IFM discovery unlocks new power for piezoelectric effect

AT A GLANCE 

• IFM researchers have made the discovery that solvate ionic liquids can also generate the piezoelectric effect – previously shown to be generated predominantly in solid materials. 

• The piezoelectric effect, used to power electronic devices such as sensors, is typically found in solid materials that can generate electricity when their shape is compressed. Research has shown solvate ionic liquids can generate the effect and enhance energy storage capacity. 

• The research has been published in Materials Horizons, which also features co-author Dr Bhagya Dharmasiri in its Emerging Investigator series. 

Solid materials have been key to generating the piezoelectric effect, however researchers at the Institute for Frontier Materials have demonstrated for the first time that liquids can not only generate the piezoelectric effect but enhance energy storage technologies. 

The piezoelectric effect is typically found in certain solid materials that can generate electricity when their shape is compressed. This phenomenon is used to power every-day electronic devices such as microphones, laptops and sensors. The first practical use of piezoelectric materials was during World War I for sonar technology to detect and locate submarines. 

In a paper published in Materials Horizons, IFM researchers Masters student Žan Simon, Dr Bhagya Dharmasiri, PhD candidate Tim Harte, Professor Luke Henderson and RMIT’s Dr Peter Sherrell, demonstrated that solvate ionic liquids can generate the piezoelectric effect with bulk electrical potential when pressure is applied. 

The IFM research group had previously investigated the use of solvate ionic liquids with carbon fibre for energy storage devices. Unusual observations led the team to investigate whether the piezoelectric effect could occur with their solvate ionic liquid as it does with an energy storage electrolyte. 

“The piezoelectric effect has been studied in many materials before, but never in solvate ionic liquids,” Mr Simon said. 

“By investigating this effect in solvate ionic liquids, we are exploring a completely new territory in which these liquids themselves could have an additive effect to energy storage devices.  

“The potential implications are significant. If solvate ionic liquids can generate electricity when stressed, it could lead to more efficient energy storage devices.  

“Imagine a battery that not only stores energy but also generates additional power when it’s squeezed or bent during normal use. 

“These findings open new possibilities for designing more efficient, multifunctional energy storage systems that could have far-reaching implications in fields ranging from portable electronics to electric vehicles and beyond.  

“While these voltages might seem small, they could make a big difference in certain applications. In structural supercapacitors made with carbon fibres, this extra bit of voltage generation could significantly boost overall performance.” 

 

Piezoelectric effect and solvate ionic liquids – how it works 

The solvate ionic liquids are made of salts mixed with a specific type of solvent, which according to Mr Simon, give them unique properties for energy storage applications, particularly in terms of safety, electrochemical stability and almost-zero vapour formation.  

“When using the solvate ionic liquid on its own, a bulk electrical potential difference of up to 150 mV was observed when pressure was applied and, more importantly, this response was proportional to the applied force,” he said. 

“In the solid polymer electrolyte, a smaller but still significant potential response was observed, reaching a maximum output of ~35 mV. This lower value is due to the smaller volume of the liquid at the interface where the potential was measured within the polymer matrix. 

“This research showed that applying force and subsequent pressurisation and depressurisation led to electrical potential generation, demonstrating a direct piezoelectric effect in these materials.  

“This suggests that pressure can cause transient structural changes in these liquids from liquid to crystalline form, which is related to their electromechanical properties and the output we were able to observe.” 

New discovery could revolutionise energy storage systems 

Mr Simon said previously solvate ionic liquids were valued for their low vapour pressure and high thermal and chemical stability. 

“This research reveals that they also possess electromechanical and piezoelectric properties, expanding our understanding of their potential applications,” he said. 

“These properties also translate to full scale electrolytes, opening avenues for their use in structural energy storage composites. These effects are present both in pure solvate ionic liquids and in composite materials, via the solid polymer electrolyte, suggesting that these properties could be leveraged at various scales and in different material configurations.” 

Mr Simon said the research challenges us to think about energy storage materials not just as passive reservoirs of charge, but as active, responsive components that that can both store and generate energy in response to mechanical stress, through pressure or movement and therefore enhance device performance. 

“This dual functionality could revolutionise how we design energy storage devices, as well as improve efficiency not just through better chemistry or capacity, but also through mechanical design that takes advantage of these newly discovered properties,” he said. 

New multifunctional energy storage systems could inform the design of new electronic vehicles, aircrafts, self-powered sensors for infrastructure and health monitoring, laptops and smart phones. 

“Most, if not all, of these applications already use carbon fibre in their design and manufacture due to its desirable properties such as lightweighting of these parts and high strength-to-weight ratio,’ Mr Simon said. 

“Therefore, large modifications to existing manufacture processes would not be necessary to incorporate these materials in a way that would support multifunctionality of the end products. 

“This research could lead to a new generation of devices and structures that are not only more energy-efficient but also more functional and resilient.” 

Dr Bhagya Dharmasiri named Emerging Investigator 

In the same edition of Materials Horizons, co-author Dr Bhagya Dharmasiri was featured in the journal’s Emerging Investigator Series. The series features exceptional work by early-career researchers working in the field of materials science. 

Dr Dharmasiri, under the mentorship of Professor Luke Henderson, has combined her expertise in chemistry and material science to focus on surface functionalisation of carbon fibres and developing advanced polymer synthesis and composite fabrication techniques. 

She says this latest paper is just the beginning of a “proof of concept” for demonstrating the piezoelectric effect in solvate ionic liquids. 

“There’s much more to explore,” Dr Dharmasiri said. “Our next steps will involve investigating this effect across a broader range of polymers and ionic liquids.  

“We’ll also look into ways to harness this energy and use it within the same system, potentially opening new avenues for energy generation and storage. Additionally, we’ll work on enhancing this effect by incorporating various additives.  

“A key focus will be scaling up these materials into carbon fibre structural supercapacitor composites, where the supercapacitor can be charged by the energy generated through the application of pressure on the composites.  

“This could lead to groundbreaking advances in multifunctional composite materials with significant real-world applications.” 

Dr Dharmasiri said the mentorship provided by Professor Luke Henderson has been invaluable in this body of research. 

“Professor Henderson’s commitment to fostering a collaborative and explorative research environment has been crucial in making this possible,” she said. 

“This work on the piezoelectric effect in solvate ionic liquids is a prime example of what can be achieved when brilliant minds from different disciplines come together.  

“By combining our diverse talents, we’ve been able to pioneer innovative multifunctional materials that have the potential to revolutionise energy storage technologies.”