Performance and Stability Improvement of Layered NCM Lithium-Ion Batteries at High Voltage by a Microporous Al₂O₃ Sol–Gel Coating

Abstract

A simple and low-cost polymer-aided sol–gel method was developed to prepare γ-Al 2 O 3 protective layers for LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) cathode materials. The selected polyvinyl alcohol polymer additive not only facilitates the formation of a uniform and thin γ-Al 2 O 3 layer on the irregular and rough cathode particle surface to protect it from corrosion but also serves as a pore-forming agent to generate micropores in the film after sintering to allow fast transport of lithium ions, which guaranteed the excellent and stable battery performance at high working voltage. Detailed studies in the full battery mode showed that the leached corrosion species from the cathode had a more profound harmful effect to the graphite anode, which seemed to be the dominating factor that caused the battery performance decay.

Exploiting the Degradation Mechanism of NCM523Graphite Lithium‐Ion Full Cells Operated at High Voltage

“…For example, Wu et al. did not observe an early rollover failure within 100 cycles for NCM622 graphite full cells (2.75–4.5 V; 0.5 C charge‐discharge rate; 20 °C) [87] . A major difference compared to our study was that their used reference electrolyte system already included 2 wt % vinylene carbonate (VC) in LP57 [87] .…”

“…did not observe an early rollover failure within 100 cycles for NCM622 graphite full cells (2.75–4.5 V; 0.5 C charge‐discharge rate; 20 °C) [87] . A major difference compared to our study was that their used reference electrolyte system already included 2 wt % vinylene carbonate (VC) in LP57 [87] . In order to verify the beneficial impact of VC in our system, we also evaluated NCM523 graphite full cells (Figure S16) and could observe that the severe rollover failure is prevented by adding 2 wt % VC, while detecting a comparable capacity retention as found by Wu et al [87] .…”

Metal‐Ion Coupled Electron Transfer Kinetics in Intercalation‐Based Transition Metal Oxides

“…Apart from the SEI/CEI layers, which arise due to the reduction/oxidation of the electrolyte components at the surfaces of electrode material particles, artificial surface layers (protective coatings, which prevent the reactions of high‐voltage cathode materials with the electrolyte [ 73,74 ] and carbon coatings, which are produced to maximize the electronic conductivity of composite electrodes [ 75 ] ) can also modify the kinetics of surface charge transfer processes. This modification is especially pronounced in the case of high‐voltage cathode materials, where the increase in the cathode impedance is demonstrated to be inhibited due to the less reactive nature of the coated surfaces.…”

“…This modification is especially pronounced in the case of high‐voltage cathode materials, where the increase in the cathode impedance is demonstrated to be inhibited due to the less reactive nature of the coated surfaces. [ 73,76 ] As for the carbon‐coated materials, much more subtle effects of the carbon coating on the intercalation pathways were recently reported, such as the decrease in the phase‐separation and new phase nucleation rates in LiFePO 4 materials. [ 77,78 ] Still, the degree of certainty in the conclusions regarding the effects of the artificial surface coatings on the intercalation kinetics is frequently compromised by the nonuniformity of the coatings and the cracking/morphology changes in the coating during continuous cycling, which are to be explored further.…”

Research Progress on the Surface of High-Nickel Nickel–Cobalt–Manganese Ternary Cathode Materials: A Mini Review

“…Sol-gel, hydrothermal, and spray drying methods, as well as other preparation methods, are also available. Sol-gel method is used to prepare γ-Al 2 O 3 -coated NCM622 (Wu et al, 2019 ) and tungsten oxide-coated NCM-811 (Becker et al, 2019 ). LiNi 0.7 Co 0.15 Mn 0.15 O 2 is prepared by hydrothermal method (Tian et al, 2015 ).…”