Interface Interaction Behavior of Self-Terminated Oligomer Electrode Additives for a Ni-Rich Layer Cathode in Lithium-Ion Batteries: Voltage and Temperature Effects

Abstract

Self-terminated oligomer additives synthesized from bismaleimide and barbituric acid derivatives improve the safety and performance of lithium-ion batteries (LIBs). This study investigates the interface interaction of these additives and the cathode material. Two additives were synthesized by Michael addition (additive A) and aza-Michael addition (additive B). The electrochemical performances of bare and modified LiNi0.6Mn0.2Co0.2O2 (NMC622) materials are studied. The cycling stability and rate capability of NMC622 considerably improve on surface modification with additive B. According to the differential scanning calorimetry results, the exothermic heat of fully deliathiated NMC622 is dramatically decreased through surface modification with both additives. The electrode surface kinetics and interface interaction phenomena of the additives are determined through surface plasma resonance measurements in operando gas chromatography–mass spectroscopy (GCMS) and in situ soft X-ray absorption spectroscopy (XAS). The binding rate constant of additive B onto NMC622 particles is 1.2–2.3 × 104 M–1 s–1 in the temperature range of 299–311 K, which is ascribed to the strong binding affinity toward the electrode surface. This affinity enhances Li+ diffusion, which allows the electrode modified by additive B to provide high electrochemical performance with superior thermal stability. In operando GCMS reveals that gas evolution due to the electrolyte degradation at the NMC622 surface contributes to safety hazards in the bare NMC622 material. In situ soft XAS indicates the occurrence of structural transformation in the bare NMC622 material after it is fully charged and at elevated temperatures. The NMC622 material is stabilized by incorporating additives. The unique performance of additive B can be attributed to its linear structure that allows superior electrode surface adhesion compared with that of additive A. Therefore, this study presents an optimized working principle of self-terminated oligomers, which can be developed and applied to improve the safety and performance of LIBs.

In Situ Co–O Bond Reinforcement of the Artificial Cathode Electrolyte Interphase in Highly Delithiated LiCoO2 for High-Energy-Density Applications

“…R-Si-O-LiCoO 2 was produced through in situ Co–O bond reinforcement on the surface of LiCoO 2 when LiCoO 2 was in a highly delithiated state. Several studies have indicated that branched oligomers have high potential for absorbing heat during thermal runaway. − Thus, in the present study, the amino groups in APTES were made to react with a branched oligomer through the aza-Michael addition reaction to produce an artificial cathode electrolyte interphase (ACEI).…”

Bifunctional Surface Coating of LiAlO2/Si1–xAlxO2 Hybrid Layer on Ni-Rich Cathode Materials for High Performance Lithium-Ion Batteries

“…We observed two binding energy peaks at 72.8 and 73.7 eV in the Al 2p spectrum of NCM@LSAO, which corresponded to Al–O in the LiAlO 2 and Si 1– x Al x O 2 (Figure b). Therefore, the above results indicated that a LiAlO 2 /Si 1– x Al x O 2 hybrid coating layer is formed on the NCM particle surface. − To obtain the weight of LiAlO 2 and Si 1– x Al x O 2 , the Al and Si content of NCM@LSAO was determined by ICP-OES analysis, and the results are listed in Table S2. As seen in Table S2, the Al and Si content in the NCM@LSAO was 0.29% and 0.88%, respectively.…”

The Study of Photocatalytic Degradation Kinetics and Mechanism of Malachite Green Dye on Ni–TiO2 Surface Modified with Polyaniline

“…Furthermore, the conjugated polymers (CPs) are receiving great attention in modifying photocatalyst because of their plausible applications environmental remediation [23,24]. CPs also have shown remarkable advantages in renewable energy devices [25,26] due to their unique behavior [27].…”