Jieyun Zheng

A Well-Defined Silicon Nanocone–Carbon Structure for Demonstrating Exclusive Influences of Carbon Coating on Silicon Anode of Lithium-Ion Batteries

Nanotechnology and carbon coating have been applied to silicon anodes to achieve excellent lithium-ion batteries, but the exclusive influence of carbon coating on solid-electrolyte interphase (SEI) formation is difficult to exhibit distinctly because of the impurity and morphological irregularity of most nanostructured anodes. Here, we design a silicon nanocone-carbon (SNC-C) composite structure as a model anode to demonstrate the significant influences of carbon coating on SEI formation and electrochemical performance, unaffectedly as a result of pure electrode component and distinctly due to regular nanocone morphology. As demonstrated by morphological and elemental analysis, compared to the SNC electrode, the SNC-C electrode maintains a thinner SEI layer (∼10 nm) and more stable structure during cycling as well as longer cycle life (>725 cycles), higher Coulombic efficiency (>99%), and lower electrode polarization. This well-defined structure clearly shows the interface stability attributed to carbon coating and is promising in fundamental research of the silicon anode.

Gas treatment protection of metallic lithium anode

The effects of different coating layers on lithium metal anode formed by reacting with different controlled atmospheres (argon, CO2–O2(2:1), N2, and CO2–O2–N2(2:1:3)) have been investigated. The obtained XRD, second ion mass spectroscopy (SIMS), and scanning probe microscope (SPM) results demonstrate the formation of coating layers composed of Li2CO3, Li3N, and the mixture of them on lithium tablets, respectively. The Li/Li symmetrical cell and Li/S cell are assembled to prove the advantages of the protected lithium tablet on electrochemical performance. The comparison of SEM and SIMS characterizations before/after cycles clarifies that an SEI-like composition formed on the lithium tablets could modulate the interfacial stabilization between the lithium foil and the ether electrolyte.

A low cost composite quasi-solid electrolyte of LATP, TEGDME, and LiTFSI for rechargeable lithium batteries*

The composite quasi solid state electrolytes (CQSE) is firstly synthesized with quasi solid state electrolytes (QSE) and lithium-ion-conducting material Li1.4Al0.4Ti1.6(PO4)3 (LATP), and the QSE consists of [LiG4][TFSI] with fumed silica nanoparticles. Compared with LATP, CQSE greatly improves the interface conductance of solid electrolytes. In addition,it has lower liquid volume relative to QSE. Although the liquid volume fraction of CQSE is droped to 60%, its conductivity can also reach 1.39×10−4 S/cm at 20 °C. Linear sweep voltammetry (LSV) is conducted on each composite electrolyte. The results show the possibility that CQSE has superior electrochemical stability up to 5.0 V versus Li/Li+1. TG curves also show that composite electrolytes have higher thermal stability. In addition, the performance of Li/QSE/LiMn2O4 and Li/CQSE/LiMn2O4 batteries is evaluated and shows good electrochemical characteristics at 60 °C.

Size effect of Si particles on the electrochemical performances of Si/C composite anodes

A series of Si/C composites were fabricated based on pitch and Si powders with particle sizes of 30, 100, 500, and 3000 nm. The size effects of the Si particles in the Si/C composites were investigated for lithium-ion battery anodes. The nanoscale Si and Si/C composites exhibited good capacity retentions. Scanning electron microscopy showed that exterior and interior cracks emerging owing to volume expansion as well as parasitic reactions with the electrolyte could well explain the performance failure.