So far, most industrial Li-ion battery recycling processes are conducted using the following two methods: hydrometallurgical method and pyrometallurgical method that completely decompose the electrodes to elemental constituents. Although improvements in term of product quality and process complexity have been made over the industrial Li-ion battery recycling processes, they are still considered to be process-intensive and energy-consuming, while also wasting the initial energy embodied during the production of the cathode materials system. ^1-2

In this work, we demonstrate a novel approach to recycle LiMn₂O₄ as used in aqueous electrolyte batteries. LiMn₂O₄ cathode material was extracted from commercial aqueous battery that was cycled over several thousand cycles.³ The aged LiMn₂O₄ cathode material showed lower specific capacity than its uncycled counterpart. The material was then recycled by reacting it with a lithium source through two different methods: (a) solid-state reaction and (b) hydrothermal reaction. We recycled LiMn₂O₄ cathode material by directly relithiating the aged LiMn₂O₄ with a lithium source and without breaking it down into elemental form and re-synthesizing it. The advantages of this method are three folds: (1) it reduces usage of high temperature process to break down cathode materials into element form or other compound, (2) it decreases complexity of chemical process, and (3) it reduces usage of different chemicals for element refinement. This study shows the feasibility of recycling aged LiMn₂O₄through a simple and energy-efficient approach and recovering its lost capacity.

The outcomes of the using these two recycling methods are compared in term of phase purity, morphology, and electrochemical capacity. Our results show that the hydrothermally recycled product had superior phase purity and electrochemical capacity, and compared favorably even with uncycled material

The effect of process parameters in the hydrothermal process such as molar ratio of reactants, reaction temperature and reaction time is discussed and rated. The results show that by adjusting these process parameters, we are able to regenerate aged LiMn₂O₄through a simple hydrothermal reaction.

Reference:

1. Xu, J.; Thomas, H. R.; Francis, R. W.; Lum, K. R.; Wang, J.; Liang, B., A review of processes and technologies for the recycling of lithium-ion secondary batteries. J Power Sources 2008, 177(2), 512-527.

2. Georgi-Maschler, T.; Friedrich, B.; Weyhe, R.; Heegn, H.; Rutz, M., Development of a recycling process for Li-ion batteries. J Power Sources 2012, 207, 173-182.

3. Whitacre, J. F.; Shanbhag, S.; Mohamed, A.; Polonsky, A.; Carlisle, K.; Gulakowski, J.; Wu, W.; Smith, C.; Cooney, L.; Blackwood, D.; Dandrea, J. C.; Truchot, C., A Polyionic, Large-Format Energy Storage Device Using an Aqueous Electrolyte and Thick-Format Composite NaTi2(PO4)(3)/Activated Carbon Negative Electrodes (vol 3, pg 20, 2015). Energy Technol-Ger 2015, 3 (8), 796-798.