Nanoengineering Porous Silica for Thermal Management

Abstract

Thermal insulation of solid materials originates from the nanoscale porous architectures to regulate thermal management in energy-critical applications from energy-efficient buildings to heat-sensitive energy devices. Here, we show nanoengineering of porous silica materials to control the architecture transition from mesoporous to nanocage networks. A low thermal conductivity of such a porous silica network is achieved at 0.018 W/(m K) while exhibiting a porosity of 92.05%, specific surface area of 504 m²/g, and pore volume of 2.37 cm³/g after ambient pressure drying. Meanwhile, the crosslinking of the porous silica and ceramic fiber frameworks show a tensile Young's modulus of 2.8 MPa while maintaining high thermal insulation, which provides an effective thermal runway mitigation strategy for rechargeable lithium-ion batteries. The nanoengineering strategy reported here would shed light on achieving superthermal insulation of nanostructures for energy-critical applications.

Keywords: nanoscale; porous material; structure engineering; thermal insulation; thermal management.

Figure 1.

Sol−gel synthesis of porous silica materials. (a) TEOS-based silica porous networks composed of individual mesoporous nanoparticles. Here, the initial pH value could be adjusted as 2.55, 7, and 8. The corresponding TEM image shows the mesoporous skeleton composed of porous single nanoparticles. (b) TMOS-based silica cage self-assembly, and the TEM images show the cage assembly. (c) MTMS-based silica cage self-assembly.

Figure 2.

Structural and thermal conductivity of porous silica materials. (a) Nitrogen adsorption−desorption isotherms of the samples from different precursors by the Brunauer−Emmett−Teller (BET) theory. (b) Pore size distribution by the BJH method. (c) SSA and mean pore size of porous networks based on different precursors. (d) Thermal conductivity and total pore volume of porous networks based on different precursors.

Figure 3.

TEM images of nanoscale porous nanoparticle building blocks and mesoporous skeletons: (a) 0.01 g/mL CTAB; (b) 0.05 g/mL CTAB; and (c) 0.1 g/mL CTAB. (d) Nitrogen adsorption−desorption isotherms of the samples from different CTAB concentrations by the Brunauer−Emmett−Teller (BET) theory. The inset shows pore size distribution by the BJH method. (e) SSA and total pore volume of samples with different CTAB concentrations. (f) Thermal conductivity and porosity vs CTAB concentration. Here, the other chemicals are TEOS = 100 mL, urea = 60 g, TMB = 4 mL, and H₂O = 400 mL.

Figure 4.

SEM images of silica aerogels with initial pH values of (a) 2.55 and (b) 8, and the insets show the optical images showing transparency and opaque white, respectively, with a scale bar of 5 mm. (c) Nitrogen adsorption−desorption isotherms of the samples with different initial pH values by the Brunauer−Emmett−Teller (BET) theory. (d) Pore size distribution by the BJH method. (e) SSA and total pore volume of samples with different initial pH values. (f) Thermal conductivity and porosity vs initial pH values. Here, the other chemicals are TEOS = 100 mL, urea = 60 g, TMB = 4 mL, and H₂O = 400 mL.

Figure 5.

All ceramic thermal insulation nanocomposites. (a) SEM image of the fiber-aerogel nanocomposite, and the inset figure shows silica aerogels. (b) Cross-section SEM image and the inset schematic figure shows the silica aerogel distribution among fiber frameworks. (c)Thermal conductivity vs aerogel concentration via an in situ soaking method. The sample thickness is 1.1 and 1.5 mm. (d) Stress vs strain for the fiber-aerogel composite with aerogel concentration from 0, 10, 30, to 40 wt %.

Figure 6.

Thermal runway mitigation using lightweight flexible insulation materials. (a) IR image of the thermal insulation composite with various thicknesses (2, 3, 4, and 5 mm) with a heating temperature of 80 °C for 30 min. (b) Corresponding surface temperature of the thermal insulation composites. (c) Charging/discharging profiles of lithium-ion batteries without and with different thermal insulation composites under a heating temperature of 80 °C. (d) Nyquist plots of lithium-ion batteries without and with protection of printed insulation containers on a hotplate under heating temperatures of 50 and 80 °C for 10 min.