Multi-scale 3D investigations of a commercial 18650 Li-ion battery with correlative electron- and X-ray microscopy

Abstract

In the present study, a commercial 18650 Li-ion cylindrical cell is investigated with nondestructive 3D X-ray microscopy across a range of length scales, beginning with a survey of the entire cell and non-destructively enlarging a smaller section. Active materials are extracted from a disassembled cell and imaging performed using a combination of sub-micron X-ray microscopy and 2D scanning-electron microscopy, which point toward the need for multi-scale analysis in order to accurately characterize the cell. Furthermore, a small section is physically isolated for 3D nano-scale X-ray microscopy, which provides a measurement of porosity and enables the effective diffusivity and 3-dimensional tortuosities to be calculated via computer simulation. Finally, the 3D X-ray microscopy data is loaded into a correlative microscopy environment, where a representative sub-surface region is identified and, subsequently, analyzed using electron microscopy and energy-dispersive X-ray spectroscopy. The results of this study elucidate the microstructural characteristics and potential degradation mechanisms of a commercial NCA battery and, further, establish a technique for extracting the Bruggeman exponent for a real-world microstructure using correlative microscopy. IntroductionThere is considerable and growing research interest in Li-ion batteries driven largely by an increase in dependence on energy storage solutions, for applications ranging from mobile electronics to stationary power supplies and electric vehicles [1][2][3]. In the coming years, increasingly demanding applications from mW to MW, will require advanced Li-ion batteries to operate under extremes of temperature, rate, and pressure. Li-ion batteries are expected to deliver high performance, over long lifetimes, at a reduced cost as compared to existing solutions. With growing dependence on Li-ion technologies, in particular due to the growing popularity of hybrid-and fully-electric vehicles [2], it is of paramount importance to understand how batteries 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 perform, age, and degrade under real-world conditions [4,5]. Recent high profile failures have emphasized the need to better understand these processes [6][7][8]. *Manuscript text (with figures and captions embedded) -clean Click here to view linked ReferencesThere are a range of Li-ion battery architectures commercially available, such as pouch, prismatic, and spiral wound cells; by far the most common geometry is the 18650 cell, which has found diverse applications from consumer electronics [9] to aerospace equipment [10] and automotive power trains [11]. While the chemistry within these cells may vary, there are common components across most available commercial cells: the functional cell comprises two porous electrodes, electrically isolated by a porous separ...

Macro-to-nano scale investigation of wall-plate joints in the acorn barnacle Semibalanus balanoides: correlative imaging, biological form and function, and bioinspiration

“…This work represents the first correlative multi-modal and multi-scale study of barnacle morphological and mechanical structure across multiple dimensions. Correlative microscopy overcomes the multi-scale ‘needle in a haystack’ challenge of working in complex 3D volumes, and has proved successful for accurately locating specific regions of study in human-made materials; examples include lithium ion batteries [35] and corrosion in magnesium alloys [36]. Additionally, the technique is well established across a range of applications in the life sciences [37–40].…”

A Ceramic‐Based Separator for High‐Temperature Supercapacitors

“…Figure 2d is the relationshipb etween tensile strength and the content of PTFE in the separator. Thet ensile strengthb ecomes larger with more PTFE added to the separator and 20 wt %c ontent herew as determined as the optimal ratio of fumed SiO 2 and PTFE,b ecause more PTFE would dramatically decreaset he wettabilityb etween the electrolytea nd separator ( Figure S4, Supporting Information) and less PTFE would not only reduce the tensile strengthb ut also increase the difficulty of preparing such a separator, as encountered in our experiments.I na dditiont o the good tensiles trength, the fumed SiO 2 /PTFE separator also possesses outstanding flexibility ( Figure S5, Supporting Information), whichi se specially important for HTSC applications because the fabrication of energy storage devices usuallyi nvolves the winding of the separator, [29] which requires good flexibility.T he SiC NPs/PTFE separator shows similar physical properties in terms of thermal stability (Figure S6 a, ba nd Figure S7), tensiles trength ( Figure S6 c, d), and wettability ( Figure S4),a ll shown in the Supporting Information. Table 1c omparest he essential physical properties of the ceramic NPs/PTFE (80:20 wt %) separators and commercial PP/PE/PPs eparator.…”

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