Highly Porous Free-Standing rGO/SnO2 Pseudocapacitive Cathodes for High-Rate and Long-Cycling Al-Ion Batteries

Timotheus Jahnke,Daniel Hotz,Joachim Bill,Achim Max Diem,Andrea Knöller,Zaklina Burghard,Leila Raafat

doi:10.3390/nano10102024

Abstract

Establishing energy storage systems beyond conventional lithium ion batteries requires the development of novel types of electrode materials. Such materials should be capable of accommodating ion species other than Li+, and ideally, these ion species should be of multivalent nature, such as Al3+. Along this line, we introduce a highly porous aerogel cathode composed of reduced graphene oxide, which is loaded with nanostructured SnO2. This binder-free hybrid not only exhibits an outstanding mechanical performance, but also unites the pseudocapacity of the reduced graphene oxide and the electrochemical storage capacity of the SnO2 nanoplatelets. Moreover, the combination of both materials gives rise to additional intercalation sites at their interface, further contributing to the total capacity of up to 16 mAh cm−3 at a charging rate of 2 C. The high porosity (99.9%) of the hybrid and the synergy of its components yield a cathode material for high-rate (up to 20 C) aluminum ion batteries, which exhibit an excellent cycling stability over 10,000 tested cycles. The electrode design proposed here has a great potential to meet future energy and power density demands for advanced energy storage devices.

Highlights

Electrochemical energy storage systems based on lithium ions are nowadays a well-established concept, which enables the application of a broad spectrum of technologies, ranging from microelectronics over portable electronic devices to even electrical cars
Constant stirring for 10 min was applied to ensure a good dispersion of the graphite flakes in the H2SO4, whereas afterwards, 3 g KMnO4 (Merck KGaA, Darmstadt, Germany) was added, and the temperature adjusted to 35 ◦C and held for 6 h, while continuing the stirring
Their dimensions were determined by scanning electron microscopy (SEM), revealing a thickness of a few nanometers and a lateral dimension of several tens of nanometers, with a tendency to form agglomerates with a size of 100 nm (Supporting Figure S1b)

Summary

Introduction

Electrochemical energy storage systems based on lithium ions are nowadays a well-established concept, which enables the application of a broad spectrum of technologies, ranging from microelectronics over portable electronic devices to even electrical cars. Such lithium ion batteries (LIBs) offer excellent energy density and long-term stability. Researchers have been investigating monovalent ion batteries, like sodium and potassium-based electrochemical systems as alternatives [2,3], due to the high abundance and cost efficiency of these elements. Aluminum-based electrochemical systems have become one of the most promising candidates, owing to the aluminum’s natural abundance, low cost and inherent safety [6,7,8,9]. The three-valent aluminum could significantly boost the energy storage capacity compared to the single-valent lithium [10]

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Conclusion