Wang Chun-Fang,Zhang Shi-Wei,Huang Lan,Zhu Yuan-Min,Liu Feng,Wang Jian-Chuan,Tan Li-Ming,Zhi Chun-Yi,Han Cui-Ping
Calcium-ion batteries (CIBs) have generated intense interest due to the growing demand for safer, cheaper, and large-scale energy storage systems. However, their development is still in its infancy, owing to the lack of suitable cathodes for sustaining reversible Ca 2+ intercalation/deintercalation. Herein, layered H 2 V 3 O 8 (HVO) with Zn 2+ pre-insertion (ZHVO) is reported as a high-rate and highly durable cathode material for CIBs. The existence of Zn 2+ and H 2 O pillars could expand the interlayer spacing up to 1.8 nm, which is favorable for the diffusion of bulky Ca 2+ . The formation of Zn–O bonds facilitates electron transfer and enhances electrical conduction. Consequently, the ZHVO cathode achieves superior capacity performance (213.9 mAh·g −1 at 0.2 A·g −1 ) and long lifespan (78.3% for 1,000 cycles at 5 A·g −1 ) compared to pristine HVO. Density functional theory (DFT) calculations revealed that Zn 2+ moved during Ca 2+ intercalation, thereby reducing the diffusion energy barrier and facilitating Ca 2+ diffusion. Finally, a safe aqueous calcium ion cell was successfully assembled. Graphical abstract
Chunyan Zhang,Rui He,Jichen Zhang,Yang Hu,Zhiyong Wang,Xianbo Jin
Graphite is an attractive cathode material for energy storage because it allows reversible intercalation/deintercalation of many compound anions at high potentials. However, because the sizes of the compound anions are greatly larger than the lamellar spacing of graphite, common graphite used as cathode may suffer from slow kinetics and large volume expansion. Here, it is demonstrated that graphite with high crystallinity and nanosheet-bricked porous structure can be an excellent cathode for aluminum-ion batteries. This porous graphite is derived from carbon black via a simple electrochemical graphitization in molten CaCl2, and the high crystallinity and thin layer characters facilitate the high capacity and high rate storage of aluminum tetrachloride ions. Moreover, the bricked porous structure endows the fabricated cathode with a providential porosity to perfectly match the huge volume expansion of graphite (650% against a charging capacity of 100 mA h g–1), thus this electrochemical graphite exhibits integrated high gravimetric and volumetric capacities as well as high structural stability during cycling.
The Li3VO4@C microsphere composite was first reported as a novel cathode material for rechargeable aluminum-ion batteries (AIBs), which manifests the initial discharge capacity of 137 mAh g–1 and and remains at 48 mAh g–1 after 100 cycles with almost 100% Coulombic efficiency. The detailed intercalation mechanism of Al into the orthorhombic Li3VO4 is investigated by ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) of Li3VO4@C electrodes and the nuclear magnetic resonance aluminum spectroscopy (27Al NMR) of ionic liquid electrolytes in different discharge/charge states. First-principle calculations are also carried out to investigate the structural change as Al inserts into the framework of Li3VO4. It is revealed that the Al/Li3VO4@C battery goes through electrochemical dissolution and deposition of metallic aluminum in the anode, as well as the insertion and deinsertion of Al3+ cations in the cathode in the meantime. The rechargeable AIBs fabricated in this work are of low cost and high safety, which may make a step forward in the development of novel cathode materials based on the acidic ionic liquid electrolyte system.
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