This is the last installment of the Battery Series. For a recap of what has been covered so far, see the evolution of battery technology, the energy problem in context, the reasons behind the surge in lithium-ion demand, and the critical materials neededto make lithium-ion batteries.
There’s no doubt that the lithium-ion battery has been an important catalyst for the green revolution, but there is still much work to be done for a full switch to renewable energy.
The battery technology of the future could:
Right now, scientists see many upcoming battery innovations that have the promise to do this. However, the road to commercialization is long, arduous, and filled with many unexpected obstacles.
For the foreseeable future, the improvement of battery technology relies on modifications being made to already-existing lithium-ion technology. In fact, experts estimate that lithium-ions will continue to increase capacity by 6-7% annually for a number of years.
Here’s what’s driving those advances:
Tesla has already made significant advances in battery design and production through its Gigafactory:
Most of the recent advances in lithium-ion energy density have come from manipulating the relative quantities of cobalt, aluminum, manganese, and nickel in the cathodes. By 2020, 75% of batteries are expected to contain cobalt in some capacity.
For scientists, its about finding the materials and crystal structures that can store the maximum amount of ions. The next generation of cathodes may be born from lithium-rich layered oxide materials (LLOs) or similar approaches, such as the nickel-rich variety.
While most lithium-ion progress to date has come from cathode tinkering, the biggest advances might happen in the anode.
Current graphite anodes can only store one lithium atom for every six carbon atoms – but silicon anodes could store 4.4 lithium atoms for every one silicon atom. That’s a theoretical 10x increase in capacity!
However, the problem with this is well-documented. When silicon houses these lithium ions, it ends up bloating in size up to 400%. This volume change can cause irreversible damage to the anode, making the battery unusable.
To get around this, scientists are looking at a few different solutions.
1. Encasing silicon in a graphene “cage” to prevent cracking after expansion.
2. Using silicon nanowires, which can better handle the volume change.
3. Adding silicon in tiny amounts using existing manufacturing processes – Tesla is rumored to already be doing this.
Lastly, a final improvement that is being worked on for the lithium-ion battery is to use a solid-state setup, rather than having liquid electrolytes enabling the ion transfer. This design could increase energy density in the future, but it still has some problems to resolve first, such as ions moving too slowing through the solid electrolyte.
Here are some new innovations in the pipeline that could help enable the future of battery technology:
Cathode: Porous carbon (Oxygen)
Promise: 10x greater energy density than Li-ion
Problems: Air is not pure enough and would need to be filtered. Lithium and oxygen form peroxide films that produce a barrier, ultimately killing storage capacity. Cycle life is only 50 cycles in lab tests.
Variations: Scientists also trying aluminum-air and sodium-air batteries as well.
Cathode: Sulphur, Carbon
Promise: Lighter, cheaper, and more powerful than li-ion
Problems: Volume expansion of up to 80%, causing mechanical stress. Unwanted reactions with electrolytes. Poor conductivity and poor stability at higher temperatures.
Variations: Many different variations exist, including using graphite/graphene, and silicon in the chemistry.
Vanadium Flow Batteries
Promise: Using vanadium ions in different oxidation states to store chemical potential energy at scale. Can be expanded simply by using larger electrolyte tanks.
Problems: Poor energy-to-volume ratio. Very heavy; must be used in stationary applications.
Variations: Scientists are experimenting with other flow battery chemistries as well, such as zinc-bromine.