How researchers at Tohoku University used SIMS (Secondary Ion Mass Spectrometry) in lithium battery research to measure the lithium diffusion coefficient.
More details about this study are available in a PDF report from CAMECA.
Lithium Diffusion Coefficient in Battery Development
In battery and fuel cell development, it’s useful to know the lithium diffusion coefficient in the cathode material during ion transport. This information can then be used to improve battery design, lifetime and optimise charge/discharge performance.
However, establishing the lithium diffusion coefficient can be challenging. Characterisation methods such as NMR and electrochemical techniques are indirect and fail to provide reliable results.
Researchers at Tohoku University used SIMS (Secondary Ion Mass Spectrometry) to precisely determine the coefficients and gain significant insights into lithium-ion behaviour.
Instrumentation
The team at Tohoku University used the CAMECA IMS 7f universal magnetic sector SIMS. This is the forerunner of the current IMS 7f-Auto:
CAMECA IMS 7f-Auto
- Measure challenging light and trace elements eg lithium.
- Excellent sensitivity, with low detection limits.
- Low background.
- Rugged and reliable.
- Superior depth/diffusion profiling.
- Versatile instrument.
Dr Takamichi Miyazaki, Tohoku University, said, “That design means you can achieve much lower detection limits than a time-of-flight SIMS, where you couldn’t get such optimised, stable vacuum levels. Our university has a TOF SIMS. But when they heard these new detection limits, many researchers gave up using it and came over to the CAMECA SIMS.”
The IMS 7f has a high-density primary ion beam with superior beam current stability, as well as sub-micron lateral resolution and nanometre depth resolution.
Dr Takamichi Miyazaki, Tohoku University, went on to say, “That stability is comparable to our field emission electron beam analyser. And you get excellent performance with small beam diameters, enabling high spatial resolution.”
Stable Measurements
To measure the tracer diffusion coefficient, they used a combination of depth profiling and planar point analysis. This required long-term stability and optimised primary beam focusing.
The study focused on the tracer diffusion coefficient of lithium manganese oxide (LiMn2O4) thin films. The coefficient was measured using isotope ion-exchange and SIMS line analysis.
The 6Li and 7Li isotopes in the tracer exhibited the same chemical properties, so their ionisation and detection efficiencies remained almost constant. This enabled quantitative isotope ratios to be calculated from SIMS counting rates.
In contrast to TOF-SIMS, magnetic detector SIMS consistently delivered highly reproducible data.
SIMS was used in conjunction with complementary TEM/SEM data for an additional perspective on the extremely fine-scale information.
More details about the study are available in a PDF from CAMECA.
Versatile Technique
The IMS 7f is extremely versatile. Tohoku University and researchers around the world have used it for a varied range of applications, including geology, chemistry, basic physics research, and even diverse studies such as hydrogen embrittlement in steel and radioactive materials in animal horns.
More Information
To find out more about SIMS and how it could be used in your area of work, contact us for details and demonstrations.
Blue Scientific is the official distributor for CAMECA instruments in the UK, Ireland and Finland. For more information or quotes, please get in touch.
Contact us on +44 (0)1223 422 269 or info@blue-scientific.com
