Recent progress in layered double hydroxide based materials for electrochemical capacitors: design, synthesis and performance

Abstract

As representative two-dimensional (2D) materials, layered double hydroxides (LDHs) have received increasing attention in electrochemical energy storage and conversion because of the facile tunability between their composition and morphology. The high dispersion of active species in layered arrays, the simple exfoliation into monolayer nanosheets and chemical modification offer the LDHs an opportunity as active electrode materials in electrochemical capacitors (ECs). LDHs are favourable in providing large specific surface areas, good transport features as well as attractive physicochemical properties. In this review, our purpose is to provide a detailed summary of recent developments in the synthesis and electrochemical performance of the LDHs. Their composites with carbon (carbon quantum dots, carbon black, carbon nanotubes/nanofibers, graphene/graphene oxides), metals (nickel, platinum, silver), metal oxides (TiO, CoO, CuO, MnO, FeO), metal sulfides/phosphides (CoS, NiCoS, NiP), MOFs (MOF derivatives) and polymers (PEDOT:PSS, PPy (polypyrrole), P(NIPAM-co-SPMA) and PET) are also discussed in this review. The relationship between structures and electrochemical properties as well as the associated charge-storage mechanisms is discussed. Moreover, challenges and prospects of the LDHs for high-performance ECs are presented. This review sheds light on the sustainable development of ECs with LDH based electrode materials.

Experimental and Theoretical Investigation of the Effect of Oxygen Vacancies on the Electronic Structure and Pseudocapacitance of MnO2

“…Additionally, the ROV‐ m and OOV‐ n samples had a smaller semicircle diameter in the high‐frequency region, implying that they had faster charge‐transfer kinetics and lower charge‐transfer resistance. Meanwhile, the equivalent serial resistance ( R s ), determined from the intercept on the real axis, decreased, which indicated better electrical conductivity induced by oxygen vacancies . Specifically, the starting points for ROV‐2h and OOV‐1h were much lower than those of the other ROV‐ m and OOV‐ n samples, respectively, suggesting a lower internal resistance owing to the higher conductivity caused by oxygen vacancies.…”

“…Meanwhile, the equivalent serial resistance (R s ), determined from the intercept on the real axis, decreased, which indicatedb etter electrical conductivity induced by oxygen vacancies. [51] Specifically,t he starting points for ROV-2h and OOV-1h were much lower than those of the other ROV-m and OOV- n samples, respectively,s uggestingalower internal resistance owing to the higher conductivity caused by oxygen vacancies. Oxygenv acancies not only increased the electronic conductivity but also provide additional active sites for redox reactions.…”

Self‐Assembled Nickel Pyrophosphate‐Decorated Amorphous Bimetal Hydroxides 2D‐on‐2D Nanostructure for High‐Energy Solid‐State Asymmetric Supercapacitor

“…The amorphous nature of the 2D bimetallic hydroxide provides abundant grain boundaries and an ion diffusion path for the electrochemical reactions. In addition, the high redox activity of the bimetallic hydroxide contributes to the pseudocapacitance for charge storage …”

Integrated Nanostructural Electrodes Based on Layered Double Hydroxides

“…From the initial discovery to the present, the development of LDHs has undergone continuous updating, both in terms of synthesis strategies, material designs, and application fields . Generally, the evolution of structure could reflect the development of LDHs for advanced electrodes to some extent.…”