Nanolayers of Al2O3 and TiO2 coatings were applied to lithium‐ and manganese‐rich cathode powder Li1.2Ni0.13Mn0.54Co0.13O2 using an atomic layer deposition (ALD) method. The ALD coatings exhibited different surface morphologies; the Al2O3 surface film appeared to be uniform and conformal, while the TiO2 layers appeared as particulates across the material surface. In a Li‐cell, the Al2O3 surface film was stable during repeated charge and discharge, and this improved the cell cycling stability, despite a high surface impedance. The TiO2 layer was found to be more reactive with Li and formed a LixTiO2 interface, which led to a slight increase in cell capacity. However, the repetitive insertion/extraction process for the Li+ ions caused erosion of the surface protective TiO2 film, which led to degradation in cell performance, particularly at high temperature. For cells comprised of the coated Li1.2Ni0.13Mn0.54Co0.13O2 and an anode of meso‐carbon‐micro‐beads (MCMB), the cycling stability introduced by ALD was not enough to overcome the electrochemical instability of MCMB graphite. Therefore, protection of the cathode materials by ALD Al2O3 or TiO2 can address some of the capacity fading issues related to the Li‐rich cathode at room temperature.

Cellulose is the most abundant renewable material in nature. In this work, ordered cellulose nanocrystals (CNCs) have been transformed into porous carbon with an increased short-range ordered lattice and percolated carbon nanofiber at a relatively low carbonization temperature of 1000 ºC. When evaluated as anode for sodium-ion batteries (SIBs), the CNC derived porous carbon shows superior performances including a high reversible capacity of 340 mAh/g at a current density of 100 mA/g, which is one of the highest capacity carbon anodes for SIBs. Moreover, the rate capability and cycling stability of the porous carbon are also excellent. The excellent electrochemical performance is attributed to the larger interlayer spacing, porous structure, and high electrical conductivity arising from the ordered carbon lattice and the percolated carbon nanofiber. The formation of nano-sized graphitic carbon from the ordered CNC at the low carbonization temperature of 1000 °C is supported by both molecular dynamic simulations and as well as in-situ TEM measurements. This study shed light on the fundamental understanding of converting hydrocarbon biopolymer from wood to high quality carbon with a large domain of ordered lattice.

In situ electrochemical lithiation and delithiation processes inside a nanobattery consisting of an individual amorphous Si nanorod and ionic liquid were explored. Direct formation of the crystalline Li(22)Si(5) phase due to the intercalation of Li ions was observed. In addition, the role of the electrolyte-nanorod interface was examined. It was observed that the lithiation of Si nanorods is dominated by surface diffusion. Upon the delithiation process, partial decomposition of Li(22)Si(5) particles was observed which can explain the irreversible capacity loss that is generally seen in Si anodes. This study shows that the radial straining due to lithiation does not cause cracking in nanorods as small in diameter as 26 nm, whereas cracks were observed during the lithiation of 55 nm Si nanorods.

In the present work, taking advantage of aberration-corrected scanning transmission electron microscopy, we show that the dynamic lithiation process of anode materials can be revealed in an unprecedented resolution. Atomically resolved imaging of the lithiation process in SnO2 nanowires illustrated that the movement, reaction, and generation of b = [1[overline]1[overline]1] mixed dislocations leading the lithiated stripes effectively facilitated lithium-ion insertion into the crystalline interior. The geometric phase analysis and density functional theory simulations indicated that lithium ions initial preference to diffuse along the [001] direction in the {200} planes of SnO2 nanowires introduced the lattice expansion and such dislocation behaviors. At the later stages of lithiation, the Li-induced amorphization of rutile SnO2 and the formation of crystalline Sn and LixSn particles in the Li2O matrix were observed.