Absolute Local Quantification of Li as Function of State-of-Charge in All-Solid-State Li Batteries via 2D MeV Ion-Beam Analysis

Abstract

Direct observation of the lithiation and de-lithiation in lithium batteries on the component and microstructural scale is still difficult. This work presents recent advances in MeV ion-beam analysis, enabling quantitative contact-free analysis of the spatially-resolved lithium content and state-of-charge (SoC) in all-solid-state lithium batteries via 3 MeV proton-based characteristic x-ray and gamma-ray emission analysis. The analysis is demonstrated on cross-sections of ceramic and polymer all-solid-state cells with LLZO and MEEP/LIBOB solid electrolytes. Different SoC are measured ex-situ and one polymer-based operando cell is charged at 333 K during analysis. The data unambiguously show the migration of lithium upon charging. Quantitative lithium concentrations are obtained by taking the physical and material aspects of the mixed cathodes into account. This quantitative lithium determination as a function of SoC gives insight into irreversible degradation phenomena of all-solid-state batteries during the first cycles and locations of immobile lithium. The determined SoC matches the electrochemical characterization within uncertainties. The presented analysis method thus opens up a completely new access to the state-of-charge of battery cells not depending on electrochemical measurements. Automated beam scanning and data-analysis algorithms enable a 2D quantitative Li and SoC mapping on the µm-scale, not accessible with other methods.

Quantitative Lithiation Depth Profiling in Silicon Containing Anodes Investigated by Ion Beam Analysis

“…The study used MeV ion-beam analysis (IBA) for investigating the lithiation depth and lateral profiles of a SiOx-containing graphite active material lithiated in a coin cell. The problems observed in mixed cathode and electrolyte analysis of significant immobile lithium, which deteriorates the accuracy for the mobile lithium fraction [40], are not relevant for the analysis of anodes/anode materials presented here. The low immobile Li background of 0.2% is negligible for the overall signal beyond a few 1% SoC.…”

“…In the literature, IBA of cathodes [36,37], electrolytes [38], and full cell assemblies with µm-resolution of its components ex-situ and operando was proven quite recently by a few groups [39][40][41]. This work first goes a step back and investigates the fundamental possibilities of several IBA methods and parameters suitable for conducting such an analysis.…”

In‐Operando Lithium‐Ion Transport Tracking in an All‐Solid‐State Battery

“…Against that background, ion beam analysis [4][5][6][7][8][9][10][11] and 6 Li(n,α) 3 H thermal neutron-induced nuclear reactions [12][13][14][15][16][17] have been used to quantitatively track the transport of lithium ions in all-solid-state battery-related materials to date. However, due to fundamental limitations of these approaches, both methods have only succeeded in analyzing the depth distribution of lithium ions in the battery in specific charged and discharged states, [4][5][6][7][8][9][10][11][12][13][14]17] or in tracking their transport with very poor statistics.…”

“…Against that background, ion beam analysis [4][5][6][7][8][9][10][11] and 6 Li(n,α) 3 H thermal neutron-induced nuclear reactions [12][13][14][15][16][17] have been used to quantitatively track the transport of lithium ions in all-solid-state battery-related materials to date. However, due to fundamental limitations of these approaches, both methods have only succeeded in analyzing the depth distribution of lithium ions in the battery in specific charged and discharged states, [4][5][6][7][8][9][10][11][12][13][14]17] or in tracking their transport with very poor statistics. [15,16] Ion beam analysis utilizing, for example, the 7 Li(p,α) 4 He nuclear reaction and elastic recoil detection, is hampered by a small reaction cross-section [18,19] and large irradiation damage, [11] while using a neutron-induced nuclear reaction faces the obstacles of a low natural abundance of lithium-6 and the small number of high-intensity thermal neutron facilities.…”

“…However, due to fundamental limitations of these approaches, both methods have only succeeded in analyzing the depth distribution of lithium ions in the battery in specific charged and discharged states, [4][5][6][7][8][9][10][11][12][13][14]17] or in tracking their transport with very poor statistics. [15,16] Ion beam analysis utilizing, for example, the 7 Li(p,α) 4 He nuclear reaction and elastic recoil detection, is hampered by a small reaction cross-section [18,19] and large irradiation damage, [11] while using a neutron-induced nuclear reaction faces the obstacles of a low natural abundance of lithium-6 and the small number of high-intensity thermal neutron facilities. [20,21] Nevertheless, the use of thermal neutrons has the significant advantage that irradiation damage caused by the incident neutron beam is almost negligible allowing an all-solid-state device to be analyzed over extended periods, for example, 1 month, while still functioning as a battery.…”