Abstract
The need to recover valuable metals from spent lithium-ion batteries (LIBs) is undisputed. However, the environment and the climate are also affected by emissions from the recycling processes. Therefore, the call for environmentally friendly recycling methods is currently louder than ever. In the field of hydrometallurgical recovery of metals from spent LIBs, inorganic acids have so far proved to be an effective, but environmentally problematic, leaching agent, since the pollution of wastewater by high salt loads and the emission of toxic gases cannot be avoided. This has recently led to a trend towards the application of organic acids, as these have significantly more environmentally friendly properties. In order to continue this approach, and to improve it even further from an environmental point of view, this work focuses on the utilization of low leaching temperatures in combination with organic acids for the recovery of valuable metals from spent lithium-ion batteries. This can drastically reduce the required energy demand. Furthermore, attention is paid to higher (50–100 g·L−1) solid-liquid ratios, which are indispensable, especially with regard to the economic establishment of the tested process. The experimental verification of the feasibility using citric, oxalic, and formic acid showed the possibility of an efficient recovery of cobalt, nickel, and lithium. In particular, citric acid in combination with hydrogen peroxide as a reducing agent appears to be a suitable and environmentally friendly alternative to classical inorganic acids, even at low process temperatures, for the hydrometallurgical recycling of lithium-ion batteries.
Highlights
The definition of the European Union’s climate policy targets and the need to minimize CO2 emissions worldwide means that there is no way of avoiding a change in the transportation sector
Sales of plug-in hybrids and battery electric vehicles have increased considerably in recent years, which will be reflected in a rapid growth rate in the coming years
For the conducted tests a thermally preRecycling 2022, 7, x FOR PEER REVIEtWreated active material was applied, to exclude organic compo7noefn1ts6 that would interfere in the hydrometallurgical processes
Summary
The definition of the European Union’s climate policy targets and the need to minimize CO2 emissions worldwide means that there is no way of avoiding a change in the transportation sector. Sales of plug-in hybrids and battery electric vehicles have increased considerably in recent years (see Figure 1a), which will be reflected in a rapid growth rate in the coming years. The sales of 6.4 million EVs are expected in 2021, representing a growth of 98% compared to 2020 (see Figure 1b). Depending on the scenario assumed, sales of EVs will increase to between 13.1 and 20 million by 2025, while by 2030 they are already expected to reach between 25.8 and 46.8 million units [1,2]. Considering the increasing sales of electric vehicles and the composition of lithium-ion batteries, with a focus on the cathode and anode materials used, the need for sustainable and climate-friendly recycling processes becomes obvious. Due to the multitude of possible cathode systems (NMC, NCA, LTO, LFP, etc.), the difficulty of establishing a uniform recycling process for spent LIBs becomes apparent [3,4]
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