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Graphene films are accepted as excellent heat dissipation materials due to their ultrahigh thermal conductivity. In general, the graphene film uses graphene oxide (GO) as the raw material through self-assembly, carbonization, and graphitization processes. However, the production and accumulation of a large amount of gas during the carbonization can produce high gas pressure, which causes damage to the ordered stacking structure and seriously affects the thermal conductivity of the graphene film. In this work, we propose a strategy of diamine reagents to crosslink and reduce GO for constraining volume expansion during carbonization. The amine group undergoes nucleophilic substitution and condensation reactions with oxygen-containing functional groups (−COOH, – C–O–C) to form – C–N bonds, which broaden the temperature range of gas production by changing the chemical structure. Compared to dimethylaminopropylamine and N-isopropylethylenediamine, ethylenediamine with symmetrical primary amines can react sufficiently with GO to form a robust structure. Based on these observations, the ethylenediamine-modified film shows a lower expansion rate (115.2%) and higher in-plane thermal conductivity (∼1180 W m–1 K–1) than the pure graphene film (152.6% and ∼980 W m–1 K–1, respectively). This work could be significant in the preparation of graphene films with high thermal conductivity. [ABSTRACT FROM AUTHOR]

Activated carbons (AC) play a key role in enabling the reaction kinetic of cathodes in lithium ion batteries (LIBs). However, the charge transfer dynamics and reaction kinetics mechanism of AC composited cathodes along their thickness direction are still poorly understood. Herein, we systematically compare the internal reactive process evolutions of AC modified LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) cathodes and pristine NCM622 cathodes at high C-rates. The charge transfer dynamic is revealed by the time of flight secondary ion mass spectrometry and X-ray photoelectron spectra analyzes. The addition of AC endows the NCM622 cathode regions close to the current collector possess higher lithium ion concentrations, meanwhile more Ni2+ can be converted into Ni3+. The results of COMSOL Multiphysics simulations based on the porous electrode theory is analyzed to explore reaction kinetics mechanism. AC in NCM622 cathodes homogenizes the reaction distributions, contributing to the boosted reaction kinetic, eventually, resulting in the high utilization of active materials. These findings provide a direct way to reduce solid-state diffusion resistances and accelerate reaction kinetics of electrodes, which is critical for developing batteries with long cycle stability and rate performance at high rates. [Display omitted] [ABSTRACT FROM AUTHOR]