Lithium-ion batteries have been an industry staple for years. Where many look for alternative power sources, others look for ways to enhance current technologies. From adding zinc to adding cobalt to developing new battery structures, vast amounts of research money are being pumped into increasing the energy density of lithium-ion batteries while also making them safer and smaller.
Another contender in this arena is the concept of battery anodes composed of silicon, which raise the possibility for a huge increase in Li-ion battery energy density.
Silicon-Based Anodes for Lithium-Ion Batteries
As a Li-ion battery charges, lithium ions stream onto the anode, which in most cases today is composed of carbon. Those ions and the carbon form an energy-rich complex, ready to be broken down to release electrical energy as the battery discharges. A given amount of stored energy requires that a corresponding volume of the lithium and carbon compound must be generated.
A new area of Li-ion battery research involves substituting the carbon anode with an anode composed largely of silicon. As the battery charges, an energy-dense compound of lithium and silicon is formed.
The key difference is that a given amount of energy can be stored in a smaller volume of lithium and silicon than could previously have been stored in a lithium carbon complex.
The result is, to store any amount of energy, the volume of the necessary battery based on a silicon anode will be smaller than its carbon anode predecessor.
The problem is that the silicon anode gets larger when it charges and become smaller again with discharge. This waxing and waning of the anode’s size causes structural damage to the battery, leading to failure.
Halting the Destruction of the Silicon Anode During Charge-Discharge Cycles
A possible solution to this battery size issue was described in a 2017 thesis written by Marte Skare of the Norwegian University of Science and Technology. The suggestion can be inferred from the paper's title: "A Method for Controlled Oxide and Carbon Coating of Silicon Nanoparticles as Anode in Lithium-Ion Batteries".
Rather than employing elemental silicon, silicon nanoparticles were employed. They are coated, coincidently with carbon, and the coating reduces the swelling of the electrode, making the employment of silicon electrodes more plausible.
Coating silicon with carbon. Image from the Norwegian University of Science and Technology
Also working on the research end is Kiel University in Kiel, Germany, which claims that their Institute for Material Sciences has been studying silicon as an energy resource for over 30 years. In 2017, they launched what's known as the PorSSi project, abbreviated from porous Si film anodes for lithium-sulphur-silicon energy storage. The project works with RENA Technologies
A solid silicon wafter. Image from Kiel University
According to Dr. Sandra Hansen, head of the PorSSi project, "Theoretically, silicon is the best material for anodes in batteries. It can store up to 10 times more energy than graphite anodes in conventional lithium-ion batteries." Part of the reason Hansen believes in silicon's potential is the fact that it's extraordinarily abundant, second only to oxygen.
Li-Ion Forever? Batteries vs. Other Energy Sources
Speaking of abundant resources, silicon-based batteries will need to compete with other energy sources that seek to increase the effectiveness of resources.
Presently, solar or wind energy that is not immediately needed is devoted to pumping water up to containing vessels located a few stories upward. Then, when the sun doesn’t shine and the wind doesn’t blow, that elevated water is allowed to descend back to ground-level, generating electricity in the manner of generator located at the bottom of a waterfall.
A study conducted at London’s Imperial College predicts that in the foreseeable future, improved Li-ion batteries will outpace the efficacy of pumped water and mechanical compliances as flywheels. How?
According to a sustainable energy systems lecturer at the college, Dr. Iain Staffell, “We have found that lithium-ion batteries are following in the footsteps of crystalline silicon solar panels.” Dr. Staffell also pointed out that lithium-ion batteries, too, were very expensive when they were first released. This meant that they were initially used in a very limited capacity, though their current popularity means that their manufacturing volume is growing as costs drop.
Pumped water and other mechanical technologies cannot be projected to decrease in cost. Below is a screenshot of video graph of such factors as Lowest Cost of Storage (LCOS) projected over time for various energy technologies.
Lowest cost of storage over time. See the full video from Imperial College
Other Organizations Working on Silicon Electrodes for Lithium-Ion Batteries
This is an area of research that may very well cause big changes in the ever-expanding universe of Li-ion battery applications. It’s likely that effects of these efforts may be apparent sooner rather than later because it is not only universities that are involved, but also profit motivated organizations. As might be expected, details are NOT forthcoming.
Some examples include:
- Enovix, a company developing a "3D cell architecture" for silicon Li-ion batteries that they claim boosts energy density between 30%-80%. Judging by the fact that Intel and Qualcomm are backers of Enovix, it’s not only entities interested in utility-scale storage that are interested in increasing the energy density of LiBs.
- Enevate, which is developing silicon electrode batteries with the automotive industry in mind. Enevate is partially funded by Alliance Ventures, the strategic venture capital arm of Renault-Nissan-Mitsubishi.
- Sila Nanotechnologies, which highlights the ability for battery manufacturers to implement the change to silicon-dominant batteries without changing present production equipment.
The backers and goals of all three companies demonstrate how far silicon batteries have developed already.
So despite that Li-ion batteries have taken some knocks in the past several years, what with their famous ability to explode inside commercial devices, it's possible that they'll be the power source of choice across the industry for years to come.
What are your thoughts on the power sources that are available to you today? Share your thoughts in the comments below.