Tesla’s battery research group in Canada has filed a new patent application for a way to analyze an electrolyte in a lithium cell, which could help prevent cell failure.
The patent was filed through Tesla’s battery research group led by Jeff Dahn in Halifax.
Jeff Dahn is considered a pioneer in Li-ion battery cells. He has been working on the Li-ion batteries pretty much since they were invented. He is credited for helping increase the life cycle of the cells, which helped their commercialization. His work now focuses mainly on a potential increase in energy density and durability.
In 2016, Dahn transitioned his research group from their 20-year research agreement with 3M to a new association with Tesla under the newly formed ‘NSERC/Tesla Canada Industrial Research’.
Through the agreement, Tesla invested in a new research lab close to Dahn’s group near Halifax, Nova Scotia.
We haven’t heard much from Dahn over the past few years, but we previously reported that his group has been working on additives to the electrolyte in order to increase the performance of Li-ion battery cell chemistry.
The group started filing patents on battery technology for Tesla earlier this year and now a new one was made public today.
It’s called ‘Method and System for Determining Concentration of Electrolyte Components for Lithium-ion Cells’.
They described the invention in the abstract of the patent application:
“A computer-implemented method for determining a concentration of a component of an electrolyte in a lithium-ion or for a lithium-ion cell is provided. The method includes providing, to a spectrometer, instructions to capture a spectrum of a sample solution of the electrolyte and generate a signal. The method includes analyzing the signal to determine one or more spectral features of the spectrum. The method includes preparing a database of spectra corresponding to solutions having predetermined concentrations of the component of the electrolyte wherein the database includes a plurality for spectral features for each solution. The method further includes determining a machine learning (ML) model using the database of spectra. The method includes determining the concentration of the component of the electrolyte in the sample solution using the machine learning model.”
Tesla describes the problem with current electrolytes and how to analyze their state:
A major cause of failure in lithium-ion batteries or cells, especially in high voltage cells, is the degradation of the electrolyte, particularly at the surface of the charged electrodes. Existing solutions to address cell failure and electrolyte degradation are focused on the films of electrolyte decomposition products which build up on the surfaces of the electrodes. These films contain chemical moieties derived from both the electrolyte solvents and the electrolyte salt, such as, lithium hexafluorophosphate (LiPF 6). For example, LiPF 6 decomposes into LiF and PF 5, and the latter readily hydrolyzes to form HF and PF 3O. These two hydrolysis products are highly reactive on both the electrodes, and their unavoidable presence in LiPF 6 solutions may have a detrimental impact on the electrodes’ performance. Although mechanisms for the consumption of the electrolyte solvents and the electrolyte salt LiPF 6 in lithium-ion cells have been determined, there does not exist an inexpensive and accurate way to characterize an unknown electrolyte and thus determine the extent to which the electrolyte has degraded.
Typically, quantitative analyses of electrolyte solutions focus on expensive analytical tools, such as nuclear magnetic resonance (NMR) spectrometers, gas chromatograph-mass spectrometers (GC-MS), high-performance liquid chromatography (HPLC) instruments, and inductively coupled plasma optical emission spectrometers (ICP-OES), and require significant time to perform the analysis. Further, some analytical tools cannot even measure the concentration of electrolyte components directly. For example, the columns or detectors used in chromatography-based methods cannot be exposed to the high temperature decomposition products of LiPF 6, so these methods focus only on the organic portions of the electrolyte, after the water-soluble portions of the electrolyte have been removed.