Ca-ion Batteries Research Articles

Three-dimensional porous phosphorus-graphdiyne as a universal anode material for both K- and Ca-ion batteries with high performance

Motivated by the recent synthesis of 2D boron-graphdiyne and P-doped graphdiyne, for the first time we report a 3D porous phosphorus-graphdiyne (termed 3D-PGDY) with an ultra-low mass density of 0.48 g cm−3, which is stable thermally and dynamically. Moreover, the unique bonding environment of sp-hybridizing provide multiple adsorption sites for K and Ca ions, and the uniformly distributed pores provide the channel for ion transport, exhibiting ultrahigh specific capacity of 1064.56 (2129.12 mAhg−1), low diffusion barriers of 0.1 (0.35 eV), the low open-circuit voltage of 0.27 (0.35 V), and small volume expansion of 2.43 (2.32%) for K (Ca) ion. These outstanding properties demonstrate that assembling graphdiyne into 3D porous structures is very promising for developing novel battery materials.

Layered potassium vanadate K2V6O16 nanowires: A stable and high capacity cathode material for calcium-ion batteries

Calcium-ion batteries are promising candidate as alternative to lithium-ion batteries with appealing features of abundant resource and high theoretical specific capacity up to 1337 mAh g−1. However, the development of calcium-ion batteries is primarily hindered by the lack of satisfactory electrode materials due to the large radius and charge density of calcium ion. Herein, we report the reversible calcium ion intercalation in layered potassium vanadate K2V6O16·2.7H2O as stable cathode with impressive electrochemical performance for Ca ion battery. The potassium vanadate nanowires obtained by facile hydrothermal process (typical lengths of 0.5–1.5 μm, widths of 70–100 nm) deliver a high initial capacity of 113.9 mAh g−1 at current density of 20 mA g−1 and high capacity retention of 78.30% at 50 mA g−1 after 100 cycles. In addition, the reversible intercalation of calcium ion in this layered potassium vanadate material with stable crystal structure is verified by ex-situ XPS and XRD techniques, demonstrating that layered K2V6O16·2.7H2O could be a potential cathode material for calcium-ion batteries.

Defect, transport, and dopant properties of andradite garnet Ca3Fe2Si3O12

There is growing interest to discover suitable calcium containing oxides that can be used as electrode materials in calcium ion batteries. A comprehensive computational investigation of ionic defects and Ca-ion diffusion in Ca-bearing oxide materials at the atomic level is important so as to predict their suitability for use in Ca-ion batteries. In this study, we apply atomistic simulation techniques to examine the energetics of defects, dopants, and Ca-ion diffusion in Ca3Fe2Si3O12. The calculations suggest that the Ca/Fe anti-site defect is the most favorable intrinsic defect causing such significant disorder, which would be sensitive to synthesis conditions. Diffusion of Ca2+ ions within Ca3Fe2Si3O12 is three-dimensional, with the activation energy of migration of 2.63 eV inferring slow ionic conductivity. The most favorable isovalent defects are Mn2+, Sc3+, and Ge4+ on Ca, Fe, and Si, respectively, for this process. The formation of extra calcium was considered to increase the capacity and diffusion of Ca in this material. It is found that Al3+ and Mn2+ are the candidate dopants on the Si and Fe sites, respectively, for this process and there is a reduction observed in the activation energies. The electronic structures of favorable dopant configurations are discussed using density functional theory simulations.

Functionalized Two-Dimensional Nanoporous Graphene as Efficient Global Anode Materials for Li-, Na-, K-, Mg-, and Ca-Ion Batteries

Two-dimensional nanoporous graphene (NPG) with uniformly distributed nanopores has been synthesized recently and shown remarkable electronic, mechanical, thermal, and optical properties with potent...

