A novel and clean process for selective recovery of lithium from spent LiFePO4 cathode material by oxidative roasting-water leaching process

Abstract

The recovery of lithium from spent lithium-ion batteries (LIBs) is of great importance in addressing lithium shortages and environmental issues. In this study, a novel and clean process for selective separation of lithium from spent LiFePO4 cathode material by low temperature oxidative roasting and water leaching was proposed. The effect of several important factors, such as roasting temperature, roasting time, and molar ratio of ferric chloride (FeCl3∙6H2O) to lithium iron phosphate (LFP), on the leaching efficiency of lithium and iron was systematically investigated by using single factor experimental method. The results show that approximately 97.1% lithium element was recovered by being converted to water-soluble LiCl at a roasting temperature 350 ℃, a roasting time 120 min and a FeCl3∙6H2O/LFP molar ratio of 1:1, and iron element was enriched in the leaching residue in the form of insoluble FePO4. High-purity lithium carbonate products could be prepared from the leching solution by adding Na2CO3 after removing iron. The establishment of new cleaning process can provide a scalable, environmentally friendly and simple way to recover valuable metals from spent LFP batteries.

1. Introduction

As the economy recovers from the coronavirus outbreak, the price of Li2CO3 has soared to its highest level. Over the past two decades, lithium-ion batteries (LIBs) have been widely used in electric vehicles, electronic devices and energy storage, becoming an indispensable part of our daily lives [1, 2]. Among many cathode materials, olivine structure lithium iron phosphate (LFP) is considered to be the most promising material for electric and hybrid vehicles, due to its high theoretical specific capacity (170 mA·h/g), low price, stable structure, high safety and environmental friendliness [3 −6]. The spent batteries generated by the use of LFP batteries can cause serious environmental pollution, because they contain some harmful chemicals and metal resources such as lithium and iron [7, 8]. Therefore, it is very necessary to develop a clean and feasible recycling process for waste LIBs, which is important to save resources and protect the environment [9, 10].

Currently, the methods for disposing of spent lithium-ion batteries mainly include direct regeneration and metallurgical recovery [11]. Direct regeneration technology refers to the direct repair or modification of cathode materials through some means. Indirect recycling refers to the recovery of valuable metals or compounds for reuse. Direct regeneration methods can be subdivided into electrochemical treatment [12], hydrothermal reduction [13−16], ionic thermalization [17], molten salt reduction [18], and solid-state sintering [19 −21]. The electrochemical performance of regenerated LIBs is usually worse than that of original LIBs, and the reused battery cathode materials still face the problems of scrapping [22]. In recent years, the research on the hydrometallurgical and pyrometallurgical processes for recovering spent LIBs has become the focus [23−25]. In the leaching process, some reducing agents such as H2O2, NaHSO3 and glucose are usually added to the solution to increase the recovery of metals [26, 27]. A large number of corrosive reagents are inevitably used in hydrometallurgical process [28]. Non-selective leaching can also lead to complex separation processes. Pyrometallurgy is the process of treating spent LIBs at extremely high temperatures to reduce and melt valuable metals into alloys [29]. Although this process is commonly used in industrial production, a large number of harmful gases are released to pollute the environment. Therefore, t