Spinel Li Mn_(2)O_(4)integrated with coating and doping by Sn self-segregation

The development of high-performance and low-cost cathode materials is of great significance for the progress in lithium-ion batteries.The use of Co and even Ni is not conducive to the sustainable and healthy development of the power battery industry owing to their high cost and limited resources.Here,we report LiMn_(2)O_(4)integrated with coating and doping by Sn self-segregation.Auger electron energy spectrum and soft X-ray absorption spectrum show that the coating is Sn-rich LiMn_(2)O_(4),with a small Sn doping in the bulk phase.The integration strategy can not only mitigate the Jahn–Teller distortion but also effectively avoid the dissolution of manganese.The as-obtained product demonstrates superior high initial capacities of 124 mAh·g^(-1)and 120 mAh·g^(-1)with the capacity retention of 91.1%and 90.2%at 25℃and55℃after 50 cycles,respectively.This novel material-processing method highlights a new development direction for the progress of cathode materials for lithium-ion batteries.

Synergistic effects of carbon doping and coating of TiO_(2) with exceptional photocurrent enhancement for high performance H2 production from water splitting

The"one pot"simultaneous carbon coating and doping of TiO_(2) materials by the hydrolysis of TiCl4 in fructose is reported.The synergistic effect of carbon doping and coating of TiO_(2) to significantly boost textural,optical and electronic properties and photocurrent of TiO_(2) for high performance visible light H2 production from water splitting has been comprehensively investigated.Carbon doping can significantly increase the thermal stability,thus inhibiting the phase transformation of the Titania material from anatase to rutile while carbon coating can suppress the grain aggregation of TiO_(2).The synergy of carbon doping and coating can not only ensure an enhanced narrowing effect of the electronic band gap of TiO_(2) thus extending the absorption of photocatalysts to the visible regions,but also promote dramatically the separation of electron-hole pairs.Owing to these synergistic effects,the carbon coated and doped TiO_(2) shows much superior photocatalytic activity for both degradation of organics and photocatalytic/photoelectro chemical(PEC)water splitting under simulated sunlight illumination.The photocatalytic activity of obtained materials can reach 5,4 and 2 times higher than that of pristine TiO_(2),carbon doped TiO_(2) and carbon coated TiO_(2),respectively in the degradation of organic pollutants.The carbon coated and doped TiO_(2) materials exhibited more than 37 times and hundreds of times photocurrent enhancement under simulated sunlight and visible light,respectively compared to that of pristine TiO_(2).The present work providing new comprehensive understanding on carbon coating and doping effect could be very helpful for the development of advanced TiO_(2) materials for a large series of applications.

One-time sintering process to modify xLi2MnO3(1-x)LiMO2 hollow architecture and studying their enhanced electrochemical performances

To solve the critical problems of lithium rich cathode materials, e.g., structure instability and short cycle life, we have successfully prepared a ZrO2-coated and Zr-doping xLi2MnO3·(1–x)LiMO2 hollow architecture via one-time sintering process. The modified structural materials as lithium-ion cathodes present good structural stability and superior cycle performance in LIBs. The discharge capacity of the ZrO2-coated and Zr-doped hollow pristine is 220 mAh g-1 at the 20th cycle at 0.2 C(discharge capacity loss, 2.7%)and 150 m Ah g-1 at the 100 th cycle at 1 C(discharge capacity loss, 17.7%), respectively. However, hollow pristine electrode only delivers 203 m Ah g-1 at the 20 th cycle at 0.2 C and 124 mAh g-1 at the 100 th cycle at 1 C, respectively, and the corresponding to capacity retention is 92.2% and 72.8%, respectively.Diffusion coefficients of modified hollow pristine electrode are much higher than that of hollow pristine electrode after 100 cycles(approach to 1.4 times). In addition, we simulate the adsorption reaction of HF on the surface of ZrO2-coated layer by the first-principles theory. The calculations prove that the adsorption energy of HF on the surface of ZrO2-coated layer is about-1.699 e V, and the ZrO2-coated layer could protect the hollow spherical xLi2MnO3·(1–x)LiMO2 from erosion by HF. Our results would be applicable for systematic amelioration of high-performance lithium rich material for anode with the respect of practical application.

