In Situ Derivatization for Boosted Lithium Storage Performance of Fe₇S₈/C Hollow Nanospheres

Abstract

In this paper, Fe3O4 nanoparticles (Fe3O4 NPs) with an average diameter of 10 nm were grown in situ on the shell of hollow mesoporous carbon nanospheres (HMCNs) to form a new type of sesame balls‐like Fe3O4/C hollow nanospheres (HNSs) by thermal decomposition. After vulcanization and phosphating, Fe3O4/C HNSs are transformed into Fe7S8/C HNSs and Fe(PO3)2/Fe2O3/C HNSs, respectively. Compared with Fe3O4/C HNSs and Fe(PO3)2/Fe2O3/C HNSs, Fe7S8/C HNSs display good cycling stability as anode material for lithium ion batteries. When the current density is 1 A g−1, the reversible specific capacity of Fe7S8/C HNSs is 1006 mA h g−1 after 250 cycles. The rate performance and electrochemical properties of Fe7S8/C HNSs are significantly improved. Research shows that the capacitive behavior plays a major role in specific capacity contribution of Fe7S8/C HNSs electrode. The anchoring of Fe7S8 NPs on the shell of HMCNs avoids the aggregation of Fe7S8 NPs, promote the conductivity of composite and boost the delivery of electrons. This idea and expedient method of construction can be broadened to synthesize other hollow nanostructured material with preferable electrochemistry performance.

The Contact Interface Engineering of All‐Sulfide‐Based Solid State Batteries via Infiltrating Dissoluble Sulfide Electrolyte

“…The main peak centered at ≈1.22 V is most probably attributed to the oxidation of Fe 0 and Li 2 S (Equation 5) forming Li 2 FeS 2 , followed by a small shoulder at ≈1.95 V which can be associated to the further delithiation of Li 2 FeS 2 to form Li 2-x FeS 2 (Equation 4). [10,[56][57][58][59] The second and the third CV curves almost overlap with each other, indicating good stability and reversibility of the redox reactions of the Fe 7 S 8 @C, which suggests that after initial charge/discharge process, the volume changes improve the contact between Fe 7 S 8 particles and SEs, enhancing the diffusivity of Li + . Therefore, the corresponding peaks of the reaction in CV curves will also be more clearly defined.…”

“…Cyclic voltammetry (CV) tests were recorded in the voltage range from 0.5 to 3.0 V (vs Li–In/Li + ) at a scan rate of 0.1 mV s −1 for initial three cycles of IN–Fe 7 S 8 ( Figure a) at room temperature. In the initial discharge CV curve, there is no obvious reduction peak except a broad peak from 0.9 to 0.5 V. Due to the relatively slow kinetics systems in the initial discharge, [ 56 ] the intercalation of lithium into Fe 7 S 8 to form Li x Fe 7 S 8 was most probably buried, which could be described as Equation (). [ 56 ] The broad peak can be attributed to the formation of Li 2 S and Fe 0 which could be described as Equation ().…”

“…In the initial discharge CV curve, there is no obvious reduction peak except a broad peak from 0.9 to 0.5 V. Due to the relatively slow kinetics systems in the initial discharge, [ 56 ] the intercalation of lithium into Fe 7 S 8 to form Li x Fe 7 S 8 was most probably buried, which could be described as Equation (). [ 56 ] The broad peak can be attributed to the formation of Li 2 S and Fe 0 which could be described as Equation (). [ 57 ] The following charge is characterized by a main peak and a small shoulder.…”