Entropy-Stabilized Multication Fluorides as a Conversion-Type Cathode for Li-Ion Batteries-Impact of Element Selection.

Metal fluorides (e.g., FeF and FeF) have received attention as conversion-type cathode materials for Li-ion batteries due to their higher theoretical capacity compared to that of common intercalation materials.

Multifunctional Effect of Fe Substitution in Na Layered Cathode Materials for Enhanced Storage Stability.

Developing stable cathode materials that are resistant to storage degradation is essential for practical development and industrial processing of Na-ion batteries as many sodium layered oxide materials are susceptible to hygroscopicity and instability upon exposure to ambient air. Among the various layered compounds, Fe-substituted O3-type Na(NiMn)FeO materials have emerged as a promising option for high-performance and low-cost cathodes. While previous reports have noted the decent air-storage stability of these materials, the role and origin of Fe substitution in improving storage stability remain unclear.

A Carboranyl Electrolyte Enabling Highly Reversible Sodium Metal Anodes via a "Fluorine-Free" SEI.

Realization of practical sodium metal batteries (SMBs) is hindered due to lack of compatible electrolyte components, dendrite propagation, and poor understanding of anodic interphasial chemistries. Chemically robust liquid electrolytes that facilitate both favorable sodium metal deposition and a stable solid-electrolyte interphase (SEI) are ideal to enable sodium metal and anode-free cells. Herein we present advanced characterization of a novel fluorine-free electrolyte utilizing the [HCB H ] anion.

Dual-Salt Electrolytes to Effectively Reduce Impedance Rise of High-Nickel Lithium-Ion Batteries.

Simply mixing several lithium salts in one electrolyte to obtain blended salt electrolytes has been demonstrated as a promising strategy to formulate advanced electrolytes for lithium metal batteries (LMBs) and lithium-ion batteries (LIBs). In this study, we report the use of dual-salt electrolytes containing lithium hexafluorophosphate (LiPF) and lithium difluorophosphate (LiDFP) in ethylene carbonate/ethyl methyl carbonate (EC/EMC) mixture and tested them in layered high-nickel LIB cells. LiNiCoO was synthesized through a coprecipitation method and was used as a representative high-nickel cathode for the U.

Localized Polysulfide Injector for the Activation of Bulk Lithium Sulfide.

The activation of commercial LiS remains to be one of the key challenges against its commercialization as a starting cathode material for a sulfur-based Li-ion battery system. In this work we take advantage of the lower oxidation potential of commercial NaS (1-3 wt%) to serve as an and local polysulfide injector for the activation of commercial LiS (70 wt%). In contrast to applying pre-solvated redox mediators, this technique allows for the activation of commercial LiS at lower voltages with an electrolyte content as low as 3 μL mg at 3 mgmg cm and 4 μL mg at 6.

Interfacially Induced Cascading Failure in Graphite-Silicon Composite Anodes.

Silicon (Si) has been well recognized as a promising candidate to replace graphite because of its earth abundance and high-capacity storage, but its large volume changes upon lithiation/delithiation and the consequential material fracturing, loss of electrical contact, and over-consumption of the electrolyte prevent its full application. As a countermeasure for rapid capacity decay, a composite electrode of graphite and Si has been adopted by accommodating Si nanoparticles in a graphite matrix. Such an approach, which involves two materials that interact electrochemically with lithium in the electrode, necessitates an analytical methodology to determine the individual electrochemical behavior of each active material.

An artificial interphase enables reversible magnesium chemistry in carbonate electrolytes.

Magnesium-based batteries possess potential advantages over their lithium counterparts. However, reversible Mg chemistry requires a thermodynamically stable electrolyte at low potential, which is usually achieved with corrosive components and at the expense of stability against oxidation. In lithium-ion batteries the conflict between the cathodic and anodic stabilities of the electrolytes is resolved by forming an anode interphase that shields the electrolyte from being reduced.

Systematic Investigation of the Alucone-Coating Enhancement on Silicon Anodes.

Polyvinylidene fluoride (PVDF) is the most popular binder in commercial lithium-ion batteries but is incompatible with a silicon (Si) anode because it fails to maintain the mechanical integrity of the Si electrode upon cycling. Herein, an alucone coating synthesized by molecular layer deposition has been applied on the laminated electrode fabricated with PVDF to systematically study the sole impact of the surface modification on the electrochemical and mechanical properties of the Si electrode, without the interference of other functional polymer binders. The enhanced mechanical properties of the coated electrodes, confirmed by mechanical characterization, can help accommodate the repeated volume fluctuations, preserve the electrode structure during electrochemical reactions, and thereby, leading to a remarkable improvement of the electrochemical performance.

Structure and Reactivity of Alucone-Coated Films on Si and Li(x)Si(y) Surfaces.

Coating silicon particles with a suitable thin film has appeared as a possible solution to accommodate the swelling of silicon upon lithiation and its posterior cracking and pulverization during cycling of Li-ion batteries. In particular, aluminum alkoxide (alucone) films have been recently deposited over Si anodes, and the lithiation and electrochemical behavior of the system have been characterized. However, some questions remain regarding the lithium molecular migration mechanisms through the film and the electronic properties of the alucone film.

Hierarchical porous framework of Si-based electrodes for minimal volumetric expansion.

A tunable hierarchical porous framework is fabricated to house the volumetric changes outputted by Si. The nSi@cPAN/cPAN electrodes only expand by 14.3% at full initial lithiation and remain within 23% expansion from its uncycled state after 20 cycles with remarkable cycling stability and high coulombic efficiencies in excess of 99.

Reversible high-capacity Si nanocomposite anodes for lithium-ion batteries enabled by molecular layer deposition.

The molecular-layer deposition of a flexible coating onto Si electrodes produces high-capacity Si nanocomposite anodes. Using a reaction cascade based on inorganic trimethylaluminum and organic glycerol precursors, conventional nano-Si electrodes undergo surface modifications, resulting in anodes that can be cycled over 100 times with capacities of nearly 900 mA h g(-1) and Coulombic efficiencies in excess of 99%.

Face-centered-cubic lithium crystals formed in mesopores of carbon nanofiber electrodes.

In the foreseeable future, there will be a sharp increase in the demand for flexible Li-ion batteries. One of the most important components of such batteries will be a freestanding electrode, because the traditional electrodes are easily damaged by repeated deformations. The mechanical sustainability of carbon-based freestanding electrodes subjected to repeated electrochemical reactions with Li ions is investigated via nanotensile tests of individual hollow carbon nanofibers (HCNFs).

Facile conductive bridges formed between silicon nanoparticles inside hollow carbon nanofibers.

This paper reports on a simple and effective method for improving the electrochemical performance of silicon nanoparticle-core/carbon-shell (Si-core/C-shell) nanofibers. Instead of increasing the encapsulation amount of Si nanoparticles, additional conductive paths between the Si nanoparticles were formed by incorporating a small percentage of multi-walled carbon nanotubes (MWNTs) (e.g.

Effect of pores in hollow carbon nanofibers on their negative electrode properties for a lithium rechargeable battery.

The effect of pores in hollow carbon nanofibers (HCNFs) on their electrochemical performance is investigated because the carbon shell itself acts as a reservoir for accommodating Li-ions through intercalation and simultaneously becomes a transport medium through which Li-ions migrate into the core materials in HCNFs. Porous HCNFs (pHCNFs) are prepared by the coaxial electrospinning of a sacrificial core solution and an emulsified shell solution containing sacrificial islands for pore generation. After a thermal treatment, a systematic study is carried out to relate the resulting pore size in pHCNFs to the sacrificial islands in the emulsified shell.