A Hybrid Ionic and Electronic Conductive Coating Layer for Enhanced Electrochemical Performance of 4.6 V LiCoO.

The LiCoO cathode undergoes undesirable electrochemical performance when cycled with a high cut-off voltage (≥4.5 V versus Li/Li). The unstable interface with poor kinetics is one of the main contributors to the performance failure.

Realizing Compact Lithium Deposition via Elaborative Nucleation and Growth Regulation for Stable Lithium-Metal Batteries.

Metallic lithium (Li) has been regarded as an ideal candidate for anode materials in next-generation high-energy-density batteries. However, a ubiquitous spongy Li deposition results in low reversibility, huge interfacial impedance, and even safety issues, hindering its practical application. Herein, we proposed a bifunctional electrolyte (BiFE) to avoid the spongy Li deposition, in which lithium nitrate (LiNO) facilitates a uniform granular Li nucleation via forming a kinetically favorable solid electrolyte interphase and silicon dioxide (SiO) adsorbs anions to stabilize the electric field distribution near the electrode surface.

Structural Distortion-Induced Charge Gradient Distribution of Co Ions in Delithiated LiCoO Cathode.

Layered LiCoO has drawn tremendous attention as a modeling cathode for Li-ion batteries, while its structural instability, especially in the high delithiation region, remains unsolved. With the aim of revealing the structural fundamentals, LiCoO electrodes are investigated at a long delithiation range using both in situ and ex situ techniques. In the highly delithiated LiCoO electrode, the unique charge compensation process leads to a spatial charge gradient of Co/Co/Co ions from surface to bulk, which can be further manipulated by structural distortion, Li extraction, and surface side reactions.

Probing the Structural Transition Kinetics and Charge Compensation of the P2-NaAlNiMnO Cathode for Sodium Ion Batteries.

Although the layered P2-type NaNiMnO materials show high discharge voltage and specific capacity, they suffer from severe structural instabilities and surface reaction upon Na exchange for sodium-ion batteries (SIBs). Therefore, it is quite necessary to reveal the underlying structural evolution mechanism and diffusion kinetics to improve the structural/electrochemical stability for application in SIBs. Here, we synthesize a P2-type NaAlNiMnO material by a small dose of Al replacing the Mn, aiming at enhancing the structural stability without sacrificing the average discharge voltage and theoretical capacity.

Kinetically Determined Phase Transition from Stage II (LiC) to Stage I (LiC) in a Graphite Anode for Li-Ion Batteries.

The electrochemical insertion of Li into graphite initiates a series of thermodynamic and kinetic processes. An in-depth understanding of this phenomenon will deepen the knowledge of electrode material design and optimize rechargeable Li batteries. In this context, the phase transition from dense stage II (LiC) to stage I (LiC) was comprehensively elucidated in a graphite anode via both experimental characterizations and first-principles calculations.

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.

Transport of External Lithium Along Phase Boundary in LiF-Ti Nanocomposite Thin Films.

The electronic and ionic conductivity of the LiF-Ti nanocomposite films prepared by the co-sputtering have been investigated by the method of impedance spectrum (IS), current-voltage curves (IV) and isothermal transient ionic current (ITIC) measurements. It is found that the ionic conductivity of the obtained LiF-Ti nanocomposite film is very low. After electrochemical and chemical lithiation, ionic conductivities of the lithiated composite films are increased to be 10-3 and 10-4 S/cm separately.

Thick solid electrolyte interphases grown on silicon nanocone anodes during slow cycling and their negative effects on the performance of Li-ion batteries.

Thickness, homogeneity and coverage of the surface passivation layer on Si anodes for Li-ion batteries have decisive influences on their cyclic performance and coulombic efficiency, but related information is difficult to obtain, especially during cycling. In this work, a well-defined silicon nanocone (SNC) on silicon wafer sample has been fabricated as a model electrode in lithium ion batteries to investigate the growth of surface species on the SNC electrode during cycling using ex situ scanning electronic microscopy. It is observed that an extra 5 μm thick layer covers the top of the SNCs after 25 cycles at 0.

Effect of electrochemical dissolution and deposition order on lithium dendrite formation: a top view investigation.

Rechargeable metallic lithium batteries are the ultimate solution to electrochemical storage due to their high theoretical energy densities. One of the key technological challenges is to control the morphology of metallic lithium electrode during electrochemical dissolution and deposition. Here we have investigated the morphology change of metallic lithium electrode after charging and discharging in nonaqueous batteries by ex situ SEM techniques from a top view.

3D visualization of inhomogeneous multi-layered structure and Young's modulus of the solid electrolyte interphase (SEI) on silicon anodes for lithium ion batteries.

The microstructure and mechanical properties of the solid electrolyte interphase (SEI) in non-aqueous lithium ion batteries are key issues for understanding and optimizing the electrochemical performance of lithium batteries. In this report, the three-dimensional (3D) multi-layered structures and the mechanical properties of the SEI formed on a silicon anode material for next generation lithium ion batteries have been visualized directly for the first time, through a scanning force spectroscopy method. The coverage of the SEI on silicon anodes is also obtained through 2D projection plots.

Electrochemical performances and volume variation of nano-textured silicon thin films as anodes for lithium-ion batteries.

Electrochemical behaviors of nano-textured silicon thin film (NTSTF) coated with Al2O3 or Cu layers as anodes for lithium-ion batteries have been investigated. The cyclic performance of NTSTF electrodes is superior to dense Si thin films. The NTSTF with a 5 nm thick Cu coating layer shows superior cyclic performance and rate performance to other NTSTF samples.