Experimental Considerations for Operando Metal‐Ion Battery Monitoring using X‐ray Techniques

Abstract

Operando experiments represent a powerful tool for the monitoring of internal processes upon battery cycling that provide valuable insights regarding the fundamental electrochemical redox mechanisms and ageing phenomena in battery materials. However, obtaining high-quality, representative and exploitable data from operando measurements requires careful control of many experimental parameters such as the cell configuration, the nature of the cell components, the electrode preparation approach, the optical/goniometer geometry, data acquisition protocols and data interpretation methodology. In this work we discuss the impact of all these factors in X-ray scattering and spectroscopic techniques based on experimental results obtained from different electrode materials using a multifunctional electrochemical in situ cell developed at our laboratory.

Crystal Structure of Na2V2(PO4)3, an Intriguing Phase Spotted in the Na3V2(PO4)3–Na1V2(PO4)3 System

“…This is probably because (i) the Na 3 V 2 (PO 4 ) 3 powder contains relatively large particles (see Figure S1) and (ii) the electrodes without a binder can induce a higher overpotential. 45 This is further confirmed by the observation of the large polarization of ∼150 mV using the in situ cell compared to a low polarization of 30 mV observed using a normal coin cell, cycled at the same C-rate of 0.11 C (Figure S5). Figure S6 shows operando SXRPD data collected during six cycles with the C- rates of 0.37−0.77−0.77−0.77−0.37−0.77 C (which are about three to seven times higher current densities than 0.11 C).…”

“…Even though the C -rates used in this study were relatively low, the battery cells already reached a nonequilibrium condition. This is probably because (i) the Na 3 V 2 (PO 4 ) 3 powder contains relatively large particles (see Figure S1) and (ii) the electrodes without a binder can induce a higher overpotential . This is further confirmed by the observation of the large polarization of ∼150 mV using the in situ cell compared to a low polarization of 30 mV observed using a normal coin cell, cycled at the same C -rate of 0.11 C (Figure S5).…”

“…Figure shows a comparison of the SXRPD patterns among the Na x V 2 (PO 4 ) 3 ( x = 1, 2, and 3) compositions. The strong background in the SXRPD patterns originates from the cell components, such as the electrolyte and the glass windows . Importantly, a careful evaluation of the SXRPD pattern of Na 2 V 2 (PO 4 ) 3 reveals the appearance of a weak Bragg peak at a very low 2θ angle (∼3.85°, d hkl = 12.29 Å).…”

“…The strong background in the SXRPD patterns originates from the cell components, such as the electrolyte and the glass windows. 45 Importantly, a careful evaluation of the SXRPD pattern of Na 2 V 2 (PO 4 ) 3 reveals the appearance of a weak Bragg peak at a very low 2θ angle (∼3.85°, d hkl = 12.29 Å). Through an operando technique, this weak Bragg peak at such a low angle (equivalent to ∼7.2°in Cu Kα radiation) may be missed with standard laboratory X-ray equipment, while we clearly observed it with a synchrotron X-ray source.…”

Synchrotron radiation based operando characterization of battery materials

“…Customized cell setups were common in the early days of operando studies and new improved designs are being continuously developed 8 considering adaptability to somewhat different concepts (e.g all solid state cells). Yet, a gradual evolution to more standardized configurations has taken place, [9][10][11] with high energy experiments allowing measurements on conventional setups (pouch, or stainless steel coin and 18650). An interesting approach to enable the use of these cells with lower beam energies is to modify them, such as laser thinning the top coin case to 50 m.…”