(3ap) Structured Polymers for Energy Generation and Storage

Reduction of both greenhouse gas emissions and U.S. dependence on foreign oil will require the widespread adoption of electric vehicles, renewable power generation, and smart electrical grids. The current bottleneck to extensive deployment of both electric vehicles and smart electrical grids is the battery.  Adoption by major utility companies of renewable energy plants, such as those based on photovoltaics, is hindered for two reasons.  Stabilization of the intermittent power generation requires inexpensive long-life battery systems, which are yet to be developed.  Additionally, power derived from photovoltaics is still too expensive to compete with electricity derived from fossil fuels.  Deploying these applications will call for entirely new energy generation and storage innovations.  In my poster presentation I will highlight examples both from my graduate research and from my accomplishments at Seeo Inc., the start-up company I co-founded.  I will discuss how electrochemistry can be used to control assembly of block copolymers and, reciprocally, how structured nanomaterials can be used to control electrochemical device function, particularly in the case of stable high energy batteries.  Building on my past work, I will describe my plans to create a research program aimed at obtaining a fundamental understanding of the structure-property-function relationships in nano-structured polymers as they apply to devices for advanced energy generation and storage.

During my graduate work, I synthesized and studied organometallic block copolymers, wherein one block was composed of alternating ferrocene and dialkylsilane units in the main chain.  Similarly to typical organic block copolymers, they underwent self-assembly to form microphase-separated ordered structures, and I characterized the phase behavior and thermodynamic interactions of the poly(ferrocenyldimethylsilane) system with multiple copolymers.  The thermodynamic interactions in poly(ferrocenyldimethylsilane) diblock copolymers were systematically adjusted by oxidizing the ferrocene moieties with silver salts and examined using SAXS and depolarized light scattering. The polymers retained microphase separated ordered structures upon oxidation and showed systematic changes in the location of the order-disorder transition as a function of extent of oxidation.  By controlling the redox properties of the ferrocene moiety in the backbone of the polymer, I developed a method for controlling the self-assembled microstructure and hence bulk material properties.  Furthermore, using electrochemical techniques, a novel means of controlling the order-disorder transition of block copolymers was discovered.  By applying very small electrochemical potentials to disordered solutions of the organometallic block copolymers, oriented ordered grains were formed near one electrode, the result of electrochemical reactions.  After reversing the electrical bias on the system, the ordered grains disappeared and new oriented ordered regions were formed at the opposite electrode.  Our work established a fundamentally new mechanism for controlling the self-assembly of block copolymers.

More recently as Director of Materials Development at Seeo Inc., I have focused on developing commercially viable lithium battery systems based on solid-state polymeric electrolytes. Solid-state batteries have long been a goal of rechargeable battery development.  Today’s conventional batteries rely exclusively on organic liquid electrolytes, whose volatility and reactivity are responsible for the most significant limitations to battery life and safety.  Liquid electrolytes continuously react with electrodes at maximum cell voltages and upon cycling, causing reduced lifetime through impedance rise and capacity fade.  In contrast, polymer electrolytes limit the mobility of reactive electrolyte species, forming solid interfaces that can remain stable over long periods of time and over many charge/discharge cycles.  Remarkably, this drastic enhancement in interfacial stability can yield extremely low rates of degradation and capacity fade, even in cells employing otherwise reactive high energy electrodes.  Before the widespread commercialization of lithium ion batteries, solid polymer electrolyte technology was considered to be among the most promising routes to enabling lithium-based batteries. However, despite strong government and private-sector funding, academic and commercial efforts to develop batteries based on solid polymer electrolytes consistently failed.  At the heart of each of these failures lay the inability to overcome a single fundamental constraint.  Ion transport in polymers is coupled to the motion of the surrounding molecules that are solvating the ions.  The presence of mobile molecules is thus essential to allow for a conductive medium; however, the same mobility of molecules is detrimental to the polymer’s structural integrity.  In all cases, polymer electrolytes with high ionic conductivity failed due to mechanical reasons while mechanically robust ion conductors were severely limited in conductivity.  At Seeo, we have employed advanced self-assembled polymer nanostructures to break free from this principal constraint.  We are commercializing our proprietary polymeric electrolytes in lithium-based batteries for electric vehicle and grid-tied storage applications.  I believe my four-year experience leading an industrial research and development team gives me a unique understanding of how to create an academic research program with capabilities of exploratory science, intellectual property generation, and translation to practical application.