Urea-Assisted Nickel-Manganese Phosphate Composite Microarchitectures with Ultralong Lifecycle for Flexible Asymmetric Solid-State Supercapacitors: A Binder-Free Approach

Abstract

The limited energy density and cyclability of supercapacitors are major roadblocks to their development as energy storage devices. To address these issues, a binder-free nickel−manganese (Ni−Mn) phosphate composite (NMP series) microarchitecture has been synthesized by the hydrothermal method on a nickel foam (NF) substrate using various urea dosages. Due to the influence of urea, microrod-/microplate-like morphologies of NMP series thin films evolved to micropetals. This study demonstrates a synergy between Ni and Mn metal ions and also the influence of different urea contents on the physicochemical properties of mesoporous NMP series thin films. Notably, the NMP-4 microarchitecture has a large surface area (7.5 m 2 g −1 ), which provides more electroactive sites in electrochemical measurements. Accordingly, in the NMP series electrodes, the NMP-4 thin film demonstrated high electrochemical properties (the maximum specific capacity was found to be 901 C/g at a 5 mV/s scan rate) and retained 127% capacity over 6000 cycles, indicating good durability with a well-preserved microstructure throughout the cycling. Furthermore, a flexible asymmetric solid-state (FASS) supercapacitor was designed utilizing NMP-4 and reduced graphene oxide (rGO) as a cathode and an anode, respectively, in the poly(vinyl alcohol)-KOH (PVA-KOH) gel electrolyte with an extended operational voltage of +1.8 V. This FASS device provides a high specific capacity (192 C/g at 0.6 A/g current density), supreme energy density (48.2 Wh kg −1 ) at a power density of 575 W kg −1 , and a desirable longevity of 108% over 5000 cycles. Moreover, the FASS device also demonstrated its practical applicability. The long-term stability suggests that the binder-free urea-assisted Ni−Mn phosphate composite is a good candidate for energy storage devices.

An Interfacial Engineering Approach of Flower-like Li+ Preintercalated Co–Cu Phosphate for Solid-State Hybrid Energy Storage Device

“…In this study, the distinctive characteristic peaks at 457, 555, 595, and 650 cm –1 correspond to the Cu–O vibration mode. − In addition, well-distinguished Co–O and O–Co–O Raman peaks were detected at 169, 200, 222, 290, 333, 380, 457, 555, 595, and 650 cm –1 . − Interestingly, the peaks at 457, 555, 595, and 650 cm –1 indicate similar chemical bonding in Cu–O, Co–O, and the combined Co–Cu–O. However, a comprehensive analysis of Co–Cu–O revealed a slight peak shift of some cm –1 , and peak intensities were also enhanced when compared to those of pristine Co–O and Cu–O, plausibly due to coordination interactions between Co and Cu in bimetallic samples, including Li as an alkali metal. , Moreover, the strong and sharp Raman peaks at 870, 953, 999, 1045, and 1077 cm –1 for all prepared samples are ascribed to the asymmetric O–P–O stretching, symmetric stretching, and vibrational mode of the PO 4 3– group. , Similarly, the peaks in the 3073–3390 cm –1 range are ascribed to adsorbed water (vibration mode of the −OH group). − No other bands were observed in any of these spectra except for the Co–O, Cu–O, and Co–Cu–O vibrations, indicating the successful synthesis of Li + preintercalated Co–Cu phosphate materials.…”

“…In the XPS spectrum of Cu 2p (Figure d), the peak at 934.8 eV (Cu 2p 3/2 ) corresponds to Cu 2+ and is in tandem with two satellite peaks at 938.7 and 943.0 eV, assigned as “Sat.” , Similarly, the sharp Cu 2p 1/2 peak at 954.7 eV corresponds to Cu 2+ , whereas the two satellite peaks (Sat.) at 958.9 and 962.5 eV are assigned to Cu 2p 1/2 . , The peaks of Co 2p 3/2 and Cu 2p 3/2 in the aforementioned XPS profiles (Co 2p and Cu 2p) were slightly shifted toward lower binding energies (0.20 eV) in the spectra of the Li-CoCuP4 thin film due to Li-ion preintercalation, which indicates that Co/Cu was reduced by accepting electrons during the preintercalation process. , Moreover, the P 2p peak was observed at 133.1 eV for the CoCuP and Li-CoCuP4 thin films (Figure e), which indicates the existence of a phosphate (PO 4 3– ) group with P–O bonding. , In addition, the O 1s XPS profiles of the Li + -free and Li + -intercalated CoCuP electrodes (Figure f) show three deconvoluted peaks at 529.2 (O1), 530.9 (O2), and 532.4 eV (O3), attributed to metal–oxygen, phosphate, or phosphorus–oxygen and −OH bonds, respectively . Overall, Li ions were effectively incorporated into the host material, as indicated by the peak of the Li ions in the spectra of the Li-CoCuP4 thin film.…”

“…) group with P−O bonding. 42,46 In addition, the O 1s XPS profiles of the Li + -free and Li + -intercalated CoCuP electrodes (Figure 2f) show three deconvoluted peaks at 529.2 (O1), 530.9 (O2), and 532.4 eV (O3), attributed to metal−oxygen, phosphate, or phosphorus− oxygen and −OH bonds, respectively. 41 Overall, Li ions were effectively incorporated into the host material, as indicated by the peak of the Li ions in the spectra of the Li-CoCuP4 thin film.…”

Cucumis melo var agrestis based activated carbon/manganese ammonium phosphate @ carbon hollow sphere in dual redox additives for supercapattery device

“…The complexation of various constituents associated with 50 mg CS intercalated MnAP structure has been analyzed through photoelectron spectroscopy (XPS) studies to confirm the localizations of the inherent states associated with them as follows (Figure 4E‐I). The deconvolutions at binding energies (BE) 640.3 eV and 652.4 eV (Figure 4E) are responsible for Mn 2P 3/2 and Mn 2P 1/2 states 49‐52 . Figure 4F shows O 1s states of oxygen moieties attached to Mn 2+ metal atoms and OH/OC bondings respectively at 529.6 and 531.2 eV 53 .…”

“…The deconvolutions at binding energies (BE) 640.3 eV and 652.4 eV (Figure 4E) are responsible for Mn 2P 3/2 and Mn 2P 1/2 states. [49][50][51][52] Figure 4F shows O 1s states of oxygen moieties attached to Mn 2+ metal atoms and O H/O C bondings respectively at 529.6 and 531.2 eV. 53 The N 1s states (Figure 4G) are deconvoluted at 400 eV indicating the presence of NH 4…”