Electrothermally Driven Nucleation Energy Control of Defective Carbon and Nickel–Cobalt Oxide-Based Electrodes

Abstract

Multielement metal/metal oxides/carbon-based support hybrids are promising candidates for high-performance electrodes. However, conventional solid-state synthesis utilizing slow heating−cooling rates is limited by discrepancies in their phase transition temperatures. Herein, we report a rational strategy to control the nucleation energy of defective carbon fibers (DCFs) and Ni−Co-oxide-based electrodes capable of electrochemical activation using electrothermal waves (ETWs). The ETWs, triggered by Joule heating passing through CFs and Ni−Co precursors, induce programmable high-temperature processes via adjustable input powers and durations. The first ETW (∼1500 °C) fabricates the presculpted DCFs, while the second ETW (∼600 °C) directly synthesizes NiCo 2 O 4 spinel nanoparticles on the DCFs. Predesigning DCFs through the Gibbs free energy theory enables tunable control of nucleation energy and solution compatibility with Ni−Co precursors, allowing the morphological and compositional design of the optimal NiCo 2 O 4 @DCFs hybrids. Furthermore, they are electrochemically activated to change the morphologies and oxidation states of Ni−Co to more stable wrinkled structures strongly anchored to carbon supports and Ni−Co cations with low oxidation numbers. The activated NiCo 2 O 4 @DCFs electrodes exhibit outstanding specific capacitance and long-term cyclic stability (∼1925 F g −1 and ∼115−123% for 20 000 cycles). The ETWs offer a facile yet precise method to predesign carbon supports and subsequently synthesize hybrid electrodes.

Studies toward Morphological Changes of Silver/Carbon Fiber Composites and Their Optimization for High-Performance Electrochemical Electrodes

“…In the case of the sample produced by applying a 100 ms pulse three times, the capacitance decreases significantly, which is in contrast to that produced by using 50 and 75 ms pulses because the Ag particles excessively penetrate the CFs destroying the fibers. Similarly, in the case of Ag-CFs manufactured by applying five pulses, CFs show a considerable number of defects in all the cases, and the capacitance is highly degraded because the destroyed CFs reduce conductivity [39].…”

“…A binder-free silver sphere-embedded CF sheet was directly fabricated using the ETP (Figure 1). Prolonged exposure to high temperature during ETP can damage the CF and lower the electronic conductivity and stability of electrodes [39]. However, the decomposition of the precursor to the intended active material is required.…”

“…Consequently, these materials have been extensively utilized as electrode substrates for manufacturing electrochemical devices [37,38]. Additionally, the desired surface characteristics of carbon-based materials could be achieved via heat treatment [39][40][41]. This enables concurrent synthesis, modification, and optimization of the active material, support substrate, and integrated compound.…”

Eutectic Electrolytes Convoying Low-Temperature Metal-Ion Batteries

“…To date, numerous studies have focused on the electrochemical stability/reversibility of the metal anode, the study mechanism mainly is based on the electro-plating/​stripping process of M x + /Mn. ,,,, As aforementioned in the aqueous case, the hydrated M x + experiences a series of interrelated processes during the electrodeposition, including mass transfer, desolvation, charge transfer, and electro-crystallization, etc. , Among these process, the nucleation overpotential (η n ) and growth overpotential (η g ) are the primary parameters that are used for assessing the cycle performance of half- and full-cell devices (bottom inset in Figure b). η is the driving force for typical M x + electrodeposition processes, which shows the difference between the actual electrode potential ( E ) and equilibrium electrode potential ( E θ ), which can be determined using the polarization and exchange (depending on electrodes, electrolytes with various salt categories and concentrations, and others) current density. , Voltage–time/capacity profiles have been explored as an insight tool to explain a dependent relationship between the voltage and crystal nuclei. According to these profiles, Δη (distinguishing from η n ) is the driving force required during above electrodeposition processes. , Accordingly, metal cations in electrolytes are reduced to metal atoms (M 0 , e.g., Li 0 and Zn 0 ) and gather to form metal nuclei.…”