Design of Degradable Rechargeable Batteries

Transient or degradable electronics based on materials, devices and systems that disappear after a stable operating period with minimal or undetectable residues can help reduce the enormous amounts of electronic waste [1]. Ideally, the battery is integrated into these devices and degrades along with them. However, conventional batteries are optimized for long-term operation and contain a whole range of hazardous and/or expensive components. Therefore, transient batteries must be designed so that they can be disposed of without negatively impacting the environment. For efficient degradation, it is also important that the components and materials can decompose in an aqueous environment. However, some of the most important electrically conductive materials, e.g., copper and aluminum, which play a major role in batteries, do not fall into this category. For such materials, special concepts have to be developed on how they can be decomposed.<br/>In this presentation, a wide range of materials, fabrication methods, and assembly techniques will be presented to develop transient lithium-ion, sodium-ion, and zinc-ion batteries. Special emphasis will be placed on the development and characterization of separator-electrolyte systems based on biodegradable polymers. These separator-electrolyte systems were combined with a Li metal anode and a vanadium oxide cathode and packaged in a biodegradable case, resulting in a transient rechargeable lithium-ion battery (LIB) that can operate for over 400 cycles, but quickly dissolved in water within 15 minutes [2]. In order to be able to degrade copper and aluminum as well, a packaging concept was developed based on a water-soluble polymer composite film containing an oxidizing agent. When triggered with water, the film released the oxidant into the solution, which reacted with the copper and aluminum current collectors and led to their degradation [3]. For sodium-ion batteries biodegradable separators composed of agarose and nanocellulose were applied and tested in half-cell configurations with Na₃V₂(PO₄)₃ and Na₂Fe₂(SO₄)₃ as cathode materials [4]. Both separators showed promising electrochemical performances with high specific capacities and good cyclability, opening new avenues for the use of these renewable resources for sustainable energy storage devices beyond lithium-ion batteries. Finally, a carefully tailored bottom-up design of a transient zinc ion battery will be introduced that combined both excellent transience properties with outstanding electrochemical performance [5]. The battery consisted of a biopolymeric hydrogel electrolyte based on environmentally friendly polysaccharides, a Zn anode, and a biocompatible polydopamine-based cathode. A polysaccharide-based packaging made it possible to control the degradation of the battery, which is essential to maintain its functionality for as long as desired. This carefully tuned battery design displayed an open circuit voltage of 1.12 V and a specific capacity of 157 mAh g^-1 (current density of 50 mA g^-1) for over 200 cycles. The battery exhibited a pronounced transiency under composting conditions, evidenced by a weight loss of 50 wt.% after 63 days.<br/><br/>[1] N. Mittal, A. Ojanguren, M. Niederberger, E. Lizundia, Adv. Sci. 2021, 8, 2004814<br/>[2] N. Mittal, A. Ojanguren, N. Cavasin, E. Lizundia, M. Niederberger, Adv. Funct. Mater. 2021, 31, 2101827<br/>[3] N. Mittal, T. M. Jang, S. W. Hwang, M. Niederberger, J. Mater. Chem. A 2023, in print<br/>[4] N. Mittal, S. Tien, E. Lizundia, M. Niederberger, Small 2022, 18, 2107183<br/>[5] N. Mittal, A. Ojanguren, D. Kundu, E. Lizundia, M. Niederberger, Small 2023, 19, 2206249