Evaluating the Intrinsic Zinc Storage Capacity of Cation-Preintercalated Cathode with Electrochemically Active Surface Area

The guest cation preintercalation strategy has been widely adopted to improve the performance of zinc-vanadium batteries. However, existing studies always ignore the deintercalation of guest cations. This work focuses on the severe and universal deintercalation phenomenon and confirms the unaltered capacity after deintercalation, indicating that the capacity improvement mechanism cannot be attributed to the role of guest cations. Therefore, after excluding all of the previously researched factors for capacity improvement, the decisive factor is identified as the morphology (surface area). Based on the electrochemically active surface area (ECSA), a quantitative relationship with intrinsic capacity is established for the first time. This guides us to enhance battery capacity via enhancing ECSA through liquid-phase ultrasonic crushing to achieve the highest capacity of cation-preintercalated V₂O₅·<i>n</i>H₂O (333.7 mAh g^-1 at 10 A g^-1). We believe that the enhanced ECSA is a plausible explanation for the improved performance of hydrated vanadium oxides.