10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Aerosol Chemical Vapor Deposition of Nanostructured Thin Films for Lithium-Ion Battery Negative Electrodes
CLAYTON KACICA, Louis Wang, Tandeep Chadha, Pratim Biswas, Washington University in St Louis
Abstract Number: 298 Working Group: Materials Synthesis
Abstract Electrochemical energy storage has become increasingly important in recent years due to increasing numbers of electric vehicles in use and the expanded deployment of intermittent renewable energy. Improvements in current battery technologies, such as increased longevity and higher energy density, are necessary for these new applications. Lithium-ion batteries (LIBs) are the most promising candidate for use in these applications due to their many advantageous properties.
Current research is focusing on the development of new electrode materials and electrode morphologies. Metal oxides, such as tin dioxide (SnO2), have been the focus of much work for utilization as negative electrodes due to their high theoretical capacities. However, these materials undergo a large volume expansion when charged that can lead to rapid capacity fade or battery failure. Using nanostructured morphologies, such as nanospheres, nanotubes, and nanorods, has been shown to significantly reduce the instability of these electrode materials. Using aerosol techniques, we can synthesize nanostructured metal oxide materials in a way that is both scalable and economically feasible.
One such technique is aerosol chemical vapor deposition (ACVD), in which a vapor phase organometallic precursor is fed into a reactor where it undergoes thermal degradation to for metal oxide monomers. Nucleation and condensational growth of particles occur before the particle deposit onto a heated substrate and sinter into films of various morphologies. Using various system parameters, the characteristic times for the processes occurring in the reactor can be controlled and used to determine the final morphology of the deposited material. Because ACVD can be used to deposit directly onto a current collector, the post-processing steps usually required for electrode fabrication are eliminated.
In this work, highly oriented columnar nanostructured SnO2 electrodes were fabricated using ACVD and utilized as high-capacity negative electrodes in LIBs. The nanostructured electrodes exhibited an initial specific discharge capacity of 1433 mAh g-1 and after 100 galvanostatic charge-discharge cycles at a charge rate of 1 C retained a specific discharge capacity of 445 mAh g-1. However, when increasing the charge rate to 2 C significantly more capacity fade is observed resulting in specific discharge capacity of 251 mAh g-1 after 100 cycles. In order to enhance the capacity retention of the electrodes, a thin layer of TiO2 was applied to prevent irreversible parasitic reactions from occurring. The TiO2 coated SnO2 electrodes exhibited a specific capacity of 497 mAh g-1 after 100 charge-discharge cycles at a rate of 2 C, with coulombic efficiencies over 99% after the first cycle. Diffusion studies were conducted to ensure that the TiO2 coating was not impeding the movement of Li+ ions. The study showed that the diffusion coefficient of Li+ was not impeded for coatings of TiO2 that was less than 26 nm.