Electrostructural Compatibility of Battery-Type Diffuse-Porous Co₉S₈–NiCo₂S₄/Defective Reduced Graphene Oxide and Flaky FeS/Nitrogen-Doped Defective Reduced Graphene Oxide for Ultra-High-Performance All-Solid-State Hybrid Pseudocapacitors

Abstract

In order to engineer pseudocapacitor devices with high rates of energy and power delivery, and long cycle life, herein facile controlled material growth strategies are adopted to synthesize batterytype diffuse-porous Co 9 S 8 −NiCo 2 S 4 /defective reduced graphene oxide (Co 9 S 8 −NiCo 2 S 4 /D-rGO) and flaky FeS/nitrogen-doped defective reduced graphene oxide (FeS/ND-rGO) as positive and negative electrode materials, respectively. The physicochemical studies demonstrate microstructural distinctiveness in the context of permitting the bulk diffusibility of electrolyte ions, uniform heterostructurization, and added number of reactive equivalents in the electrode materials. During electrochemical studies, the Co 9 S 8 −NiCo 2 S 4 /D-rGO demonstrates thorough kinetic reversibility, enhanced rate efficiency, bias-potentialindependent series resistance, charge-transfer resistance and relaxation time, and Warburg profile corresponding to minimum diffusion resistance. Similarly, FeS/ND-rGO offers good kinetic reversibility and a wide negative potential window. Further, the fabricated Co 9 S 8 −NiCo 2 S 4 /D-rGO∥FeS/ND-rGO all-solid-state hybrid pseudocapacitor device majorly shows diffusion-controlled charge storage physiognomies and lowly impeded charge transfer, operates at a wide potential window of 1.9 V, and delivers high rate specific capacitance and capacity, promising rate specific energy density at high power density, and 96.9% capacitance/capacity retention after 11 000 successive charge−discharge cycles. The enhanced pseudocapacitive charge storage efficiency of the Co 9 S 8 −NiCo 2 S 4 /D-rGO∥FeS/ND-rGO device is ascribed to the electromicrostructural compatibility of Co 9 S 8 −NiCo 2 S 4 /D-rGO and FeS/ND-rGO; nonstoichiometry induced multiple redox-active Co, Ni, and Fe ions; ion-buffering-pool-like behavior of materials' bulk; and integrated charge transfer efficiency of D-rGO and ND-rGO. Additional electrochemical studies also reveal that the use of the solid electrolyte (PVA-KOH) offers a sufficient advantage over the liquid electrolyte (aqueous KOH) in the Co 9 S 8 −NiCo 2 S 4 /D-rGO∥FeS/ND-rGO hybrid pseudocapacitor device. KEYWORDS: Co 9 S 8 −NiCo 2 S 4 , defective rGO, nitrogen-doped defective rGO, all-solid-state hybrid pseudocapacitor, electromicrostructural compatibility, high-rate energy density

Hierarchical MnO2/NiS–MnS with Rich Electro-Microstructural Physiognomies for Highly Efficient All-Solid-State Hybrid Supercapacitors

“…Factually, the electrochemical activation leads to partial pore opening and activation of the electroactive sites present in the bulk of the electrode materials during redox reactions for a long duration. This leads to an increase in the charge storage efficiency of the electrode materials during redox cycling. ,, Notably, the specific capacitance retention (after 11,000 charge–discharge cycles) of the MnO 2 /Ni–Mn–S||N-rGO ASSHSC device is significantly higher than the same for some recently reported hybrid supercapacitor devices fabricated with electrode materials based on Ni/Mn-based sulfides, as presented in Table S2 in the Supporting Information. The extraordinary operational steadiness (at high reaction rate conditions) of the MnO 2 /Ni–Mn–S||N-rGO ASSHSC device is attributed to the supreme electro-microstructural physiognomies of MnO 2 /Ni–Mn–S and N-rGO. ,, Essentially, the efficiency of OH – ion dissemination in the matrices of MnO 2 /Ni–Mn–S and N-rGO remains nearly unchanged throughout the charge/discharge cycles .…”

“…Factually, the electrochemical activation leads to partial pore opening and activation of the electroactive sites present in the bulk of the electrode materials during redox reactions for a long duration. This leads to an increase in the charge storage efficiency of the electrode materials during redox cycling 5,10,11. Notably, the specific capacitance retention (after 11,000 charge−discharge cycles) of the MnO 2 /Ni−Mn−S||N-rGO ASSHSC device is significantly higher than the same for some recently reported hybrid supercapacitor devices fabricated with electrode materials based on Ni/Mn-based sulfides, as presented in TableS2in the Supporting Information.…”

“…The advancement in new energy storage technologies has emerged as one of the most focused topics for researchers in the last decade . Among the number of energy-storing devices, supercapacitors are truly imperative as they can deliver high power density comparable to that of conventional capacitors and energy density comparable to that of conventional batteries. − The remarkably high cyclic efficiency, quick charging capability, excellent performance durability, and miniature dimension of supercapacitors add to their advantageous integrations in contemporary high-performance electronic architectures. , Based on the electrochemical processes, supercapacitors can store charge by (i) continuous formation and depletion of double layers on the active surface of electrode materials and (ii) potentially induced oscillatory redox reactions occurring in the diffused active sites of the electrode materials. , Essentially, supercapacitors with charge storage processes controlled by the surface double-layer formation and active site-specific redox reactions offer superior energy density without compromising with the deliverable power density . In this regard, hybrid supercapacitor systems with redox-active positive electrodes and double-layer prompting negative electrodes show promising Ragone efficiency (high power and energy density) and have become ominously important in modern-day technologies .…”

“…1−3 The remarkably high cyclic efficiency, quick charging capability, excellent performance durability, and miniature dimension of supercapacitors add to their advantageous integrations in contemporary high-performance electronic architectures. 4,5 Based on the electrochemical processes, supercapacitors can store charge by (i) continuous formation and depletion of double layers on the active surface of electrode materials and (ii) potentially induced oscillatory redox reactions occurring in the diffused active sites of the electrode materials. 6,7 Essentially, supercapacitors with charge storage processes controlled by the surface double-layer formation and active site-specific redox reactions offer superior energy density without compromising with the deliverable power density.…”

Archetypical 2D sheet-like Cu2MoS4 for all-solid-state symmetric pseudocapacitors with ultra-steady performance efficiency

“…[1][2][3][4] Among the various supercapacitors, pseudocapacitors, in which charge storage occurs through effective redox reactions on the electrode materials, are very fascinating, given that these devices deliver supplemented charge storage and show electrochemical durability for extended cycles. 5,6 The kinetically faster electrochemical reactions and facilitated charge transfer play major roles in the excellent energy storage efficiency of pseudocapacitors. [7][8][9] However, the unsatisfactory energy density (lower than that of conventional batteries) of pseudocapacitors hinders their potential integration in ultra-efficient electronic architectures.…”