The mass adoption of electric vehicles relies on the advancement of battery technology without prolonged charging times and range limitations.
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Electric vehicle batteries of the future must be faster charging, with higher energy densities and lower material costs than current lithium-ion (Li-ion) battery technology. To make them commercially viable, new batteries should be producible at existing battery production facilities.
In one promising development, new Li-ion battery technology from the California-based Enevate delivers charging times as much as 10 times faster than typical Li-ion batteries. Enevate's anode technology features higher energy densities, greater safety, and low-temperature operation, which is favorable for use in cold climates. The technology is well-suited to high-volume commercialization and manufacturing.
Current commercial options only use silicon as an electrode additive, considerably restricting some potential benefits. Enevate’s system, in contrast, utilizes a silicon-dominant anode strategy that works with a broad range of cathode components and battery designs. Compared to conventional Li-ion batteries, Enevate's technology translates to a 30% increase in electric vehicle range and faster charging.
Fast-Charging Electric Vehicle Technology
In 2020, the company said the latest generation of its fast-charging technology is able to charge a battery to 75% capacity in five minutes, thanks to energy densities of around 800 watt-hours (Wh) per liter. Enevate's anode material cost is lower than graphite in terms of dollar per kWh.
The Solution to Fast-Charging Overheating
At rapid charging speeds, Li-ion batteries are prone to overheating, which causes them to break down as time passes. Additionally, the surface of the anode in a Li-ion battery is prone to a buildup of lithium, an occurrence referred to as lithium plating. This considerably decreases the battery’s capacity and residual lithium can ultimately form needle-like structures called dendrites that grow throughout the electrolyte. If they make contact with the cathode, a short circuit is produced, causing the battery to ignite or explode. Because of these problems that are associated with rapid charging, all-electric vehicle batteries have onboard charge ports that establish charging speed limits.
According to Enevate, its silicon-dominant system is resistant against lithium plating, sidestepping performance degradation, and safety issues. The rapid charging times of batteries also mean Enevate can test cells quickly. Whereas some companies can take up to six months to assess their battery systems, Enevate’s technology has reduced this time to two months or less. The company also states that its technology is scalable for large-format cells and suitable for assorted battery modules and pack frameworks.
As battery research worldwide pushes technology boundaries, cost targets are a vital consideration with respect to accessibility and affordability. Because of this, the versatility and manufacturability of battery technology are essential. Enevate has stated those are defining attributes of its technology. The company's anode technology is also appropriate for existing Li-ion cathode chemistries and solid-state electrolytes.
The novel anode technology can be produced using current high-speed production lines and equipment, thanks to an innovative roll type of silicon. The company’s constant roll-to-roll process could be manufactured at rates of more than 80 meters per minute. Typically, silicon technology is challenging to use in high-speed volume production.
Making a Solid-State Electrolyte More Viable
Although Enevate is making progress on anode technology, it is only one piece of the puzzle.
For quite some time, scientists have attempted to realize the potential of solid-state electrolytes, which can hold considerably more energy per volume, and can charge in much less time than conventional Li-ion batteries. However, the stability of batteries with a solid-state electrolyte has always been low.
In a promising development announced in May 2021, Harvard researchers said they had developed a dependable, lithium-based, solid-state battery system that could withstand more than 10,000 charge-discharge cycles, which is many more cycles than existing energy densities.
Using its high density, the battery could lead to electric vehicle batteries that fully charge in 10 to 20 minutes.
To address the key issue of dendrite development, the Harvard team created a multilayer battery system that stacks different components of differing stabilities between the electrodes. Using multiple layers and materials, the battery controls and contains dendrites, as opposed to preventing their formation altogether.
In the novel Harvard battery, a graphite-coated lithium anode sits in a solid electrolyte that is stable but vulnerable to dendrite infiltration. Located on the other side of this electrolyte, toward the cathode, a second electrolyte layer has less stable interactions with lithium but is resistant to dendrites. In this layout, dendrites can grow out of the graphite layer and into the first electrolyte but cannot penetrate the second electrode. The chemistry of the battery is such that it can backfill openings produced by the dendrites.
The Harvard team said its proof-of-concept design demonstrates that solid-state batteries may be able to compete with commercial Li-ion batteries.
Resources and Further Reading
Frost & Sullivan. Enevate Lauded by Frost & Sullivan for its Next-Generation Silicon Battery Technology. [Online] Available at: https://ww2.frost.com/news/press-releases/enevate-lauded-by-frost-sullivan-for-its-next-generation-silicon-battery-technology/
Burrows, L. Battery breakthrough for electric cars. The Harvard Gazette. [Online] Available at: https://news.harvard.edu/gazette/story/2021/05/researchers-design-long-lasting-solid-state-lithium-battery/