Modulating the hydration number of calcium ions by varying the electrolyte concentration: Electrochemical performance in a Prussian blue electrode/aqueous electrolyte system for calcium-ion batteries

Ca 2+ (ionic radius 1.18 Å) and its multivalent nature. [7] Several electrode materials with large lattice spacing (e.g., V 2 O 5 and CaCo 2 O 4 ) or open frameworks (e.g., Prussian blue analogs) have been explored for CIBs. [8] Recently, a rechargeable CIB has been developed based on a dual-ion configuration, however, the electrochemical performances, particularly the rate capability (55% capacity retention at 0.4 A g −1 ) were still far from actual demands. [4c] A hybrid-ion strategy combining the respective advantages of different ions has been confirmed to be a feasible approach to enhance reaction kinetics of sluggish ions with large radius. [9] For example, the rate performance and cycling life of magnesium-ion batteries have been optimized significantly via a hybrid Li + /Mg 2+ design. [9c,e] In this report, we present a calcium-ion based energy storage device with a triion configuration (Ca 2+ /Li + /PF 6 − ). It was found that hybridizing calcium-ion based electrolyte with a small amount of Li + ions could significantly reduce the charge transfer resistance due to its small ionic radius and fast diffusion kinetics. After optimization, the as-fabricated CIBs delivered high rate capability of 15 C and superior cycling performance over 1500 cycles with 86% capacity retention at 5 C at room temperature, which is the best result of reported calcium-ion based full batteries.The configuration of the calcium-ion based tri-ion battery (CTIB) is featured with a rationally designed electrolyte with appropriate ratios of Ca 2+ , Li + , and PF 6 − ions, as shown in Figure 1a. Several metals that can alloy with Ca 2+ and Li + ions were selected as both the active anode materials and current collectors, while the expanded graphite was chosen as the cathode. During charging, Ca 2+ and Li + transport through the electrolyte to the metal anode and form alloys. Meanwhile, the intercalation of PF 6 − ions into the graphite occurs on the cathode side. The discharging process occurs reversibly.Owing to the high intercalation potential of PF 6 − ions, the stability of the hybrid electrolyte was evaluated with EC+EMC+PC+DMC (3:3:1:1 v/v/v/v) as the solvent. Linear sweep voltammetry (LSV) measurements of the pure solvent and electrolyte (0.6 m) with different Li contents (0 at.%, 15 at.%, 35 at.%, 50 at.%, 75 at.%, and 100 at.%) were conducted in the potential range of 3-5 V using stainless steel plates as the working electrode and the counter electrode. As shown in Figure S1, Supporting Information, oxidative current densities of the pure solvent and electrolyte with different Li contents are limited to 0.03-0.17 mA cm −2 , which are much lower than the standard cutoff value 0.5 mA cm −2 , suggesting high stability of the prepared electrolyte. Electrochemical Calcium-ion batteries (CIBs) are promising energy storage devices due to the merits of natural abundance, similar standard reduction potential to lithium, and bivalent-ion characteristic of calcium. However, the development of CIBs is hindered by the low rate capabilit...

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“…Generally, lower E a directly correlates to faster reaction kinetics, leading to higher rate performance . According to the Arrhenius equation

1 / R_{c t} = A \exp (- E_{a} / R T)

…”

supporting

confidence: 68%

Room‐Temperature Rechargeable Ca‐Ion Based Hybrid Batteries with High Rate Capability and Long‐Term Cycling Life

Lang

Jiang

Fang

et al. 2019

Advanced Energy Materials

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“…PBA materials have also been regarded as promising hosts for reversible insertion/extraction of multivalent ions (e.g., Zn 2+ , [ 49 ] Mg 2+ , [ 38 ] Ca 2+ , [ 122 ] Al 3+[ 123,124 ] ), due to their 3D open framework with large interstitial sites for fast reaction kinetics. The robust 3D frameworks of PBAs are stable toward the insertion/extraction of various multivalent ions, and the correlated applications in various kind of batteries could be illustrated as follows:…”

