The redox aspects of lithium-ion batteries.

This article aims to present the redox aspects of lithium-ion batteries both from a thermodynamic and from a conductivity viewpoint. We first recall the basic definitions of the electrochemical potential of the electron, and of the Fermi level for a redox couple in solutions. The Fermi level of redox solids such as metal oxide particles is then discussed, and a Nernst equation is derived for two ideal systems, namely an ideally homogenous phase where the oxidised and reduced metal ions are homogeneously distributed and two segregated phases where the oxidised and the reduced metal ions are separated in two distinct phases such as observed, for example, in biphasic lithium iron phosphate.

Revealing how internal sensors in a smart battery impact the local graphite lithiation mechanism.

Smart batteries, i.e., equipped with internal and external sensors, are emerging as promising solutions to enhance battery state of health and optimize operating conditions.

Effect of Size and Shape on Electrochemical Performance of Nano-Silicon-Based Lithium Battery.

Silicon is a promising material for high-energy anode materials for the next generation of lithium-ion batteries. The gain in specific capacity depends highly on the quality of the Si dispersion and on the size and shape of the nano-silicon. The aim of this study is to investigate the impact of the size/shape of Si on the electrochemical performance of conventional Li-ion batteries.

Publisher Correction: Architectured ZnO-Cu particles for facile manufacturing of integrated Li-ion electrodes.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Architectured ZnO-Cu particles for facile manufacturing of integrated Li-ion electrodes.

Designing electrodes with tailored architecture is an efficient mean to enhance the performance of metal-ion batteries by minimizing electronic and ionic transport limitations and increasing the fraction of active material in the electrode. However, the fabrication of architectured electrodes often involves multiple laborious steps that are not directly scalable to current manufacturing platforms. Here, we propose a processing route in which Cu-coated ZnO powders are directly shaped into architectured electrodes using a simple uniaxial pressing step.

Correlated X-Ray 3D Ptychography and Diffraction Microscopy Visualize Links between Morphology and Crystal Structure of Lithium-Rich Cathode Materials.

The search for higher performance, improved safety, and lifetime of lithium-ion batteries relies on the understanding of degradation mechanisms. Complementary to methods and studies on primary particles or crystalline structure on bulk materials, here we use spatially correlated ptychographic X-ray computed nanotomography with a 35 nm resolution and scanning X-ray diffraction microscopy with 1 μm resolution to visualize in 3D the hidden morphological and structural degradation processes in individual secondary particles of lithium-rich nickel, cobalt, and manganese oxides. From comparative examination of pristine and cycled particles, we suggest that morphological degradation could have radial dependency and secondary particle size dependency.

How reliable is the Na metal as a counter electrode in Na-ion half cells?

Despite the extensive research on Na-ion batteries little is known about the stability of the Na-metal counter electrode in a half-cell configuration. Therefore, in our study we focus on identifying the key factors responsible for its high interfacial resistance and often premature degradation in carbonate-based electrolytes.

Phosphorus anionic redox activity revealed by operando P K-edge X-ray absorption spectroscopy on diphosphonate-based conversion materials in Li-ion batteries.

When cycling diphosphonate-based organic-inorganic hybrid materials as negative battery electrodes, specific charges exceeding the maximum for a metal redox reaction are recorded. Classical explanations are electrolyte reduction and solid electrolyte interphase (SEI) oxidation. Using operando X-ray absorption spectroscopy (XAS) at the P K-edge experiment, we demonstrate an additional contribution of reversible ligand co-cycling based on the P-atoms of the diphosphonate ligands, upon delithiation occurring during the first potential plateau, which matches perfectly to previous investigations using Fe K-edge XAS.

Monitoring the chemical and electronic properties of electrolyte-electrode interfaces in all-solid-state batteries using operando X-ray photoelectron spectroscopy.

Understanding the degradation of the solid electrolyte-electrodes interface during cycling is currently one of the most challenging obstacles in the development of all-solid-state batteries. Here, we introduce operando X-ray photoelectron spectroscopy (XPS) as a combined approach for real-time monitoring of the (i) (electro-) chemical interfacial reactions between different components of the composites electrode and (ii) surface electronic properties. The dedicated electrochemical cell, capable of maintaining high mechanical pressure, offers reliable electrochemistry and versatility in terms of materials application.

