Improved thermal conductivity and excellent electrical insulation properties of polysiloxane nanocomposite-incorporated functional boron nitride sheets via in situ polymerization.

Benefiting from its high thermal conductivity (κ) and superior insulation, the boron nitride nanosheet (BNNS) is widely investigated as a promising filler for thermal nanocomposites. However, poor dispersibility and weak interaction with polymer matrix hinder the further improvement of BNNS-based thermal composites. Here, inspired by side-chain liquid crystal polysiloxane (SCLCP) with good mesomorphic structures, highly thermoconductive nanocomposites prepared via in situ polymerization using SCLCP with 2D BNNS are reported. The surface of BNNS is silanized with γ-(methacryloxy)propyltrimethoxysilane (KH-570) to introduce double bonds (defined as f-BNNS), and it is directly linked with SCLCP chains during polymerization. Therefore, the alternating stacking of f-BNNS and microscopic ordered structure of SCLCP yielded a high κ of 2.463 W m-1 K-1 at only 30 wt% f-BNNS content, improving dramatically the κ of pure SCLCP by ∼9 times. Further, the volume electrical resistivity reached 2.11 × 1014 Ω cm, which is five orders of magnitude higher than the critical resistance for electrical insulation (109 Ω cm). Also, the f-BNNS/SCLCP composites as thermal management materials decreased the temperature of the LED chip by 17.5 °C, exhibiting superior thermal management performance. Along with high κ and excellent electrical resistance, this type of nanocomposites displays great advantages in thermal properties for electronic packaging and thermal management of electronics.

An Organic Redox Mediator with a Defense-Donor for Lithium Anode in Lithium-Oxygen Batteries.

Lithium-oxygen batteries (LOBs) suffer from large charge overpotential and unstable Li metal interface, which can be attributed to the inefficient charge transport at the insulating Li2 O2 /cathode interface and the severe oxygen corrosion issue on the Li anode surface. The use of soluble redox mediators (RMs) can effectively enhance the charge transport between Li2 O2 and cathode, thus greatly reducing the charge overpotential. However, oxidized RMs will also shuttle to the anode side and react with the Li metal, which not only results in the loss of both the RMs and the electrical energy efficiency but also exacerbates the Li anode corrosion. Herein, an organic compound-acetylthiocholine iodide (ATCI), in which a big cation group is contained, is proposed as a defense-donor RM for lithium anode in LOBs to simultaneously address the above issues. During charge, it can accelerate the oxidation kinetics of Li2 O2 via its iodide anion redox couple (I- /I3 - ). Meanwhile, its cation segment (ATC+ ) can move to the anode surface via electric attraction and in situ forms a protective interfacial layer, which prevents the Li anode from the attack of oxidized RM and oxygen species. Consequently, the ATCI-containing LOBs can achieve both a low charge potential (≈3.49 V) and a long cycle life (≈190 cycles).