Finding a technological solution for safe energy storage with high capacity and fast discharge rates is vital for the transition to the carbon neutral economy and oil independence in the USA. The required parameters for electricity storage can potentially be achieved for Li metal polymer batteries and some Li+ ion batteries, but one must resolve the central bottleneck of all lithium battery technologies related to the fundamental problems of interfacial mass/charge transport, i.e. the growth of dendrites. They are the source of rapid decrease the performance upon cycling and serious fire safety concerns. This leads to the acute need of new concepts in ion-conducting membranes (ICMs) preventing dendrite growth. Based on theoretical analysis of transport processes at the ICM-electrode boundary, it was theoretically established that dendrite growth can be inhibited entirely by an ICM with a shear modulus of G ¡Ã7 GPa. Presently, there are no materials available satisfying this and other key requirements, such as ionic conductivity ¡à 10- 4 S/m. To resolve this bottleneck and to impart seemingly contradictive material characteristics, new manufacturing methods are needed to engineer interfacial processes/properties and achieve the technological targets for battery materials.
Intellectual Merit: This project will utilize (1) layer-by-layer assembly (LBL) and (2) ultrastrong Kevlar nanofibers to obtain a new generation of ICMs that can completely suppress dendrite growth. LBL is very simple inexpensive technique leading to films with exceptional uniformity and high Young¡¯s modulus. Their mechanical properties will be further enhanced with Kevlar. This polymer will be used in an unconventional form as nanofibers dispersion with a diameter of 50-70 nm and a length of 1-3 microns. Based on encouraging preliminary results, the PIs plan to achieve proof-of-concept. The Objectives are:
(1) to reach ion-conductivity in 10-4-10-3 S/m range using ion templating of ion-conducting polymers; and
(2) to attainG¡à 7 GPa by using inherently strong LBL components and controlled interfacial cross-linking between them. Both of these objectives are intrinsically related to the interfacial and mass transport processes of the materials, where the group has extensive expertise and technical capabilities. This is a fundamentally innovative method for manufacturing of ICMs and does not have an established pool of researchers with expertise in dendrite formation.
Besides the introduction of LBL technique as a novel method for manufacturing the ICMs, facilitation of ion transport in solid materials provides unique opportunities for the development of batteries as well as other energy conversion technologies. Such technologies also include fuel cells and osmotic energy generators. The utilization of nanoscale fibers of Kevlar represents a great change from the traditional view of potential uses of this well-established flexible armor material. Additional intellectual impact is also expected from the development of lithium ion-templating process which would be difficult to realize before without nanoscale control of interfaces in ICMs.
Broader Impact: The proposed work makes a significant step toward alleviating the technological bottlenecks on the way to CO2¨Cneutral (energy) economy. The development of new ICMs can greatly reduce CO2 emissions by making possible competitive full electric options for electrical vehicles and high capacity electrical storage systems for solar energy and wind farms. Safety of intermediate electrical storage blocks is another fundamental challenges for large scale batteries which is being addressed here as well. The research work will be accompanied by aggressive dissemination of information about importance of new materials for energy research. This part of the project will be done with strong involvement of the high school students from Community High School in Ann Arbor, MI with whom we have established relationships from 2007, and undergraduates from the UM Department of Electrical and Computer Engineering. Together with them, the investigators will develop a web-site explaining the principles of key components of the chain of electricity generation and consumption now and in the future. The joint work of undergraduates and high school students is expected to have a strong positive impact on the carrier choices of upper classmen and will help bringing greater number of highly qualified underrepresented minority and female students to engineering.
PI/Co-PI Name: Nicholas Kotov Finding a technological solution for safe energy storage with high capacity and fast discharge rates is vital for the transition to the carbon neutral economy and oil independence in the USA. The required parameters for electricity storage can potentially be achieved for Li metal polymer batteries and some Li+ ion batteries, but one must resolve the central bottleneck of all lithium battery technologies related to the fundamental problems of interfacial mass/charge transport, i.e. the growth of dendrites. They are the source of rapid decrease the performance upon cycling and serious fire safety concerns. This leads to the acute need of new concepts in ion-conducting membranes (ICMs) preventing dendrite growth. To resolve this bottleneck and to impart seemingly contradictive material characteristics, new manufacturing methods are needed to engineer interfacial processes/properties and achieve the technological targets for battery materials. We investigated layer-by-layer assembled (LBL) and ultrastrong Kevlar nanofibers to obtain a new generation of ICMs that can more efficiently suppress dendrite growth. LBL is very simple inexpensive technique leading to films with exceptional uniformity and high Young’s modulus. Their mechanical properties will be further enhanced with Kevlar. This polymer will be used in an unconventional form -- as nanofibers dispersion with a diameter of 50-70 nm and a length of 1-3 microns. We achieved two Objective 1 ion-conductivity in 10-5 S/m and Objective 2 Young’s modulus of 100+ GPa in ICMs made by LBL assembly of polymers. By using inherently strong LBL components and controlled interfacial cross-linking between them we were able to form very thin ion-conducting membranes capable of suppressing dendrite growth in copper and other metals. We also prepared prototype of high discharge rate Li+ ion battery using LBL-made ICM which performed better than its close analogs. We also introduced LBL technique as a novel method for manufacturing the ICMs and other nanocomposite materials with structure that can facilitating ion transport in solids. Such materials provides unique opportunities for the development of batteries as well as other energy conversion technologies including fuel cells and osmotic energy generators. In terms of broader impact the outcomes of this proposal made a significant step toward alleviating the technological bottlenecks on the way to CO2–neutral economy. The development of new ICMs can greatly reduce CO2 emissions by making possible competitive full-electric options for electrical vehicles and high capacity electrical storage systems for solar-energy and wind farms. Safety of electrical storage devices is another fundamental challenge for large scale batteries which can be addressed with new ICMs. The research work was accompanied by aggressive dissemination of information about importance of new materials for energy research. This part of the project was done with strong involvement of the high school students from Community High School in Ann Arbor, MI and Montessori School. The PI participated in two Math and Science Olympics as a judge and mentor.