SnO Model Electrode Cycled in Li-Ion Battery Reveals the Formation of LiSnO and LiSnO Phases through Conversion Reactions.

SnO is an attractive negative electrode for Li-ion battery owing to its high specific charge compared to commercial graphite. However, the various intermediate conversion and alloy reactions taking place during lithiation/delithiation, as well as the electrolyte stability, have not been fully elucidated, and many ambiguities remain. An amorphous SnO thin film was investigated for use as a model electrode by a combination of postmortem X-ray photoelectron spectroscopy supported by density functional theory calculations and scanning electron microscopy to shed light on these different processes.

Ligand influence in Li-ion battery hybrid active materials: Ni methylenediphosphonate vs. Ni dimethylamino methylenediphosphonate.

The influence of a ligand on the structural, morphological and electrochemical properties of organic-inorganic hybrid nickel diphosphonates was assessed using Ni methylenediphosphonate (NiMeDP) and Ni dimethylamino methylenediphosphonate (NiDMAMDP) as model electrode materials.

Elucidating the Surface Reactions of an Amorphous Si Thin Film as a Model Electrode for Li-Ion Batteries.

We investigated during the first lithiation/delithiation process the electrochemical reaction mechanisms at the surface of 30 nm n-doped amorphous silicon (a-Si) thin film used as a negative model electrode for Li-ion batteries. Usage of thin film allowed us to accurately discern the different reaction mechanisms occurring at the surface by avoiding interference from carbon and binder components. The potential dependency of the evolution of the solid electrolyte interphase (SEI) and the reactions on the a-Si and on the copper current collector were elucidated by coupling galvanostatic cycling with postmortem X-ray photoemission spectroscopy and scanning electron microscopy analyses.

Electrode Engineering of Conversion-based Negative Electrodes for Na-ion Batteries.

Due to lower costs and higher abundance of sodium, Na-ion battery technology can offer a good alternative to Li-ion batteries. Much research is focusing on developing new cathode and anode materials but the importance of the electrode engineering on the electrochemical performance is often neglected. The electrode composition is especially crucial for conversion reaction-based materials where the composite electrode (active material, conducting additive and binder) has to buffer the huge volume change occurring upon cycling.

Lithium chromium pyrophosphate as an insertion material for Li-ion batteries.

Lithium chromium pyrophosphate (LiCrP2O7) and carbon-coated LiCrP2O7 (LiCrP2O7/C) were synthesized by solid-state and sol-gel routes, respectively. The materials were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and conductivity measurements. LiCrP2O7 powder has a conductivity of ~ 10(-8) S cm(-1), ~ 10(4) times smaller than LiCrP2O7/C (~ 10(-4) S cm(-1)).

Combined operando X-ray diffraction-electrochemical impedance spectroscopy detecting solid solution reactions of LiFePO4 in batteries.

Lithium-ion batteries are widely used for portable applications today; however, often suffer from limited recharge rates. One reason for such limitation can be a reduced active surface area during phase separation. Here we report a technique combining high-resolution operando synchrotron X-ray diffraction coupled with electrochemical impedance spectroscopy to directly track non-equilibrium intermediate phases in lithium-ion battery materials.

Understanding Inhomogeneous Reactions in Li-Ion Batteries: Operando Synchrotron X-Ray Diffraction on Two-Layer Electrodes.

To understand inhomogeneous reactions perpendicular to the current collector in an electrode for batteries, a method combining operando synchrotron X-ray diffraction and two-layer electrodes with different porosities is developed. The two layers are built using two different active materials (LiNiCoAlO and LiMnO), therefore, tracing each diffraction pattern reveals which active material is reacting during the electrochemical measurement in transmission mode. The results demonstrate that the active material close to the separator is obviously more active than that one close to the current collector in the case of low porosity electrodes.

Influence of conversion material morphology on electrochemistry studied with operando X-ray tomography and diffraction.

X-ray diffraction and X-ray tomography are performed on intermetallic particles undergoing lithiation in a porous electrode. Differences between ensemble phase evolution and that at a single-particle level are explored. It is found that all particles evidence core-shell lithiation; however, particles with internal porosity are more mechanically robust and exhibit less fracture.