Battery technology has a long history, as the first batteries were invented in 1800 by Alessandro Volta. Progress has been continual, but slow. The requirement is to store as much electrical energy as possible in something with the lowest weight, while allowing repeated recharging – all at a reasonable cost. Lithium-ion batteries in general do the best job to date.
However, as users of everything from cell phones to portable computers to electric and hybrid cars know, existing batteries either don’t seem to go long enough between recharging or they add too much weight. The need for improvements is becoming even more urgent, since much more battery capacity will be required to store electrical energy from renewable but intermittent sources like wind and solar.
The main problem with current lithium-ion batteries is the limited capacity of battery anodes made of carbon. Anodes made of silicon (carbon’s closest chemical relative) could permit the storage of much more energy. However, silicon particles in anodes need to be coated with a more conductive material. Carbon is still being used for this, but due to repeated swelling and shrinking of the silicon during the charge/discharge cycle, contact with the carbon degrades. The new development here is a conductive polymer material that can replace the carbon and still maintain tight contact with the silicon particles.
A team of scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has designed a new kind of anode that can absorb eight times the lithium of current designs, and has maintained its greatly increased energy capacity after over a year of testing and many hundreds of charge-discharge cycles.
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.