Inorganic Cyanogels and Their Derivatives for Electrochemical Energy Storage and Conversion

Abstract

Nanostructured gels have emerged as a unique material platform for various applications such as energy storage and catalysis thanks to the tunable composition and structure, porous framework for mass transfer, and ease of synthesis and functionalization. Recently, cyanogels and their derivatives have aroused considerable research interests owing to their high composition tunability, large surface area, and hierarchical porosity for charge and mass transport, which contribute to the high performance when applied to energy storage and conversion devices. This Perspective highlights the key features of cyanogels and their derivatives toward electrochemicalenergy-related applications, summarizes the synthesis and functionalization of cyanogels, discusses recent advances in material design and synthetic routes of various cyanogel-derived functional nanomaterials in energy-related applications, and proposes future directions for their scientific and technological development.

Chemically Binding Scaffolded Anodes with 3D Graphene Architectures Realizing Fast and Stable Lithium Storage

“…, Sn(IV)−Ni(II) cyanogel (), can be obtained through simply mixing aqueous solutions of SnCl 4 and K 2 Ni(CN) 4 . After mixing, the nitrogen end from cyano ligand coordinates with Sn(IV) center, forming bridges between Ni(II) and Sn(IV) centers (Ni–C≡N–Sn), and this coordination reaction generates the extended cyano bridges and final cyanogels [21, 28–33]. For the GO part, polyvinyl pyrrolidone (PVP), a hydrogen-bond acceptor, acts as an efficient cross-linker for the gelation of GO, and the hydrogen-bond interaction between PVP chains and GO sheets can be responsible for the formation of the GO hydrogel, as revealed in [34, 35].…”

“…Moreover, the interconnected 1D to 3D alloy platform and continuous graphene skeleton together with strong interfacial Sn–O–C bonding provide fast pathways for electrons [12–17, 22–27], and the internally abundant nanopores promote the contact between the electrolyte and dual framework electrode [19–21, 36–38]. Thanks to the unique mixed conducting networks for both electron and Li-ion, the Sn−Ni/G dual framework exhibits greatly enhanced charge-transport and high-rate capabilities.…”

“…Nevertheless, these anodic guests often exist in the form of nanoparticles, physically attached to graphene hosts, and therefore tend to detach from graphene matrices and aggregate into large congeries, causing considerable capacity fading under repeated Li insertion/extraction. As compared with 0D nanomaterials, anisotropic nanostructures with higher dimensions especially 3D scaffolded architectures manifest collective advantages of both nano-building units and microsized assemblies and thus greatly enhanced structural stability and capacity retention [18–21]. Moreover, interface chemistry engineering plays an increasingly significant role in designing progressive energy materials, and chemically bonded hybrid anodes are able to exhibit further-enhanced lithium-storage kinetics and performance than the ones hybridized in physical level [22–27].…”

Gel Electrocatalysts: An Emerging Material Platform for Electrochemical Energy Conversion

“…Cyanogels, as another type of important inorganic gel material, contain both main‐group metals (In, Al, or noble metals, such as Pd, Pt) and catalysis‐active transition metals in the polymer backbones (such as Fe, Co, and Ni, Figure 8d). [ 38 ] Fang et al. proposed an InFeCo‐cyano‐bridged coordination polymer gel catalyst for OER in a strongly acidic electrolyte with no noticeable degradation after more than 3000 cycles and 40 h at 5 mA cm −2 (Figure 8e).…”

Multiscale Understanding and Architecture Design of High Energy/Power Lithium‐Ion Battery Electrodes

“…[ 4,5 ] For instance, researchers are seeking various possibilities by simultaneously looking into strategies on material chemistry, [ 6–8 ] battery configuration, [ 9–11 ] to nanoarchitecture design. [ 12,13 ] Theoretically, the full energy storage capability of a specific material could be predicted based on their chemical compositions, energy diagrams and crystal structures, which are mostly based on intrinsic thermodynamic properties. By novel material design, recent progress on exploiting lithium ion hosts with high operating voltage and/or specific capacities are promising to effectively boost energy density.…”