Defects and Dopants in CaFeSi2O6: Classical and DFT Simulations

Calcium (Ca)-bearing minerals are of interest for the design of electrode materials required for rechargeable Ca-ion batteries. Here we use classical simulations to examine defect, dopant and transport properties of CaFeSi2O6. The formation of Ca-iron (Fe) anti-site defects is found to be the lowest energy process (0.42 eV/defect). The Oxygen and Calcium Frenkel energies are 2.87 eV/defect and 4.96 eV/defect respectively suggesting that these defects are not significant especially the Ca Frenkel. Reaction energy for the loss of CaO via CaO Schottky is 2.97 eV/defect suggesting that this process requires moderate temperature. Calculated activation energy of Ca-ion migration in this material is high (>4 eV), inferring very slow ionic conductivity. However, we suggest a strategy to introduce additional Ca2+ ions in the lattice by doping trivalent dopants on the Si site in order to enhance the capacity and ion diffusion and it is calculated that Al3+ is the favourable dopant for this process. Formation of Ca vacancies required for the CaO Schottky can be facilitated by doping of gallium (Ga) on the Fe site. The electronic structures of favourable dopants were calculated using density functional theory (DFT).

Practical Aqueous Calcium-Ion Battery Full-Cells for Future Stationary Storage

There is a pressing need for high rate cycling, and cost-effective stationary energy storage systems in concomitance with the fast development of solar, wind and other types of renewable sources of energy. Aqueous rechargeable Ca-ion batteries have the potential to meet the growing demands of stationary energy storage devices because of their natural abundance, safety, low-cost proposition and higher volumetric capacity. In this study, a low cost, safe aqueous Ca-ion battery based on low potential, lower specific weight in-situ polymerized polyaniline as an anode and a high redox potential open framework structured potassium copper hexacyanoferrate as a cathode is demonstrated. The charge-discharge mechanism of this battery include dopind/dedoping of NO3- at the anode and intercalation and deintercalation of Ca-ion at the cathode. This Ca-ion battery works successfully in 2.5 M Ca(NO3)2 aqueous electrolyte, exhibiting 70 Wh kg-1 specific energy at 250 W kg-1 and even maintains 53 Wh kg-1 at 950 W kg-1 attributing to a good rate capability. At 0.8 A g-1 the battery provides an average specific capacity of 130 mAh g-1, exhibiting high Coulombic efficiency (~ 96%), with 95% capacity retention over 200 cycles life span, acquiring a new achievement in the electrochemical performance of aqueous Ca-ion batteries. Furthermore, the calcium-ion storage mechanism is investigated using high-end XANES and EXAFS measurements. Thus, this significant electrochemical performance of anode and cathode makes the battery as a promising candidate for grid-scale storage applications.

Ca Cobaltites as Potential Cathode Materials for Rechargeable Ca-Ion Batteries: Theory and Experiment

Rechargeable Ca-based batteries can potentially achieve higher energy capacity than Li-ion batteries. The development of Ca-ion batteries, however, remains in its infancy, especially due to the cha...

VOPO4·2H2O as a new cathode material for rechargeable Ca-ion batteries.

VOPO4·2H2O, as a new cathode material for Ca-ion batteries, exhibits a discharge capacity of 100.6 mA h g-1, excellent cycling stability (200 cycles) and good rate performance (42.7 mA h g-1 at 200 mA g-1). In situ X-ray diffraction and in situ Raman results demonstrate the calcium-ion-storage mechanism of VOPO4·2H2O is a single-phase reaction based on asymmetric Ca2+ insertion and deinsertion.

Exploits, advances and challenges benefiting beyond Li-ion battery technologies

The battery market is undergoing quick expansion owing to the urgent demand for mobile devices, electric vehicles and energy storage systems, convoying the current energy transition. Beyond Li-ion batteries are of high importance to follow these multiple-speed changes and adapt to the specificity of each application. This review-study will address some of the relevant post-Li ion issues and battery technologies, including Na-ion batteries, Mg batteries, Ca-ion batteries, Zn-ion batteries, Al-ion batteries and anionic (F- and Cl-) shuttle batteries. MH-based batteries are also presented with emphasize on NiMH batteries, and novel MH-accommodated Li-ion batteries. Finally, to facilitate further research and development some future research trends and directions are discussed based on comparison of the different battery systems with respect to Li-ion battery assumptions. Remarkably, aqueous systems are most likely to be given reconsideration for intensive, cost-effective and safer production of batteries; for instance to be utilized in (quasi)-stationary energy storage applications.

