Editors’ Choice—4D Neutron and X-ray Tomography Studies of High Energy Density Primary Batteries: Part II. Multi-Modal Microscopy of LiSOCl2 Cells

Ralf F Ziesche,Paul R Shearing,Lukas Helfen,Alessandro Tengattini,Nikolay Kardjilov,Winfried Kockelmann,Dan J L Brett,Nicolas Lenoir,James B Robinson,Ingo Manke,Henning Markötter,Robert Bradbury

doi:10.1149/1945-7111/abbfd9

Abstract

The ability to track electrode degradation, both spatially and temporally, is fundamental to understand performance loss during operation of lithium batteries. X-ray computed tomography can be used to follow structural and morphological changes in electrodes; however, the direct detection of electrochemical processes related to metallic lithium is difficult due to the low sensitivity to the element. In this work, 4-dimensional neutron computed tomography, which shows high contrast for lithium, is used to directly quantify the lithium diffusion process in spirally wound Li/SOCl2 primary cells. The neutron dataset enables the quantification of the lithium transport from the anode and the accumulation inside the SOCl2 cathode to be locally resolved. Complementarity between the collected neutron and X-ray computed tomographies is shown and by applying both methods in concert we have observed lithium diffusion blocking by the LiCl protection layer and identified all cell components which are difficult to distinguish using one of the methods alone.

Highlights

Editors’ Choice—4D Neutron and X-ray Tomography Studies of High Energy Density Primary Batteries: Part II
The increase of the internal resistance can be traced back to diffusional limitations of the Li-ions by e.g. lithium diffusion blocking by remnants of the lithium chloride (LiCl) protection layer or gas evolution in the SOCl2 electrode
This delay is caused by the protective LiCl layer, which is formed on the lithium metal surface during storage and increases the internal cell resistance, reducing the initial cell potential

Summary

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Editors’ Choice—4D Neutron and X-ray Tomography Studies of High Energy Density Primary Batteries: Part II. At the end of the discharging process, the amount of SOCl2 in cells is not sufficient to dissolve all of the SO2 gas which forms during the reaction, resulting in a pressure build up which requires hermetic sealing of the cell to avoid a release of the toxic gas.[21] Taking these issues into consideration when designing and optimising the cell geometry can go some way to improving cell performance and lifetime. The combination of X-ray and neutron CT provides complementary imaging contrast, and facilitates the identification of mechanical degradation, tracking of the Li diffusion and the evaluation of the rate of electrolyte consumption as previously reported by the authors.[44] Extending our previous study, here for the first time, operando neutron CT is utilised to study the electrochemical changes inside two spirally wound ER14505M Li/SOCl2 battery cells under two different discharge conditions. X-Act, the beamline software, was used alongside the FBP algorithm to reconstruct images with an effective pixel size of 19.8 μm.[42]

Results and Discussion

Anode Cathode Anode Cathode

Conclusions