Lithium metal battery with over 500 Wh/kg developed
Current batteries in electric cars typically have an energy density of 200 to 250 Wh/kg, which is already a comparatively high value. Home energy storage systems are at best half this value.
Nevertheless, such a battery with a practicable capacity of perhaps 70 watt hours weighs around 300 kg (660 lbs). An increased energy density could therefore save an enormous amount of mass, which in turn would reduce consumption and increase driving dynamics.
The battery presented by the University of Science and Technology of China (USTC) in Hefei with an energy density of 505.9 Wh/kg could therefore save 150 kg (330 lbs) of ballast in one fell swoop.
Just for comparison: the energy density of gasoline and diesel is around 10,000 Wh/kg. However, the efficiency of the combustion engine is considerably worse and once fuel has been burned, it cannot simply be recharged.
Molecular distances adjusted
This nevertheless high value is possible with a lithium-metal battery, which in previous experiments remained far from surviving 50 charging cycles. According to the study, previous experiments in this area were aimed at increasing the concentration of the electrolyte.
The structure of the new battery, which at 500 Wh/kg survived 130 cycles with little loss of capacity, is significantly different. At only 400 Wh/kg, still significantly higher than commercial battery cells, over 300 charging cycles were achieved.
Instead of the usual concentrate with lithium ions, anions and other inorganic particles, a compact structure with a large number of lithium ions is used, which transports electrons together and also delivers them to the anode in larger packets.
In this much larger structure, which is around 50 times larger than before, the lithium ions are closer together. Around one hundred instead of just one give off electrons in concentrated form. This creates a solid electrolyte above the anode, which results in significantly improved stability.
It will certainly be interesting to see how far the principle can be optimized. After all, even 300 charges are still a little short. If the battery were to travel 500 km (300 miles), a drop in capacity would have to be expected after 150,000 km (90,000 miles).
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