Drexel University analyses the use nanomaterials for future energy storage

Materials World magazine
,
6 Jan 2020

Highlighting the importance of nanoscopic materials, a new report analyses the use of nanomaterials and their contributions to sustainable energy storage.

Recommendations for future sustainable energy sources was published by an international team of researchers, collaborating to present a comprehensive review of the use of nanomaterials for energy storage over the last two decades.

Led by researchers at Drexel University, USA, the report, Energy storage: the future enabled by nanomaterials, published in Science, assessed the versatility of nanomaterials, their limitations, and potential applications, such as in supercapacitors and lithium-ion batteries.

‘There has been a significant effort that led, for example, to the introduction of silicon nanoparticles instead of graphite into battery anodes,’ Drexel University Materials Science and Engineering Professor, Yury Gogotsi told Materials World. ‘Silicon can store much more energy than graphite, and companies like Sila Nanotechnologies, USA, have been introducing them into car and cellphone batteries.

‘However, the goal is to actually enable batteries that use other ions, such as sodium, magnesium, calcium, aluminium or zinc, which are more abundant, less expensive and can potentially store more energy than lithium – zinc or aluminium may be able to transfer to electrons per ion compared to one in the case of lithium. Use of those ions could also resolve geopolitical challenges related to lithium deposits located in just a couple of countries.’

Storage wars

Renewable energy sources such as solar and wind power are increasingly favourable, but the unpredictable and intermittent generation has made it difficult to merge these renewable sources into national energy grids.

To combat this, advancing battery storage technology has become increasingly central to renewable energy development. The reversibility of storage and release of electricity is essential to meet consumer demand for electronics, medical devices, electric vehicles and electric grids. In addition, the inconsistency of renewable sources pushes the need for larger and diversified energy storage technology necessary to harness and facilitate the energy generated.

‘The better we become at harvesting and storing energy, the more we will be able to use renewable energy sources that are intermittent in nature,’ Gogotsi said. ‘Batteries are like the farmer’s silo – if it’s not large enough and constructed in a way that will preserve the crops, then it might be difficult to get through a long winter. In the energy industry right now, you might say we are still trying to build the right silo for our harvest – and that’s where nanomaterials can help.’

A nano solution

Nanomaterials’ potential for electrodes and devices could improve the performance and development of existing energy storage systems. The electrochemical performance is becoming more advanced due to nanostructuring – which introduces particles, tubes, flakes and stacks of nanoscale materials as the new components of batteries, capacitors and supercapacitors. This nanostructuring has the capacity to exploit a range of charge storage mechanisms including surface-based ion adsorption, pseudocapacitance, and diffusion-limited intercalation processes.

According to the study, combining nanomaterials in hybrid architectures, such as carbon-silicon and carbon-sulphur with the development of versatile methods of nanostructuring, can overcome challenges related to large volume change typical for alloying and conversion materials.

These are an indication of how nanostructured materials and nanoarchitectured electrodes can provide solutions for and developing high-energy, high-power, and long-lasting energy storage devices.

‘Ions that lithium-ion batteries use to store charge move slowly in solid ceramic or graphite grains that constitute electrodes of modern batteries,’ said Gogotsi. ‘That’s why charging your computer or cellphone takes a while. When two-dimensional nanomaterials, such as graphene, MXene, or nanoparticles of a few nanometers in size are used, the entire storage process happens on the surface, so the charge can be stored, or delivered almost instantly.’

Energy potential

As presented, nanomaterials have huge potential in energy storage devices, but also have limitations due to their high surface area, causing parasitic reactions with electrolytes as well as their agglomeration. In order to overcome these, the smart structuring and assembly of nanomaterials into architectures with controlled geometry has become a central focus of future strategies.

In addition, the report stated that it is necessary to combine nanomaterials with complimentary functionalities, including high electronic conductivity of graphene or MXenes, operating voltage and redox activity of oxides.

‘Building sophisticated electrode architectures requires innovative manufacturing approaches, such as printing, knitting, spray deposition, and so on,’ the report read. ‘Already-developed techniques such as 3D printing, roll-to-roll manufacturing, self-assembly from solutions, atomic layer deposition, and other advanced techniques should be used to manufacture devices from nanomaterials that cannot be made by conventional slurry-based methods.’

Reflected throughout the study, the team expects that nanomaterials will largely impact the production of batteries in the future, predicting increased charging rate, the ability to harvest and store, and incorporate more battery use in everyday life.