To address the challenges of capacity fading and poor electronic conductivity of hard carbons as anode in Li-ion batteries (LIBs), we report here the catalytic graphitization of resorcinol–formaldehyde xerogel (RFX)-derived hard carbon via a single-step synthesis by incorporating two transition metal catalysts (Co and Ni) with different loadings (5 and 10%) at a modest temperature of 1100 °C. Loading of both the catalysts affects the extent of graphitization and other physiochemical properties that have a direct influence on the anodic performance of as graphitized RFX-derived hard carbon. A 10% Ni catalyst in RFX-derived carbon induces the highest degree of graphitization of 81.4% along with partial amorphous carbon and nickel phases. This improved crystallinity was conducive enough to facilitate rapid electron and Li-ion transfer while the amorphous carbon phase contributed to higher specific capacity, resulting in overall best anodic performance as ever reported for RFX-derived carbon. A specific capacity of 578 mAh/g obtained after 210 cycles at 0.2 C with coulombic efficiency greater than 99% confirms the potential of graphitized RFX-derived carbon as an anode for high-performance LIBs.

TiO2-(B)/SnO2 nanostructured composites have been prepared by the combination of an oil-in-water (O/W) microemulsion reaction method (MRM) and a hydrothermal method. Its electrochemical properties were investigated as anode materials in lithium-ion battery, and characterization was carried out by XRD, BET, Raman, FE-SEM, EDXS, and TEM. The as-prepared composites consisted of monoclinic phase TiO2-(B) nanoribbons decorated with cassiterite structure SnO2 nanoparticles. The electrochemical performance of the TiO2-(B)/SnO2 50/50 nanocomposite electrode showed higher reversible capacity of 265 mAh/g than that of the pure SnO2 electrode, 79 mAh/g, after 50 cycles at 0.1 C in a voltage range of 0.01-3.0 V at room temperature. In addition, the coulombic efficiency of the TiO2-(B)/SnO2 50/50 nanocomposite remains at an average greater than 90% from the 2nd to the 50th cycles. The TiO2-(B)/SnO2 50/50 nanocomposite presented the best balance between the mechanical support effect provided by TiO2-(B) that also contributes to the LIB capacity and the SnO2 that provides high specific capacity.

The choice of materials that constitute electrodes and the way they are interconnected, i.e., the microstructure, influences the performance of lithium-ion batteries. For batteries with high energy and power densities, the microstructure of the electrodes must be controlled during their manufacturing process. Moreover, understanding the microstructure helps in designing a high-performance, yet low-cost battery. In this study, we propose a systematic algorithm workflow for the images of the microstructure of anodes obtained from a focused ion beam scanning electron microscope (FIB-SEM). Here, we discuss the typical issues that arise in the raw FIB-SEM images and the corresponding preprocessing methods that resolve them. Next, we propose a Fourier transform-based filter that effectively reduces curtain artifacts. Also, we propose a simple, yet an effective, global-thresholding method to identify active materials and pores in the microstructure. Finally, we reconstruct the three-dimensional structures by concatenating the segmented images. The whole algorithm workflow used in this study is not fully automated and requires user interactions such as choosing the values of parameters and removing shine-through artifacts manually. However, it should be emphasized that the proposed global-thresholding method is deterministic and stable, which results in high segmentation performance for all sectioning images.

Organic gels obtained by sol–gel polycondensation reaction followed by subcritical drying in ambient conditions are termed as xerogels which are pyrolyzed to yield carbon xerogels. Resorcinol formaldehyde (RF) derived carbon xerogels have received considerable attention due to their higher carbon yield and ease of tuning their microstructure and therefore physiochemical properties. Recent advances in the synthesis of carbon xerogels have allowed porous as well as non-porous but large external surface area morphologies. Further efforts have been made about increasing the surface area by activation or changing the microstructure by doping with foreign elements. These advances in the area of carbon xerogels synthesis led to their use as high performance anode materials for Li ion batteries recently. This review summarizes these recent studies on electrochemical performance of carbon xerogels to clearly demonstrate their potential as high capacity anode material for Li ion batteries. Notably, given the potential not only for Li ion batteries but also for latest sodium-ion batteries and super-capacitors, this review provides a much needed attention of scientific community to so far unnoticed carbon xerogel materials.

The objective of this investigation was to utilize the first-principles molecular dynamics computational approach to investigate the lithiation characteristics of empty silicon clathrates (Si46) for applications as potential anode materials in lithium-ion batteries. The energy of formation, volume expansion, and theoretical capacity were computed for empty silicon clathrates as a function of Li. The theoretical results were compared against experimental data of long-term cyclic tests performed on half-cells using electrodes fabricated from Si46 prepared using a Hofmann-type elimination–oxidation reaction. The comparison revealed that the theoretically predicted capacity (of 791.6 mAh/g) agreed with experimental data (809 mAh/g) that occurred after insertion of 48 Li atoms. The calculations showed that overlithiation beyond 66 Li atoms can cause large volume expansion with a volume strain as high as 120%, which may correlate to experimental observations of decreasing capacities from the maximum at 1030 mAh/g to 553 mA h/g during long-term cycling tests. The finding suggests that overlithiation beyond 66 Li atoms may have caused damage to the cage structure and led to lower reversible capacities.

