What insertion species is electrochemically intercalated into the LiNiO2 electrode in aqueous solutions?

Stabilizing the Nanosurface of LiNiO2 Electrodes by Varying the Electrolyte Concentration: Correlation with Initial Electrochemical Behaviors for Use in Aqueous Li-Ion Batteries

“…As is well known, the intercalation potential is proportional to the concentration of the intercalation species, demonstrated by the Nernst equation. 30,32 When the activity of cations increases by 10-fold in the electrolyte, the redox potential increases by 59.1 mV. Considering the activity of species as the concentration simply, the variation of intercalation potentials by the increase of the concentration of Li + ions in this system can be calculated by the Nernst equation, theoretically, as follows: ∼27.3 mV from 55:1 to 11:1 electrolyte and ∼33.7 mV from 55:1 to 6:1 electrolyte.…”

“…The detailed synthetic process and characterization of LNO powder were described in our previous reports. 32,33 LNO electrodes were prepared using the same way previously reported. 33 2.2.…”

“…It is well known that LNO can form some impurities including Li 2 CO 3 on the surface by combining with H 2 O and CO 2 even under air, which can be produced during material synthesis and preparation as well as during electrochemical cycles in aqueous solutions. 32,33 Actually, the peak corresponding to Li 2 CO 3 was observed in the XPS spectra of C 1s at an Ar-etching time of 0 s for all electrodes (Figure S6). Therefore, the fact that none of the peaks of Ni 2p appeared at an Ar-etching time of 0 s in XPS spectra of all electrodes may result from the presence of inorganic impurities, including Li 2 CO 3 , very thinly covering the surface.…”

“…In particular, we attempted to stabilize the nanosurface by varying the electrolyte concentration, which was expected to be closely related to the interface condition between the LNO surface/lithium bis­(trifluoromethanesulfonyl)­imide (LiTFSI)-based aqueous electrolytes in EDL. LNO has been reported as a promising electrode material for high energy density in ALIBs, because it has some advantages such as high theoretical capacities and low cost, in our previous studies. , To observe the nanosurface morphology of LNO, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) measurements were used after initial electrochemical cycles. In addition, various electrochemical and structural analyses including the galvanostatic intermittent titration technique (GITT) and in situ X-ray diffraction (XRD) were performed, and the results supported the notion that stabilization of the nanosurface of LNO through variation of the electrolyte concentration can have a positive influence on the initial electrochemical behaviors of this system.…”

“…The detailed methods of the calculation were described in our previous reports. 32 The calculated lattice parameters of LNO are shown in Figure 5, demonstrating that the volume of LNO was more seriously contracted with an increase in the electrolyte concentration during the deintercalation of Li + ions. This implies that more Li + ions were de-intercalated from a more stable LNO surface in the concentrated electrolyte.…”