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

Abstract

<jats:p>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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>M</mml:mi></mml:math>V<jats:sub>3</jats:sub>O<jats:sub>8</jats:sub> (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mi>M</mml:mi><mml:mo>=</mml:mo><mml:mtext>Li</mml:mtext></mml:math>, K), CaV<jats:sub>2</jats:sub>O<jats:sub>6</jats:sub>, and CaV<jats:sub>6</jats:sub>O<jats:sub>16</jats:sub>·7H<jats:sub>2</jats:sub>O (CVO) via a molten salt method. Firstly, using 1D CVO as electrode materials, we show high capacity 205 mA h g<jats:sup>-1</jats:sup>, long cycle life (&gt;97% capacity retention after 200 cycles at 3.0 C), and high-rate performance (117 mA h g<jats:sup>-1</jats:sup> 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.</jats:p>

Alkali Ions Pre‐Intercalated Layered MnO2 Nanosheet for Zinc‐Ions Storage

“…[9,11,17,18,24,33] The good cycling stability could be explained by the pre-intercalated K + and H 3 O + in the KMO structure, as a result of charge balancing, [28] which acts as pillars to stabilize the layered structures. [29] The high K-ion insertion capacity, rate capability and capacity retention reported for the present KMO in aqueous Zn-ion battery positively compares with most of the other previously reported Zn-MnO 2 batteries [5,14,15,17,18,33,34,[36][37][38][39] (see Table S1, Supporting Information). Additionally, the rapid and simple synthesis route and the limited synthesis temperature used to prepare our NMO (350 °C) and KMO (380 °C) makes the process and materials competitive versus all the MnO 2 used as cathode in Zn-ion batteries listed in Table S1, Supporting Information.…”

“…[26] Since salt is at a molten state, ions have a higher diffusion coefficient (10 −5 to 10 −8 cm 2 s −1 ) [27] and diffuse faster than the conventional solid-state chemistry route (diffusion coefficient is in the order of 10 −18 cm 2 s −1 ), [27] resulting in an enhancement of the reaction kinetics and homogeneous mixing of reactants. [27][28][29] In our experiments, nitrate powder was firstly heated in air to reach a molten state (Figure 1a). The precursor powder (MnSO 4 ) was then added to the melt and the reaction time was kept to only 1 min, leading to the formation of solid product well dispersed in the colorless molten salt (Figure 1b).…”

The Promise of Calcium Batteries: Open Perspectives and Fair Comparisons

“…Thus far, the approaches to electrolyte and cathode development generally seek to employ Ca-equivalents from other metal systems, such as Mg owing to its valency (2+) and Na for its similar ionic radius (102 pm). Examples include Li- and Mg-inspired salts such as Ca­(TFSI) 2 and Ca­(B­(Ohfip) 4 ) 2 and cathodes such as sodium vanadate, magnesium vanadate, and sodium vanadium phosphates. − Other examples explored in Ca-ion batteries (some of which are aqueous) include calcium manganate, layered vanadium phosphates, and potassium copper hexacyanoferrate. − While trying Ca analogues among others has provided some headway, more fundamental understanding of the unique coordination and transport properties (in electrolytes, cathodes, and SEI) will be needed to inspire more out-of-the-box thinking to discover material systems better tailored to the unique properties of Ca 2+ .…”

Cathode Design for Aqueous Rechargeable Multivalent Ion Batteries: Challenges and Opportunities

“…Moreover, Simon and co‐workers synthesized highly ordered 1D CaV 6 O 16 ·7H 2 O (CVO) via a high‐yield and ultrafast (several grams in few minutes) molten salt method (Figure 14b). [ 190 ] It shows remarkable stability (88% after 500 cycles) under a low current density (20 mA g −1 ) and this was attributed to two aspects: a) the 1D‐nanostructured architecture avoids volume expansion/contraction during charge/discharge cycles; b) the interlayer spacing is increased by crystalline water in the CVO layers.…”