Dilithium Benzenediacrylate As Organic Electrode Material: Life, Death and Rise of the Lithium Phoenix

Organic materials issued from biomass could constitute a viable option as replacements for inorganic materials in Li-ion battery electrodes. Due to their low-cost production, recyclability and structural diversity, many organic materials have been investigated as electrodes for Li-ion cells, such as organic sulfurs, nitroxide radicals, conjugated carbonyl derivatives and disulfides [1,2]. Conjugated carboxylates have become the perhaps most promising type of organic electrode material due to their high theoretical capacity, fast reaction kinetics and structural diversity [3].

The example chosen for this study is dilithium trans-trans benzenediacrylate, an organic material with a practical capacity of approx. 200 mAh*g^-1 and an average potential of 1.2 V vs Li⁺/Li⁰ [4]. We have previously reported on several properties of this material and its cycling behavior in half cells [5]. Due to that this compound is easily soluble in water and insoluble in organic solvents (such as the carbonates used as electrolytes), a method of extraction from spent cells and recycling of this compound has been used with promising results. This method is based on the extraction of the active material by dissolution in water followed by filtrations/drying sequences. Its insolubility in organic solvents allows separation of the active material from other components by a washing step [6], after which it can be combusted to Li₂CO₃. This method is also dependant on the choice of battery electrolyte, and better performance can be observed using an electrolyte system with stability in presence of water. According to these properties, an idealized recycling process can be obtained, presented in Fig. 1. This facilitates the recycling of lithium from the battery, and a new cell can be constructed from the ashes of a spent device, with only addition of new biomass-derived materials – a Phoenix-like transformation.

Fig. 1. Idealized recycling process of organic electrode materials from spent batteries.

So far, this method has mainly been applied to prototype cells in which the organic compound was cycled vs. Li or LFP. Here, a similar method is presented using pouch cells, with addition of binders whose separation from active material pose a problem, not least if water soluble components such as CMC (carboxymethylcellulose) are used. Therefore, additional steps in the procedure have been included to better separate the binder from the active material.   

Moreover, the cycling behavior of the active organic material in full cells will be presented, as well as recycling strategies from spent batteries.

References:

1. M. Armand, S. Grugeon, H. Vezin, S. Laruelle, P. Ribière, P. Poizot, J.M. Tarascon, Nat. Mater., 2009, 8, 120-125.

2. H. Chen, M. Armand, G. Demailly, F. Dolhem, P. Poizot, J.M. Tarascon, ChemSusChem, 2008, 1, 348-355.

3. Z. Song, H. Zhou, Energy Environ. Sci., 2013, 6, 2280-2301.

4. S. Renault, D. Brandell, T. Gustafsson, K. Edström, Chem. Comm., 2013, 49, 1945-1947.

5. S. Renault, V.A. Mihali, D. Brandell, Electrochem. Comm., 2013, 34, 174-176.

6. S. Renault, D. Brandell, K. Edström, ChemSusChem, 2014, 7, 2859-2867.