Ionically Conductive Tunnels in h‐WO₃ Enable High‐Rate NH₄⁺ Storage

Abstract

Compared to the commonly applied metallic ion charge carriers (e.g., Li + and Na + ), batteries using nonmetallic charge carriers (e.g., H + and NH 4 + )generally have much faster kinetics and high-rate capability thanks to the small hydrated ionic sizes and nondiffusion control topochemistry. However, the hosts for nonmetallic charge carriers are still limited. In this work, it is suggested that mixed ionic-electronic conductors can serve as a promising host for NH 4 + storage. Using hexagonal tungsten oxide (h-WO 3 ) as an example, it is shown that the existence of ionic conductive tunnels greatly promotes the high-rate NH 4 + storage. Specifically, a much higher capacity of 82 mAh g -1 at 1 A g -1 is achieved on h-WO 3 , in sharp contrast to 14 mAh g -1 of monoclinic tungsten oxide (m-WO 3 ). In addition, unlike layered materials, the insertion and desertion of NH 4 + ions are confined within the tunnels of the h-WO 3 , which minimizes the damage to the crystal structure. This leads to outstanding stability of up to 200 000 cycles with 68% capacity retention at a high current of 20 A g -1 .

A Highly Reversible Aqueous Ammonium‐Ion Battery based on α‐MoO3/Ti3C2Tz Anodes and (NH4)xMnO2/CNTs Cathodes

“…Small redox peaks are observed at low rates (Figure S5), which probably can be ascribed to the redox reactions for NH 4 + upon insertion/extraction in the α‐MoO 3 structure. Similar results have been reported for h ‐WO 3 , [24] but not h ‐MoO 3 [2a] . The corresponding GCD curves (Figure 3b) reveal that the capacity of this electrode is 107 mAh g −1 (∼117 mAh cm −3 ) at 0.2 A g −1 .…”

Ammonium ion pre-intercalation stabilized tunnel h-WO3 for fast NH4+ storage

“…30 Zhang et al also confirmed that tunnel h -WO 3 has a better NH 4 + storage capacity than m -WO 3 . 31 Although the above studies have preliminarily confirmed that metal oxides with tunnel structure have excellent NH 4 + storage performance. However, it has poor structural stability during charge storage, and is prone to dissolve in (weakly) acidic aqueous solutions, resulting in abnormal structural collapse.…”

“…(ii) Using layered metal oxide electrodes with large interlayer sites to achieve high capacity through the interlayer topological chemistry of NH4 + , such as Ti 3 C 2 MXenes, 28 metal oxides (V 2 O 5 , 21 NH 4 V 4 O 10 , 29 MnO x , 20 and MoO 3 Zhi's group reported the tunnel structure of the h-MoO 3 anode and proposed that there is reversible NH 4+ intercalation/de-intercalation and formation/ fracture of H bonds in the tunnel structure, and it exhibits fast electrode dynamics 30. Zhang et al also conrmed that tunnel h-WO 3 has a better NH 4 + storage capacity than m-WO 3 31. The prepared (NH 4 ) x WO 3 //MnO 2 A-HSCs exhibit an ultrahigh areal capacitance of 2239.7 mF cm À2 at 2 mA cm À2 , and a wide operating voltage window of 0-1.8 V. They also delivered an outstanding areal energy density of 1010.1 mWh cm À2 and a peak areal power density of 18.0 mW cm À2 .…”

Controlled Growth of the Interface of CdWOx/GDY for Hydrogen Energy Conversion

“…Moreover, tungsten trioxide (WO 3 ) is an abundant, versatile oxide and has been widely applied for catalysis, batteries, and electrochemical devices due to its intrinsic properties and unique characteristics for chemical/structural modifications. [35,36] WO 3 is also notable for its ability to intercalate different metal atoms to improve its performance. [37] For example, Mo-doped W 18 O 49 nanowires showed sevenfold higher catalytic activity than that of pristine W 18 O 49 .…”