Activation Mechanism of LiNi_0.80Co_0.15Al_0.05O₂: Surface and Bulk Operando Electrochemical, Differential Electrochemical Mass Spectrometry, and X-ray Diffraction Analyses

Abstract

The lithium (de)-insertion mechanism from Li-Ni 0.80 Co 0.15 Al 0.05 O 2 (NCA) has been investigated by means of combined electrochemical analysis, operando differential electrochemical mass spectrometry (DEMS) experiments, and in situ X-ray diffraction (XRD) experiments during the first three cycles. Qualitative analysis of cyclic voltammetry data illustrated a possible irreversible activation of the material. Operando DEMS and internal cell pressure measurements combined with ex situ XRD and electrochemical impedance spectroscopy demonstrated that Li 2 CO 3 surface film on the NCA electrode degrades on oxidation and reforms on reduction, which has an effect on the lithium (de)-insertion reaction kinetics. In situ XRD studies clearly show mechanistic differences in the reaction pathways between the first and second cycle/following cycles. While the first charge reveals a combination of an irreversible two-phase transition plus a reversible solid solution reaction mechanism, the second charge is mainly dominated by a solid solution process. Such differences have been ascribed to changes in two factors, the electronic conductivity and the Li ion mobility of the NCA electrode.

Prospect and Reality of Ni‐Rich Cathode for Commercialization

“…In particular, the residual lithium compounds mainly affect the gas evolution because of the electrochemical decomposition and side reaction with the electrolyte during charging process. [10,14,28] As mentioned above, the chemically unstable nickel-rich surface reacts with the moisture and air, resulting in the formation of LiOH and Li 2 CO 3 by extracting the lithium ion in the host structure (Figure 1a). During the storage in the air atmosphere, the insulating passivation layer consisted of the residual lithium compounds can be continuously formed, which causes substantial increase of the charge transfer resistance.…”

“…[8][9][10][11] The Li 2 CO 3 significantly promotes the gas evolution and increase the moisture of the cathode powder, which strongly related to the safety issue. [12][13][14] Furthermore, the LiOH on the cathode increases the powder pH value, causing the gelation of the slurry during the electrode fabrication process. The nickel-rich cathode with nickel content of ≤60% have acceptable amount of residual lithium compounds for the practical use.…”

Studies of the Electrochemical Behavior of LiNi0.80Co0.15Al0.05O2Electrodes Coated with LiAlO2

“…On the other hand, charging above 4.2 V leads to a faster structural instability caused by the oxygen loss, generation of microstrains, and to degradation of the material. 16,17 Degradation also occurs during storage at elevated temperatures (60 • C) due to accelerated interfacial reactions with battery solutions. 17 One of the promising approaches to eliminate the above mentioned drawbacks of NCA and NCM materials is their coating (surface modification) with thin surface layers, like SiO 2 and Ni 3 (PO 4 ) 2 .…”

Understanding the Role of Solution Equilibrium and Precipitation Rate on Precursor Composition for Lithium-ion Battery Active Materials

“…Especially with regards to cathode materials, lithium-ion batteries do not have a single material structure or composition that dominates but have many different materials that may be suited to a particular performance or cost objective . Many current and future commercial cathode materials are multicomponent transition metal oxides including LiNiCoAlO2 [17][18][19][20][21] , LiNi1/3Mn1/3Co1/3O2 [13][14][15][16] , LiNi0.5Mn0.5O2, LiMn1.5Ni0.5O4 [22][23][24][25][26][27][28][29][30][31][32][33]35 , and (x)LiMn2O3(1-x)LiNMC. Many of these materials have been reported to have material structure and electrochemical performance that is highly sensitive to the stoichiometry of the final material.…”

“…One method that is very popular in the literature is co-precipitation of precursors followed by calcination to final active. Co-precipitation has the advantages that it is relatively easy to perform in the lab, is scalable, allows tunable and monodisperse particle morphologies 18, and provides homogeneous mixing of the multiple transition metal components throughout the secondary particles. While co-preciptation has many advantages and there are many reports in the battery literature synthesizing high performance materials using this method, one common assumption of materials produced via co-precipitation is that the particles retain the stoichiometry of the feed solution.…”