In this study, we synthesized a Li-containing "BTJ-L" hybrid oligomerobtained through polymerization of bismaleimide (BMI) with a polyether monoamine (i.e., Jeffamine-M1000, JA), trithiocyanuric acid (TCA), and LiOHand coated it as an additive in various amounts (0.5−2 wt %) onto the surface of a Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode active material, forming BTJ-L@NCM811 electrodes for lithiumion batteries (LIBs). Relative to CR2032 coin-type cells incorporating a pristine NCM811 electrode, the cells with the 1 wt % BTJ-L@NCM811 electrode demonstrated a slightly higher initial discharge capacity (173 mAh g −1 vs171 mAh g −1 ) and higher values of average Coulombic efficiency, CE avg (99.5% vs98.9%) and capacity retention, CR (86.1% vs72.9%) after 100 cycles at 1C. Electrochemical impedance spectroscopy revealed that the decrease in the charge transfer resistance (R ct : 46.7 Ω vs171.1 Ω) and the superior Li + ion diffusivity (D Li + : ∼1.09 × 10 −12 cm 2 s −1 vs ∼1.61 × 10 −13 cm 2 s −1 ) of the cells incorporating the BTJ-L@NCM811 electrode after cycling at 1C could be attributed to the excellent wettability toward the electrolyte and the extra Li + ions contributed by the hybrid BTJ-L oligomer additive. Therefore, the BTJ-L oligomer coating layer functioned much like an artificial cathode electrolyte interphase (CEI) layer, impairing the dissolution of transition metals (TMs) from the cathode materials into the carbonate-based electrolytes. Furthermore, in situ microcalorimetry manifested that the total exothermic heat generation (Q t ) of the coin cells containing the 1 wt % BTJ-L@NCM811 electrode operating at 1C in isothermal modes (35 and 55 °C) during the charging process was dramatically lower (by ca. 45%) relative to that of the cells incorporating the pristine NCM811 electrode. On the basis of an ARC-HWS analysis, the delithiated pristine NCM811 electrode shows thermal reactivity with the electrolyte at a much earlier stage in comparison to the 1 wt % BTJ-L@NCM811 counterpart (843 min vs 1039 min) between 171 and 192 °C. Thus, Ni-rich NCM811 cathode materials coated with trace amounts (i.e., 1 wt %) of the BTJ211-L1 hybrid oligomer additives displayed both enhanced electrochemical performance and remarkably improved thermal stability. Accordingly, this Li-containing BTJ-L hybrid oligomer appears to be a great candidate material for coating high-Ni oxide cathode materials to enhance the safety and electrochemical performance of LIB cells.

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Quaternary Ni-rich layered cathodes are one of the most intriguing yet challenging next-generation cathode materials, and their high Ni content has made it difficult to obtain long-term cyclability. In this paper, we report the improved electrochemical performance of high-power long-life Ni-rich layered cathode materials (LiNi 0.90 Co 0.04 Mn 0.03 Al 0.03 O 2 , denoted NCMA), synthesized in a Couette−Taylor reactor, after depositing a homogeneous surface coating of Li 2 ZrO 3 (LZO). Morphological analyses revealed that the thickness of the LZO coating was approximately 2.5 nm and spread uniformly on the NCMA surface. X-ray photoelectron spectroscopy indicated that the content of Li residues on the surface had greatly decreased after coating with LZO. The electrochemical performance of the coated samples was greater than that of the bare NCMA; in particular, the 1 wt % LZOcoated cathode material had a capacity retention of 90.2% after 100 cycles at 1C (vs 74.6% for the bare NCMA). Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and the galvanostatic intermittent titration technique (GITT) indicated that the coating agent acted as a bridge that lowered the activation energy and polarization potential for a better Li + ion transport. The polarization potential also decreased significantly after coating with LZO, leading to improved electrochemical kinetics. Postmortem studies after long cycling confirmed that the LZO coating layer enhanced the structural stability of the cathode.

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