Bosch is developing a solid state battery with twice the energy density of a lithium ion (Li-ion) cell, effectively doubling the range of electric vehicles with no increase in weight. A Tesla Model S equipped with an 85 kWh Li-ion battery pack has an estimated range of 426 km (265 miles). Swap out the Li-ion battery and replace it with a solid state battery and the car could go 852 km (530 miles) on a single charge. Even better, the new battery doesn’t use a flammable liquid electrolyte, so no more battery fires! And the icing on the cake: the solid state battery would come at a lower cost. Bosch claims that this next generation of batteries could be on the market in five years.





Li-ion batteries include a negative anode made of carbon (usually in the form of graphite), a positive cathode made of a composite material that includes lithium, and a porous separator through which the lithium ions travel during charge and discharge. A liquid electrolyte carries the lithium ions from anode to cathode and back.

Carbon is relatively heavy; in order to improve energy density, a lighter material is preferred. Since lithium is the 3rd lightest element on the periodic table, it would be desirable to make the anode from lithium, as shown below:

The problem is that lithium expands and contracts during the charge and discharge cycles, resulting in uneven cracks along the surface, like potholes on a road. Dendrites build up in the cracks, eventually short-circuiting the battery.

Bosch won’t say exactly how they’ve solved that problem, but in 2014 researchers at Stanford University made a breakthrough that could provide the answer. To protect the fragile lithium surface, Stanford engineers developed a thin layer of carbon domes that they call a nanosphere. It forms a honeycomb structure - just 20 nanometers thick - that’s flexible, uniform, and inert. The nanosphere blocks the chemical reactions that cause dendrite formation.

According to Stanford researchers, the nanotubes improve the coulombic efficiency - a measure of how well electrons are transferred during an electrochemical reaction - from 96% to 99%. Ideally, a coulombic efficiency of 99.9% or higher is needed to make a practical rechargeable battery. Engineers at Stanford believe that goal is achievable with new electrolytes and a little more engineering work, making Bosch’s five year estimate seem pretty reasonable.

In addition to its use in cars, a solid state lithium battery would give longer life to notebook computers, tablets, phones, and other consumer electronics. Just don't text while driving your electric vehicle, okay? In addition to its use in cars, a solid state lithium battery would give longer life to notebook computers, tablets, phones, and other consumer electronics. Just don't text while driving your electric vehicle, okay?

Images courtesy of Bosch





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