Author(s): Kenneth Smith
Mentor(s): Jason Porter
Institution BYU
Lithium-ion batteries are widely used in applications ranging from smartphones to power tools, and their use in electric vehicles has led to increasing demand for higher performance. However, stresses on batteries during operation can cause premature failure, leading researchers to seek a better understanding of what causes batteries to fail and how failure can be mitigated. One known cause of lithium-ion battery failure is the formation of lithium-metal deposits on the interior of the battery, which deposits can grow and bridge between electrodes, short-circuiting the battery. To fully understand what causes these deposits to form and how they propagate, it is essential to study batteries under actual operating conditions. The Microscopy and Optical Diagnostics for Energy Systems Laboratory (MODES Lab) at Brigham Young University has developed a custom electrochemical cell which can be used to image lithium-metal deposits during cell operation. The cell was designed with a geometry and operational parameters that reflect realistic battery conditions including proper electrode spacing, current density, and electrolyte concentrations. The cell is sealed to exclude oxygen and moisture, both of which can significantly interfere with battery performance and skew experimental results. Components on the interior of the cell are stable when in contact with highly reactive materials like lithium and in the presence of aggressive solvents, while simultaneously meeting the requirements for electrical isolation where needed. The cell design provides optical access for high-resolution spectroscopic measurements of battery electrolytes with simultaneous imaging of any deposits that form. This cell is being used now in the MODES Lab to collect infrared absorption spectra which are analyzed to quantify ion concentration gradients forming in the electrolyte and their role in the appearance of lithium-metal deposits. Real-time observations of the growth of deposits between lithium electrodes during cell operation reveal complex interactions occurring between the electrolyte and electrodes, the understanding of which is essential for documenting trends relevant to real-world applications.