Co S is considered a promising candidate as the anode material in lithium-ion batteries (LIBs) because of its remarkable electrical conductivity, high theoretical capacity, and low cost. However, the practical application of Co S is greatly restricted because of its poor cycling stability and rate performance, which result mainly from the large volume expansion and dissolution of the polysulfide intermediates during the charge/discharge process. In this report, Co S embedded in N-rich carbon hollow spheres are successfully designed and synthesized through an in situ pyrolysis and sulfurization process, employing the well-known ZIF-67 as the precursor and ethanethiol as the sulfur source. Co S nanoparticles embedded in the N-rich hollow carbon shell exhibit excellent lithium storage properties at a high charge/discharge rate. A discharge capacity of 784 mAh g is obtained upon battery testing at a current density of 1 C (544 mA g ). Even upon cycling at a current density of 4 C, the as-prepared Co S /N-C can still deliver a discharge capacity of 518 mAh g . The excellent battery performance can be attributed to the hollow structure as well as the N-rich carbon encapsulation. Moreover, this metal-organic framework sulfurization route also shows good generality for the synthesis of other metal sulfide-carbon composites such as ZnS/N-C and Cu S/C.
Am olecular design strategy is used to construct ordered mesoporous Ti 3+ -doped Li 4 Ti 5 O 12 nanocrystal frameworks (OM-Ti 3+ -Li 4 Ti 5 O 12 )b yt he stoichiometric cationic coordination assembly process.T i 4+ /Li + -citrate chelate is designed as anew molecular precursor,inwhichthe citrate can not only stoichiometrically coordinate Ti 4+ with Li + homogeneously at the atomic scale,b ut also interact strongly with the PEO segments in the Pluronic F127. These features make the co-assembly and crystallization process more controllable, thus benefiting for the formation of the ordered mesostructures. The resultant OM-Ti 3+ -Li 4 Ti 5 O 12 shows excellent rate (143 mAh g À1 at 30 C) and cycling performances (< 0.005 % fading per cycle). This work could open af acile avenue to constructing stoichiometric ordered mesoporous oxides or minerals with highly crystalline frameworks.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
Uniquely structured CoS/N‐doped carbon@MoS2 (denoted as CoS/NC@MoS2) hollow spheres were successfully synthesized by using a well‐designed N‐rich Co‐metal organic framework (ZIF‐67) precursor and template. Owing to the good mechanical stability and conductivity of carbon hollow spheres, N‐doped carbon, and Co−Mo bonds, the as‐prepared CoS/NC@MoS2 composites exhibit outstanding electrochemical performance both in electrocatalytic and energy storage applications. An overpotential of 77 mV at 10 mA cm−2, and a Tafel slope of 67 mV dec−1 could be obtained in acid environment for the hydrogen evolution reaction. As an anode material for lithium‐ion batteries, the as‐prepared composites exhibit good cycling stability with a high reversible specific capacity of 802.4 mA h g−1 at a current density of 1 A g−1 after 400 cycles and good rate capability.
The application of hematite in lithium-ion batteries (LIBs) has been severely limited because of its poor cycling stability and rate performance. To solve this problem, hematite nanoparticles with oxygen vacancies have been rationally designed by a facile sol–gel method and a sequential carbon-thermic reduction process. Thanks to the existence of oxygen vacancies, the electrochemical performance of the as-obtained hematite nanoparticles is greatly enhancing. When used as the anode material in LIBs, it can deliver a reversible capacity of 1252 mAh g−1 at 2 C after 400 cycles. Meanwhile, the as-obtained hematite nanoparticles also exhibit excellent rate performance as compared to its counterparts. This method not only provides a new approach for the development of hematite with enhanced electrochemical performance but also sheds new light on the synthesis of other kinds of metal oxides with oxygen vacancies.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1783-0) contains supplementary material, which is available to authorized users.
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