From A Reliable Design
In a paper published in Advanced Functional Materials, scientists from the University of Cambridge describe their lithium-sulfur battery inspired by human small intestine lining. The new battery is capable of storing five times more energy than lithium-ion batteries.
A typical lithium-ion battery works by having positively-charged lithium ions move back and forth through the cathode (positive electrode), electrolytes, and the anode (negative electrode). The crystal structure of the electrodes usually determines how much energy can be put in the battery. A lithium-ion battery's carbon electrodes can only carry six lithium ions, limiting its capacity.
Lithium and sulfur react differently, through "a multi-electron transfer mechanism" which means that theoretically, sulfur can have a much higher capacity than lithium-ion. However, when lithium and sulfur react as the battery discharges, the sulfur turns into chain-like poly-sulphides which could enter the electrolyte as it charges and discharges, resulting in the loss of the battery's active material.
Higher Capacity Batteries
The researchers' new design makes use of a layer of zinc oxide nanowires that are grown on a scaffold on top of the cathode. The resulting structure has the same shape as the villi of the small intestine and can trap the poly-sulphides. This keeps the fragments electrochemically accessible and allows the material to be reused.
The battery does have its limitations. In fact, it still cannot match lithium-ion batteries in terms of charge cycles. But, it could be offset by the lithium-sulfur battery's higher energy density which could lead to longer times between charges.
The design is still just a proof of principle, but if it becomes commercially viable, it could usher in a new generation of high capacity batteries.
Dr Paul Coxon from Cambridge’s Department of Materials Science and Metallurgy and co-author of the study says, “We’re all tied in to our electronic devices – ultimately, we’re just trying to make those devices work better, hopefully making our lives a little bit nicer.”