Single Particle Measurement Technique Using Tweezers-Type Probe for Insertion Materials
In single particle measurement, an optical microscope was set in a globe box filled with dry Ar gas, and a measurement cell was set on this stage. A single particle of target active material was pinched with a tweezers-type probe under microscope observation, and then its electrochemical measurement was carried out. A mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (1:1 in volume) containing 1 mol dm-3 LiPF6 was used as an electrolyte solution.
Fig. 2 shows charge-discharge curves of a Si particle measured by using a tweezers-type probe. Typical charge and discharge curves of Si with potential plateaus at around 0.2 V and 0.4 V were observed . When using a needle probe, it was difficult to maintain the contact with Si particle, resulting in poor reproducibility. In contrast, even repeating cycles, the contact between the tweezers-type probe and Si particle could be maintained by using the tweezers-type probe. This result clearly shows the advantage of tweezers-type probe on evaluation of intrinsic electrochemical properties of advanced active materials with large volume changes.
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