Fabrication of voids-involved SnO2@C nanofibers electrodes with highly reversible Sn/SnO2 conversion and much enhanced coulombic efficiency for lithium-ion batteries

Abstract

Despite their potential application in lithium-ion battery electrodes, one apparent disadvantage for SnO 2based materials is that the electrodes sufferlow coulombic efficiency especially for the initial cycle, which originates from the irreversible conversion of SnO 2 to Sn, the formation of solid electrolyte interphase and the other possible side reactions. Here we design a novel nanofiber structure in which SnO 2 nanoparticles are well separated and confined by inner porous carbon framework and then hooped by outer carbon shell. The resultant SnO 2 /voids@C nanofibers electrode displays not only a high reversible capacity of 986mAh g-1 at 200 mA g-1 after 200 cycles, but also a high initial coulombic efficiency of 73.5%.It has been shown that such a rational design can efficiently reduce the side reactions and promote the reversible conversion of Sn to SnO 2 for both half and full cells.

SnO2 as Advanced Anode of Alkali‐Ion Batteries: Inhibiting Sn Coarsening by Crafting Robust Physical Barriers, Void Boundaries, and Heterophase Interfaces for Superior Electrochemical Reaction Reversibility

“…e) Cycling performances of SnO 2 /voids@C, SnO 2 @C, and SnO 2 nanofibers operated at a C‐rate of 200 mA g −1 . Reproduced with permission . Copyright 2016, Elsevier.…”

“…Xie et al created a porous nanofiber composite (Figure c) consisting of SnO 2 NPs (SnO 2 /voids@C nanofibers) separated by an internal porous carbon scaffold and wrapped by an external carbon shell. First, SnO 2 /Fe 2 O 3 nanofibers were synthesized by electrospinning and then coated with PDA in a tris‐buffer solution.…”

“…Due to the lithium storage mechanism of SnO 2 which is a combination of the alloying–dealloying reaction and conversion reaction, the working voltage of SnO 2 (≈1.0 V vs Li/Li + ) is higher than alloying reaction‐type anodes (e.g., silicon (Si, ≈0.4 V vs Li/Li + ), germanium (Ge, ≈0.5 V vs Li/Li + ), and tin (Sn, ≈0.6 V vs Li/Li + )), but lower than conversion reaction‐type anodes (e.g., transition metal oxides TMOs (M = Mn, Fe, Co, Ni, Cu, etc., TC), ≈1–2 V vs Li/Li + ) . The moderate working voltage of the SnO 2 anode (i.e., ≈1.0 V) can effectively inhibit the generation of lithium dendrites to improve the safety of LIBs; additionally, it results in an appropriate output voltage of the full LIB cells and prevents the decomposition of organic electrolytes which occurs at high potentials …”

“…Prelithiation treatments have been widely used to preform artificial SEI layers on SnO 2 anodes before assembling full cells in order to increase the initial CE. More specifically, this is done by directly contacting the SnO 2 anode with lithium foil in the presence of electrolyte for an extended period or cycling the SnO 2 anode in SnO 2 /Li half‐cells several times before assembling full cells …”

Pseudocapacitive Lithium Storage in Three‐Dimensional Cobalt‐Doped MnO/Nitrogen‐Doped Reduced Graphene Oxide Aerogels as High‐Rate Anode Material

“…Therefore, extensive efforts have been devoted to exploring advanced anode materials with both high specific capacity and excellent rate capability to replace graphitic electrode . Different from the intercalation mechanism of graphite, transition‐metal oxides (TMOs) such as CoO x , FeO x , SnO 2 , and MnO x store lithium ions through conversion reaction during cycling, leading to high theoretical capacity of 500–1000 mA h g −1 . One of the most attractive TMO‐based electrodes is MnO because of its high theoretical capacity (755.6 mA h g −1 ), low cost, environmental friendliness, and high natural abundance of Mn element .…”