Patel Group

Energy is a significant component of the global economy and drives the technological advances of our society. Materials innovation, in part, plays a critical role in meeting the increasing energy demands. High performance electronics devices were enabled through discovery of the transistor. In turn, the discovery of intercalation materials led to the commercialization of lithium-ion batteries – now making electronic devices readily portable and ubiquitous in society. Such game-changing materials discoveries and continued engineering are paramount to address the energy needs. At the PME, the Patel Group will focus on addressing energy related challenges that will lead to a more sustainable, cleaner and safer energy technologies.

The Patel Group focuses on functional polymers – soft materials that have material processing properties of traditional polymers (i.e. “plastics”), but with the ability to transport neutral molecules, ions, or electrons. Moreover, functional polymers have the ability to be redox-active, optically-active, and responsive to external stimuli such as temperature. Therefore, the properties of functional polymers can be tuned through molecular design to fit the needs of a wide-array of applications. With this versatility, functional polymers can be leveraged to regulate charge transport in electrochemical devices, convert solar energy to electricity, convert thermal energy to electricity, and purify water.  Beyond energy applications, these materials can be applied to biomedical systems such as controlled drug release or the development of degradable implantable electronic devices. While the current focus of the group is on batteries and thermoelectrics (devices that interconvert heat and electricity), we will continue to look for interesting and innovative applications areas that allow us to leverage the diverse nature of functional polymers.

The Patel Group has a strong expertise in the characterization of materials from the molecular- to macroscopic-scale.  We combine complementary experimental scattering, spectroscopy and microscopy techniques with electrical and electrochemical measurements to reveal critical structure and property relationships of functional polymers.  To truly understand the performance within devices, we look to implement in-situ, in-operando and non-invasive characterization techniques. We pay particular attention to interfacial effects, which frequently limits the performance of functional polymers. Experiments alone will not reveal the critical scientific underpinnings. Accordingly, a mission of the research group will be to establish collaborations with theory and simulation groups in order to complement our experimental expertise. In turn, we can develop new materials with our synthetic collaborators to fully exploit the innovations of functional polymeric materials for energy conversion and storage.

The battery-related research efforts in the Patel group will focus on the following:

1) Using functional polymeric materials to enable inherently safer lithium battery technologies.

2) Leveraging polymer-based macromolecular architectures as redox-active materials in flow batteries for the next generation grid-storage technologies. We are particularly interested in investigating the morphological and charge transport properties of redox-active polymers in solution and the corresponding influence on battery performance.

3) Probing the polymer/electrode and polymer/active-material interfaces with the goal of understanding the structural and charge transport characteristics at the molecular level.

Prof. Patel has a joint staff appoint at Argonne National Lab (ANL).  Many of our battery research programs will work closely with leading researchers in batteries at ANL and utilize various state-of-art battery-focused facilities.  The following links describes battery research at ANL in more detail.

Battery and Energy Storage at ANL

Joint Center for Energy Storage Research (JCESR)

Engineering materials with high efficiency (related to the figure of merit, ZT) is one of the great challenges of thermoelectrics (TE) devices.  A thermoelectric module comprises of electron conducting (n-type) and hole conducting (p-type) materials, which are connected electrically in series and thermally in parallel. Consequently, under a temperature difference (ΔT), a carrier concentration gradient results in a voltage (ΔV), known as the Seebeck coefficient, α ~ ΔV/ΔT. The challenge lies in the development of materials that simultaneously have low thermal conductivity (κ), high electrical conductivity (σ), and high Seebeck coefficient (α).

Conventional TE modules are based on inorganic materials (e.g. Bi, Te), which have a low natural abundance, high costs in materials and manufacturing, and where the manufactured modules are rigid and brittle, thus limiting the versatility. Semiconducting polymers will overcome the limitations of inorganic materials due to the inherent low thermal conductivity and the ability to modulate between from insulating to electrically conductive state through chemical doping. Moreover, polymeric materials allow for innovative and cost-effective pathways to manufacture thermoelectric modules by leveraging the processibility of polymers. Ultimately, organic thermoelectric devices based on doped semiconducting polymers will enable the development of thermal harvesters of low-grade heat (<200 °C), self-powered wearable devices, and local temperature control.

To fully realize the potential of doped semiconducting polymers for thermoelectrics will require a better understanding of the connection between processing and resulting thermoelectric properties. As a consequence, the Patel group is focused on developing better doping routes and advancing our fundamental understanding of structure-property relationships of doped semiconducting polymers. The selected publications below outline such efforts.

Innovations in electrochemical materials for thermogalanvic (TG) devices will have a profound impact in thermal energy harvesting.  Ideal electrochemical materials for TG devices are redox couples with a high entropy of reaction (ΔSrc), which is correlated to the temperature dependence of the electrochemical potential (electrochemical Seebeck coefficient, αe). A conventional TG device consist of a redox couple in an aqueous electrolyte that diffuses between two platinized electrodes held at different temperatures.  The applied temperature difference between the two platinized electrodes induces a difference in electrochemical potential of the redox couple and can provide continuous power under an applied load.  The focus of TG research has been limited to the benchmark Fe(CN)63-/ Fe(CN)64- redox couple, which has a high αe value around -1.4 mV/K. Consequently, a tremendous opportunity exists to explore and discover redox couples that go beyond the Fe(CN)63-/ Fe(CN)64- redox couple for the next generation of TG devices.  Practically, TG systems are limited to below 100 °C due to the aqueous electrolyte and lack scalability when designing TG modules for practical power generation.  Accordingly, transitioning to non-aqueous and polymer membranes will be vital to for versatile flexible and conformal TG modules and boost efficiency due to higher operating temperatures.

The Patel group has a strong expertise in the structural characterzation of functional polymers from molecular to the macroscopic scale.  We frequently will utilize various synchrotron X-ray and spectroscopy facilities, such as the Advanced Photon Source, to elucidate key structure-property relationships of functional polymers.