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How Nanotechnology is Facilitating Battery Development

April 15, 2021

Nanotechnology is science at the nanoscale, working at the atomic or molecular level of matter. A nanometer is one billionth of a meter -- invisible to the eye. Nanotechnology is being used to innovate in many different fields including medicine, the environment, technology, and energy storage. The concept of nanoscience first started in 1959 when physicist Richard Feynman spoke about manipulating and controlling individual atoms and molecules. The field as we now know it began in 1981, when the scanning tunneling microscope was developed, which allowed scientists to see individual atoms and begin research at the nanoscale. In the battery industry, many companies are working to incorporate nanotechnology into batteries and battery production processes in hopes of improving material mining and battery performance and capacity.

How is nanotechnology improving material mining?

Lithium is currently the most coveted material needed for batteries. With the continuous growth of portable technology and EVs, and an increasing need for energy storage, analysts predict that the demand for lithium will increase tenfold by 2029. 70% of lithium is mined via brine extraction, which involves pumping salt-rich waters into a series of evaporation ponds. The water evaporates and pure lithium is eventually extracted from the ponds. However, this process is not only water-intensive, affecting the water supply to nearby residents and farmers, but also only extracts 30 to 50% of the available lithium.

One company is working to make use of nanotechnology to improve the efficiency of this process. EnergyX makes use of a nanotechnology called Metal Organic Framework (MOF) to separate lithium from the other materials in the water. An MOF is a porous material, consisting of metal ions and organic ligands that form a cage-like structure. They can act like a sieve to segregate materials, which is how EnergyX is making use of it. The small pores of the MOF allow lithium to pass through, but stop other ions like magnesium or calcium, allowing for a more efficient way to extract lithium. The company designed their technology to incorporate into the current brine ponds system, maximizing the mining process. Creating more efficient, sustainable, and environmentally-friendly mining processes can be a big help in meeting the demand for lithium and other battery materials

How is nanotechnology improving batteries?

There are currently numerous projects around using nanotechnology to create better batteries. These range from increasing the surface area of electrodes in order to increase capacity to improving the safety and stability of the battery.

The advanced materials company TruSpin Nanomaterial Innovation makes use of silicon nanofibers to increase the energy capacity of lithium-ion batteries. Silicon has long been a favored choice as a battery anode because of its high ion-carrying capacity. However, due to its tendency to expand and shatter throughout charge/discharge cycles, manufacturers are facing difficulties in incorporating it into a battery. Nanotechnology can help to address this issue. By using nanofibers, TruSpin is able to work around these expansion issues, and make the manufacturing process highly scalable and cost-efficient.

Amprius is another company leveraging nanotechnology to make silicon more usable for batteries. They designed egg-like capsules to protect the silicon from reacting negatively with the electrolyte, which causes the anode to develop a non-conductive solid-electrolyte interphase layer and reduces capacity. The structure also gives room for the silicon to expand and contract safely. In their design, a silicon nanoparticle is surrounded by a highly conductive carbon shell that lithium ions could pass through. With this configuration, their team found that the anode still retained 74% of its capacity after 1000 charge/discharge cycles.

Pure lithium metal is also a highly favored battery material. However, since it is highly reactive, dendrites tend to form on the surface of the anode, creating branch-like structures that can pierce and damage the battery. To counteract this, scientists at Rice University made use of carbon nanotube film to coat the lithium metal foil. The coating discourages li-ions from latching onto the lithium metal anode and prevents dendrite growth.

Despite its miniscule size, nanotechnology has the potential to make big waves in battery development, research, and manufacturing. Good, high quality battery test equipment allows researchers to notice patterns and gaps in a battery’s performance, and discover areas which nanotechnology could potentially help to fill.

5 Criteria to Assess Battery Materials

December 21, 2020

With researchers testing different materials for a fresh take on the battery, how should we assess whether a certain material is a viable option? Integrating materials like silicon, graphene, and even sodium into battery chemistries is currently being studied. Here are 5 factors to consider when assessing whether a certain battery material is feasible.

Material cost

Material costs greatly affect the feasibility of using a certain material within batteries. With batteries so heavily relied upon nowadays, and demand only continuing to grow, choosing the right materials to keep prices low is imperative.

In 2010, a lithium-ion battery pack cost more than USD1000/kwh. This dropped significantly to USD156/kwh by 2019, and is projected to drop below USD100/kwh in the coming years.

The reducing cost of the battery has allowed more and more people to buy into batteries as a permanent energy solution for large applications such as electric vehicles or grid storage, facilitating the shift towards clean energy.

However, certain materials commonly used within lithium-ion batteries contribute to the high cost of the battery. For instance, cobalt is pricey and its cost tends to fluctuate due to limited supply and high demand. The case is similar for nickel. As the supply of these metals tend to be concentrated in certain parts of the world -- the Democratic Republic of Congo for cobalt, and Indonesia for nickel -- their prices would be dependent on the export policies of these countries.

Abundance and sustainability

The abundance and supply of a material not only affects its price but also long-term sustainability. Some analysts predict that the supply of the rare metals used in current batteries could deteriorate in just a few years. Industry insiders project that there would be a shortage of cobalt by 2022. In order to support the increasing demand for batteries, researchers are searching for alternatives.

