A paradigm
shift in aqueous rechargeable batteries has seen the
development of nonmetal ammonium ions (NH
4
+)
as charge carriers. NH
4
+ ions have a molecular weight of
18 g mol–1 and hydrated ionic size of 3.31 Å,
which are smaller than those of metal ions, leading to faster kinetics
during charge transfer. Yet few electrode materials have been studied
for this type of battery. This work is the first effort to show that
polyaniline (PANI) is an excellent material for NH
4
+ ion
storage, and thus further proves that NH
4
+ ions
can be used as effective charge carriers in aqueous ion battery systems.
A facile solution method is used to prepare emeraldine salt polyaniline
(ES-PANI) on the carbon felts (CFs) as the cathode material. The battery
cell based on the ES-PANI cathode material shows a good discharge
capacity of 160 mAh g–1 at a specific current of
1 A g–1. At 5 A g–1, it shows
a good capacity retention of 82% after 100 cycles and also exhibits
excellent rate capability. Furthermore, it is found that the ES-PANI/CFs
washed with water deliver higher capacity than those washed with ethanol,
because washing with ethanol causes the oligomers to dissolve in the
solution and thus decreases the storage capacity of ES-PANI for NH
4
+ ion storage. The intercalation/deintercalation of NH
4
+ ion is shown to be highly reversible in the ES-PANI electrode doped
with Cl‑ ions, due to the stable redox properties
of nitrogen in ES-PANI polymer chains. As such, this work sheds new
insight into the exploration of alternative electrode material for
ammonium ion storage, which can lead to new electrochemical energy
technology.
Non-metal ammonium (NH þ 4 ) ions have recently been explored as effective charge carriers in battery systems due to their abundancy, light weight, small hydration shells in water. The research concerning the use of NH þ 4 redox chemistry in batteries, particularly in flexible batteries, is still in its infancy. For the first time, we report a flexible full NH þ 4 ion battery (AIB) composed of a concentrated hydrogel electrolyte sandwiched between NH 4 V 3 O 8 • 2.9H 2 O nanobelts cathode and polyaniline (PANI) anode, for enhanced performance. The hydrogel electrolyte is simply synthesized by using ammonium sulfate, xanthan gum and water. As a reference, the AIB based on the liquid aqueous electrolyte is prepared first, which exhibits a capacity of 121 mAh g À 1 and a capacity retention of 95 % after 400 cycles at a specific current of 0.1 A g À 1 . On the other hand, the simple synthesis of the hydrogel electrolyte allows us to facilely tune and optimize the salt contents in the electrolyte, to maximize the ionic conductivity, transport kinetics, mechanical characteristics, and consequently the battery performance. It is found that the flexible battery based on the hydrogel electrolyte prepared from 3 M ammonium sulfate solution shows the best electrochemical performance, i. e., a capacity of 60 mAh g À 1 while maintaining a capacity retention of 88 % after 250 cycles at a specific current of 0.1 A g À 1 . Moreover, the flexible AIB retains excellent electrochemical performance when bent at different angles, demonstrating remarkable mechanical strength and flexibility. Therefore, this study sheds new light on the utilization of concentrated hydrogel electrolyte in the AIB chemistry, for developments of novel electrochemical energy storage technology with high safety and low cost.
Batteries using a
water-based electrolyte have the potential to
be safer, more durable, less prone to thermal runaways, and less costly
than current lithium batteries using an organic solvent. Among the
possible aqueous battery options, ammonium-ion batteries (AIBs) are
very appealing because the base materials are light, safe, inexpensive,
and widely available. This review gives a concise and useful survey
of recent progress on emerging AIBs, starting with a brief overview
of AIBs, followed by cathode materials, anode materials, electrolytes,
and various devices based on ammonium-ion storage. Aside from summarizing
the most updated electrodes/electrolytes in AIBs, this review highlights
fundamental mechanistic studies in AIBs and state-of-the art applications
of ammonium-ion storage. The present work reviews various theoretical
efforts and the spectrum studies that have been used to explore ionic
transport kinetics, electrolyte structure, solvation behavior of ammonium
ions, and the intercalation mechanism in the host structure. Furthermore,
diverse applications of ammonium-ion storage apart from aqueous AIBs
are discussed, including flexible AIBs, AIBs that can operate across
a wide temperature range, ammonium-ion supercapacitors, and battery–supercapacitor
hybrid devices. Finally, the review is concluded with perspectives
of AIBs, challenges remaining in the field, and possible research
directions to address these challenges to boost the performance of
AIBs for real-world practical applications.
Current commercial batteries are mainly metal-based, with metal elements in charge carriers and/or electrode materials, which poses potential economic and environmental concerns due to the heavy use of nonrenewable metals....
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