Understanding the Gap between Academic Research and Industrial Requirements in Rechargeable Zinc‐Ion Batteries

Abstract

Rechargeable Zn‐ion batteries (RZIBs) are considered to be promising energy storage systems for large‐scale applications owing to their relatively high energy densities and inherently low costs, environmental benignity, as well as safety. With increasing interest and effort being devoted to this field, RZIBs are being tremendously advanced and are very likely to be commercialized in the near future. However, some challenges remain that need to be addressed. Moreover, reported results are quite often overstated through artificial exaggeration and cannot be translated to industrial applications as they were obtained under ideal testing conditions. Therefore, in this perspective, we discuss key parameters that need to be carefully considered when translating laboratory‐developed RZIBs into commercial reality. We also present a critical mini‐review on RZIBs and devote effort to issues that are overlooked in academic research. We believe that this perspective provides new or seldom‐discussed insight for future work and bridges the gap between academia and industry.

Open challenges and good experimental practices in the research field of aqueous Zn-ion batteries

“…Current academic research efforts to increase the energy content of aqueous Zn-ion batteries generally focus on developing new cathode materials with high specific capacity (e.g., >200 Ah/kg 9 ). At the same time, however, the role of the utilization of the zinc-based negative electrode and of its Coulombic efficiency on the electrochemical performance of the battery is widely ignored, despite its heavy influence on the specific energy of a full Zn-ion cell (Eq.…”

“…1 ). The Zn-based anodes routinely employed consist of Zn foils, metallic zinc deposited on a substrate, or composite electrodes with Zn particles within their formulation 7 , 9 . In order to understand the great challenges that hide behind the Zn-based anode utilization (often referred to as depth of discharge, DOD), it is helpful to consider the equi-energy curves, which are a graphical representation of Eq.…”

“…Unfortunately, the operational conditions that are mostly used in academic research employ an anode even more than eight times oversized with respect to the cathode, as the positive electrode is usually tested with low active mass loadings of around 1–2 mg/cm 2 while a metallic Zn foil anode usually has a Zn loading up to 1000 mg/cm 2 9 .…”

“…However, it is generally known that the higher the C-rate, the slower the aging processes of an insertion material 9 , 20 , 21 . In order to collect non-misleading and meaningful results on a realistic estimation of the cycle life of anode and cathode materials, it is critical to choose a 1 C rate for the aging test, as this mimics the rate required for aqueous ZIBs intended to be used as storage devices for the power grid.…”

“…The Zn-ion concept usually consists of a Zn-based negative electrode, onto/from which metallic zinc is electrodeposited and dissolved, and a positive electrode deinserting and inserting Zn 2+ cations from/within its lattice during the battery cycling 4 , 8 , 9 . In mild acidic ZIBs, typical insertion materials for the positive electrodes are based on manganese oxide 10 , vanadium oxides 10 , and Prussian blue analogs (PBAs) 4 .…”