Garnet-type Solid-state Electrolyte Li7La3Zr2O12:Crystal Structure,Element Doping and Interface Strategies for Solid-state Lithium Batteries

The eetimous devedqpmaut et soid-ae elestrolyte(SSEs)has slimuliteal immese progres in the development of lllia stle batrierdA8S8s Particularly,grmestyped S8Es in fomula of Li7La3Zr2O12(LLZO)are under intesive invesigtion如eaplit their advantage im high lithium ious condaxtiriy(>1 mSicm)wide cletrochemical window(>5V),and good chenical electrochemical stability for lithium,which are critical factors to ensure a stabl,and high performance ASSBs.This review will focus on the challages related to LLZOs-based electrolyte,and update the recent developments in structurl design of LLZOs,which are disussed in three major sections;(i)crystal structure and the lithium-ion transport mechanismn of LLZ0;(ii)single-site and multi-ite doping of Li sites,La sites and Zr sites to enhance Li ions conductivity(LIC)and sability of LLZO;(iii)interface strategies between electrodes and LLZ0 to decrease inertaee re-pcife reistence(ASR).

Al-doping effects on the photovoltaic performance of inverted polymer solar cells

The properties of Al-doped Zn O(AZO) play an important role in the photovoltaic performance of inverted polymer solar cells(PSCs), which is used as electron transport and hole blocking buffer layers. In this work, we study the effects of Al-doping level in AZO on device performance in detail. Results indicate that the device performance intensely depends on the Al-doping level. The AZO thin films with Al-doping atomic percentage of 1.0% possess the best conductivity. The resulting solar cells show the enhanced short current density and the fill factor(FF) simultaneously, and the power conversion efficiency(PCE) is improved by 74%, which are attributed to the reduced carrier recombination and the optimized charge transport and extraction between AZO and the active layer.

The role of tungsten-related elements for improving the electrochemical performances of cathode materials in lithium ion batteries

Lithium ion batteries using Ni-Co-Mn ternary oxide materials(NCMs)and Ni-Co-Al materials(NCAs)as the cathode materials are dominantly employed to power the electric vehicles(EVs).Increasing the driving range of EVs necessitates an increase of Ni content to improve the energy densities,which,however,degrades the cycle stability.Here we review the doping/coating of tungsten and related elements to improve the electrochemical performance of these cathodes especially the cycle stability.The selection of tungsten and related elements is based on their special properties including the high valence state,strong bonding with oxygen and the large ionic radius.The improvement of cycle stability mainly results from two features:(1)the enhancement of bulk structure stability upon doping(Mo,W,Ta,Nb)and(2)the resistance of side reactions of electrode/electrolyte by the surficial layer induced by direct coating(V,W,Nb)or bulk doping.For the recent high Ni materials,the formation of Ni2+and its migration to the Li layer induced by these doped/coated tungsten-related elements,and the presence of spinel or rock-salt phase before cycling contributes to improving the cycle stability.The key challenges are the selection of an optimized additive concentration and the fundamental understanding of the reaction mechanism,which will provide insightful guidance for maximizing the electrochemical performance of the state-of-the-art lithium-ion batteries at minimal additional process costs.

Improving the performance of inverted organic solar cells by adjusting the concentration of precursor solution of Al-doped ZnO

Al-doped ZnO(AZO) has been used as an electron transport and hole blocking buffer layer in inverted organic solar cells(IOSCs). In this paper, the AZO morphology, optical and structural properties and IOSCs performance are investigated as a function of precursor solution concentration from 0.1 mol/L to 1.0 mol/L. We demonstrate that the device with 0.1 mol/L precursor concentration of AZO buffer layers enhances the short-circuit current and the fill factor of IOSCs simultaneously. The resulting device shows that the power conversion efficiency is improved by 35.6% relative to that of the 1.0 mol/L device, due to the improved surface morphology and transmittance(300–400 nm) of AZO buffer layer.

Effects of different CdCl_2 annealing methods on the performance of CdS/Cd Te polycrystalline thin film solar cells

In this paper, the effects of different Cd Cl2 annealing methods, including vapor annealing and dip-coating annealing, on the performance of Cd S/Cd Te polycrystalline thin-film solar cells are studied. After annealing, the samples are lightly etched with 1% bromine in methanol to remove surface oxides. Both annealing methods give Cd Te polycrystalline thin films with good crystallinity and complete structure. For solar cells containing the annealed Cd Te films, cell efficiency first increases and then decreases as the concentration of Cd Cl2 solution used for dip-coating annealing increases, and the optimized Cd Cl2 concentration is 12%. The uniformity of the performance of all cells is analyzed by calculating the relative standard deviation for each parameter. The uniformity of cell performance can be improved dramatically by dip-coating annealing instead of vapor annealing. Most notably, an appropriate concentration of Cd Cl2(12%) acts as a protective layer that is conducive to realizing uniform high-performance Cd S/Cd Te solar cells. According to the location of depletion regions, the Cd Te films treated by dip-coating annealing show a relatively low doping concentration, except for the sample treated with a Cd Cl2 concentration of 6%, which is consistent with the changes of short-circuit current density of the cells. It is believed that these results can be applied to the large-scale production of Cd Te polycrystalline thin-film solar cells.