In the development of hexagonal boron nitride (h-BN)-based polymeric composites with high thermal conductivity, it is always challenging to achieve a dense filling of h-BN fillers to form a desired high-density thermal transfer network. Here, a series of boron nitride nanosheets (BNNSs)/epoxy resin (EP) bulk composites filled with ultrahigh BNNSs content (65−95 wt %) is successfully constructed through a well-designed mechanical-balling prereaction combined with a general pressure molding method. By means of this method, the highly filled BNNSs fillers are uniformly dispersed and strongly bonded with EP within the composites. As a result, the densely BNNSs-filled composites can exhibit multiple performances. They have excellent mechanical properties, and their maximum compression strength is 30−97 MPa. For a BNNSs/EP composite with filling ultrahigh BNNSs fraction up to 90 wt %, its highly in-plane thermal conductivities (TC) are 6.7 ± 0.1 W m −1 K −1 (at 25 °C) to 8.7 ± 0.2 W m −1 K −1 (200 °C), respectively. In addition, the minimum coefficient of thermal expansion of BNNSs/EP composites is 4.5 ± 1.3 ppm/°C (only ∼4% of that of the neat EP), while their dielectric constants are basically located between 3−4 along with their dielectric loss tangent values exceptionally <0.3 in the ultrahigh frequency range of 12−40 GHz. Additionally, these BNNSs/EP composites exhibit remarkable cycle stability in heat transfer during heating and cooling processes because of their structural robustness. Thus, this type of densely BNNSs-filled BNNSs/ EP composite would have great potential for further practical thermal management fields.

Although this kind of hexagonal boron nitride (h-BN)-filled polydimethylsiloxane (PDMS) multifunctional composite foam has been greatly expected, its development is still relatively slow as a result of the limitation of synthetic challenge. In this work, a new foaming process of BNNSs-PDMS, alcohol, and water three-phase emulsion system is employed to synthesize a series of high-quality BNNSs/PDMS composite foams (BSFs) filled with highly functional and uniformly distributed BNNSs. As a result of well-bonded interfaces between the BNNSs and PDMS, enhanced multiple functions of BSFs appeared. The BSFs can show complete resilience at a compressive strain of 90% and only 3.99% irreversible deformation after 100,000 compressing–releasing hyperelastic cycles at a strain of 60%. On the basis of their outstanding shape-memory properties, the maximum voltage value of compression-driven piezo-triboelectric (CDPT) responses of the BSFs is up to ∼20 V. Depending on the remarkable super-elastic and CDPT performances, the BSFs can be used for sensitive sensing of temperature difference and electromechanical responses. Also, in the range of 12–40 GHz, the BSF materials display ultralow dielectric constants between 1.1 and 1.4 with proper dielectric loss tangent values of <0.3 and exhibit an enhanced and broadened sound adsorption capacity ranging from 500 to 6500 Hz. Although BSFs have high porosities of >65%, their thermal conductivities can still reach up to 0.407 ± 0.039 W m–1 K–1. Moreover, the BSF materials display favorable thermal stability, obviously reduced coefficient of thermal expansion, and good flame retardancy. All of these properties render the BSFs as a new category of excellent multifunctional material.

Advanced heat dissipation materials are necessary for powerful and miniaturized electronics. Hexagonal boron nitride (h-BN) is an ideal material for thermal management due to its electrical insulation but thermal conductivity. However, its utilization is seriously restricted by the pulverulence, and multilayer and chemical inertness. Herein, highly functionalized BN nanosheets (BNNSs) are exfoliated by a boric acid-assisted chemo-mechanical method and show stable dispersion in various solvents. An ingenious chemical etch-and mechanical forceinduced exfoliation and functionalization mechanism is proposed. Due to the existence of strong interfacial interaction between BNNSs and poly(vinyl alcohol) (PVA), a series of composite films with excellent thermal stability, low dielectric constant (2−4), negligible dissipation factor (<0.2), good machinability, and flexible bending and folding performances are prepared. The BNNSs' filling content can reach ∼90 wt %, and the BNNSs/PVA films' maximum tensile strength and modulus can be as high as ∼85.5 MPa and ∼7.6 GPa, respectively. Importantly, their in-plane thermal conductivity increases monotonously with the elevated BNNS content and temperature. The maximum thermal conductivity can reach up to 27.3 and 39.3 W•m −1 •K −1 at 25 and 100 °C, respectively. Noteworthily, the BNNSs/ PVA films show rapid thermal diffusion and can be readily designed as efficient heat dissipation components for integrated and intelligent electronic devices.

The application of highly superelastic foamlike materials has gradually expanded to various high-end areas, such as filtration purification, mechanical power generation, and energy storage, showing their considerable and expected prospects. In this paper, facile freeze-drying technology combined with a gradual thermal-imidization process was employed to prepare a series of boron nitride nanosheet (BNNS)-filled polyimide (PI) composite foams. These foams can exhibit excellent mechanical properties, including their cyclic stability for considerable cycles under long compressive loading–unloading processes, and their relatively low irreversible deformation. After 10000 cycles at the compression strain of 60%, the total strain loss of the composite filled with 12 wt % is only 14%, which is 2/3 that of pure PI foam. Based on these excellent mechanical characteristics, the foam composites exhibit well a compression-driven triboelectric performance. The effects of BNNS content, compression strain, and rate on the triboelectric properties of the composites were studied in detail. We found that a higher compression strain and compression rate will lead to stronger electrical signals. More significantly, on the basis of the one-to-one relationship between electrical signal and compressive deformation, BNNSs/PI foam will likely be used in the field of control sensing. Finally, the electrical generation device based on composites was used in an insole and keyboard to transform mechanical energy generated by human movement into electrical signals.

Lithium–sulfur (Li–S) batteries with high theoretical energy density are considered as the most promising devices for rechargeable energy-storage systems. However, their actual applications are rather limited by the shuttle effect of lithium polysulfides (LiPSs) and the sluggish redox kinetics. Here, the boron nitride nanosheets are homodispersedly embedded into N-doping porous carbon fibers (BNNSs/CHFs) by an electrospinning technique and a subsequent in situ pyrolysis process. The hybridized BNNSs/CHFs can be smartly designed as a multifunctional separation coating onto the commercial PP membrane to enhance the electrochemical performance of Li–S batteries. As a result, the Li–S batteries with extra BNNSs/CHF modification deliver a highly reversible discharge capacity of 830.4 mA h g–1 at a current density of 1 C. Even under 4 C, the discharge specific capacity can reach up to 609.9 mA h g–1 and maintain at 553.9 mA h g–1 after 500 cycles, showing a low capacity decay of 0.01836% per cycle. It is considered that the excellent performance is attributed to the synergistic effect of adsorption and catalysis of the BNNSs/CHF coating used. First, this coating can efficiently reduce the charge transfer resistance and enhance Li-ion diffusion, due to increased catalytic activity from strong electronic interactions between BNNSs and N-doping CHFs. Second, the combination of polar BNNSs and abundant pore structures within the hybridized BNNSs/CHF networks can highly facilitate an adsorption for LiPSs. Here, we believed that this work would provide a promising strategy to increase the Li–S batteries’ performance by introducing hybridized BNNSs/N-doping carbon networks, which could efficiently suppress the LiPSs’ shuttle effect and improve the electrochemical kinetics of Li–S batteries.