Critical Binder-to-Powders Coverage Ratio for Faster Graphite/SiO Electrode Formulation Optimization.

Mastering electrodes' formulations is a complex and tedious task, because for each composition of electroactive material(s) it is necessary to adjust the inactive additives nature and content to optimize battery performance. In this direction, the amount of binder is proposed to be adjusted to the surface developed by all of the powders involved in the composition of the electrode, i.e.

Coordinatively Cross-Linked Binders for Silicon-Based Electrodes for Li-Ion Batteries: Beneficial Impact on Mechanical Properties and Electrochemical Performance.

A simple and versatile preparation of Zn(II)-poly(carboxylates) reticulated binders by the addition of Zn(II) precursors (ZnSO, ZnO, or Zn(NO)) into a preoptimized poly(carboxylic acids) binder solution is proposed. These binders lead systematically to a significantly improved electrochemical performance when used for the formulation of silicon-based negative electrodes. The formation of carboxylate-Zn(II) coordination bonds formation is investigated by rheology and FTIR and NMR spectroscopies.

Understanding the Capacity Decay of Si/NMC622 Li-Ion Batteries Cycled in Superconcentrated Ionic Liquid Electrolytes: A New Perspective.

Silicon-containing Li-ion batteries have been the focus of many energy storage research efforts because of the promise of high energy density. Depending on the system, silicon generally demonstrates stable performance in half-cells, which is often attributed to the unlimited lithium supply from the lithium (Li) metal counter electrode. Here, the electrochemical performance of silicon with a high voltage NMC622 cathode was investigated in superconcentrated phosphonium-based ionic liquid (IL) electrolytes.

Nanoscale Morphological Characterization of Coordinated Binder and Solid Electrolyte Interphase in Silicon-Based Electrodes for Li-Ion Batteries.

The physical crosslinking of polymeric binders through coordination chemistry significantly improves the electrochemical performance of silicon-based negative electrodes. Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy is used to probe the nanoscale morphology of such electrodes. This technique reveals the homogeneous coordination of carboxylated binder with Zn cations and its layering on the silicon surface.

Tuning the Formation and Structure of the Silicon Electrode/Ionic Liquid Electrolyte Interphase in Superconcentrated Ionic Liquids.

The latest advances in the stabilization of Li/Na metal battery and Li-ion battery cycling have highlighted the importance of electrode/electrolyte interface [solid electrolyte interphase (SEI)] and its direct link to cycling behavior. To understand the structure and properties of the SEI, we used combined experimental and computational studies to unveil how the ionic liquid (IL) cation nature and salt concentration impact the silicon/IL electrolyte interfacial structure and the formed SEI. The nature of the IL cation is found to be important to control the electrolyte reductive decomposition that influences the SEI composition and properties and the reversibility of the Li-Si alloying process.

Influence of the Polyacrylic Acid Binder Neutralization Degree on the Initial Electrochemical Behavior of a Silicon/Graphite Electrode.

The role of the physicochemical properties of the water-soluble polyacrylic acid (PAA) binder in the electrochemical performance of highly loaded silicon/graphite 50/50 wt % negative electrodes has been examined as a function of the neutralization degree in PAAHLi at the initial cycle in an electrolyte not containing ethylene carbonate. Electrode processing in the acidic PAAH binder at pH 2.5 leads to a deep copper corrosion, resulting in a significant electrode cohesion and adhesion to the current collector surface, but the strong binder rigidity may explain the big cracks occurring on the electrode surface at the first cycle.

Study of Immersion of LiNiMnCoO Material in Water for Aqueous Processing of Positive Electrode for Li-Ion Batteries.

The understanding of the phenomena occurring during immersion of LiNiMnCoO (NMC) in water is helpful to devise new strategies toward the implementation of aqueous processing of this high-capacity cathode material. Immersion of NMC powder in water leads to both structural modification of the particles surface as observed by high-resolution scanning transmission electron microscopy and the formation of lithium-based compounds over the surface (LiOH, LiCO) in greater amount than after long-time exposure to ambient air, as confirmed by pH titration and Li MAS NMR analysis. The surface compounds adversely affect the electrochemical performance and are notably responsible for the alkaline pH of the aqueous slurry, which causes corrosion of the aluminum collector during coating of the electrode.

