Stanford Breakthrough Could Drastically Improve Lithium-Ion Batteries
Lithium ion batteries have been available commercially since the early 90s, powering our cameras, phones, laptops, and all sorts of mobile electronics. And they've been doing a pretty good job. Aside from being a bit fragile, they have remained the dominant battery technology for many years, seeing the advent of mp3 players, smartphones, and tablets such as the iPad or Galaxy Tab.
But although they are almost perfect for mobile devices, lithium-ion batteries have fallen short when it comes to heavy-duty applications such as in power tools and electric vehicles. In cases like this, batteries using nickel metal-hydride or nickel cadmium chemistry are used, because of their similar energy densities and lower costs of production.
But what if we could boost the output of lithium-ion batteries and make them worth the cost?
Like any other battery, lithium-ion batteries have an anode (aka the minus sign, or black end of the battery), a cathode (aka the plus sign, or red end of the battery), and an electrolyte. Depending on whether you are charging the battery or discharging it (read: using it) lithium ions will travel through the electrolyte, either from the anode to the cathode, or vice versa. The output of the battery is limited by the specific capacity of the materials that are used for both the cathode and the anode, so different batteries use different materials, yielding different capacities. This is in part due to the fact that your battery is only as good as the cathode or anode with the lowest specific capacity - an electrical bottleneck, if you will.
Researchers at Stanford University may have found a way to use sulphur to make the cathode of their lithium ion batteries, dramatically increasing their output. Whereas most materials used for cathodes have a specific capacity of 160 milliamp hours per gram (mAh/g) to a silicon anode's 4200 mAh, sulphur has a specific capacity of 1672 mAh/g. The only thing holding battery manufacturers back from increasing the capacity of their batteries is the fact that sulphur doesn't conduct well, and would physically degrade if used as a cathode.
But Hailiang Wang and his fellow researchers at Stanford University have found a way to make it work! Instead of using just sulphur, they've coated sulphur molecules in graphene, a versatile form of carbon. The graphene adds conductivity and physical stability to the sulphur, making it much more viable as a suitable material for making battery cathodes. This is just a breakthrough though, and they are still working on optimizing their discovery. For instance, they suggest that mixing this sulphur-graphene composite material with silicon could yield much more impressive results than the composite material by itself.
Source: Technology Review
