Highly Sensitive Detection and Mapping of Incipient and Steady-State Oxygen Evolution from Operating Li-Ion Battery Cathodes via Scanning Electrochemical Microscopy

Abstract

Lattice oxygen loss during cathode charging significantly limits the charge storage capacity of lithium-ion batteries (LiBs). Therefore, elucidating the oxygen loss and subsequent surface reconstruction phenomena remains an ongoing pursuit with practical implications. We report an in situ oxygen detection strategy using scanning electrochemical microscopy (SECM) that reveals an unprecedented two-stage oxygen evolution behavior from commercial cathodes. This highly sensitive SECM method captured an unreported transient oxygen release at less than 3.3 V vs Li+/Li during the first charge cycle of LiCoO2, LiNi0.33Mn0.33Co0.33O2 and LiNi0.8Mn0.1Co0.1O2. At the main oxygen loss process above 3.3 V vs Li+/Li, SECM mapping highlighted spatial and temporal heterogeneities. Finite element simulations were used to quantify the rate of instantaneous oxygen release, with rates of ~30 pmol/cm2s for the steady-state oxygen evolution. This SECM approach revealed incipient degradation processes and created new quantitative and spatially resolved opportunities for investigating degradation in operating LiB cathodes.

Scanning Electrochemical Microscopy for Chemical Imaging and Understanding Redox Activities of Battery Materials

“…Mishra et al observed two-stage oxygen evolution behavior when commercial LIB cathode materials, transition metal oxide cathodes (TMOC), were studied using SECM. Additionally, a heterogeneity of oxygen evolution from different cathode locations was observed in the study with SECM mapping, which is consistent with the morphological heterogeneity of TMOC . Although SECM has shown great potential for the in situ surface chemical investigation of LIB cathode materials, most studies have used SECM microelectrodes for chemical investigation and surface mapping.…”

“…In situ analytical methods provide several advantages in operando or ex situ since they allow probing of the environment in the actual electrolyte under applied potential bias. One such method is scanning electrochemical microscopy (SECM), which is a scanning probe technique that leverages an ultramicroelectrode (UME) that receives electrochemical feedback from the surface (discussed in more detail below) and has been used in several applications to investigate the charging/discharging mechanism of battery anodes . Other analytical techniques including Raman spectroscopy have been proven to be an invaluable tool to investigate the solvation of Li ions at the SEI layer, structural ordering around the SEI layer, and Li metal intercalation mechanism .…”

A Surface Modification Strategy Towards Reversible Na-ion Intercalation on Graphitic Carbon Using Fluorinated Few-Layer Graphene

“…Na + uptake and release from the substrate was tracked through stripping at the HgSC tip via SECM redox competition mode. [54][55][56] A recently developed chronoamperometric pulsing protocol 56,57 was applied at the tip to track Na + fluxes while preventing Hg oversaturation. 56 An ideal amalgamation/stripping response of Na + with HgSCs is shown in Fig.…”

Basics of the scanning electrochemical microscope and its application in the characterization of lithium-ion batteries: a brief review

“…In addition to the investigation of metal dissolution from the electrode, SECM has also been used to characterize the oxygen loss behavior of transition metal oxide cathodes by Mishra et al recently. 98 SECM measurements indicated two oxygen evolution behaviors of LCO, LiNi 0.33 Mn 0.33 Co 0.33 O 2 (NMC111) and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811), where a transient oxygen loss occurred at 2.9–3.4 V ( vs. Li/Li + ), while a continuous oxygen release at a more positive potential (>3.6 V vs. Li/Li + ). They also obtained SECM mapping of average currents plotted as a function of potential and UME tip position and observed that oxygen evolution behavior varied in different locations (Fig.…”