Nanoporous materials are attractive for electrochemical energy storage applications. For insertion battery electrodes, these pores provide improved morphological stability during charge-discharge cycles through accommodation of large volumetric changes. However, relationships between morphological structure and performance are still, in general, lacking; in particular, complex multi-component and multi-scale materials should enable significant improvements in performance. For example, carbon coating of metal oxides or silicon provides improved performance in comparison to graphite or pure metal oxide. This project seeks to provide a fundamental framework for the design and characterization of hybrid materials for Li insertion battery electrodes using well-defined model materials in conjunction with an in-situ multiscale (atomic and meso) characterization and testing program.
Self-assembled ordered materials provide model electrodes to enable fundamental insight into how morphology evolution and distortion during cycling impacts long term battery capacity. In this work, we propose to use cooperative self assembly of phenolic resin (carbon precursor) and (1) sol-gel Li-doped vanadium pentoxide or (2) silicon nanoparticles to fabricate ordered mesoporous nanocomposites as model materials by which structure-property relationships can be elucidated. This self-assembly route enables near monodisperse pore sizes, wall thickness and transport paths for fundamentally examining the impact of pore size and nanoparticle (Li-V2O5 or Si) content on the performance of these nanocomposite materials as insertion battery electrodes. The nanocomposite matrix allows for significant incorporation of Li (through insertion in Li-V2O5 or Si) and high electrode conductivity (through continuous carbon pathways). The PI proposes to systematically vary the nanoparticle:carbon ratio and the nanoparticle size/sol aging to develop an improved understanding of morphology-property relationships, enhanced by their well-defined mesoscale structure. A suite of characterization tools (including TEM, porosimetry, and scattering) will enable correlation of structure to standard electrochemical performance tests. Of particular interest are structural changes involving swelling, de-swelling, and distortion under charge-discharge conditions that will be elucidated by in-situ grazing incidence small angle x-ray scattering and rotational small angle neutron scattering to address fundamental material challenges associated with electrode stability. Novel in-situ small angle scattering studies during electrochemical testing are proposed to elucidate solid-electrolyte interphase formation and potential routes to mitigate performance loss through nanostructuring and improved control of charge-discharge cycles. Combined these studies will provide improved basic understanding of structure-property relations for porous Li ion battery anodes and potentially provide new engineering solutions for high performance batteries.
Advances in battery technology from improved fundamental understanding developed could lead to improved battery efficiency, battery usage in higher power applications and increased battery lifetime. Due to the growing utilization of Li insertion batteries in consumer and industrial applications, the potential impact from even modest advances in efficiency and lifetime is quite large. There are both economic and environmental benefits to consider as increased battery lifetime will decrease the replacement rate for batteries in applications, especially considering the growing market for batteries from consumer electronics to transportation. Dissemination of concepts associated with this research will be disseminated to a broader, public audience through partnership with UA-St. Vincent?s High School (STVM) and the Akron Global Polymer Academy (AGPA) that provides materials to K-12 teachers nationwide; additional local outreach effort will include trips to classrooms for grades 6-10, through AGPA connections.
