低过电位、长循环非水系镁—二氧化碳电池

Low Overpotential of Long Cycle Non-aqueous Mg-CO_(2) Batteries

镁—二氧化碳(Mg-CO_(2))电池以温室气体二氧化碳为正极活性物质,既能实现高效的能量储存,又能实现二氧化碳的增值利用,是新一代极具吸引力的电池候选产品。然而,与其他金属—二氧化碳电池体系相比,由于镁—二氧化碳电池在非水环境中存在一些关键问题(包括氧化还原反应动力学相对较慢、放电产物分解能垒较大、多电子三相正极反应可逆性较差等),因而迄今为止其受到的关注较少。为解决前述正极充放反应可逆性较差、碳酸镁等放电产物分解能垒较大、电池过电势较高等问题,通过调控二氧化碳电化学氧化还原路径的策略,采用碳化钼—碳纳米管(Mo_(2)C-CNTs)作为正极催化剂,将放电产物由热力学稳定难以分解的碳酸镁(MgCO_(3))换为草酸镁(MgC_(2)O_(4)),使Mg-CO_(2)电池实现了极低的过电位(0.25 V),增大了其能量效率。并且,其工作时间长达2300 h以上。这项工作为可同时解决能源和环境问题的可充电非水系Mg-CO_(2)电池研究奠定了基础。

Magnesium carbon dioxide(Mg-CO_(2))batteries,in which use greenhouse gas carbon dioxide was used as the positive electrode active material,have the advantages of efficient energy storage and value-added utilization of carbon dioxide,making them an attractive candidate for a new generation of battery.However,compared with other metal carbon dioxide battery systems,Mg-CO_(2) batteries have received little attention so far,due to several severe issues,including relatively slow redox reaction kinetics in non aqueous environments,large decomposition energy barriers of discharge products and poor reversibility of multi electron three-phase positive electrode reactions.In order to solve these problems,molybdenum carbide carbon nanotubes(Mo_(2)C-CNTs)were used as positive electrode catalysts,and the discharge product was changed from the difficult to decompose magnesium carbonate(MgCO_(3))to magnesium oxalate(MgC_(2)O_(4)),resulting in an extremely low overpotential(0.25 V)for the Mg-CO_(2) battery,increased energy efficiency,and a working time of up to 2300 hours..This work lays the foundation for the research of rechargeable non-aqueous Mg-CO,batteries that can simultaneously address energy and environmental issues.