Energy storage in structural composites by introducing CNT fiber/polymer electrolyte interleaves

Evgeny Senokos,Federico Sket,Juan J Vilatela,Rebeca Marcilla,Yunfu Ou,Juan Jose Torres,Carlos González

doi:10.1038/s41598-018-21829-5

Abstract

This work presents a method to produce structural composites capable of energy storage. They are produced by integrating thin sandwich structures of CNT fiber veils and an ionic liquid-based polymer electrolyte between carbon fiber plies, followed by infusion and curing of an epoxy resin. The resulting structure behaves simultaneously as an electric double-layer capacitor and a structural composite, with flexural modulus of 60 GPa and flexural strength of 153 MPa, combined with 88 mF/g of specific capacitance and the highest power (30 W/kg) and energy (37.5 mWh/kg) densities reported so far for structural supercapacitors. In-situ electrochemical measurements during 4-point bending show that electrochemical performance is retained up to fracture, with minor changes in equivalent series resistance for interleaves under compressive stress. En route to improving interlaminar properties we produce grid-shaped interleaves that enable mechanical interconnection of plies by the stiff epoxy. Synchrotron 3D X-ray tomography analysis of the resulting hierarchical structure confirms the formation of interlaminar epoxy joints. The manuscript discusses encapsulation role of epoxy, demonstrated by charge-discharge measurements of composites immersed in water, a deleterious agent for ionic liquids. Finally, we show different architectures free of current collector and electrical insulators, in which both CNT fiber and CF act as active electrodes.

Highlights

The rapid development of mobile electric technologies such as portable electronics, electric vehicles, vessels and aircraft has created considerable demand for energy storage systems with higher gravimetric and volumetric efficiency
The method consists in producing a lay-up of carbon fibers (CF) (Hexcel G0926) with a thin electric-double layer supercapacitors (EDLC) interleaf between layers, and infusing the fabrics with a thermosetting resin
The interleaf is itself a thin sandwich structure comprising a polymer electrolyte membrane (100–120 μm) between two carbon nanotubes (CNT) fiber sheets deposited on a thin aluminum support

Summary

Introduction

The rapid development of mobile electric technologies such as portable electronics, electric vehicles, vessels and aircraft has created considerable demand for energy storage systems with higher gravimetric and volumetric efficiency. An alternative approach is to build a structural supercapacitor around unidirectional fabrics of CNTs. The fabrics are arrays of macroscopic fibers of CNTs, which combine filament mechanical properties in the high performance range, with a large SSA of 256 m2 g−1 and electrical conductivity 3.5 × 105 S m−1 when assembled as fabrics[19]. The fabrics are arrays of macroscopic fibers of CNTs, which combine filament mechanical properties in the high performance range, with a large SSA of 256 m2 g−1 and electrical conductivity 3.5 × 105 S m−1 when assembled as fabrics[19] These materials can function as active material and current collector[20]

Methods

Results

Conclusion