Direct recycling of anode active material from Li-ion batteries using TiNb2O7 anode

Abstract

As the demand for large lithium-ion batteries (LIBs) for automotive and other applications rapidly grows, recycling of electrode materials has become essential owing to the large amount of waste material generated by battery manufacturing (e.g., battery scrap) and end-of-life (EOL) batteries. While there have been many studies on recycling of cathode materials, we propose a direct recycling process for anode material using TiNb2O7 (TNO) as the active material, as it offers high capacity and long life. Calcination was introduced to separate the anode active material from the current-collecting foil, and a regeneration method was investigated for TNO anodes from scrap and EOL battery waste. After calcination, the active material can be easily separated from the aluminum current-collecting foil owing to the binder disappearing. The structure of the active material was investigated using X-ray diffraction and scanning electron microscopy. TNO active material recycled from scrap and EOL was found to maintain the structure of virgin material. A cell was fabricated using recycled TNO and cell performance was evaluated. The cell capacity and rate capacity were found to be almost equivalent to those of virgin material. In terms of the carbon footprints of products (CFP), CO2 emissions during the recycling process were compared between recycled material and virgin material, and it was found that CO2 emissions were reduced to 0.7-CO2eq/kg for scrap material and 3.8-CO2eq/kg for EOL waste material, compared with 4.8-CO2eq/kg for virgin material. Thus, the feasibility of low CO2 emissions during TNO anode direct recycling was confirmed in principle. A simple and low CO2 emission recycling loop can thus be constructed by employing a stable TNO active material structure and direct-recycling process with calcination.