7 Application of Mössbauer Spectroscopy to Li-Ion and Na-Ion …
341
Fig. 7.6 a Modified 2325-type coin cell and b experimental set up for in situ Mössbauer measurements. a Reprinted with permission from Ref. [27]. Copyright 1999 American Physical Society.
b Image courtesy Mössbauer Effect Data Centre, Dalian Institute of Chemical Physics, Chinese
Academy of Sciences [64]
Ariyoshi et al. proposed an aluminum-laminated polyethylene bag containing Li
metal with stainless steel sheet as current collector placed outside the γ-ray beam
and working electrode on aluminum foil [66]. A pouch cell was also used by Ionica
et al. consisting of an airtight aluminized plastic bag with electrodes made according
to the Bellcore technology [67].
Chamas et al. used a modified Swagelok tube union with PMMA windows transparent to γ-rays, called Cell 1 in this chapter, and less fragile than Be windows
to maintain the cohesion of the internal cell configuration [68]. The electrodes are
lithium foil and powdered active material spread on a Be window for electronic
conduction. They are both in electrical contact with hollow steel tubes as cell terminals (Fig. 7.7a). Such a cell is interesting for the characterization of powdered alloying
or conversion materials that suffer from large volume variations. Another type of
Swagelok cell, called Cell 2 in this chapter, as first proposed for in situ XRD measurements in reflection mode [69], was modified for γ-ray transmission (Fig. 7.7b). A
similar cell but with a large Be window in contact with the active material was used in
both reflection and transmission geometries, making combined XRD and Mössbauer
measurements possible [70].
A potentiostat-galvanostat system is used to apply and control the voltage or
current to the in situ electrochemical half-cell. Most of the operando Mössbauer
experiments are carried out in galvanostatic regime, i.e. by imposing a constant
current, in order to insert a constant number of Li
+ or Na
+ ions per time unit in
the working electrode. The acquisition time of an operando Mössbauer spectrum
should be rather short to have a snapshot of the electrochemical reaction but should
also be rather long for a good signal-to-noise ratio. The acquisition time depends on
the current injected to the cell that should be as low as possible to approach thermodynamic equilibrium conditions. However, a too low current leads to long-term
experiments, typically more than several weeks per electrochemical cycle, which
341
Fig. 7.6 a Modified 2325-type coin cell and b experimental set up for in situ Mössbauer measurements. a Reprinted with permission from Ref. [27]. Copyright 1999 American Physical Society.
b Image courtesy Mössbauer Effect Data Centre, Dalian Institute of Chemical Physics, Chinese
Academy of Sciences [64]
Ariyoshi et al. proposed an aluminum-laminated polyethylene bag containing Li
metal with stainless steel sheet as current collector placed outside the γ-ray beam
and working electrode on aluminum foil [66]. A pouch cell was also used by Ionica
et al. consisting of an airtight aluminized plastic bag with electrodes made according
to the Bellcore technology [67].
Chamas et al. used a modified Swagelok tube union with PMMA windows transparent to γ-rays, called Cell 1 in this chapter, and less fragile than Be windows
to maintain the cohesion of the internal cell configuration [68]. The electrodes are
lithium foil and powdered active material spread on a Be window for electronic
conduction. They are both in electrical contact with hollow steel tubes as cell terminals (Fig. 7.7a). Such a cell is interesting for the characterization of powdered alloying
or conversion materials that suffer from large volume variations. Another type of
Swagelok cell, called Cell 2 in this chapter, as first proposed for in situ XRD measurements in reflection mode [69], was modified for γ-ray transmission (Fig. 7.7b). A
similar cell but with a large Be window in contact with the active material was used in
both reflection and transmission geometries, making combined XRD and Mössbauer
measurements possible [70].
A potentiostat-galvanostat system is used to apply and control the voltage or
current to the in situ electrochemical half-cell. Most of the operando Mössbauer
experiments are carried out in galvanostatic regime, i.e. by imposing a constant
current, in order to insert a constant number of Li
+ or Na
+ ions per time unit in
the working electrode. The acquisition time of an operando Mössbauer spectrum
should be rather short to have a snapshot of the electrochemical reaction but should
also be rather long for a good signal-to-noise ratio. The acquisition time depends on
the current injected to the cell that should be as low as possible to approach thermodynamic equilibrium conditions. However, a too low current leads to long-term
experiments, typically more than several weeks per electrochemical cycle, which