As stores of electrical charge, batteries are critically important in many aspects of modern life. Lithium-ion batteries, which offer good energy density (energy per weight or volume) are routinely packed into mobile phones, laptops and electric cars, to name just a few common uses. However, to increase the range of electric cars to match that of petrol-powered competitors – not to mention the battery lifetime between charges of mobile phones and laptops – battery energy density needs to be improved dramatically.
Batteries are typically composed of two electrodes, a positive terminal known as a cathode, and a negative terminal known as an anode, with an electrolyte in between. This electrolyte allows ions to move between the electrodes to produce current. In lithium-ion batteries, the anode is composed of graphite, which is relatively cheap and durable. However, researchers have begun to experiment with silicon anodes, which would offer much greater power capacity.
One engineering challenge is that silicon anodes tend to suffer structural failure from swelling and shrinking during charge-discharge cycle. Over the last year, researchers have developed possible solutions that involve the creation of silicon nanowires or nanoparticles, which seem to solve the problems associated with silicon’s volume expansion when it reacts with lithium. The larger surface area associated with nanoparticles and nanowires further increases the battery’s power density, allowing for fast charging and current delivery.
Able to fully charge more quickly, and produce 30%-40% more electricity than today’s lithium-ion batteries, this next generation of batteries could help transform the electric car market and allow the storage of solar electricity at the household scale. Initially, silicon-anode batteries are expected to begin to ship in smartphones within the next two years.