One such alternative is sodium. Sodium is the sixth most abundant element on earth -- comparatively, lithium is the 25th. This means the sodium is a strong rival to lithium in terms of long-term availability. The sodium-ion battery is potentially cheaper and easier to produce than its lithium-ion counterpart, though there is still much to improve upon before it becomes a solid contender in terms of energy density.

For now, graphite is the preferred anode material, but much research is being put into silicon as a cheaper alternative. Silicon is the second most abundant element in the earth’s crust, making it a good choice for future batteries.

Material deterioration

However, just because a material is abundant, it doesn’t mean it is necessarily suitable to use in a battery. While silicone is a favored substitute, many researchers have found that silicon tends to deteriorate quickly when used in a battery. Although its capacity is theoretically higher than graphite, the silicon anode tends to swell almost 300% when receiving ions. This causes the anode to crack and deteriorate, thus quickly reducing the energy density of the battery.

Different materials react differently in different combinations. For instance, although energy dense, pure lithium metal reacts negatively with the electrolyte and promotes the growth of dendrites as ions deposit unevenly on the surface of the anode. When assessing battery materials, its reactivity and long-term performance needs to be taken into consideration.

Safety

The safety of the battery is a key concern. The dendrites formed inside the battery could potentially pierce the separator and cause the battery to short-circuit. Moreover, although lithium-ion batteries are generally stable, they have also been known to catch fire or combust when damaged. This is largely due to the flammability of the liquid electrolyte used inside the battery. Semi-aqueous or solid-state electrolytes are viable replacements to create a safer battery.

Environmental impact

In large quantities, certain materials are toxic to the environment. Cobalt and nickel are currently being used in lithium-ion batteries, however there are long-term environmental impacts associated with them, especially without proper disposal or recycling measures.

With the large number of batteries reaching end-of-life and being disposed of, heavy metals can accumulate and pose a safety hazard to people and the environment. If improperly disposed, these heavy metals can leak into the ground and water supply and affect the health of people and animals.

How materials are extracted from the environment and the effect this has should also be taken into account. Lithium mining has been found to cause habitat destruction and pollution, and damages the soil of surrounding agriculture operations.

Alternatively, the process of extracting sodium is much more environmentally friendly, another reason why it is a favorable option.

Each material has its pros and cons and these should all be measured when assessing its practicality. As batteries seek to facilitate a greener and cleaner future, the processes which this is achieved should also be examined. Sustainability should be considered alongside cost and battery chemistries in order to find balanced and viable alternatives for batteries.

Can we make batteries that can repair themselves?

April 16, 2020

Self healing batteries have been a notable area of battery research and development in the past few years, especially as research around the dendrites and how they affect performance has also grown. Since batteries run on chemical reactions, there are certain side effects that people may not have much control over. The gradual build up of ions within the battery is one of them. There currently has not yet been a commercial breakthrough with self-healing batteries, but initial research has opened the door to the possibility of safer and longer-lasting batteries.

What are dendrites?

Lithium-ion batteries have been the most used commercial battery since the 1990s. In the past few years, researchers have discovered branch-like structures tend to form within the battery cell. Commonly referred to as dendrites, they form as lithium ions group together on the surface of the anode inside the cell. As more ions attach, the dendrites grow.

Not all dendrites cause serious damage to the battery. Researchers found that in some instances, dendrites grow evenly along the surface of the anode. In these cases, battery performance remained stable and posed little to no damage to the battery.

However, there have been cases where dendrite growth is excessive and affects the structural and chemical stability of the battery cell. The dendrites can lead to unwanted reactions between the electrolyte and lithium, and cause hotspots or electrical shorts. They have also been found to pierce through the separator of the battery, compromising the electrochemical stability of the cell. It is speculated that some battery fires and explosions are a result of dendrite growth.

Because of the formation of these dendrites, there has been hesitation to adopt lithium-metal batteries. These would have a higher energy density but at the same time their chemical makeup would further encourage dendrite growth. This is why researchers are trying to uncover more efficient and durable materials.

How would self-healing batteries work?

In theory, self-healing batteries would not only provide a safer energy storage solution by reducing the risk of electrochemical instability, they would also be longer lasting because the internal damage that is generated can be reduced. Currently, there are two types of batteries that have been tested and shown potential. These are a solid-polymer electrolyte battery, and a potassium-based battery.

Last year, researchers at the University of Illinois developed a solid-polymer electrolyte that could self-heal after damage. The electrolyte consists of network polymer. They found that the cross-linking point of the electrolyte could undergo exchange reactions and swap polymer strands. This means that the polymer becomes stiffer when heated and effectively deters dendrite growth as ions are unable to group together.

On the other hand, the potassium-based battery self-heals by reversing dendrite growth. Researchers found a way to raise the temperature inside the battery just enough to encourage the dendrites to self-heal off the anode. They applied just enough heat to encourage diffusion, smoothing the accumulated metal off the anode, but not enough to melt the potassium metal and compromise the battery.

What could this lead to in the future?

Both types of batteries are still in the early stages of development, but the technology has shown its promise in creating safer and more stable batteries.

In the case of the solid-polymer electrolyte, it would also reduce the current danger from the flammable liquid electrolyte commonly found inside lithium-ion batteries.

Batteries that are safer and can maintain efficiency with greater longevity would benefit renewable and green technologies such as grid storage, EVs, and renewable energy, propelling the world into more sustainable and long-term energy solutions.