Search

Because they are safer and less costly than state-of-the-art Li-ion batteries, aqueous zinc-ion batteries (AZIBs) have been attracting more attention in stationary energy storage and industrial energy storage. However, the electrochemical reaction of H + in all of the cathode materials of AZIBs has been puzzling until now. Herein, highly oriented VO 2 monocrystals grown on a Ti current collector (VO 2 -Ti) were rationally designed as the research model, and such a well-aligned VO 2 cathode also displayed excellent zinc-ion storage capability (e.g., a reversible capacity of 148.4 mAh/g at a current density of 2 A/g). To visualize the H + reaction process, we used time-of-flight secondary-ion mass spectrometry. With the benefit of such a binder-free and conductor-free electrode design, a clear and intuitive reaction of H + in a VO 2 cathode is obtained, which is quite significant for unraveling the accurate reaction mechanism of VO 2 in AZIBs.

For solving the drawbacks of low conductivity and the shuttle effect in a sulfur cathode, various nonpolar carbon and polar metal compounds with strong chemical absorption ability are applied as sulfur host materials for lithium-sulfur (Li-S) batteries. Nevertheless, previous research simply attributed the performance improvement of sulfur cathodes to the chemical adsorption ability of polar metal compounds toward lithium polysulfides (LPS), while a deep understanding of the enhanced electrochemical performance in these various sulfur hosts, especially at the molecular levels, is still unclear. Herein, for a mechanistic understanding of superior metal phosphide host in Li-S battery chemistry, an integrated phosphide-based host of CF/FeP@C (carbon cloth with grown FeP@C nanotube arrays) is chosen as the model, and this binder-free cathode can exclude interference from the binder and conductive additives. With a systematic electrochemical investigation of the loading sulfur in such oxide- and phosphide-based hosts (CF/Fe 3 O 4 @C and CF/FeP@C), it is found that CF/FeP@C@S shows much superior Li-S performances. The greatly enhanced performance of CF/FeP@C@S suggests that FeP can well suppress the shuttle effect of LPS and accelerate their transformation during the charge-discharge process. The first-principles calculations reveal the performance variations of Fe 3 O 4 and FeP in Li-S batteries mainly because the shifts of the p band of the FeP could accelerate the interfacial electronics transfer dynamics by increasing the electronic concentration in the Fermi level of adsorbed Li 2 S 4 . The current work sheds light on the promising design of superior Li-S batteries from both theoretical and experimental aspects.

To solve the serious problems (the agglomeration of nano-Fe 0 , dissolution of polysulfide, and low electronic conductivity of Li 2 S) of earth-abundant pyrite (FeS 2 ) cathodes for lithium batteries, a simple in situ encapsulation and transformation route has been successfully developed to synthesis pitaya-structured porous carbon embedded with FeS 2 nanoparticles. Due to such a hierarchical architecture design, this cathode of pitaya-structured FeS 2 @C can effectively avoid the serious agglomeration and coarsening of small Fe nanoparticles, reduce the dissolution of polysulfide, and provide superior kinetics toward lithium storage, resulting in enhanced reversibility and rate capability. Cycling in the voltage region of 1.0-3.0 V at 0.3 A g -1 , the current conversion-based FeS 2 @C cathode displays a high and stable energy density (about 1100 Wh kg -1 ), ultrahigh rate capability (a reversible capability of 660, 609, 554, 499, 449, and 400 mA h g -1 at 0.2, 0.5, 1.0, 2.0, 5.0, and 10 A g -1 , respectively), and stable cycling performance.