Superior Lithium Storage Capacity of α‐MnS Nanoparticles Embedded in S‐Doped Carbonaceous Mesoporous Frameworks

Abstract

stability, power density, and safety. [1,3,4] Among the alternative electrode materials, transition metal sulfides (TMSs) are quite appealing due to their improved safety and high theoretical capacity (e.g., CuS: 560 mAh g −1 ; CoS 2 : 870 mAh g −1 ; and FeS 2 : 894 mAh g −1 , as calculated for the full conversion reaction). [4] Important, compared to other conversion materials, e.g., oxides, TMSs usually show improved electronic conductivity as well as faster reaction kinetics due to the weaker metal-sulfur bond (compared to the metal-oxygen bond), making the conversion reaction easier. [4] In addition, the voltage hysteresis of sulfides (≈0.7 V) is distinctly lower than that of oxides (≈0.9 V), thus promising better energy efficiencies. [5] Manganese sulfide (α-MnS) is particularly appealing as anode material for LIBs, as it possesses a large theoretical capacity (616 mAh g −1 ) and a lower redox potential compared to other TMSs, such as copper, cobalt, and iron sulfides-besides being highly abundant, ecofriendly, and less expensive. [3,6,7] Despite these advantages, the application of α-MnS as anode material in LIBs has been hampered due to common problems of TMSs such as: (i) serious volume variation during repeated (dis)charge processes leading to poor cycling stability, and (ii) low rate capability arising from low electronic conductivity and Li-ion mobility. [3,7] In order to improve the lithium-ion storage performance of TMSs, many approaches have been proposed. One of the most efficient strategies, so far, is to fabricate nano/microstructured composite materials, Herein, a Mn-based metal-organic framework is used as a precursor to obtain well-defined α-MnS/S-doped C microrod composites. Ultrasmall α-MnS nanoparticles (3-5 nm) uniformly embedded in S-doped carbonaceous mesoporous frameworks (α-MnS/SCMFs) are obtained in a simple sulfidation reaction. As-obtained α-MnS/SCMFsshows outstanding lithium storage performance, with a specific capacity of 1383 mAh g −1 in the 300th cycle or 1500 mAh g −1 in the 120th cycle (at 200 mA g −1 ) using copper or nickel foil as the current collector, respectively. The significant (pseudo)capacitive contribution and the stable composite structure of the electrodes result in impressive rate capabilities and outstanding long-term cycling stability. Importantly, in situ X-ray diffraction measurements studies on electrodes employing various metal foils/disks as current collector reveal the occurrence of the conversion reaction of CuS at (de)lithiation process when using copper foil as the current collector. This constitutes the first report of the reaction mechanism for α-MnS, eventually forming metallic Mn and Li 2 S. In situ dilatometry measurements demonstrate that the peculiar structure of α-MnS/SCMFs effectively restrains the electrode volume variation upon repeated (dis)charge processes. Finally, α-MnS/SCMFs electrodes present an impressive performance when coupled in a full cell with commercial LiMn 1/3 Co 1/3 Ni 1/3 O 2 cathodes.

Construction of Rich Conductive Pathways from Bottom to Top: A Highly Efficient Charge‐Transfer System Used in Durable Li/Na‐Ion Batteries at −20 °C

“…Apart from the main peaks in Figure A, several weak peaks located at region II are also found (Figure B). As reported previously, these feature peaks observed here could be attributed to the partial oxidation of Mn 2+ to a higher oxidation state of MnS 1+ z (0< z ≤1) and partial side reactions involving the Cu current collectors . What is more, the intensities and integral areas of the redox peaks in the subsequent CV profiles are almost identical to those in the second one, suggesting the excellent reversibility of the electrochemical reactions in the α‐MnS@ N ‐C/FG electrode.…”

“…For example, aw ell-defined a-MnS/S-doped carbon microrodc omposite prepared by Ma et al could retain 1383 mA hg À1 in the 300th cycle with good rate capability. [7] However,a lthough much progress has been made in recent years, the low-temperature (LT) performances of these well-architectured electrodes have rarely been investigated. Besides showinge xcellent cycle performance andr ate capacities at room temperature (RT), ad ecent performance at LT is also very significant for LIBs, especially if employedi ne xtreme environments.…”

“…For example, a well‐defined α‐MnS/S‐doped carbon microrod composite prepared by Ma et al. could retain 1383 mA h g −1 in the 300th cycle with good rate capability . However, although much progress has been made in recent years, the low‐temperature (LT) performances of these well‐architectured electrodes have rarely been investigated.…”

Pitch‐Based Laminated Carbon Formed by Pressure Driving at Low Temperature as High‐Capacity Anodes for Lithium Energy Storage Systems

“…In particular, b = 0.5 representst he lithium ion insertion/extraction between carbon layers, whereas b = 1i sg enerally considered as ac apacitor behavior. [41] Twop eaks located at 0.01 Va nd 0.3 Va re used for kinetic analysis. It is found that b is about 0.49 for the sharp peak at 0.01 V, suggesting ad iffusion-controlled process.…”

Metal–Organic Framework Derived Fe7S8 Nanoparticles Embedded in Heteroatom‐Doped Carbon with Lithium and Sodium Storage Capability

“…The moderate porosity of Fe 7 S 8 @HD-C is in line with other MOF-derived materials previously reported by our group. [16] The carbon and iron sulfide content in the Fe 7 S 8 @HD-C composite were estimated by thermogravimetric analysis (TGA) measurements in oxygen ( Figure S4a, Supporting Information). The TGA curve exhibits multiple steps upon heating from room temperature to 800 °C.…”