Battery recycling

Battery recycling

The new energy vehicle industry is developing rapidly, and the demand for power lithium batteries is growing rapidly. The batteries have entered the routine replacement stage, and the power batteries contain a large number of recyclable high-value metals, such as lithium, cobalt, nickel, etc., which can produce great economic benefits after recycling. A large number of waste-power lithium batteries are expected to generate a huge recycling market.

When the number of cycles of a ternary battery is about 2500, the battery capacity decays to 80%, and then its relative capacity declines rapidly with the increase of the number of cycles. The step utilization value is very low, but it contains rich nickel, cobalt, and manganese valuable metals, which are usually directly disassembled and recycled. The capacity of lithium iron phosphate battery decreases slowly with the increase of the number of cycles, so it has a higher utilization value.

Some lithium-iron phosphate batteries meet the requirements of echelon utilization and will first enter the echelon utilization scenario after decommissioning. The proportion of retired three-way batteries will be higher than that of retired lithium iron phosphate batteries. With the passage of time, the decommissioning amount of lithium iron phosphate batteries will gradually increase, accounting for a higher contribution.

Utilization of steps

After the complete lithium battery pack of the new energy vehicle is recycled, it can be disassembled into modules or cells to form small batteries for low-speed electric vehicles, solar street lights, and other products, or multiple complete battery packs can be combined together to save energy for wind, photoelectric and other scenarios.

At present, the stepwise utilization technology mainly includes PACK(multistage series-parallel battery module)+BMS(battery management system), which is the mainstream choice. The PACK process is divided into three parts: processing, assembly, and packaging. The core of the pack is to connect multiple single cells in series and parallel through mechanical structures to form battery packs. In the specific operation process, it is necessary to consider the mechanical strength and system matching of the whole battery pack, involving a large number of mature technologies such as thermal management, current control and detection, module assembly design, and computer virtual development. The main function of the BMS battery management system is to intelligently manage and maintain each battery unit, prevent the overcharge and over-discharge of the battery, and monitor the battery status in real-time, so as to protect the battery life. For the cascade utilization of power batteries, BMS determines the scope of application, life, and overall value of reused batteries.

From the technical point of view, due to the poor consistency and different life of the power battery, the data of the BMS system will deviate from the actual condition of the battery, which makes the step utilization process face challenges in safety, product quality, and other aspects. Because of the different battery models, the battery quantity base will be large when pairing, screening, pairing, and processing costs are relatively high, only a few enterprises with mature technology can obtain economic benefits.

Regeneration and utilization

Disassembly and recycling (recycling) are to disassemble retired batteries through chemical, physical, biological, and other means to recover Ni, Co, Mn, Li, Cu, and other metal elements and other recoverable materials. The content of Ni, Co, Mn, and other metal elements in ternary lithium batteries is much higher than that in raw ore. Taking NCM523 as an example, the stoichiometry of the three elements is 30.4%, 12.2%, and 17.1%, respectively. The 1.1% lithium content in the lithium iron phosphate battery is higher than that of the raw ore with a grade of 0.8% ~ 1.4%(Li2O) (corresponding to the Li content of 0.4% ~ 0.7%).

There are three technologies in the recycling process, which are physical, fire, and wet. At present, the representative recycling enterprises in China, such as Green Beauty and Bang Pu, mainly use the wet processes and combine them with the firing process.

Method of physics

The waste power battery internal components, such as electrode active material, fluid collection, and battery shell components, through a series of means such as crushing, screening, magnetic separation, fine grinding, and classification, to obtain valuable products, and then the next step of recycling. The advantage is that the operation is simple, but it can not completely separate the components of the lithium battery, and in the physical operation process, it is difficult to effectively recover the metal materials in the battery.

Firstly, it is necessary to conduct automatic discharge and classification of the battery. Through vibration screening and magnetic separation, the metal shell and electrode material parts are separated. The electrode material parts which have been physically broken are put into the dry arc furnace for high-temperature roasting, and the organic adhesive, electrolyte, and carbon-containing organic matter are removed, so as to separate the components of the lithium battery. The carbon and organic matter will be burned off at high temperatures, which will produce reducing gas and protect the metal elements in the electrode. Finally, the fine powdery material containing metal and metal oxides can be obtained by screening. The advantages are a simple operation process, rapid reaction under high-temperature conditions, relatively high efficiency, can removal of the residual adhesive, and suitability for dealing with a large number of or more complex structures of the battery; But the disadvantage is that the energy consumption is large, in the process of treatment is easy to produce harmful gases, the pollutants treatment cost is high. Foreign lithium battery recovery technology is mainly fire.

Most enterprises in our country use, and usually must combine fire methods. The specific process is:

Pretreatment, which involves fire;

Leaching: Dissolve the electrode material in an acid-base solution, and extract some valuable metal elements, can be directly acid leaching or acid-base two-step leaching;

Extraction: The leached various valuable metals are separated and recovered separately. The commonly used methods are extraction, precipitation, or electrodeposition to extract the remaining valuable metals.

Wet recovery has become the mainstream technology due to its high recovery rate, high purity of products, and low energy consumption. However, it has a long process and needs to add hydrochloric acid and other corrosive solutions in the treatment process, so the cost of pollution control is high.

Selection of process

There are three methods involved in the recycling process, but the main difference lies in the core process. The core process of the physical method is material repair after crushing and screening, which is a relatively pure physical process. The core process of pyrotechnics is high-temperature pyrolysis to obtain metal oxides. The core process of the wet process is to extract metal by adding a chemical reagent to the electrode powder.

Cobalt-nickel collinear:

In the wet process, nickel and cobalt share the same production line. After extraction of 507, nickel salt and cobalt salt are proposed successively. Because different companies have different apportion standards for co-linear nickel-cobalt processing costs, it is reflected in the co-nickel coefficient in the material pricing.

Production line switch:
The recycled material smelter is the same as the intermediate product smelter, only the raw materials are different and the process is the same. Therefore, when the recovery profit is large, some intermediate smelters will move to the recovery market. Similarly, recently the recovery market profit continues to squeeze, and some recovery smelters will switch raw materials to mineral intermediates.

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