Rechargeable lithium-oxygen batteries are believed to be the most promising energy storage system to date. Particularly in the field of powering electric vehicles (EVs) Lithium-oxygen batteries can exceed the energy output of conventional Li-ion batteries almost ten times. This increase in stored energy can potentially extend the driving range of an EV from ~100km to more than 600km per charge. The main reason for this energy density boast is the utilisation of oxygen from air to electrochemically react with a metallic lithium anode through a carbon-based air cathode to generate large amounts of electricity. The heavy, commonly used cathode materials of Li-ion batteries are replaced by a much lighter catalyst cathode. The implementation of this revolutionary technology involves the development of precise structurally engineered materials as well the integration of highly catalytic active constituents to unleash its full potential.
Previous studies already identified the significant improvement potential of porous carbon-based materials addressing the poor cyclability of the air cathode in lithium-oxygen batteries. Furthermore, several approaches to increase their energy efficiency have been investigated including doping techniques or the utilisation of metal oxides and precious metals.
The team of scientists under the supervision of Professor Guoxiu Wang successfully prepared a ruthenium nanocrystal-functionalised porous graphene cathode catalyst that provides remarkable cycling performance and stability.
Dr Bing Sun said, “The combination of hard templating techniques using silicon nanoparticles and impregnation methods allowed us to accurately design and control the nano-architecture and functionalisation of this novel catalyst material.”
The NANO Letters paper outlines the test results of the ruthenium functionalised porous graphene catalyst, which creates a lithium-oxygen battery that can deliver an initial capacity of 17 700 mAh/g at the current density of 200 mA/g combined with 86.8% energy efficiency. The material also demonstrated extraordinary cycling stability for up to 200 charge/discharge cycles at a restricting capacity of 1000 mAh/g.
A lithium-oxygen battery equipped with this exciting new material could help this technology to overcome some of its existing obstacles on the journey to revolutionise the way we look at electric vehicles. A realistic solution to decelerate global warming and climate change.