Effect of Lithium Borate Additives on Cathode Film Formation in LiNi_0.5Mn_1.5O₄/Li Cells

Abstract

A direct comparison of the cathode-electrolyte interface (CEI) generated on high-voltage LiNiMnO cathodes with three different lithium borate electrolyte additives, lithium bis(oxalato)borate (LiBOB), lithium 4-pyridyl trimethyl borate (LPTB), and lithium catechol dimethyl borate (LiCDMB), has been conducted. The lithium borate electrolyte additives have been previously reported to improve the capacity retention and efficiency of graphite/LiNiMnO cells due to the formation of passivating CEI. Linear sweep voltammetry (LSV) suggests that incorporation of the lithium borates into 1.2 M LiPF in EC/EMC (3/7) electrolyte results in borate oxidation on the cathode surface at high potential. The reaction of the borates on the cathode surface leads to an increase in impedance as determined by electrochemical impedance spectroscopy (EIS), consistent with the formation of a cathode surface film. Ex-situ surface analysis of the electrode via a combination of SEM, TEM, IR-ATR, XPS, and high energy XPS (HAXPES) suggests that oxidation of all borate additives results in deposition of a passivation layer on the surface of LiNiMnO which inhibits transition metal ion dissolution from the cathode. The passivation layer thickness increases as a function of additive structure LiCDMB > LPTB > LiBOB. The results suggest that the CEI thickness can be controlled by the structure and reactivity of the electrolyte additive.

Er-Doped LiNi0.5Mn1.5O4 Cathode Material with Enhanced Cycling Stability for Lithium-Ion Batteries

“…The characteristic diffraction peaks of the Er-doped LiNi 0.5 Mn 1.5 O 4 sample are indexed to LiNi 0.5 Mn 1.5 O 4 (JCPDS No. 80-2162) [23]. This indicates that the substitution of Er 3+ ions for partial nickel and manganese ions has very little effect on the intrinsic structure [24,25,26,27].…”

Role of binders in solid electrolyte interphase formation in lithium ion batteries studied with hard X-ray photoelectron spectroscopy

“…19 Samples were transported under Ar at atmospheric pressure in a sealed vessel and installed in the X-24A endstation while a positive pressure of Ar was flown outward through the installation glovebag. The facility and our experimental procedures, including calculation of atomic concentrations 20 and estimates of the SEI thickness, 21 are described elsewhere. Thickness estimates used Si concentrations restricted to include only the area of the elemental Si contribution to the spectra, as obtained through fits to the experimental data using Voigt shapes.…”

Regulation of Cathode‐Electrolyte Interphase via Electrolyte Additives in Lithium Ion Batteries

“…Also, significant advances have been made in other anode materials, for example, alloy-type [12,13] and Li metal anode materials [14,15] . The widely studied cathode materials for LIBs mainly include: layered lithium transition metal oxides, such as LiRO 2 (LRO, R = transition metal), [16] LiNi x Co y Mn (1-x-y) O 2 (NCM) [17,18] , [19] Li-Ni 0.8 Co 0.15 Al 0.05 (NCA), [20] spinel structural compounds, typical representatives are LiMn 2 O 4 (LMO) [21,22] , LiNi 0.5 Mn 1.5 O 4 (LNMO) [23,24] , polyanion structural compounds, the most repre- sentative is LiFePO 4 (LFP) [10,25,26] . As the "blood" of the battery, the electrolyte is an indispensable solvent for the transport and dissolution of Li + ions.…”