All‐Electrochemical Nanofabrication of Stacked Ternary Metal Sulfide/Graphene Electrodes for High‐Performance Alkaline Batteries

Abstract

Energy‐storage materials can be assembled directly on the electrodes of a battery using electrochemical methods, this allowing sequential deposition, high structural control, and low cost. Here, a two‐step approach combining electrophoretic deposition (EPD) and cathodic electrodeposition (CED) is demonstrated to fabricate multilayer hierarchical electrodes of reduced graphene oxide (rGO) and mixed transition metal sulfides (NiCoMnSx). The process is performed directly on conductive electrodes applying a small electric bias to electro‐deposit rGO and NiCoMnSx in alternated cycles, yielding an ideal porous network and a continuous path for transport of ions and electrons. A fully rechargeable alkaline battery (RAB) assembled with such electrodes gives maximum energy density of 97.2 Wh kg−1 and maximum power density of 3.1 kW kg−1, calculated on the total mass of active materials, and outstanding cycling stability (retention 72% after 7000 charge/discharge cycles at 10 A g−1). When the total electrode mass of the cell is considered, the authors achieve an unprecedented gravimetric energy density of 68.5 Wh kg−1, sevenfold higher than that of typical commercial supercapacitors, higher than that of Ni/Cd or lead–acid Batteries and similar to Ni–MH Batteries. The approach can be used to assemble multilayer composite structures on arbitrary electrode shapes.

Versatile electrochemical manufacturing of mixed metal sulfide/N-doped rGO composites as bifunctional catalysts for high power rechargeable Zn–air batteries

“…30 As demonstrated in previous publications, initial attempts to deposit MTMSs directly on the GF surface proved unsuccessful, leading to inadequate adhesion of the NCMS material, with detached flakes or cracks. 2 The preliminary coating of NrGO serves as a primer, interacting with metal sulfides owing to the oxygen functional groups on its surface. Additionally, NrGO acts as a binder and a conductive spacer, facilitating subsequent deposition of the NCMS layer.…”

“…EPD coating of NrGO was achieved by applying a DC potential of −20 V for 10 minutes. 2 A very thin layer (∼60 nm) of NrGO with a mass loading of ∼0.3 mg cm −2 was obtained on a GF matrix. Then, the NrGO-GF electrodes were dried at 70 °C for 30 minutes to remove the solvents.…”

“…Several possible alternative energy storage and conversion systems have been suggested, focusing on utilizing eco-friendly aqueous electrolytes. These options include rechargeable alkaline batteries, 2 water electrolyzers, 3 fuel-cells, 4 and metal-air batteries. 5 Among metal-air battery technologies, rechargeable zinc-air batteries (ZABs) have spurred extensive attention owing to their remarkable features.…”

“…Notably, this approach was successfully applied to carbon fibers, 30 as well as 3-dimensional foams, 31 allowing us to achieve precise control over the architecture, composition, and properties of the resulting materials. Subsequently, these compounds were utilized as electrode materials for asymmetric micro-supercapacitors, 32 Li-ion batteries, 31 or rechargeable alkaline batteries, 2 demonstrating high performances.…”

Surface chemistry and structure manipulation of graphene-related materials to address the challenges of electrochemical energy storage

“…In this way, we fabricated multilayer hierarchical electrodes of RGO and mixed transition metal sulfides (NiCoMnS x ) directly on 3D graphene foam (GF) substrates. 33 In the composite stack, RGO interlayer coatings favoured a uniform distribution of NiCoMnS x nanosheets (Fig. 8(c) and (d)).…”