A team of researchers from the University of Cambridge, Diamond Light Source and Argonne National Laboratory in the US have demonstrated a new approach that could fast-track the development of lithium-ion batteries that are both high-powered and fast-charging.
In a bid to tackle rising air pollution, the UK government has banned the sale of new diesel and petrol vehicles from 2040, and the race is on to develop high performance batteries for electric vehicles that can be charged in minutes, not hours. The rechargeable battery technology of choice is currently lithium-ion (Li-ion), and the power output and recharging time of Li-ion batteries are dependent on how ions and electrons move between the battery electrodes and electrolyte. In particular, the Li-ion diffusion rate provides a fundamental limitation to the rate at which a battery can be charged and discharged.
The conventional approach to improving the Li-ion diffusion rate is to create electrodes with nanoscale structures, which decrease the distance Li-ions must travel, and greatly increase the surface area of the electrode that is in contact with the electrolyte. However, there are many downsides to this approach: it reduces the volumetric energy density (the amount of energy the battery can store), and producing electrodes with nano-architectures is slow and expensive, and can produce large amounts of chemical waste products.
In a paper recently published in Nature, researchers have demonstrated a completely different approach to developing new materials for battery electrodes, which does not rely on nanoscaling, but instead goes back to the drawing board to find materials with better ionic diffusion properties.
Their results show that these two materials are capable of multi-electron reduction on both niobium and tungsten, leading to high capacities. It was also discovered that the oxides have Li-ion diffusion rates several orders of magnitude above those of current electrode materials, even when the niobium tungsten oxide particles are micrometre sized. This means batteries made with these materials would combine both high power and fast charging properties, and would operate in a similar voltage region to the well-studied, and generally considered ‘safe’ anode materials currently in use.
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