The new type of lithium-sulfur battery is said to have five times the energy density of a typical lithium-ion battery. The battery has been developed at the University of Cambridge.
Although lithium-sulfur batteries have great potential, they have an inherent problem in terms of degradation of the battery caused by the loss of material within it (this is the accumulation of poly-sulfides.) Too overcome this weakness physicists made a left-field turn and looked at biological constructs. Inspiration of the new battery has come from observing the way cells in the human intestines absorb nutrients.
The reason why these batteries are theoretically more powerful is because sulfur and lithium react in different ways. This is via a multi-electron transfer mechanism, which means elemental sulfur provides a greater theoretical capacity than a standard lithium-ion battery.
To develop the battery required research at the nano-scale. Here a team led by Dr. Vasant Kumar designed a lightweight nanostructured material which resembled villi. Villi are the finger-like protrusions which line the small intestine. To obtain a large surface area, the inside wall of the small intestine is lined with tiny villi. These protrusions provide the necessary surface area for food absorption. Villi contain blood capillaries to carry away the absorbed food molecules.
With the battery, the villi are formed from tiny zinc oxide wires. These are located on one of the battery’s electrodes. These appendages function to capture fragments of the active material and allow the material to be used, preventing degradation. This works because the villi-like appendages provide additional surface area.
The crystal structure of the electrode materials determines how much energy can be put into the battery; therefore improving the efficiency of the electrode is key to improving battery power.
The battery model is at the prototype stage and it has yet to be developed commercially. The team behind the invention are considering funding options. The findings have been reported in the journal Advanced Functional Materials. The research paper is titled “Advanced Lithium–Sulfur Batteries Enabled by a Bio-Inspired Polysulfide Adsorptive Brush.”
