Operando Magnetometry Probing the Charge Storage Mechanism of CoO Lithium‐Ion Batteries

Abstract

reactions), indicating the existence of undiscovered extra charge reservoirs inside the system. [6-9] To shed light on this surprising behavior, Tarascon and co-workers proposed that it is the reversible formation/dissolution of polymeric films around the reduced Co nanoparticles that leads to the unusually large capacity, [10,11] which has been widely accepted. [6,7,12] However, using in situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses, Kim et al. demonstrated that the electrolyte decomposition cannot make major contributions to the extra capacity in RuO 2 LIBs. [13] In addition, Maier and co-workers presented an interfacial charge storage mechanism between Li salts and transition-metal nanocrystals. [14-16] Just recently, we demonstrated that the surface capacitance on metal nanoparticles involving spin-polarized electrons is the dominant source of the extra capacity in Fe 3 O 4 LIBs. [17-19] Therefore, the possible contribution of polymeric/gel films to the unusual capacity in CoO deserves to be revisited and clarified in more details, which can foster innovations in modern battery technologies based on this new storage mechanism.

Recent Progress on In Situ/Operando Characterization of Rechargeable Alkali Ion Batteries

“…[18] c) Operando magnetic responses of pure nano-sized CoO (p-n-CoO) in LIBs. [19] Reproduced from ref. [11,19] with permission from Wiley-VCH.…”

“…Operando magnetic monitoring technique also confirms that cobalt nanoparticles play a catalytic role in formation of gel polymer film (Figure 5c). [19] As anode for LIBs, the discharge capacity of CoO mainly consists of three parts namely redox phase transformation reaction, surface spin polarized capacitance of Co particles, and the reversible formation/decomposition of gelatinous polymer membrane under the catalysis of cobalt metal. The latter two behaviors are the main reasons for the extra capacity.…”

“…[7] Based on the evolution of optics, electronics, thermodynamics and magnetism, various in-situ/operando techniques including X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM), Raman spectra and magnetometry have been developed (Table 1). [8][9][10][11][12][13][14][15][16][17][18][19] Among these techniques, Raman spectra is a powerful tool to characterize the short-range order (local environment) structure of lattice and electronic properties, though it is hard to achieve quantitative analysis. In-situ Raman mainly reveals the interfacial and structural changes like the formation process of SEI layer, and the electronic properties of ionic graphite intercalation compounds (GICs).…”

“…b) In-situ XRD/magnetometry of Fe 3 O 4 in LIBs [18]. c) Operando magnetic responses of pure nano-sized CoO (p-n-CoO) in LIBs [19]. Reproduced from ref [11,19].…”

Novel Lithium-Ion Capacitor Based on a NiO-rGO Composite

“…However, their power density is fairly low (less than 100 W h kg −1 ) and a poor cycle life limits their practical applications. Meanwhile, SCs can offer high power density (10 kW kg −1 ) and excellent cycle stability, but feature low energy density (5-10 W h kg kg −1 ), impeding their utility as singular energy storage devices [10][11][12]. These differences derive from the different energy storage mechanisms of these systems; LIBs store energy by inserting lithium ions into, or extracting them from, most electrodes, whereas SCs store energy through the adsorption/desorption of ions on the electrode surface [13].…”