Quick-charging, more durable batteries are essential for the growing EV industry, but today’s Li-Ion batteries fall short of what’s needed because of their weight, cost, charging capacity, and charging duration.
Li-Ion batteries also have an inherent flaw: dendrites. These tree-like pieces of lithium form sharp points eventually ends up piercing the batteries, causing short circuits and other harmful problems. These structures ultimately shorten their lifespan, leaving room for improvement.
So, what if we switch from Li-Ion to lithium metal batteries? Theoretically, lithium metal batteries are lighter, more powerful, longer-lasting, and cheaper. Unfortunately, when scientists experimented with these batteries in the past, they often exploded due to their instability. That’s why scientists have been putting efforts to stabilize the lithium battery to unleash its potential in many applications and bring it into the marketplace.
What’s With Lithium Metal Batteries, Anyway?
According to Xin Li of Harvard’s John A Paulson School of Engineering and Applied Science, lithium metal batteries are the holy grail for battery innovation due to their high density and capacity. However, there’s so much left to do, due to their instability.
The Problem With Lithium Batteries
Preventing dendrite formation is critical for battery design because removing its volatile portion greatly reduces any adverse outcomes. Dendrites are known to grow like roots inside the electrolyte, eventually piercing the barrier that separates the cathode and anode, causing fires. To fix this, Li and his team have designed a battery with a multilayered barrier to prevent the penetration of dendrites by containing them.
Now, they have designed a stable battery that can be charged and discharged up to a thousand times at a current high density. This battery – which is far more successful than previous trials – is paired with a commercial high-density cathode material.
This innovation could extend EVs and gasoline cars’ lifespan for up to 10-15 more years without the need for replacing the battery. Its high current density could also enable EVs to get fully charged in less than 25 minutes.
How Do Lithium Metal Batteries Work?
Think of it as a BLT sandwich. The bread will be the lithium metal anode, followed by a layer of lettuce – a graphite coating. Next, the layer of tomatoes and bacon will be the first and second electrolyte, respectively. Lastly, after another layer of tomatoes, top it off with the last bread piece – the cathode.
The first electrolyte (Li5.5PS4.5Cl1.5) is more stable but prone to dendrite formation. The second electrolyte (Li10Ge1P2S12) is less stable but can control the dendrites. Here, dendrites are allowed to grow but eventually will be stopped by the second electrolytes. In other words, dendrites may pierce the tomato and lettuce but will get stopped at the bacon. That’s because the anchor quickly becomes too tight for dendrites to pierce through.
The lithium metal battery can also backfill holes created by the destructive dendrites, which means it has some form of healing properties.
Li added that proof-of-concept could allow lithium metal batteries to be competitive with commercial Li-Ion batteries someday, and its dynamic and flexible multilayer design makes it potentially possible for large-scale industrial applications.
What does this mean for the future of electric cars and battery design? If the design proves successful, it could open the door for these batteries to enter the competitive market. For instance, the significant reduction of EVs’ failure rate, as well as their overall weight, could allow for more savings.