ABSTRACT
Rechargeable aqueous Zn-Mn batteries have garnered extensive attention for next-generation high-safety energy storage. However, the charge-storage chemistry of Zn-Mn batteries remains controversial. Prevailing mechanisms include conversion reaction and cation (de)intercalation in mild acid or neutral electrolytes, and a MnO2 /Mn2+ dissolution-deposition reaction in strong acidic electrolytes. Herein, a Zn4 SO4 ·(OH)6 ·xH2 O (ZSH)-assisted deposition-dissolution model is proposed to elucidate the reaction mechanism and capacity origin in Zn-Mn batteries based on mild acidic sulfate electrolytes. In this new model, the reversible capacity originates from a reversible conversion reaction between ZSH and Znx MnO(OH)2 nanosheets in which the MnO2 initiates the formation of ZSH but contributes negligibly to the apparent capacity. The role of ZSH in this new model is confirmed by a series of operando characterizations and by constructing Zn batteries using other cathode materials (including ZSH, ZnO, MgO, and CaO). This research may refresh the understanding of the most promising Zn-Mn batteries and guide the design of high-capacity aqueous Zn batteries.
ABSTRACT
We choose copper(II) ions to salinize maleic acid, then form a layered copper maleate hydrate and apply this as an anode material for LIBs for the first time. The as-prepared material exhibits admirable electrochemical performance (404.6 mA h g-1 at 0.2 A g-1). A new hypothesis is developed for a better understanding of the unusual in situ XRD results and reaction mechanism.
ABSTRACT
Selenium sulfide as a new alternative cathode material can effectively address the inferior electronic conductivity of sulfur, which is the main cause for poor electrochemical reactivity of conventional lithium-sulfur batteries (Li-S batteries). Therefore, in this work, hollow carbon spheres loaded with NiSe2 nanoplates were prepared as SeS2 hosts for Li-SeS2 batteries. The unique micro-mesoporous hollow carbon spheres not only provide channels for the diffusion of SeS2, but also afford spaces for alleviating the volume expansion of the active substance. Besides, the external polar NiSe2 nanoplates increase active sites for capturing polysulfides or polyselenides during the charge/discharge process. Meanwhile, the excellent electronic conductivity of NiSe2 can accelerate the catalytic reaction on the surface, thus reducing the loss of soluble intermediate products and finally suppressing the "shuttle effect". These extraordinary features of the as-proposed cathode offer many superiorities in electrochemical performances in terms of a high initial discharge capacity of 1139 mA h g-1 at a current rate of 0.1C and an excellent cycling life of up to 1000 cycles at 1C.
ABSTRACT
Designing sulfur host materials with unique functions such as physical constraint or chemical catalysis to suppress the shuttle effect and promote the fast conversion of polysulfides is a prerequisite for lithium-sulfur batteries (LSBs). Herein, we construct hollow Co(OH)2 nanotubes connected by Ti3C2Tx nanosheets (denoted as Co(OH)2@Ti3C2Tx) as host materials for sulfur through a simple self-assembly method at room temperature. The large void spaces of Co(OH)2 nanotubes not only confine higher sulfur loading but also mitigate the volumetric expansion in the process of lithiation. Moreover, the conductive Ti3C2Tx layers facilitate fast electron transfer and catalyze the transition of sulfur based on the terminations on the surface. Combining those two materials can also act as an efficient polysulfide anchor to enable outstanding electrochemical performance. The Co(OH)2@Ti3C2Tx@S cathode presents a high discharge capacity of 1400 mAh g-1 at 0.1C and long-cycling stability at 1C for 500 cycles. Moreover, the obtained capacity of Li2S precipitation and the dissolution capacity reach 193.3 and 291.1 mAh g-1, respectively. Consequently, this work demonstrates a facile strategy to design multifunctional materials that effectively confine the polysulfides and enhance the performance of LSBs.
ABSTRACT
In this work, nanoflower-like Na0.5VOPO4·2H2O with a large interlayer distance of 6.5295 Å is synthesized via a simple chemical precipitation method at room temperature. It is the first time that the potential of the Na0.5VOPO4·2H2O electrode as a cathode material for SIBs has been investigated, and it exhibits a high specific capacity (127 mA h g-1 at 0.2C), outstanding long-term cycling stability and superior reaction kinetics.
ABSTRACT
Exploitation of superior anode materials is a key step to realize the pursuit of high-performance sodium-ion batteries. In this work, a reduced graphene oxide-wrapped FeSe2 (FeSe2 @rGO) composite derived from a metal-organic framework (MOF) was synthesized to act as the anode material of sodium-ion batteries. The MOF-derived carbon framework with high specific surface area could relieve the large volumetric change during cycling and ensure the structural stability of electrode materials. Besides, the rGO conductive network allowed to promote the electron transfer and accelerate reaction kinetics as well as to provide a protection role for the internal FeSe2 . As a result, the FeSe2 @rGO composite exhibited a high capacity of 350â mAh g-1 after 600â cycles at 5â A g-1 . Moreover, in situ XRD was conducted to explore the reaction mechanism of the FeSe2 @rGO composite upon sodiation/de-sodiation. Importantly, the presented method for the synthesis of MOF-derived materials wrapped by rGO could not only be used for FeSe2 @rGO-based sodium-ion batteries but also for the different transition metal-based composite materials for electrochemical devices, such as water splitting and sensors.
