Geng Chu

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.

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.

Conductivity and applications of Li-biphenyl-1,2-dimethoxyethane solution for lithium ion batteries*

The total conductivity of Li-biphenyl-1,2-dimethoxyethane solution (Li x Bp(DME)9.65, Bp = biphenyl, DME = 1,2-dimethoxyethane, x = 0.25, 0.50, 1.00, 1.50, 2.00) is measured by impedance spectroscopy at a temperature range from 0 °C to 40 °C. The Li1.50Bp(DME)9.65 has the highest total conductivity 10.7 mS/cm. The conductivity obeys Arrhenius law with the activation energy , ). The ionic conductivity and electronic conductivity of Li x Bp(DME)9.65 solutions are investigated at 20 °C using the isothermal transient ionic current (ITIC) technique with an ion-blocking stainless steal electrode. The ionic conductivity and electronic conductivity of Li1.00Bp(DME)9.65 are measured as 4.5 mS/cm and 6.6 mS/cm, respectively. The Li1.00Bp(DME)9.65 solution is tested as an anode material of half liquid lithium ion battery due to the coexistence of electronic conductivity and ionic conductivity. The lithium iron phosphate (LFP) and Li1.5Al0.5Ti1.5(PO4)3 (LATP) are chosen to be the counter electrode and electrolyte, respectively. The assembled cell is cycled in the voltage range of 2.2 V–3.75 V at a current density of 50 mA/g. The potential of Li1.00Bp(DME)9.65 solution is about 0.3 V vs. Li+/Li, which indicates the solution has a strong reducibility. The Li1.00Bp(DME)9.65 solution is also used to prelithiate the anode material with low first efficiency, such as hard carbon, soft carbon and silicon.