Rechargeable asymmetric zinc–nitrate/glycerol batteries synergizing chemical valorization and energy conversion

Abstract

Aqueous rechargeable zinc (Zn)-based batteries are promising for safe and sustainable energy storage. In addition to energy storage, Zn-based batteries, such as Zn–nitrate batteries and Zn–CO₂ batteries, can be utilized for value-adding electro-reduction reactions, but their rechargeability and cycling stability are limited by inefficient and irreversible charging reactions, particularly the sluggish oxygen evolution reaction (OER). Here, we propose rechargeable asymmetric Zn batteries (aZBs) as a novel strategy for simultaneously achieving energy storage and chemical valorization. As a proof of concept, our aZB employs an asymmetric redox configuration to replace the energy-intensive OER with a thermodynamically favorable and value-generating glycerol oxidation reaction (GOR). This dual-function asymmetric battery configuration enables low-voltage charging and high energy efficiency while producing ammonia and formic acid during discharge and charge, respectively—two chemicals with widespread applications in agriculture, pharmaceuticals, and clean fuel systems. Assisted by a bifunctional electrocatalyst, the system delivers an energy efficiency of 62.2% and a stable cycling lifespan of over 200 hours at 2 mA cm⁻². Flow-cell aZBs demonstrate continuous discharging/value-adding cycles for 120 h at 5 mA cm⁻², showcasing the potential for the sustainable coproduction of value-added chemicals. This work establishes a new battery design paradigm that synergizes asymmetric redox reactions and biomass-derived molecule utilization, paving the way for integrated energy–chemical co-production systems beyond traditional reversible redox battery configurations.