First principles study of alkali and alkaline earth metal ions adsorption and diffusion on penta-graphene

Developing carbon based anode materials for alkali and alkaline earth metal ion batteries is important for the development of non-Li metal ion batteries. From density functional theory calculations, we studied alkali metal (Li, Na, K, and Rb) and alkaline earth metal (Be, Mg, Ca, Sr, and Ba) ions adsorption on penta-graphene (PG), which is a novel two dimensional (2D) carbon isomer composed of both sp2 and sp3 hybridized C-atoms. Strong correlations are observed between the adsorption energy and the electronegativity of the M-atoms, namely, smaller electronegativity corresponds to lower adsorption energy. The suitable Ca-ion intercalation potential (~117 mV), metallic electronic structures of Ca-ion adsorbed PG, low Ca-ion diffusion energy barriers (0.36 eV to 0.51 eV), and high specific capacity (1487.6 mAh/g) suggest that PG can be applied as an excellent anode material for Ca-ion batteries.

Reversible Calcium Plating and Stripping at Room Temperature Using a Borate Salt

Interest has rekindled in reversible calcium plating and stripping, renewing hopes for the development of Ca-ion batteries. However, the development of an electrolyte that operates at room temperature and is stable to oxidation at practical potentials remains a significant barrier. Here we report the synthesis and crystal structure of a new fluorinated alkoxyborate Ca(B(Ohfip)4)2·4DME salt. Reversible plating and the dissolution of calcium from pure solutions of this salt in dimethoxyethane are demonstrated at 25 °C with capacities of 1 mAh cm–2 at a rate of 0.5 mA cm–2 over 30–40 cycles, with an anodic stability of >4.1 V vs Ca/Ca2+ (and up to 4.9 V in dimethyltriflamide). The dominant product is calcium, accompanied by CaF2 that forms by the reduction of the fluorinated anion. Whereas the cathodic stability requires improvement, this work shows that facile calcium plating and stripping at room temperature can be achieved using bulk electrodes.

TiSe2 cathode for beyond Li-ion batteries

Multivalent-ion batteries (MVIBs) provide economical and energy-dense alternatives to Li-ion batteries. In the academic pursuit to finding high-performance beyond Li-ion batteries, identifying a suitable cathode is a primary issue. More specifically, a cathode that supports high energy density, competitive charge/discharge rates, diffusion kinetics, and cyclability is desireable. In this regard, we computationally investigate layered TiSe2 as a cathode for beyond Li-ion batteries. We find voltages as high as 2.0, 2.0, 1.1, and 1.8 V for Li, Na, Mg, and Ca respectively. We compute voltage profiles, diffusion energy barriers, and formation energies, as well as consider the impact of swelling and electronic properties. While we consider several intercalants, we are especially interested in Ca, which we find to experience an energy barrier of approximately 0.4 eV, similar to the energy barrier experienced by Li, and lower than that of Mg. While Mg is the popular choice for multivalent-ion battery materials, we find that TiSe2 is able to accept more Ca per formula unit than Mg, and exhibits higher voltages than Mg, while experiencing improved diffusion kinetics. We advocate for the exploitation of TiSe2 layered cathodes for beyond Li-ion batteries, and especially for Ca-ion batteries.

DFT investigation of Ca mobility in reduced-perovskite and oxidized-marokite oxides

Progress in the development of rechargeable Ca-ion batteries demands the discovery of potential cathode materials. Transition metal oxides are interesting candidates due to their theoretical high energy densities, but with the drawback of a low Ca mobility. Previous computational/experimental investigations associate the electrochemical inactivity of various oxides (CaMO3-perovskite, CaMn2O4-post-spinel and CaV2O5) to high energy barriers for Ca migration. The introduction of oxygen and/or Ca vacancies in ternary transition metal oxides is a likely way to reshape the local topology and hence improve the Ca diffusivity. In this work, the energy barriers for Ca migration are calculated and discussed for (i) oxygen-deficient perovskites within the related Ca2Fe2O5-brownmillerite and Ca2Mn2O5 structures, and (ii) tunnel CaMn4O8, a derivative of the CaMn2O4-marokite with Ca vacancies.

