Freestanding Lamellar Porous Carbon Stacks for Low‐Temperature‐Foldable Supercapacitors

Abstract

High‐performance supercapacitors (SCs) are important energy storage components for emerging wearable electronics. Rendering low‐temperature foldability to SCs is critically important when wearable devices are used in a cold environment. However, currently reported foldable SCs do not have a stable electrochemical performance at subzero temperatures, while those that are performing are not foldable. Herein, a freestanding pure‐carbon‐based porous electrode, namely, lamellar porous carbon stack (LPCS), is reported, which enables stable low‐temperature‐foldable SCs. The LPCS, which is fabricated with a simple vacuum filtration of a mixture of carbon fibers (CFs), holey reduced graphene oxides (HRGOs), and carbon nanotubes (CNTs), possesses a lamellar stacking of porous carbon thin sheets, in which the CFs act as the skeleton and the HRGOs and CNTs act as binders. The unique structure leads to excellent compression resilience, high foldability, and high electronic and ionic conductivity. SCs made with the LPCS electrodes and ionic liquid electrolyte show a high energy density (2.1 mWh cm−2 at 2 mA cm−2), low‐temperature long lifetime (95% capacity after 10 000 cycles at −30 °C), and excellent low‐temperature foldability (86% capacity after 1000 folding cycles at −30 °C).

Electrochemical Supercapacitors: From Mechanism Understanding to Multifunctional Applications

“…In extreme weather conditions, for example high altitudes and cold climates, the advantage of high power density of electrochemical SCs will be significantly compromised due to the increased equivalent series resistance and electrode ionic resistance, especially in aqueous and propylene carbonate (operating limit −25 °C)‐based electrolyte. [ 97,98,99 ] In order to construct low‐temperature‐tolerant SCs, alternative electrolytes with mixed salts/solvents have been developed. [ 98 ]…”

“…For example, symmetric SCs with lamellar porous carbons tack electrodes and 1‐butyl‐3‐methylimidazolium tetrafluoroborate (ice point of −72 °C) electrolyte were assembled, exhibiting specific capacitance of 76.8 and 25.2 F g −1 at 20 and −30 °C, respectively. [ 99 ] Mixing ILs with binary organic solvents was also attempted to decrease the viscosity of ILs at low temperature without narrowing the electrochemical window. [ 105–107 ] Yan et al.…”

Balsa‐Wood‐Derived Binder–Free Freestanding Carbon Foam as High‐Performance Potassium Anode

“…[ 23 ] Therefore, it is of great significance to develop a novel 3D freestanding electrode for PIBs. [ 23,31–33 ]…”

Wood‐Derived Monolithic Ultrathick Porous Carbon Electrodes Filled with Reduced Graphene Oxide for High‐Performance Supercapacitors with Ultrahigh Areal Capacitances

“…But, the low operation potentials of those materials limit the enhancement of their energy densities. [19] By contrast, carbon materials, including carbon nanotubes (CNTs), [20][21][22] graphene, [23][24][25] and porous carbon [26][27][28] show rapid applications because of their better cycle stability, higher rate capabilities, and wider working voltages than pseudocapacitive materials. [29,30] Although biomass-derived carbon materials are also promising electrode materials owing to their abundant resource, low price, and renewable feature, [31,32] their carbonized counterparts are usually in powder, losing the special anisotropy of the biomass materials.…”