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Aqueous zinc ion batteries (A-ZIBs) have been used as new alternative batteries for grid-scale electrochemical energy storage because of their low cost and environmental protection. Finding a suitable and economical cathode material, which is needed to achieve high energy density and long cycle stability, is one of the most important and arduous challenges at the present stage. Potassium manganese hexacyanoferrate (KMHCF) is a kind of Prussian blue analogue. It has the advantages of a large 3D frame structure that can accommodate the insertion/extraction of zinc ions, and is nontoxic, safe, and easy to prepare. However, regularly synthesized KMHCF has higher water and crystal defects, which reduce the possibility of zinc ions' insertion/extraction, and subsequently the discharge capacity and cycling stability. In this work, a KMHCF material with less water and low defects was obtained by adding polyvinylpyrrolidone during the synthesis process to control the reaction process. The KMHCF serves as the cathode of A-ZIBs and exhibits an excellent electrochemical performance providing a specific capacity of 140 mA h g −1 for the initial cycle at a current density of 100 mA g −1 (1 C). In particular, it can maintain a reversible capacity of 85 mA h g −1 , even after 400 cycles at 1 C. Moreover, unlike the traditional zinc storage mechanism of A-ZIBs, we found that the KMHCF electrode undergoes a phase transition process when the KMHCF electrode was activated by a small current density, which is attributed to part of the Mn on the lattice site being replaced by Zn, thus forming a new stable phase to participate in the subsequent electrochemical reaction.

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Lithium-sulfur batteries (LSB) are one of the potential candidates for the next generation of electrochemical energy storage technology, due to their advantages of high theoretical capacity and high energy density. However, sluggish redox kinetics and the shuttle effect of polysulfides in the cyclic process lead to low sulfur utilization, severe polarization and poor cyclic stability. Herein, an SnS modified porous carbon nanosheet (SnS/PCNS) hybrid material is synthesized by a simple hydrothermal method and used to modify the separator of the LSB for the first time. Specifically, SnS/PCNS can not only adsorb polysulfides, but also enhance the redox reaction of polysulfides. In addition, SnS/PCNS are shown to promote rapid nucleation and uniform deposition of Li 2 S, and to improve the discharge capacity and heighten cyclic stability. The initial capacity is 1270 mAh g −1 at 0.5 C, the slow decay rate of each cycle is 0.039% at 1 C. When the sulfur loading is improved to 6 mg cm −2 , the high reversible capacity is 955.3 mAh g −1 at 0.5 C. As a new polysulfides adsorbent, SnS provides a potential route for the commercialization of LSBs.

Lithium−sulfur (Li−S) batteries have higher theoretical capacity and higher energy density, so they are considered to be one of the most promising candidates for next-generation energy storage devices. However, electrolyte-soluble polysulfides cause a shuttle effect and lead to poor cycle stability. This is one of the main obstacles to the practical applications of LSB technology. To overcome this problem, here, we report polar Ni 2 P hollow microspheres, with multilayer nesting, as sulfur host materials. Specifically, the multilayer polar Ni 2 P can simultaneously act as a multilayer physical barrier and chemical adsorption material. In addition, the Ni 2 P microspheres serve as activation catalysts, accelerating the redox reaction kinetics. The above features allow the structure to effectively suppress the shuttle effect and improve the discharge capacity and cycle stability of LSB. For example, the three-dimensional printed Ni 2 P@S (3DP-Ni 2 P@S) cathode can provide an initial capacity of 682 mAh/g, obtaining high cycle stability with low-capacity attenuation of 0.0072% per cycle for 400 cycles under 2C. Even when the sulfur loading is increased from 6.1 to 9.3 mg/cm 2 , this material still shows good capacity retention. This work inspires the design of multifunctional cathode materials and paves a new path for the development of Li−S batteries.

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