High Energy and Power Zinc Ion Capacitors: A Dual-Ion Adsorption and Reversible Chemical Adsorption Coupling Mechanism

Abstract

Zinc ion capacitors (ZICs) hold great promise in large-scale energy storage by inheriting the superiorities of zinc ion batteries and supercapacitors. However, the mismatch of kinetics and capacity between a Zn anode and a capacitive-type cathode is still the Achilles' heel of this technology. Herein, porous carbons are fabricated by using tetra-alkali metal pyromellitic acid salts as precursors through a carbonization/ self-activation procedure for enhancing zinc ion storage. The optimized rubidium-activated porous carbon (RbPC) is verified to hold immense surface area, suitable porosity structure, massive lattice defects, and luxuriant oxygen functional groups. These structural and compositional merits endow RbPC with the promoted zinc ion storage capability and more matchable kinetics and capacity with a Zn anode. Consequently, RbPC-based ZIC delivers a high specific energy of 178.2 W h kg −1 and a peak power density of 72.3 kW kg −1 . A systematic ex situ characterization analysis coupled with in situ electrochemical quartz crystal microbalance tests reveal that the preeminent zinc ion storage properties are ascribed to the synergistic effect of the dual-ion adsorption and reversible chemical adsorption of RbPC. This work provides an efficient strategy to the rational design and construction of high-performance electrodes for ZICs and furthers the fundamental understanding of their charge storage mechanisms or extends the understanding toward other electrochemical energy storage devices.

Molecular engineering toward sustainable development of multiple-doped hierarchical porous carbons for superior zinc ion storage

“…S16) further revealed the same content evolution of O and Zn, that is, their increment during discharge and decrement during charge. The formation of zinc hydroxide sulfate hydrates was ascribed to the proton insertion into the carbon cathode while leaving OH − behind and causing pH increment at the low-potential region [13]. Therefore, these results also reflected the reversible proton (de)insertion at the cathode [68].…”

“…S14b). The I D /I G ratios of the cathode gradually increased during discharge and returned to normal values at the full charge stage, implying the reversible transformation of the disordered structure of the carbon cathode [13]. The XRD patterns (Fig.…”

“…Some sub-structures in the CV curve showed small hump peaks at around 1.0/1.2 V, suggesting the presence of certain redox processes. According to the literature, redox processes are possibly related to the faradaic redox reactions between oxygen functional groups and Zn ions, such as -C-OH [58][59][60], -C=O [13,58], or -COOH [42] (-C-OH + Zn 2+ + e − ⇌ -C-O-Zn + H + ; -C=O + Zn 2+ + 2e − ⇌ -C-O-Zn; -COOH + Zn 2+ + e − ⇌ -COO-Zn + H + ). The galvanostatic charge-discharge (GCD) profiles further reflected the superior storage performance of the Zn//N/P/O-PC-1200 device, which exhibited a high storage capacity (Fig.…”

“…Moreover, the nanostructured design and morphological control of nanocarbons boost the effective electrode/ electrolyte contact and reduce the ion transport distance, further exposing more active sites for Zn-ion storage. To this end, various structurally engineered PCs, such as hollow carbon nanospheres from MnO 2 nanoflower templates [9], carbon nanowires from MnO 2 nanowire templates [10], three-dimensional PCs from SiO 2 templates [11], K 2 CO 3 -activated PCs [12], ZnO-activated PCs [2], and a series of alkali-metal-activated PCs [13], have been reported as cathodes for ZHSCs. However, the fabrication processes are generally based on the indirect carbonization of precursors with demands for activations and templates.…”

A low-concentration eutectic electrolyte for superior cycling ability of aqueous zinc-ion capacitors

“…, porous ASAC-30 with a high surface area of ∼3000 m 2 g −1 and pore size of 0.5–4 nm) and Zn anodes as control samples providing extrinsic pseudocapacitance. 29 Simultaneously, the capacitive and diffusion-controlled contributions were further quantitatively calculated according to the equations: i = k 1 v + k 2 v 1/2 and i / v 1/2 = k 1 v 1/2 + k 2 , where k 1 and k 2 are constants, and k 1 v and k 2 v 1/2 represent the capacitive and diffusion-controlled contributions of the electrode reactions, respectively (Fig. S9†).…”