Thermomechanical Polymer Binder Reactivity with Positive Active Materials for Li Metal Polymer and Li-Ion Batteries: An XPS and XPS Imaging Study.

The lithium and lithium-ion battery electrode chemical stability in the pristine state has rarely been considered as a function of the binder choice and the electrode processing. In this work, X-ray photoelectron spectroscopy (XPS) and XPS imaging analyses associated with complementary Mössbauer spectroscopy are used in order to study the chemical stability of two pristine positive electrodes: (i) an extruded LiFePO-based electrode formulated with different polymer matrices [polyethylene oxide and a polyvinylidene difluoride (PVdF)] and processed at different temperatures (90 and 130 °C, respectively) and (ii) a Li[NiMnCo]O (NMC)-based electrode processed by tape-casting, followed by a mild or heavy calendering treatment. These analyses have allowed the identification of reactivity mechanisms at the interface of the active material and the polymer in the case of PVdF-based electrodes.

Lithium n-Doped Polyaniline as a High-Performance Electroactive Material for Rechargeable Batteries.

The discovery of conducting lithium-doped polyaniline with reversible redox chemistry allows simultaneous unprecedented capacity and stability in a non-aqueous Li battery. This compound (lithium emeraldinate) was synthesized by lithium-proton exchange on the emeraldine base in an anhydrous lithium-based electrolyte. A combination of UV/Vis-NIR spectroelectrochemistry, XPS, FTIR, and EQCM characterization allowed a unified description of the chemical and electrochemical behavior, showing facile charge delocalization of the doped states and the reversibility of the redox processes in this form of polyaniline.

Mechanism of Silicon Electrode Aging upon Cycling in Full Lithium-Ion Batteries.

Understanding the aging mechanism of silicon-based negative electrodes for lithium-ion batteries upon cycling is essential to solve the problem of low coulombic efficiency and capacity fading and further to implement this new high-capacity material in commercial cells. Nevertheless, such studies have so far focused on half cells in which silicon is cycled versus an infinite reservoir of lithium. In the present work, the aging mechanism of silicon-based electrodes is studied upon cycling in a full Li-ion cell configuration with LiCoO2 as the positive electrode.

Suspensions of carbon nanofibers in organic medium: rheo-electrical properties.

The nonaqueous suspensions of carbon nanofibers (CNFs) in 1 M lithium bis(trifluoromethanesulfonaimide) in propylene carbonate electrolyte reveal unique structural evolution and shear-induced transition due to the high aspect ratio. The rheo-electrical behavior elucidates a microstructural transition from entangled-to-aggregated networks above a distinct percolation threshold. Under shear flow, both networks show a three-regime flow curve and an inverted-bell-like conductivity curve as a consequence of shear-induced alignment (entangled network) and shear-induced breaking up (aggregated network).

Numerical and experimental study of suspensions containing carbon blacks used as conductive additives in composite electrodes for lithium batteries.

Suspensions of carbon blacks and spherical carbon particles are studied experimentally and numerically to understand the role of the particle shape on the tendency to percolation. Two commercial carbon blacks and one lab-synthesized spherical carbon are used. The percolation thresholds in suspensions are experimentally determined by two complementary methods: impedance spectroscopy and rheology.

Non-aqueous carbon black suspensions for lithium-based redox flow batteries: rheology and simultaneous rheo-electrical behavior.

We report on the rheological and electrical properties of non-aqueous carbon black (CB) suspensions at equilibrium and under steady shear flow. The smaller the primary particle size of carbon black is, the higher the magnitude of rheological parameters and the conductivity are. The electrical percolation threshold ranges seem to coincide with the strong gel rather than the weak gel rheological threshold ones.

Brownian dynamics simulations of colloidal suspensions containing polymers as precursors of composite electrodes for lithium batteries.

Dilute aqueous suspensions of silicon nanoparticles and sodium carboxymethylcellulose salt (CMC) are studied experimentally and numerically by brownian dynamics simulations. The study focuses on the adsorption of CMC on silicon and on the aggregation state as a function of the suspension composition. To perform simulations, a coarse-grained model has first been developed for the CMC molecules.