, it is necessary to find alternatives to these materials to reduce the harm of the electrolyte to the environment.
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