With the aggravation of global warming and the shortage of oil resources, the promotion of the use of new energy vehicles has become an important measure for the Chinese government to cope with the pressure of energy security and ecological protection
[1]. With the power supply of clean energy such as wind energy and solar energy, new energy vehicles have gradually become an important channel for decarbonization in the transportation and energy sectors and have produced good environmental benefits. In addition, they can also be used as portable distributed energy storage systems to store energy, thus playing a vital role in microgrid energy management
[2][3].
With the advancement of battery manufacturing technology, the current power batteries that dominate the market no longer contain heavy metal elements such as lead and cadmium, but they still have a variety of pollutants such as carbon black, graphene, and sulfuric acid
[4][5]. In recent years, the power battery’s upstream raw material, such as nickel, cobalt, lithium, and other metals, prices continued to rise
[6][7]. Taking battery-grade lithium carbonate, for example, at the beginning of 2021, its average price was only 50,000 RMB/ton, and at the beginning of 2022, the price had jumped to 290,000 RMB/ton, a rise of 480%, the highest quoted price even exceeded 300,000 RMB/ton, which makes the power battery recycling have more economic value. Therefore, based on the multi-dimensional considerations of improving power battery utilization efficiency, environmental protection, resource recycling, reducing the risk of the power battery industry supply chain, and realizing the green, low-carbon, and sustainable development of the new energy vehicle industry, it is imperative to effectively recycle and efficiently utilize the decommissioned power battery
[8][9].
2. Composition of Power Battery
At present, power batteries applied to automobiles can be divided into secondary batteries (including lead–acid batteries, nickel–metal hydride batteries, nickel–chromium batteries, and lithium-ion batteries) and fuel cells
[10]. Among them, lithium-ion batteries have better safety, recycling, and repeatable charging performance, as well as higher energy conversion efficiency and more mature manufacturing technology, coupled with China’s lithium resources being more abundant, so lithium-ion batteries have gradually become the mainstream development of power batteries and the first choice for new energy vehicles
[11][12][13]. Lithium-ion batteries can be mainly categorized into lithium iron phosphate batteries and ternary batteries. In the early stage of the development of new energy vehicles, lithium iron phosphate batteries occupied a major market share. With the battery energy density included in the subsidy reference, ternary batteries were gradually promoted and used in new energy vehicles. But since 2020, the new energy vehicle subsidy policy has gradually sloped back, and the era of high energy density in exchange for high subsidies has quietly come to an end; lithium iron phosphate batteries, which are better in safety and more cost-effective, have re-entered the field of vision of most automobile enterprises; and the proportion of various types of power battery installations from 2018 to 2022 is shown in
Figure 1.
Figure 1. Proportion of installed capacity of various types of power batteries from 2018 to 2022 (data from China Association of Automobile Manufacturers).
Lithium-ion power battery mainly consists of a positive electrode, a diaphragm, a negative electrode, an external protective case, and the electrolyte added in it
[14]. The positive electrodes are made of a lithium-containing metal compound coated on a collector and pressed into a sheet, and the lithium-containing compounds used in commercial lithium-ion batteries are usually lithium metal oxides, such as lithium cobalt oxide (LiCoO
2), lithium manganese oxide (LiMn
2O
4), lithium nickel oxide (LiNiO
2), lithium–nickel–cobalt–manganese oxide (LiNi
xCo
yMn
zO
2, 0 < x, y, z < 1, x + y + z = 1), and lithium iron phosphate (LiFePO
4). Negative electrodes are made by coating negative electrode materials (graphite, LTO) onto a copper foil (collector). The electrolyte affects the rate of energy release by controlling the mass flow rate within the cell. The diaphragm is a permeable membrane between the positive and negative electrodes of the battery, mostly made of polymers such as polyethylene or polypropylene, which, on the one hand, prevents physical contact between the electrodes and allows ion transport through the electrolyte and, on the other hand, serves as a safety device; if the battery is overheated, the porous membrane melts and irreversibly seals the electrodes. The external protective case is used to maintain the physical integrity of the battery. The positive and negative electrode materials are the most recyclable parts of a lithium-ion battery.