Section: Prospects On Future Research and Development Of Pba Cathode mentioning

confidence: 99%

Structure and Properties of Prussian Blue Analogues in Energy Storage and Conversion Applications

Qin

Shihua

et al. 2020

Adv Funct Materials

270

207

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In recent years, Prussian blue analogue (PBA) materials have been widely explored and investigated in energy storage/conversion fields. Herein, the structure/property correlations of PBA materials as host frameworks for various charge‐carrier ions (e.g., Na+, K+, Zn2+, Mg2+, Ca2+, and Al3+) is reviewed, and the optimization strategies to achieve advanced performance of PBA electrodes are highlighted. Prospects for further applications of PBA materials in proton, ammonium‐ion, and multivalent‐ion batteries are summarized, with extra attention given to the selection of anode materials and electrolytes for practical implementation. This work provides a comprehensive understanding of PBA materials, and will serve as a guidance for future research and development of PBA electrodes.

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“…[ 68 ] After the successful insertion of monovalent ions into PBAs, researchers have explored their possibility of storing multivalent ions to obtain higher energy density. Recently, many researchers [ 24,83 ] have studied the electrochemical properties of PBAs in aqueous CIBs. For instance, Yao et al.…”

Section: Cathode Materialsmentioning

confidence: 99%

“…The electrochemical performance of CuHCF was also studied using aqueous electrolytes with different Ca(NO 3 ) 2 concentrations. [ 83 ] The capacity retention was 49.1% after 1000 cycles in 1 m dilute solution, while in 8.4 m high concentration electrolyte, the capacity retention was significantly improved to 88.6%. The authors reasoned that with the increase of electrolyte concentration, the hydration number of Ca 2+ decreased, the radius of hydrated Ca 2+ shank, and the activation energy of Ca 2+ insertion into CuHCF electrode declined, so it can be successfully inserted/removed from CuHCF electrode.…”

Section: Cathode Materialsmentioning

confidence: 99%

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Recent Advances and Perspectives on Calcium‐Ion Storage: Key Materials and Devices

Yao

et al. 2020

Advanced Materials

115

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The urgent demand for cost‐effective energy storage devices for large‐scale applications has led to the development of several beyond‐lithium energy storage systems (EESs). Among them, calcium‐ion batteries (CIBs) are attractive due to abundant calcium resources, excellent volumetric and gravimetric capacities of Ca metal anode, and potential high energy density coming from the multivalent feature of Ca‐ion. Therefore, the exploration of CIBs electrode materials and the construction of CIBs devices are gaining increasing research interest. Relevant publications cover a wide range of materials by both theoretical and experimental investigations, whereas the performances of rocking‐chair CIBs have been unsatisfactory. Meanwhile, multi‐ion strategies using more than one ion as the charge carrier have been demonstrated to be feasible and promising options in realizing room temperature CIBs. The summary and reflection of previous studies would provide useful information for future exploration and optimization. In this circumstance, this paper overviews the reported CIBs electrode materials, including both anode and cathode, and presents the latest progress of multi‐ion strategies in CIBs. Fundamental challenges, potential solutions, and opportunities are accordingly proposed, mimicking other more mature EESs. This review may promote the development of electrode materials and accelerate the construction of low‐cost and high‐performance CIBs.

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Modulating the hydration number of calcium ions by varying the electrolyte concentration: Electrochemical performance in a Prussian blue electrode/aqueous electrolyte system for calcium-ion batteries

Cited by 53 publications

References 50 publications

Room‐Temperature Rechargeable Ca‐Ion Based Hybrid Batteries with High Rate Capability and Long‐Term Cycling Life

Room‐Temperature Rechargeable Ca‐Ion Based Hybrid Batteries with High Rate Capability and Long‐Term Cycling Life

Structure and Properties of Prussian Blue Analogues in Energy Storage and Conversion Applications

Recent Advances and Perspectives on Calcium‐Ion Storage: Key Materials and Devices

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