Batteries are the lifeline of consumer electronics and as scientists search for longer-lasting batteries, at least one company has found a solution that can be commercialised to make batteries last twice as long as the current ones.
SolidEnergy Systems, an MIT spinout founded in 2012, have developed an “anode-free” lithium metal battery that comes with twice the energy density than current batteries and despite this it is still safe to be used as lithium ion batteries in smartphones, electric cars, wearables, drones, and other devices. Thanks to the increased energy density, the company says that their new batteries have twice the life.
There are two options with a battery that has twice the energy density explains SolidEnergy Systems. Company’s CEO Qichao Hu explains that with twice the energy density, either the battery size can be reduced to half the size yet still achieve the same life or keep it at the same size and achieve twice the battery life.
The novelty of the battery is that it does away with the graphite anode and instead it uses high-energy lithium-metal foil that is capable of holding more ions. This increased capacity to hold more ions translates into ability to provide more energy capacity and hence greater battery life.
Further, chemical modifications to the electrolyte also make the typically short-lived and volatile lithium metal batteries rechargeable and safer to use. Moreover, the batteries are made using existing lithium ion manufacturing equipment, which makes them scalable.
SolidEnergy plans to bring the batteries to smartphones and wearables in early 2017, and to electric cars in 2018. But the first application will be drones, coming this November.
Lithium metal isn’t the best of choices when it comes to making batteries as it reacts poorly with the battery’s electrolyte. Also, it forms compounds that increase resistance in the battery and reduce cycle life. And if that is not it, the reaction also creates mossy lithium metal bumps, called dendrites, on the anode, which lead to short circuits, generating high heat that ignites the flammable electrolyte, and making the batteries generally nonrechargable.
So if measures are put into place to ensure that batteries are safer, then the energy performance of the battery suffers. To address these issues, one of the innovations by Hu was used wherein an ultrathin lithium metal foil for the anode, which is about one-fifth the thickness of a traditional lithium metal anode, and several times thinner and lighter than traditional graphite, carbon, or silicon anodes. That shrunk the battery size by half.
However, the battery only worked at 80 degrees Celsius or higher and to address this, Hu developed a solid and liquid hybrid electrolyte solution. He coated the lithium metal foil with a thin solid electrolyte that doesn’t need to be heated to function. He also created a novel quasi-ionic liquid electrolyte that isn’t flammable, and has additional chemical modifications to the separator and cell design to stop it from negatively reacting with the lithium metal.
The end result was a battery with energy-capacity perks of lithium metal batteries, but with the safety and longevity features of lithium ion batteries that can operate at room temperature.