New Electrolyte Found to Achieve Greater Energy Density in Lithium-Ion Batteries

The discovery could enable a big leap in the power-per-weight of next-generation batteries

April 3, 2021


A team of researchers at the Massachusetts Institute of Technology (MIT) and other organizations have found a novel electrolyte that could make it possible for lithium-ion batteries, which now typically can store about 260 watt-hours per kilogram, to store about 420 watt-hours per kilogram.

Researchers worldwide are continuing to push limits to achieve ever-greater energy densities — the amount of energy that can be stored in a given mass of material — to improve the performance of existing devices and potentially enable new applications such as long-range drones and robots.

One promising approach is the use of metal electrodes in place of the conventional graphite, with a higher charging voltage in the cathode. Those efforts have been hampered by various unwanted chemical reactions that take place with the electrolyte that separates the electrodes.

The latest discovery of the novel electrolyte overcomes these problems and could enable a significant leap in the power-per-weight of next-generation batteries without sacrificing the cycle life.

The research is reported in the journal Nature Energy in a paper by MIT professors Ju Li, Yang Shao-Horn, Jeremiah Johnson; postdoc Weijiang Xue; and 19 others at MIT, two national laboratories, and elsewhere. The researchers say the finding could make it possible for lithium-ion batteries to store about 420 watt-hours per kilogram. That would translate into longer ranges for electric cars and longer-lasting changes on portable devices.

Earlier this year, Mercom reported that researchers from the University of Nottingham collaborated with six research institutes of China to design a new rechargeable battery using salt as a critical ingredient to extend the range of electric vehicles.

In July 2020, Stanford University researchers claimed to have developed a new electrolyte design that boosts lithium metal batteries’ performance that could increase the driving range of EVs.

The MIT researchers say that the novel electrolyte’s basic raw materials are inexpensive (though one of the intermediate compounds is still costly because it is in limited use). The process to make it is simple and so this advance could be implemented relatively quickly.

But there are many obstacles still facing the development of such batteries, and that technology may still be years away. In the meantime, applying that electrolyte to lithium-ion batteries with metal electrodes turns out to be something that can be achieved much more quickly.

The new application of this electrode material was found “somewhat serendipitously” after it had initially been developed a few years ago by Shao-Horn, Johnson, and others, in a collaborative venture aimed at lithium-air battery development.

The type of battery electrode they have now used with this electrolyte, a nickel oxide containing some cobalt and manganese, “is the workhorse of today’s electric vehicle industry,” says Li, who is a professor of nuclear science and engineering and materials science and engineering.

Because the electrode material expands and contracts anisotropically as it gets charged and discharged, this can lead to cracking and a performance breakdown when used with conventional electrolytes. But in experiments in collaboration with Brookhaven National Laboratory, the researchers found that using the new electrolyte drastically reduced these stress-corrosion cracking degradations.

The problem was that the alloy’s metal atoms tended to dissolve into the liquid electrolyte, losing mass and leading to cracking of the metal. By contrast, the new electrolyte is highly resistant to such dissolution.