Can You Make Batteries for Operando Optical Measurements Without Sacrificing Performance?

In recent years, there has been an increased focus on studying light–battery interactions in the context of <i>operando</i> optical studies and integrated photoelectrochemical energy harvesting. A variety of optical cell designs have been used for this purpose, but they often suffer from poor electrochemical performance due to their device architecture, which differs significantly from conventional designs. This limits the conclusions that can be drawn from such experiments as well as the cycling protocols (such as high rates) which can be used.<br/><br/>Here, we propose two battery designs to enable light-battery interactions with reasonable electrochemical performance: the windowed coin cell which draws on conventional cell design, and the planar cell, which is inspired by dye-sensitized solar cells. We identify [1] suitable “light-accepting” current collectors for this class of batteries, namely, fluorine-doped tin oxide, indium-tin oxide, and silver nanowire-graphene film, along with carbon paper, carbon nanotube paper, and stainless-steel mesh.<br/><br/>We categorize these current collectors into two classes – transmissive and non-transmissive, based on the orientation of the light–electrode interaction. Various methods to prepare the electrode are highlighted, including drop casting and the fabrication of free-standing electrodes. The optical and electrical properties of these current collectors as well as their electrochemical stability are measured using linear sweep voltammetry against zinc and lithium anodes. The rate performance and long-term cycling stability of lithium manganese oxide (LiMn₂O₄) cathodes are measured against lithium anodes with these current collectors and their performance is compared. These results show which current collector to choose depends on the application and cell chemistry.<br/><br/>Finally, we highlight the utility of these cell designs for studying colour changes in battery cathodes through optical microscopy, as well as changes in the band gap of materials during electrochemical intercalation through diffuse reflectance spectroscopy (DRS) [2]. These guidelines will assist in the design of future optical cells for in-situ measurements and photoelectrochemical energy storage.<br/><br/>[1] Pujari, Arvind, et al. "Identifying Current Collectors that Enable Light–Battery Interactions", <i>Small Methods </i>(2024), 2301572.<br/>[2] Pujari, Arvind, et al. "Does Heat Play a Role in the Observed Behavior of Aqueous Photobatteries?", <i>ACS Energy Letters</i> 8.11 (2023): 4625-4633.