First design
Site theme
Sign up or log in to sign up for discussions!
Electric cars have come a long way in terms of charging. But everyone is still for the next big leap in battery technology: a battery with a particularly high power density would mean more battery life or lower prices to reach the existing range. There is still room for incremental advances in existing lithium-ion battery technology, however, there is a holy lithium grail that has not been successful for decades: abandoning its graphite anode to shrink the cell.
A lithium steel battery would only use forged lithium as an anode instead of requiring a graphite frame for lithium atoms to be compatible when the battery is charged. The challenge is that lithium does not form a surface when recharged, so the battery capacity decreases considerably, expanding to 80% in 20 speed cycles in some configurations. Noncon conforming lithium also has a tendency to form dangerous, branched, needle-shaped structures that can pierce the separator between the anode and cathode and deflect the cell.
Last year, a Company of Dalhousie labs connected to Tesla developed a lithium steel battery with slightly higher performance. Lithium atoms are placed in a copper electrode as the battery advances, then return to the traditional lithium-nickel-manganese-cobalt cathode when the rate is depleted. Thanks to a new electrolyte, they were able to ensure that this battery lasted about 90 cycles before reaching a capacity of 80% for the short circuit problem.
In a new study, the team reports an autopsy of this design that identifies the reasons for the loss of capacity. As a result, they locate an adjustment that allows them to succeed in about two hundred cycles.
This battery would be a major advance if successful in viability, maintaining approximately 60% more energy consistent with the volume unit than the lithium-ion batteries currently used. This can increase the diversity of electric cars from 400 to 680 kilometers (or 250 to 400 kilometers), the researchers note. Improved stability is due to an electrolyte composed of two lithium salts and fluoride in a biological solvent. To see what was happening inside the battery, the team analyzed the electrolyte settings over time and also tracked adjustments in the habit of forming for forged lithium in the anode.
It turned out that the electrolyte salts were fed as the battery went through speed cycles. Cathode-side reactions convert one salt into the other, however, reactions on the anode side consume any of the salts without regenerating any. Therefore, as the battery went through more and more cycles, there was less electrolyte to do its job.
Projecting the appearance of the anode under an electron microscope showed that cyclic coating and the removal of forged lithium have become increasingly less ordered repeated cycles. It begins by shaping a very elegant layer, but develops the most sensitive photograph towards cycle 50 approximately. Pockets form between ring-shaped walls, resulting in a build-up of electrically insulated amounts of lithium, as it is not played with the battery swing. (See the symbol on the most sensitive part of this page). This also means that the surface of forged lithium builds up, so more electrolyte would be needed to maintain contact everywhere.
A solution imaginable would be to increase the volume of electrolyte so that the salts take longer to deplete, as well as to maintain greater contact throughout the surface. This would minimize the power density of the battery, so the team made the decision to verify the accumulation of dissolved salt concentration in the electrolyte.
With concentration accumulation, the battery was able to maintain its capacity for more speed cycles, achieving at least 150 cycles before falling to 80%. Or, to put it another way, it took about two hundred cycles to achieve the equivalent capacity of a lithium-ion battery of this size. Another thing that’s helping is an undeniable adjustment pressure, as it encourages forged lithium to settle better. All these figures come from batteries placed in a small oscillating clamp. Without this pressure, capacity decreases much faster.
These effects show abundant progress in a persistent problem, however, this design has a long way to go to the longevity of existing lithium-ion batteries, which can exceed 1000 cycles before falling to 80%. Researchers write: “However, a longer lifespan is needed before such cells are viable for electric cars or electrified urban aviation. While additional life innovations can be made, anode-free lithium steel cells with liquid electrolytes are the simplest and cheapest direction for viable high-energy lithium batteries.
Nature Energy, 2020. DOI: 10.1038 / s41560-020-0668-8 (About DOI).
Join the Ars Orbital Transmission email for weekly updates in your inbox.