Random composites with nickel networks hosted randomly in porous alumina are proposed to realize double negative materials. The random composite for DNMs (RC-DNMs) can be prepared by typical processing of material, which makes it possible to explore new DNMs and potential applications, and to feasibly tune their electromagnetic parameters by controlling their composition and microstructure. Hopefully, various new RC-DNMs with improved performance will be proposed in the future.

Sodium ion batteries have garnered significant research attention in recent years due to the rising demand for large-scale energy storage solutions as well as the high abundance of sodium. P2-type layered oxide materials have been identified as promising positive electrode materials for sodium ion batteries. Previously, P2−Na 2/3 Ni 1/3 Mn 2/3 O 2 was shown to have a high operating voltage and high capacity but suffers from a step-like voltage curve and capacity loss during cycling, potentially due to its P2−O2 transition at high voltages. One strategy to improve cycling performance has been to dope Ni 2+ with other 2+ cations, such as Zn 2+ or Mg 2+ , which improved capacity retention but significantly decreases reversible capacity, since these ions were not electrochemically active. Since Cu 2+ has been shown to be electrochemically active, we replaced Ni 2+ with Cu 2+ , resulting in air-stable Na 2/3 Ni 1/3−x Cu x Mn 2/3 O 2 (0 ≤ x ≤ 1/3). Both Ni 2+ /Ni 4+ and Cu 2+ /Cu 3+ participate in the redox reaction during cycling, capacity retention was greatly improved, and phase changes were suppressed during cycling without sacrificing much capacity. The material retains a P2/OP4 structure even when cycled to high voltages. The doping strategy is a promising approach for the future development of positive electrode materials for sodium ion batteries.

Single crystal (SC) cathode materials with a layered structure are considered to be state-of-the-art for lithium ion batteries. However, their production involves many steps and can produce large amounts of wastewater. Here we report an all-dry method for making SC cathode materials, with LiNi0.6Mn0.2Co0.2O2 (SC-NMC) used as a specific example. It was found that a SC-NMC precursor in the form of a previously unobserved rock-salt (Ni, Mn, Co)O solid solution phase can be made phase pure by ball milling. This demonstrates that precursors with atomic scale mixing can be achieved by dry methods. It is furthermore shown that large precursor particle sizes are not necessary to form large SC-NMC particles, as is commonly believed. Instead, large crystallites could just as easily be made from submicron precursors by adjusting the sintering time in air. As a result, highly crystalline SC-NMC with precisely controlled average crystallite sizes ranging from ∼2–10 μm could be made from submicron precursor powders made using an all-dry process.

NaNi0.5Mn0.5O2 is a promising sodium-ion battery cathode material that has been extensively studied. However, the air sensitivity of this material limits practical application and is not well understood. Here, we present a detailed study of NaNi0.5Mn0.5O2 powders stored in different atmospheres (oxygen, argon, and carbon dioxide), either dry or wet. X-ray diffraction and Fourier transform infrared measurements were used to characterize the materials and their surface species before and after controlled-atmosphere storage. It was determined that the exposure of untreated NaNi0.5Mn0.5O2 powders to moisture results in desodiation and material degradation, leading to poor cycling. This effect was found to be caused by reactive surface species. From these results, a simple ethanol washing method was found to significantly reduce the air-reactivity and improve the electrochemical performance of NaNi0.5Mn0.5O2 by removing surface impurities formed by air exposure.

Nanostructured Si 1-x Ti x alloys (0 ≤ x ≤ 0.3) prepared by ball milling were studied as negative electrode materials in Li cells. The alloys comprised a nanocrystalline and amorphous Si phase and a nanocrystalline C49 TiSi 2 phase. When x ≥ 0.15 the nanocrystalline Si phase was completely eliminated and such alloys consisted only of amorphous Si and the C49 TiSi 2 phase. The alloys with x ≥ 0.15 also completely suppressed the formation of Li 15 Si 4 during cycling, resulting in good capacity retention, and, unlike other Si transition metal alloys, without introducing noticeable cell polarization. The observed capacity of the Si 1-x Ti x alloys suggested that the TiSi 2 is an inactive phase toward Li. Silicon-based materials are of high interest in the pursuit of obtaining higher energy density lithium ion batteries. Pure silicon has an outstanding theoretical capacity of 2194 Ah/L, which has been estimated to provide an increase in energy density of up to 34% in Li-ion cells, compared to cells with conventional graphite-based electrodes. However, the cycle life of Si electrodes is difficult to maintain because of its drastic volume expansion during lithiation (up to 280%). Reducing Li uptake and providing an inactive phase framework is one possible way to alleviate the expansion problem. Some inactive M-Si alloys, such as Ni-Si, 2-4 Fe-Si, 5 Cu-Si, 6 B-Si, 7 have been extensively studied in the past two decades.Si-Ti alloys are of interest as electrode materials for Li-ion batteries because of their thermal stability and because they are composed of high abundance elements. They also have low density and TiSi 2 has high electrical conductivity compared to other silicides. 8 Because of these favorable properties, this system has been studied by other groups in the past. Lee et al. synthesized Si-Ti alloys via melt spinning, forming alloys comprised of well crystallized Si and TiSi 2 phases. 9The observed capacities of these samples in Li cells were far less than expected from the amount of Si present. All the Si in these samples might not have been fully accessible to lithium ions because of the morphology that resulted from rapid solidification processing. Zhou et al. synthesized Si coated TiSi 2 nanonets via chemical vapor deposition.10 When the nanonets were cycled between 0.03-3.0 V, high capacity fade during cycling resulted because of the formation of Li 15 Si 4 . When cycling was conducted above 0.09 V, capacity retention was improved because the formation of Li 15 Si 4 was avoided. This indicates the importance of avoiding Li 15 Si 4 formation to obtain good cycling performance. Park et al. designed a TiSi 2 -coated Si anode via a silicothermic reduction process.11 The conductive silicide coating resulted in improved rate performance. It is apparent from these studies that microstructure and Li 15 Si 4 avoidance is important in obtaining good cycling in Si-Ti alloys. However, to our knowledge a systematic study of the effect of composition in the Si-Ti alloy system has not previously been reported.Here a...