The structural evolution of the “zero-strain” Li4Ti5O12 anode within a functioning Li-ion battery during charge–discharge cycling was studied using in situ neutron powder-diffraction, allowing correlation of the anode structure to the measured charge–discharge profile. While the overall lattice response controls the “zero-strain” property, the oxygen atom is the only variable in the atomic structure and responds to the oxidation state of the titanium, resulting in distortion of the TiO6 octahedron and contributing to the anode's stability upon lithiation/delithiation. Interestingly, the trend of the octahedral distortion on charge–discharge does not reflect that of the lattice parameter, with the latter thought to be influenced by the interplay of lithium location and quantity. Here we report the details of the TiO6 octahedral distortion in terms of the O–Ti–O bond angle that ranges from 83.7(3)° to 85.4(5)°.

We have developed efficient numerical algorithms for solving 3D steady-state Poisson-Nernst-Planck (PNP) equations with excess chemical potentials described by the classical density functional theory (cDFT). The coupled PNP equations are discretized by a finite difference scheme and solved iteratively using the Gummel method with relaxation. The Nernst-Planck equations are transformed into Laplace equations through the Slotboom transformation. Then, the algebraic multigrid method is applied to efficiently solve the Poisson equation and the transformed Nernst-Planck equations. A novel strategy for calculating excess chemical potentials through fast Fourier transforms is proposed, which reduces computational complexity from O(N2) to O(NlogN), where N is the number of grid points. Integrals involving the Dirac delta function are evaluated directly by coordinate transformation, which yields more accurate results compared to applying numerical quadrature to an approximated delta function. Numerical results for ion and electron transport in solid electrolyte for lithiumion (Li-ion) batteries are shown to be in good agreement with the experimental data and the results from previous studies.

The recent development of in-situ liquid stages for (scanning) transmission electron microscopes now makes it possible for us to study the details of electrochemical processes under operando conditions. As electrochemical processes are complex, care must be taken to calibrate the system before any in-situ/operando observations. In addition, as the electron beam can cause effects that look similar to electrochemical processes at the electrolyte/electrode interface, an understanding of the role of the electron beam in modifying the operando observations must also be understood. In this paper we describe the design, assembly, and operation of an in-situ electrochemical cell, paying particular attention to the method for controlling and quantifying the experimental parameters. The use of this system is then demonstrated for the lithiation/delithiation of silicon nanowires.

Rietveld refinement of LixCoO2-type cathodes (where x=0.59–1.00) has been demonstrated to yield quantitative information about the Li occupancy with an error of about ∼10%. With careful X-ray diffraction (XRD) data collection, refinement, and proper calibration, accurate values can be obtained. Rietveld refinement tends to under-predict the Li occupancy values in charged (de-lithiated) cathodes as compared to ICP measurements. A Li-gradient model that assumes a decreasing concentration of Li from the particle core to its surface is discussed to explain this observation. The observed lattice parameters for the fully lithiated LiCoO2 standard phase (R-3m symmetry) were a=2.8155(1) Å, c=14.052(1) Å. The error convention used in this paper is 3σ of standard deviations obtained from Rietveld refinement output.

The electrochemical reaction behavior of a commercial Li-ion battery (LiFePO4-based cathode, graphite-based anode) has been measured via in situ neutron diffraction. A multivariate analysis was successfully applied to the neutron diffraction data set facilitating in the determination of Li bearing phases participating in the electrochemical reaction in both the anode and cathode as a function of state-of-charge (SOC). The analysis resulted in quantified phase fraction values for LiFePO4 and FePO4 cathode compounds as well as the identification of staging behavior of Li6, Li12, Li24, and graphite phases in the anode. An additional Li-graphite phase has also been tentatively identified during electrochemical cycling as LiC48 at conditions of ∼5% to 15% SOC.

Measuring the changing thickness of a thin film, without a reference, using an atomic force microscope (AFM) is problematic. Here, we report a method for measuring film thickness based on in situ monitoring of surface roughness of films as their thickness changes. For example, in situ AFM roughness measurements have been performed on alloy film electrodes on rigid substrates as they react with lithium electrochemically. The addition (or removal) of lithium to (or from) the alloy causes the latter to expand (or contract) reversibly in the direction perpendicular to the substrate and, in principle, the change in the overall height of these materials is directly proportional to the change in roughness. If the substrate on which the film is deposited is not perfectly smooth, a correction to the direct proportionality is needed and this is also discussed.