Potassium manganese hexacyanoferrate shows great potential
as a
cathode material for potassium-ion batteries (PIBs) due to its impressive
electrochemical performance, abundant elements, and easy synthesis.
However, severe capacity fading and poor K+ diffusion kinetics
greatly limit its large-scale application. Herein, we propose a facile
anion exchange method to construct Mn–Ni Prussian blue analogue
(denoted MnNi-PBA) spheres. The introduction of Ni can stabilize the
structure to enhance the cycling performance, and rich active sites
can be provided by the formation of a unique porous spherical structure,
thus enabling shorter ion diffusion pathways during charge/discharge.
Consequently, the MnNi-PBA sphere cathode delivers an initial discharge
capacity of 130.6 mAh g–1 at 10 mA g–1, an enhanced rate capability of 66.3 mAh–1 at
200 mA g–1, and a long cycle life with 83.8% capacity
retention after 500 cycles. When assembled with a pitch-derived soft
carbon anode, a full cell exhibits excellent cycling stability and
rate performance. In addition, ex situ X-ray diffraction demonstrates
that the MnNi-PBA spheres undergo reversible structural changes (monoclinic
↔ cubic) throughout the cycling process. Therefore, this work
may offer a design strategy to synthesize Mn-based Prussian blue analogues
for the application of PIBs.
Magnesium‐ion batteries (MIBs) are emerging as potential next‐generation energy storage systems due to high security and high theoretical energy density. Nevertheless, the development of MIBs is limited by the lack of cathode materials with high specific capacity and cyclic stability. Currently, transition metal sulfides are considered as a promising class of cathode materials for advanced MIBs. Herein, a template‐based strategy is proposed to successfully fabricate metal‐organic framework‐derived in‐situ porous carbon nanorod‐encapsulated CuS quantum dots (CuS‐QD@C nanorods) via a two‐step method of sulfurization and cation exchange. CuS quantum dots have abundant electrochemically active sites, which facilitate the contact between the electrode and the electrolyte. In addition, the tight combination of CuS quantum dots and porous carbon nanorods increases the electronic conductivity while accelerating the transport speed of ions and electrons. With these architectural and compositional advantages, when used as a cathode material for MIBs, the CuS‐QD@C nanorods exhibit remarkable performance in magnesium storage, including a high reversible capacity of 323.7 mAh g−1 at 100 mA g−1 after 100 cycles, excellent long‐term cycling stability (98.5 mAh g−1 after 1000 cycles at 1.0 A g−1), and satisfying rate performance (111.8 mA g−1 at 1.0 A g−1).
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