Boffins working at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have come up with a battery anode which can store eight times the amount of Lithium of current batteries. The breakthrough means that batteries greatly increased energy capacity after over a year of testing and been charge-discharged hundreds of time.

The secret is a tailored polymer that conducts electricity and binds closely to lithium-storing silicon particles, even as they expand to more than three times their volume during charging and then shrink again during discharge. The new anodes are made from low-cost materials, compatible with standard lithium-battery manufacturing technologies. The research team reports its findings in Advanced Materials, now available online.

Gao Liu of Berkeley Lab’s Environmental Energy Technologies Division said that most of today’s lithium-ion batteries have anodes made of graphite, which is electrically conducting and expands only modestly when housing the ions between its graphene layers. Silicon can store 10 times more – it has by far the highest capacity among lithium-ion storage materials – but it swells to more than three times its volume when fully charged. Since this kind of swelling quickly breaks the electrical contacts in the anode, so researchers have concentrated on finding other ways to use silicon while maintaining anode conductivity.

"The new PF-based anode is not only superior but economical. Using commercial silicon particles and without any conductive additive, our composite anode exhibits the best performance so far,” says Gao Liu. “The whole manufacturing process is low cost and compatible with established manufacturing technologies. The commercial value of the polymer has already been recognized by major companies, and its possible applications extend beyond silicon anodes.”

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