During Battery Day, Tesla unveiled a number of advances that will further enhance the company’s electric vehicles, lower their cost, and dramatically improve the ownership experience. One very important improvement is silicon, which the company will use in the anode of the battery cell. Tesla silicon opens the door to faster charging. The Limiting Factor/YouTube takes us deeper into understanding what is the limiting factor in charging, and how Tesla silicon will solve this problem.
In a Q3 2020 Earnings Call, Tesla SVP Drew Baglino said that the fundamental limiting factor for high charge rates is lithium plating, which can be eliminated with proper electrode design and material choice. Tesla Silicon is the right material to provide the right electrode design.
Panasonic introduced 2170 nickel-cobalt-aluminum (NCA) cathode chemistry in 2017 for Tesla Model 3. But the company said it has been developing the technology, resulting in an increase in specific energy of more than 5%, and a reduction in cobalt content to at most 5%. Panasonic also plans to increase the power density of its batteries that it supplies to Tesla by 20% in five years, and to commercialize a cobalt-free version “in two to three years.”
In early November, Celina Mikolajczak, vice president of battery technology at Panasonic Energy of North America (PENA), revealed that the company is working on a new battery pack that will be based on the recently unveiled Tesla 4680 battery, and will feature fast-charging capability.
Jordan explains that the 5-20% increase in energy density is most likely to be largely driven by the higher silicon content. This gradual increase in silicon will over time lead to faster battery charging rates.
Jim Cushing of Applied Materials is developing a 30% silicon anode battery that provides a 4C charge rate (0-100% in 15 minutes). This means that, in the first five minutes, the battery can be charged from 0 to 50% if the charger is powerful enough to deliver that amount of energy.
Probably, Tesla also does this with silicon, but the public does not know how exactly the company intends to achieve this. Silicon is widely considered the next big advance because the theoretical charge capacity can be about nine times that of a typical graphite anode.
Source: The Limiting Factor/YouTube
Silicon can absorb more lithium ions because these two materials form an alloy, the theoretical capacity of which is much higher than that of graphite. Silicon also requires less voltage for charging, and allows for reduced overvoltage. In addition, silicon allows the use of an anode that is much thinner and denser than a graphite one, and has a greater ability to draw lithium ions from the ion cloud created by the concentration gradient. Therefore, the silicon particles will be charged first, after which lithium ions will be incorporated into the graphite.
All this means that a silicon anode with 30% silicon will be charged during the first 70% of a charging cycle. Thereafter, the graphite will quickly become charged but will slow down when the battery is approximately 80% charged. Thus, silicon solves the problem of lithium plating and opens the door for fast charging.
Given the advances in battery chemistry and Tesla’s Supercharging infrastructure, we can see a gradual increase in maximum vehicle charging rate by about half, along with a 20% increase in range, and a 5% decrease in cost over the next few years.