Key Takeaways & Executive Findings
- •• Efficient activation of Ni electrode employs chronopotentiostatic superoxidation. • Novel superoxide activation mechanism realizes the redox reaction with three-electron transfer (Ni ↔ Ni3+). • As-prepared CPS-Ni||Zn batteries exhibit simultaneously ultrahigh energy and power densities. • The CPS-Ni||Zn microbattery achieves exceptional energy density of 6.88 mWh cm−2 and power density of 339.56 mW cm−2, with stable operation over 10,000 cycles.
Abstract
Aqueous Ni–Zn microbatteries are safe, reliable and inexpensive but notoriously suffer from inadequate energy and power densities. Herein, we present a novel mechanism of superoxide-activated Ni substrate that realizes the redox reaction featuring three-electron transfers (Ni ↔ Ni3+). The superoxide activates the direct redox reaction between Ni substrate and KNiO2 by lowering the reaction Gibbs free energy, supported by in-situ Raman and density functional theory simulations. The prepared chronopotentiostatic superoxidation-activated Ni (CPS-Ni) electrodes exhibit an ultrahigh capacity of 3.21 mAh cm−2 at the current density of 5 mA cm−2, nearly 8 times that of traditional one-electron processes electrodes. Even under the ultrahigh 200 mA cm−2 current density, the CPS-Ni electrodes show 86.4% capacity retention with a Columbic efficiency of 99.2% after 10,000 cycles. The CPS-Ni||Zn microbattery achieves an exceptional energy density of 6.88 mWh cm−2 and power density of 339.56 mW cm−2. Device demonstration shows that the power source can continuously operate for more than 7 days in powering the sensing and computation intensive practical application of photoplethysmographic waveform monitoring. This work paves the way to the development of multi-electron transfer mechanisms for advanced aqueous Ni–Zn batteries with high capacity and long lifetime.
1. Introduction
With the growing demand for wearable electronics as enabled by the artificial intelligence of things (AIoT) revolution, micro-power sources are facing more stringent requirements, such as simultaneously high-power output operation, high capacity, small physical size, and lightweight [1–4]. A range of miniaturized power sources (a.k.a. microbatteries) featuring a footprint of ≤ 1 cm2 have been developed to meet these demands [5–7]. Furthermore, they also demonstrate a stable voltage output and are capable of delivering energy under extended operation. Aqueous battery systems have attracted extensive research interest due to their natural nontoxicity and nonflammability [8, 9]. Their safe fabrication environment opens up more prospects for advanced manufacturing techniques to be applied [10]. As a classic electrochemical system with high rate capabilities, Ni||Zn batteries are characterized by a single-electron transfer between Ni(OH)2/NiOOH with fast ion/electron transport [11, 12]. Furthermore, the high discharge voltage plateau (≈ 1.8 V) makes it a promising option compared with other Zn-based aqueous batteries (≈ 0.69–1.5 V). However, due to the low utilization of Ni electrode under traditional redox reactions, widespread adoption of nickel-zinc batteries remains a challenge [13].
The nanoengineering of nickel-based cathodes has been demonstrated to be an effective approach for enhancing electrode utilization. For example, Zhou et al. used NiS nanodots and abundant mesopores with uniform and robust adherence that enables permeating the matrix of microspheres. The improved proton-diffusion kinetic endows Ni||Zn battery with ultrahigh areal capacity of 41.3 mAh cm−2 [14]. Chen et al. designed a unique 3D hierarchical architecture consisting of nanoscale sheets and microscale supporting skeletons, enabling the effective exposure of electrochemical active materials [11]. The prepared nickel–cobalt double hydroxides (NiCo-DHs) electrode obtained a high specific capacity of 306 mAh g−1. Zhou et al. constructed a Ni metal–organic framework as a conductive scaffold for NiMoO4 nanowires, achieving an exceptional capacity of 229.2 mAh g−1 [15]. Surface modification is also a feasible strategy to improve interfacial reactivity. For example, Yao et al. constructed oxygen-rich defects on Ni nanotube arrays to modulate the surface electronic structure, thereby exhibiting strong OH− adsorption and achieving a high capacity of 334.9 mAh g−1 [16]. He et al. successfully manipulated the bimetallic sulfide nanointerfaces through water invoking interface corrosion, achieving a 200% increase in the capacity of electrodes [13]. In general, these strategies are based on traditional single-electron redox reactions for increasi
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Yixue Duan, Bolong Li, Kai Yang, Zheng Gong, Xuqiao Peng, Liang He, Derek Ho (2024). Ultrahigh Energy and Power Density in Ni–Zn Aqueous Battery via Superoxide-Activated Three-Electron Transfer. Nano-Micro Letters. https://doi.org/10.1007/s40820-024-01586-z
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Frequently Asked Questions
What is the main innovation of this paper?
The paper introduces a novel superoxide-activated Ni substrate that enables a three-electron transfer redox reaction (Ni ↔ Ni3+), significantly enhancing the energy and power densities of aqueous Ni–Zn batteries.
How does the superoxide activation mechanism work?
Superoxide activates the direct redox reaction between Ni substrate and KNiO2 by lowering the reaction Gibbs free energy, as supported by in-situ Raman and density functional theory simulations.
What are the key performance metrics of the CPS-Ni electrodes?
The CPS-Ni electrodes exhibit an ultrahigh capacity of 3.21 mAh cm−2 at 5 mA cm−2, nearly 8 times that of traditional one-electron processes, and retain 86.4% capacity after 10,000 cycles at 200 mA cm−2 with 99.2% Coulombic efficiency.
What are the energy and power densities of the CPS-Ni||Zn microbattery?
The CPS-Ni||Zn microbattery achieves an exceptional energy density of 6.88 mWh cm−2 and power density of 339.56 mW cm−2.
What practical application is demonstrated in the paper?
The power source can continuously operate for more than 7 days in powering the sensing and computation intensive practical application of photoplethysmographic waveform monitoring.
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