Two-Dimensional Carbon-Based Auxetic Materials for Broad-Spectrum Metal-Ion Battery Anodes.

Auxetic materials possess special applications due to their unique negative Poisson's ratios (NPRs). As a classic 2D carbon material, the NPR of graphene is still deliberated. Introducing the NPR in graphene would increase its extraordinary properties, and the NPR together with other properties would bring more significant applications for graphene. In this Letter, on the basis of first-principles calculations, we reconfigure the structure of graphene, and, as an example, we propose a new 2D planar carbon allotrope, xgraphene, which is constructed by 5-6-7 carbon rings. Our theoretical calculations indicate that xgraphene has an NPR and constitutes a broad spectrum of metal ion battery anodes with high performance. Its maximum storage capacities are 930/1302/744/1488 mAh/g for Li/Na/K/Ca-ion batteries. It has low metal-ion diffusion energy barriers (≤0.49 eV) and low average open-circuit voltages (≤0.53 V). Our density functional theory results also showed that it is intrinsically metallic and possesses dynamic, thermal, and mechanical stabilities. Its intrinsic NPR, which stems from the weakness of coupling of carbon-carbon bonds, is found upon loading the uniaxial strain along the armchair direction. This work not only opens up a new direction for the design of the next-generation broad-spectrum energy-storage materials with low cost and high performance but also offers a class application for auxetic materials.

Understanding Ca Electrodeposition and Speciation Processes in Nonaqueous Electrolytes for Next-Generation Ca-Ion Batteries.

Electrochemical and analytical techniques were utilized to study Ca electrodeposition in nonaqueous electrolytes. Linear sweep voltammograms obtained at Au and Pt ultramicroelectrodes (UMEs) exhibit an inverse dependence between current density and scan rate, indicative of the presence of a chemical reaction step in a chemical-electrochemical (CE) deposition process. However, the magnitude of change in current density as a function of scan rate is larger at the Au UME than at the Pt UME. COMSOL simulation reveals that the chemical reaction step rate ( kc) obtained at the Pt UME is ∼10 times faster than that at the Au UME. Field desorption ionization mass spectrometry (MS) suggests that dehydrogenation of the borohydride anions by the metal substrate is the chemical reaction step. Pt is more efficient at abstracting hydride from borohydride ions than Au, leading to larger kc. Raman spectroscopy and electrospray ionization MS data show that Ca2+ ions are strongly coordinated with tetrahydrofuran and weakly interacting with BH4- anions. Electron microscopy shows that the surface morphology of Ca electrodeposition is different between Au and Pt, with Au exhibiting a smooth deposit, while a patchier deposit is seen on Pt.

Fibroscan® and ELF score in the study of fibrosis in obese patients with chronic liver disease: A preliminary study

Developing carbon based anode materials for alkali and alkaline earth metal ion batteries is important for the development of non-Li metal ion batteries. From density functional theory calculations, we studied alkali metal (Li, Na, K, and Rb) and alkaline earth metal (Be, Mg, Ca, Sr, and Ba) ions adsorption on penta-graphene (PG), which is a novel two dimensional (2D) carbon isomer composed of both sp2 and sp3 hybridized C-atoms. Strong correlations are observed between the adsorption energy and the electronegativity of the M-atoms, namely, smaller electronegativity corresponds to lower adsorption energy. The suitable Ca-ion intercalation potential (~117 mV), metallic electronic structures of Ca-ion adsorbed PG, low Ca-ion diffusion energy barriers (0.36 eV to 0.51 eV), and high specific capacity (1487.6 mAh/g) suggest that PG can be applied as an excellent anode material for Ca-ion batteries.

