Pre-intercalation of squaric acid to construct V–O–C bonding: boosting Zn2+ storage in H11Al2V6O23.2 cathodes

Abstract

Pre-intercalation engineering has been proven to be an effective strategy for alleviating the limitations of vanadium oxide cathode materials. However, single-ion pre-intercalation suffers from issues such as limited structural regulation capability and uneven interlayer electrostatic repulsion. In view of this, this work reports a squaric acid molecule pre-intercalation engineering to enhance the high-efficiency Zn²⁺ storage capability of H₁₁Al₂V₆O_23.2 (denoted as HAVO-Sq80). The results demonstrate that squaric acid molecules form V–O–C bonds with the material to stabilize the interlayer structure, and the pre-intercalation engineering expands the interlayer spacing of the material to 1.46 nm, thus achieving a high specific capacity of ∼500 mAh g⁻¹ at 0.2 A g⁻¹ as well as excellent cycling stability, retaining 96.3% of its initial capacity after 7000 cycles at a high current density of 10 A g⁻¹. The assembled pouch cell (mass: 450 mg, 10.6 mg cm⁻²) delivers a capacity retention rate of 87% after 100 cycles at 0.1 A g⁻¹. Theoretical calculations reveal that squaric acid molecules enhance the electrical conductivity of the material, optimize the charge distribution after Zn²⁺ intercalation, and stabilize the V–O bonds of the material. This squaric acid molecular pre-intercalation strategy establishes an efficient design paradigm for boosting the performance of vanadium oxides and is expected to break the bottleneck in the development of high-performance cathode materials for aqueous zinc-ion batteries (AZIBs).