Electrochemical Ion Separations By Recyclable Electrode Cell

Abstract

Electrochemical separations using Faradaic electrodes are able to exceed the ion adsorption values as well as selectivity when compared to capacitive electrodes, which is due to the bulk reactions for the former vs. surface confined for the latter. However, the cyclability of battery/faradaic electrodes is constrained to hundreds or a few thousands of cycles. This work proposes an electrochemical ion pumping design with the unique feature of using injectable electrodes to overcome the ciclability issue and easily control the areal capacity. The idea consists on using injectable electrodes with the intention of recycling the active material once the end-of-life of the device is reached due to active material degradation. In this fashion, the active material is replaced in a straightforward deinjecting-injecting process allowing direct reuse of the inactive components of the device, thus contributing to reducing the replacement cost. This device is called Ion Pumping Injectable Cell (IPIC).Moreover, the IPIC system is a tremendously versatile technology due to the simple and easy methodology employed to replace the electrodes. In this fashion, the system was tested using different types of lithium intercalation materials (LFP and LMO), different ion capturing such as potassium (Prussian Blue Analogs, PBA´s), sodium (NMO) or more conventional activated carbon electrodes (capacitive non-selective electrode). In addition to this feature, it is important to remark that the IPIC could be used in a symmetric (e.g. LFP-LFP) or asymmetric configuration (e.g. LFP-LMO). The main difference is that the asymmetric system has the ability of storing energy while capturing ions and deliver that energy in the subsequent step. This is so due to the different electrode potential. The selectivity toward specific ions is achieved by using a chemical ion-selective separator such as an ion exchange membrane (LFP-LFP or LFP-LMO systems), or by using ion selective intercalation materials such as LFP and PBA´s without the need of selective membranes.In this work, the benefits of the injectable electrode cell architecture will be examined, the performance of different cell configurations will be discussed and the electrochemical ion separation mechanism will be analyzed for different applications. Acknowledgements : J.J. Lado and Alba Fombona-Pascual acknowledge Comunidad de Madrid for the fellowship (2020-T1/AMB-19799).