Performance of WS2 monolayers as a new family of anode materials for metal-ion (mg, Al and ca) batteries

Abstract We employed first-principle calculations to explore the possibility of using two-dimensional WS2 monolayer, as an anode material for Mg, Ca and Al ion batteries. In this study, we systematically investigated Mg, Ca and Al atoms intercalation and diffusion on the WS2 monolayer. The results show that all the studied metal atoms can be adsorbed on WS2 monolayer and the calculated density of states display metallic character for M@WS2 systems, which ensures good electronic conduction for using as battery electrodes. Study of the selected metals mobility indicates the low/moderate migration barriers on WS2, which confirm excellent cycling performance when acting as the battery electrode. In addition, Mg, Ca and Al are predicted to produce a voltage about 1.50, 1.63 and 3.13 V respectively and maximum capacity about 360.78, 326.09 and 531.58 mA h g−1, respectively. Our results suggest that WS2 monolayer can be employed as a promising anode material for the Mg, Ca and Al ion batteries with high power density and fast charge rates.

Prediction of MoO2 as high capacity electrode material for (Na, K, Ca)-ion batteries

Na, K and Ca-ion battery electrode materials with appropriate electrochemical properties are desirable candidates for replacing lithium-ion batteries (LIBs) because of their natural richness and low cost. Recently, MoO2 has been reported as the anode material in LIBs, but so far not received attention in Na and other ion batteries. In this paper, the behaviors of Na, K, and Ca on MoO2 are investigated by first-principles calculations. These metal atoms strongly absorb on the hexagonal center of MoO2 and the adsorption results in semiconducting-metallic transition. The low diffusion barrier, 0.13, 0.08, 0.22 eV for Na, K, Ca, respectively, leads to an ultrahigh diffusivity. Importantly, the maximum metal-storage phases of MoO2 monolayer correspond to Na4MoO2, K2.5MoO2 and Ca3MoO2, with considerable theoretical specific capacities of 837, 523 and 1256 mAh g−1. The electrode materials exhibit moderate average voltage of 0.30, 0.75, 0.35 V, respectively. Our findings suggest that MoO2 monolayer can be utilized as a promising anode material with high capacities and high rate performance for next generation ion batteries.

Ultrafast Synthesis of Calcium Vanadate for Superior Aqueous Calcium-Ion Battery.

Recently, multivalent aqueous calcium-ion batteries (CIBs) have attracted considerable attention as a possible alternative to Li-ion batteries. However, traditional Ca-ion storage materials show either limited rate capabilities and poor cycle life or insufficient specific capacity. Here, we tackle these limitations by exploring materials having a large interlayer distance to achieve decent specific capacities and one-dimensional architecture with adequate Ca-ion passages that enable rapid reversible (de)intercalation processes. In this work, we report the high-yield, rapid, and low-cost synthesis of 1D metal oxides MV3O8 (M = Li, K), CaV2O6, and CaV6O16·7H2O (CVO) via a molten salt method. Firstly, using 1D CVO as electrode materials, we show high capacity 205 mA h g−1, long cycle life (>97% capacity retention after 200 cycles at 3.0 C), and high-rate performance (117 mA h g−1 at 12 C) for Ca-ion (de)intercalation. This work represents a step forward for the development of the molten salt method to synthesize nanomaterials and to help pave the way for the future growth of Ca-ion batteries.

First-principles identification of spinel CaCo2O4 as a promising cathode material for Ca-ion batteries

The search for potential cathode materials is essential for the development of Ca-ion-based batteries, which are a cheap alternative to Li-ion batteries. In this work, we report a first-principles investigation into the feasibility of using spinel CaCo2O4 as a cathode for Ca-ion batteries. The results show that the spinel CaCo2O4 structure is stable, indicating that the synthesis of this compound should be feasible. The predicted voltage is consistently above 3.0 V at any Ca concentration, which is interesting for a cathode. Electronic structure analysis shows that the extracted spinel CaxCo2O4 compounds are metallic, which is indicative of good electronic conduction properties. The calculated activation energy barriers for Ca2+ migration are 0.58 and 0.22 eV at 100% Ca and 0% Ca concentrations, respectively, which suggest favorable electrode kinetics. Overall, the demonstrated structural stability, high average voltage, good electronic conductivity and excellent Ca2+ mobility highlight the promising potential of spinel CaCo2O4 as a cathode for Ca-ion batteries. The new fundamental insights presented here should stimulate further work on spinel CaCo2O4 cathodes for Ca-ion batteries.