Mesoscopic Li Distribution Analysis on an All Solid Battery

All solid batteries (ASB) are one of the most promising candidates for post Li-ion battery, especially for large scale applications such as electric vehicle, plug-in hybrid vehicle and stationary use. The most characteristic feature of ASB is that organic solvent in a Li-ion battery is replaced by inorganic solid electrolyte. It is generally expected wider operation temperature and higher thermal stability than conventional liquid Li-ion battery derived from nature of solid electrolyte.

On the other hand, there are several obstacles for the practical application of ASB. One of the major drawbacks is the poor power density of the ABS. We sometimes face to large “interfacial resistance” of electrodes in the ASB. The origin of interfacial resistance is cracks and/or resistive layer between active material and solid electrolyte. To figure out a quantitative view of the poor power density, it is useful to observe Li ion distribution in an electrode especially under working condition, i. e. in-situ observation of Li distribution in an ASB.
Recently, it was reported that the ion beam analysis is applicable to observe Li atom distributions in an electrode of Li-ion battery ^[1]. The principle of this method is to analyze Li and/or other elements by detecting γ-ray, X-ray or charged particles. When a high energy proton beam is irradiated on an electrode, characteristic X-rays are emitted from transition metal elements through ionization interaction, and , γ-ray or α-particles from ⁷Li through nuclear reaction  of ⁷Li(p, p’γ)⁷Li or ⁷Li(p, α)⁴He, respectively. At the Takasaki Institute of Japan Atomic Energy Agency, high energy proton micro-beam was irradiated on samples. The minimum diameter of the beam was focused down to about 1 μm. This means that 2D elemental images of a sample including Li can be obtained with μm resolution. We’ve tried to apply this new analysis technique to an ASB. The result will be shown in the conference and the possibility of in-situ observation will be discussed.

Acknowledgement:
This work was supported by funding received from the CONCERT-Japan Joint Call on Efficient Energy Storage and Distribution, and by the Japan Science and Technology Agency, the Spanish Ministry of Economy and Competitiveness, the German Federal Ministry of Education and Research and the German State of North Rhine-Westphalia.

Reference:
[1] K.Mima, et al.," Distribution characterization in Li-ion batteries positive electrodes containing LixNi0.8Co0.15Al0.05O2 secondary particles", Nucl. Instr. Meth. B, 290 (2012) 79-84