With the potential to transform electric vehicles, renewable energy, and a whole host of other industries, squeezing more power out of lithium-ion batteries is big business for researchers and commercial developers. Scientists the world over are testing thousands of different materials and approaches. Most would agree, however, in the importance of replacing the graphite anode used in today’s batteries with a more energy-dense material.
There are many ways to achieve this, with lithium metal and silicon based anodes making significant progress. Phosphorous is another material which potentially has much higher energy capacity than graphite, and is the focus of a new study led by scientists at Argonne National Laboratory in the United States.
Phosphorous is held back by the fact that it “inflates” to much larger volumes as the battery charges, but other characteristics make it an attractive option for additional research. “Phosphorus has a very high energy capacity,” says Gui-Liang Xu, a chemist at Argonne Labs. “When we explored the material, we found that our anode material has a very high (initial coulombic efficiency) of more than 90%.”
The group fabricated a composite anode of black phosphorous and conductive carbon using a steel ball milling process, which they say could be applied in large-scale production. This anode demonstrated an initial coulombic efficiency (ICE) of 91%, and specific capacity of around 2500 milliamp hours. The anode was integrated into a full cell battery with a nickel-cobalt-manganese cathode, which Argonne says provides proof of concept for its practicality.
Aware that black phosphorous would likely be too expensive for commercial use, the group also fabricated anodes using cheaper (but less conductive) red phosphorous. Performance figures for this anode were not provided, but Argonne states that the anode showed “similar stability and high ICE, with a very high practical capacity.” The researchers described the devices in “A practical phosphorous based anode material for high-energy lithium-ion batteries,” which was recently published in Nano Energy.
The group says its next goal will be investigating processes for large-scale production of its red phosphorous anodes. “We're trying to initiate collaboration with industry partners so we can scale up this material, so it can be commercialized in the future,” they said.
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