Weak Solvation Effect Enhancing Capacity and Rate Performance of Vanadium‐Based Calcium Ion Batteries: A Strategy Guided by Donor Number

Abstract

Calcium ion batteries (CIBs) are considered as an important candidate for post‐lithium energy storage devices due to their abundance of resources and low cost. However, CIBs still suffer from slow kinetics due to the large solvation structure and high desolvation energy of Ca2+ ions. Here, a solvation regulation strategy based on donor number (DN) is reported to achieve easy‐desolvation and rapid storage of Ca2+ in sodium vanadate (Na2V6O16·2H2O, NVO). Specially, the solvent with a low DN, represented by propylene carbonate (PC), forms the first solvation shell of calcium ions with weak binding energy and small shell structure, which facilitates the migration of Ca2+ in the electrolyte. More importantly, the low DN solvent is preferentially desolvated at the cathode/electrolyte interface, promoting the insertion of Ca2+ into the NVO electrode. Mechanism studies further confirm the highly reversible uptake/release of Ca2+ in the NVO cathode, along with the VO distance change in the coordination structure. Therefore, the NVO cathode achieves high capacity (376 mAh g−1 at 0.3 A g−1) and high‐rate performance (151 mAh g−1 at 5 A g−1). The weak solvation effect strategy further improves the electrochemical performance and provides great importance for the design of the long‐term development of CIBs.

Precise Distance Control and Functionality Adjustment of Frustrated Lewis Pairs in Metal–Organic Frameworks

“…Among the products, propylene carbonate (PC) was highly valuable, widely used as electrolytes in batteries to power vehicles, such as lithium batteries, 56 lithium-ion batteries, 57 and calcium ion batteries. 58…”

“…Initial tests showed more than 90% conversion efficiency in most of the reactions under identical conditions. Among the products, propylene carbonate (PC) was highly valuable, widely used as electrolytes in batteries to power vehicles, such as lithium batteries, lithium-ion batteries, and calcium ion batteries …”

Anion-hosting cathodes for current and late-stage dual-ion batteries

“…The battery system based on the dual-ion reaction is not confined to lithium-ion DIBs (Li-DIBs). Novel battery systems such as sodium, potassium, magnesium, zinc, aluminum, and calcium DIBs (Na-DIBs [25], K-DIBs [26][27][28][29][30], Mg-DIBs [31,32], Zn-DIBs [33], Al-DIBs [34][35][36][37], and Ca-DIBs) [38][39][40] with the excellent cycle stability and high-rate performance can be realized. The dual-ion working mechanism can be used for the development of novel battery systems [41].…”

Sodium ion pre-intercalation regulates the electron density and structural stability of vanadium oxide nanowires for Ca–ion batteries

“…It is difficult for calcium ions to enter into a hosts due to their large radius, which can easily cause the material to expand and quickly fail during the charge and discharge process. 24,27,28 Additionally, the solvent structure of calcium ions in the electrolyte is huge, and their dissolution process is particularly challenging, which will lead to a slow diffusion rate. 16,29,30 Therefore, the investigation into appropriate electrolytes and cathode materials that allow for fast reversible Ca 2+ ion storage is critically important for the development of CIBs.…”