Scientists claim breakthrough battery capacity improvement

Stanford University scientists say they have developed the ‘holy grail’ for battery technology: they claim to have developed a stable anode made of lithium instead of graphite or silicon, using a protective carbon nanolayer.

The majority of batteries and batteries for electrical equipment already contain lithium: the lithium-ion batteries. However, only the electrolyte is based on lithium; the cathode is built around metal oxides and the anode is graphite or silicon. A lithium anode would have great advantages in terms of battery capacity, but until now scientists have encountered such great difficulties developing a lithium anode that it seemed out of reach.

One of the problems is that lithium expands greatly during charging, causing cracks and holes in the anode shells. This allows lithium ions to escape, forming so-called microscopic dendrites or offshoots of lithium; they can cause short circuits and seriously shorten the life of batteries. A second problem is that the lithium reacts chemically with the electrolyte and consumes this medium between the anode and cathode. Finally, there are risks of heat build-up, as is already the case with lithium-ion batteries.

Scientists at Stanford University now claim to have overcome these problems by shielding the lithium anode with a protective layer they have named nanosphere. The layer consists of interconnected carbon domes in a honeycomb structure, with a thickness of 20 nanometers. The layer is strong, flexible and chemically stable enough to contain the expanding lithium.

The nanospheres layer greatly improves the ratio of the amount of lithium that can be extracted from the anode when the battery is used and the amount that is added during charging. With as many charge/discharge cycles as possible, that ratio should be 99.9 percent in best condition for commercial use, but with lithium anodes it was only 96 percent so far. The science team’s battery currently achieves an efficiency of 99 percent at 150 cycles, but this could be improved to the desired 99.9 percent, according to the scientists.

“With some modifications and new electrolytes, we believe we can make a practical and stable lithium anode that powers the next generation of rechargeable batteries and accumulators,” said Steven Chu of the research team. He hints that the invention could quadruple the battery capacity and double the battery life of smartphones and electric cars. The team is publishing its research in the scientific journal Nature Nanotechnology.

Scientists are working hard to improve battery technology, but many ideas do not make it into practical applications or can only bring improvements in the long term. Battery technology is reaching its limits, which means that improvements in battery life, for example, lag behind improvements in performance, such as computing power.