# Construction of Regular Hexagonal Double-Layer Hollow Nanocages by Defect Orientation and Composite Phase Change Materials with Carbon Nanotubes for Thermal Safety of Power Batteries

## TL;DR

Researchers created a new composite material to improve battery thermal safety by combining hexagonal nanocages and carbon nanotubes.

## Contribution

A hexagonal double-layer hollow nanocage combined with carbon nanotubes was developed to enhance thermal regulation and flame retardancy in batteries.

## Key findings

- The composite material achieved a thermal conductivity of 0.65 W/m·K and a phase transition enthalpy of 146.1 J/g.
- Microcalorimetric testing confirmed its flame-retardant ability due to strong adsorption and thermal conductivity improvements.
- The material shows promise for thermal safety in electronic equipment and power batteries.

## Abstract

At present, composite phase change materials are widely studied for battery thermal management. However, to ensure the battery’s thermal safety, it is necessary not only to control the temperature during regular operation, but also to prevent sudden thermal runaway. This basic function depends on the flame-retardant properties of the composite phase change materials. In this study, a hexagonal double-layer hollow nanocage S2 with defect orientation was prepared and combined with carbon nanotubes (PNT) derived from polypyrrole (PPy) tubes to form a high adsorption mixture. Multifunctional composite phase change material PNT/S2@PEG/TEP was prepared by adsorbing and coating polyethylene glycol 8000 (PEG-8000) and triethyl phosphate (TEP) with microfibrillated cellulose nanofibers (CNF) as the skeleton. The characterization shows that its thermal conductivity is 0.65 W/m·K and its phase transition enthalpy is 146.1 J/g, demonstrating its excellent thermal regulation. Microcalorimetric testing (MCC) confirmed its flame-retardant ability, attributed to the strong adsorption of PNT/S2 on PEG-8000 and TEP, the improvement in PNT’s thermal conductivity, and the contribution of CNF to flexibility. This composite phase change material, with excellent comprehensive properties, has broad application prospects in thermal safety for electronic equipment, significantly expanding its practical scope.