Owing to the high volumetric capacity and low redox potential, zinc (Zn) metal is considered to be a remarkably prospective anode for aqueous Zn‐ion batteries (AZIBs). However, dendrite growth severely destabilizes the electrode/electrolyte interface, and accelerates the generation of side reactions, which eventually degrade the electrochemical performance. Here, an artificial interface film of nitrogen (N)‐doped graphene oxide (NGO) is one‐step synthesized by a Langmuir–Blodgett method to achieve a parallel and ultrathin interface modification layer (≈120 nm) on Zn foil. The directional deposition of Zn crystal in the (002) planes is revealed because of the parallel graphene layer and beneficial zincophilic‐traits of the N‐doped groups. Meanwhile, through the in situ differential electrochemical mass spectrometry and in situ Raman tests, the directional plating morphology of metallic Zn at the interface effectively suppresses the hydrogen evolution reactions and passivation. Consequently, the pouch cells pairing this new anode with LiMn2O4 cathode maintain exceptional energy density (164 Wh kg−1 after 178 cycles) at a reasonable depth of discharge, 36%. This work provides an accessible synthesis method and in‐depth mechanistic analysis to accelerate the application of high‐specific‐energy AZIBs.
The development of fully foldable energy storage devices is a major science and engineering challenge, but one that must be overcome if next-generation foldable or wearable electronic devices are to be realized. To overcome this challenge, it is necessary to develop new electrically conductive materials that exhibit superflexibility and can be folded or crumpled without plastic deformation or damage. Herein, a graphene film with engineered microvoids is prepared by reduction (under confinement) of its precursor graphene oxide film. The resultant porous graphene film can be single folded, double folded, and even crumpled, but springs back to its original shape without yielding or plastic deformation akin to an elastomeric scaffold after the applied stress is removed. Even after thermal annealing at ≈1300 °C, the folding performance of the porous graphene film is not compromised and the thermally annealed film exhibits complete foldability even in liquid nitrogen. A solid-state foldable supercapacitor is demonstrated with the porous graphene film as the device electrode. The capacitance performance is nearly identical after 2000 cycles of single-folding followed by another 2000 cycles of double folding.
Potassium-ion
batteries (PIBs) have received significant attention
because of the abundant potassium reserves and similar electrochemistry
of potassium to that of lithium. Because of the open framework and
structural controllability, Prussian blue and its analogues (PB) are
considered to be competitive cathodes of PIBs. However, the intrinsic
lattice defects and poor electronic conductivity of PBs induce poor
cycling performance and rate capability. Herein, we propose a polypyrrole-modified
Prussian blue material (KHCF@PPy) via an in situ polymerization coating
method for the first time. KHCF@PPy possesses a low defect concentration
and improved electronic conductivity, and the electrode was found
to exhibit 88.9 mA h g–1 discharge capacity at 50
mA g–1, with 86.8% capacity retention after 500
cycles. At a higher current density of 1000 mA g–1, the initial discharge capacity was 72.1 mA h g–1, which dropped slightly to 61.8 mA h g–1 after
500 cycles. The capacity decay rate was 0.03% per cycle. Detailed
characterization showed a lack of phase transition during the charge
and discharge processes and determined that K ions were not completely
extracted from the monoclinic structure, possibly contributing to
the excellent cycling stability. This simple surface modification
method represents a promising means of mitigating issues currently
associated with PB-based cathodes for PIBs.
Porous carbon microspheres with different defects and S-doping are synthesized for K-ion batteries. The depth of K-ions insertion, the additional oxidation–reduction reaction, and the adsorption process of K-ions on active sites can be enhanced.
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