Research on Spent LiFePO4 Electric Vehicle Battery Disposal and Its Life Cycle Inventory Collection in China

1.1. The Issue of End-of-Life Vehicle Battery

In recent years, emphasis on environmental protection has expanded the global market for electric vehicles (EVs). Moreover, many automobile manufacturers have developed their own EVs, such as the Leaf (Nissan), Prius (Toyota), Volt (Chevrolet), and Model S (Tesla). In China, the electric vehicle market is developing rapidly. In 2015, 331,092 electric vehicles were sold in China, making it the largest market in the world, compared to sales of only 8159 in 2011 [1]. Subsequently, China’s electric vehicle sales have occupied a dominant position [2]. In particular, vehicle manufacturers such as the Shanghai Automotive Industry Corporation (SAIC), BYD Auto Co. Ltd. (BYD, Shenzhen, China), and FAW Group Corporation (FAW, Changchun, China) have launched their own EVs.

However, such development will result in spent vehicle batteries. The electrodes of these batteries may contain heavy metals, for example, cobalt in LiCoO2 (LCO) batteries, nickel in Ni-MH batteries, and manganese in LiMn2O4 (LMO). Each of these heavy metals may be present in nickel cobalt manganese lithium (NCM) batteries. Heavy metals can pollute the soil, water, and air if not appropriately treated. LiFePO4 (LFP) batteries do not contain heavy metals, and their solvents comprise harmless (non-toxic) carbonate mixtures, additives, etc. However, lithium hexafluorophosphate (LiPF6), which is often used for lithium salt, is highly toxic. In addition, the decomposition of LiPF6 products results in hydrogen fluoride (HF), which is extremely harmful to human health [3]. An addition safety issue relates to the combustion of organic solvents, carbonate mixtures of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), propylene carbonate (PC), etc., which is a potential safety hazard due to the generation of unburned hydrocarbons and related oxygenated compounds [4].

In the life cycle concept, the disposal phase is an essential part of a product’s life. The life cycle relates to a product’s environmental impacts and economic benefits. Numerous developments and measures have been incorporated in laws, recycling technologies, and life cycle assessment (LCA) studies.

A large number of regions and countries have issued laws and regulations related to battery recycling [5]. The European Union enacted the directive 2006/66/EC [6,7], which covers all types of batteries and accumulators. In China, the government announced regulations and standards for used battery disposal. The Technical Policy for the Recovery of Automobile Products states that EV manufacturers should be responsible for the recycling and treatment of sold EV batteries [8]. The Circular Economy Promotion Law of the People’s Republic of China regulates the recycling of waste products, such as batteries, which are included in the mandatory recycling list [9]. In 2012, the Chinese government advocated the establishment of cascade utilization and recycling management systems for EV batteries [10]. The instructions of the “Vehicle Battery Industry Standard Conditions” stipulate that battery production enterprises must (i) meet the requirements of the environmental and occupational health and safety systems; (ii) recycle or treat waste created during the manufacturing phase; and (iii) engage with the vehicle manufacturer for the disposal procedure of used vehicle batteries [11]. “The Industry Standard Conditions of New Energy Vehicle Used Battery Utilization and Interim Administrative Measures” regulates the relevant recycling and disposal technologies and their efficiency requirements, and the distribution of recycling and disposal responsibilities among the stakeholders [12].

Globally, research into battery recycling has expanded rapidly. Currently, hydrometallurgical and pyrometallurgical processes are widely used to recycle spent lithium-ion batteries [13].

Pretreatment processes, which are usually a necessary preparatory step, may consist of electrochemical, mechanical (dismantling and crushing), and heat treatments, and physical separation. The pyrometallurgical process can remove the organic binder by heating. Moreover, it may use oxidization, reduction, and decomposition to attain metals and their oxidation compounds. The hydrometallurgy process is often divided into two main stages: leaching and extraction. Chemical leaching often dissolves the cathode material in lithium-ion batteries with acid. Extraction usually separates optional target products from the solution using special solvents. Studies on the leaching process primarily focus on leaching efficiency and influential factors, including the type and concentration of acid, temperature control, reaction time control, and the solid–liquid ratio [14,15,16,17,18,19,20,21]. In general, the main recycling target is valuable metals [22], such as cobalt and nickel in the forms of Co2O3, CoC2O4, and Ni(OH)2.

In addition, many studies have been conducted on the LCA of the environmental impact of EVs and batteries. These studies have analyzed energy consumption and emissions of different EV and battery technologies to achieve methods of sustainable improvement. Fisher et al. conducted an LCA of waste portable batteries with combinations of three collection scenarios and three recycling scenarios. They then analyzed the environmental benefit and financial cost of disposal [23]. Ellingsen et al. compiled an inventory for a lithium-ion nickel-cobalt-manganese traction battery and analyzed the impacts in the cradle-to-gate phase [24]. Notter et al. compiled a detailed life cycle inventory of the LiMn2O4 battery and compared the emissions and impacts between battery electric vehicles (BEV) and internal combustion engine vehicles (ICEV) [25]. Majeau-Bettez et al. conducted an LCA of three types of batteries, namely Ni-MH, NCM, and LFP batteries for plug-in hybrid vehicles and EVs [26]. However, the authors excluded an end-of-life disposal scenario from the inventory. Zackrisson et al. conducted the LCA of LFP batteries using different solvents during cell manufacturing to examine and optimize the design of batteries [27]. However, the recycling and disposal phase of spent batteries was simplified by a 500 km transportation route. Hendrickson et al. conducted the LCA of vehicle batteries, including LFP batteries, in California. In the compilation of the inventory for battery recycling, the authors made use of the background database built-in the GREET2 model [28].