NMR studies of mass transport in Li-ion battery electrolyte solutions
EMSL Project ID
49102
Abstract
Electrification of vehicles is a critical component of DOE's efforts to reduce the dependence on foreign oil and greenhouse gas emissions. Improvements and cost reductions in lithium-ion battery technology will encourage the widespread adoption of electric and hybrid-electric vehicles. Despite of tremendous progress made, the highest power that lithium-ion batteries can deliver is still inadequate to meet the DOE targets for plug-in electric vehicles. One of the main limitations arises from the limited mobility of ions in the electrolyte.We propose to utilize solution nuclear magnetic resonance (NMR), combined with concentrated solution theory, to study the cation (Li+), anion (PF6-) and solvent transport in the non-aqueous electrolytes of lithium-ion batteries. This study will not only develop a new methodology that allows accurate characterization of mass transport in the electrolyte, but also generate transport properties with their dependence on a wide span of concentration. In addition, the obtained transport properties allow to explore the electrolyte behavior at high concentrations. The proposed study will provide fundamental insights into the transport capability of the electrolyte and therefore directly advances DOE’s mission on vehicle electrification. This study is also relevant to EMSL as it supports BER's mission to provide innovative solutions to the nation's environmental and energy production challenges by reducing greenhouse gas emissions and providing guidance for developing new energy materials.
Accurate values of transport properties have not been well-established. Reported values for diffusion coefficients in electrolyte solution vary by orders of magnitude, as side reactions and convection make accurate measurement extremely challenging, and physically-unreasonable negative transference numbers have been frequently measured.
With the aid of concentrated solution theory, we have developed a new approach to translate the self-diffusion coefficient measured by NMR to Fickian diffusivity. This approach does not require dilution solution assumption. In addition, the convection artifacts can be suppressed by using compensate pulse sequence in NMR. Consequently, more accurate and reliable properties are expected. With these advantages, this methodology has the potential to become one of the most preferred methods for transport properties measurement.
The NMR capabilities and expertise at EMSL are critical for this proposal. EMSL has 600 MHz NMR spectrometer equipped with Doty PFG probe, offering the maximum gradient strength of 31T/m and permits to measure diffusivities down to 10-15m2/s, which allows us to measure self-diffusion coefficient at highly concentrated solution even at low temperatures. We believe this methodology is a good candidate to be realized by NMR facilities at EMSL.
Project Details
Project type
Exploratory Research
Start Date
2015-10-15
End Date
2016-09-30
Status
Closed
Released Data Link
Team
Principal Investigator