Fortunately, engineers share our complaints and SolidEnergy, another start-up to come out of MIT, is boasting a new battery design that will hopefully lengthen our smartphone usage times. The technology promises twice the energy density of today's traditional lithium-ion batteries.

SolidEnergy's new technology works by replacing the battery's conventional graphite anode material with an ultra-thin sheet of lithium copper metal foil. The benefit here is that this greatly reduces the size of the battery for the same capacity, allowing the saved space to be used for extra capacity.

The use of lithium-metal electrodes in batteries has been the subject of research for many years, but there have previously been some technical barriers to their viability. Typically, lithium metal can react with battery electrolytes, which over time prevents current from flowing and leads to battery capacity degradation. The reaction also creates dendrites, which can short circuit the battery and ignite the flammable electrolyte.

To overcome these rather major problems, SolidEnergy uses both regular liquid and less reactive solid electrolytes, allowing for suitable conduction without the problematic reactions. A very thin layer of solid electrolyte is applied to the lithium metal foil in the anode, which is thin enough to avoid the lack of conduction usually associate with a thick solid layer while avoiding the short circuit issues of using lithium metals. The video below explains this different approach.