Direct recycling of EV production scrap NMC532 cathode materials†

Abstract

The transition to widespread adoption of electric vehicles (EVs) is leading to a steep increase in lithium ion battery production around the world. With this increase it is predicted there will not only be a large increase in end of life batteries needing to be recycled, but also a substantial amount of production scrap, particularly in the early stages of gigafactory set-up. The recycling of such battery electrode materials has a number of challenges which need to be considered, in particular the delamination from the current collector and removal of the binder, e.g. mainly polyvinylidene fluoride (PVDF) for cathode materials. Traditional pyrometallurgy or hydrometallurgy approaches require multiple separation steps to obtain pure metal salts before resynthesising the cathode active material, and so can be high cost, high CO₂ and high waste processes. Production scrap in particular, however, offers the potential for lower cost and lower environmental impact direct recycling processes to be employed, which preserves the manufactured value of the electrode material. To illustrate the potential of such an approach, here we demonstrate a direct recycling approach on EV production scrap cathode materials which utilises a low temperature heat treatment to decompose the binder and allow delamination of the cathode material from the Al current collector. A further higher temperature heat treatment is then employed to ensure complete binder removal and regenerate the cathode, with the results showing that the addition of a small amount of Li is required to improve electrochemical performance (first cycle discharge capacity (2.5–4.2 V) of 129(2) mA h g⁻¹ and 146(4) mA h g⁻¹ with 0 wt% and 10 wt% added lithium, respectively). Electrochemical performance can be further improved by increasing the upper voltage window to 4.3 V (first cycle discharge capacity of 146(4) mA h g⁻¹ and 164(2) mA h g⁻¹ at 2.5–4.2 V and 2.5–4.3 V, respectively).