Influence of Doping Rare Earth on Performance of Lithium Manganese Oxide Spinels as Cathode Materials for Lithium-Ion Batteries

Some rare earth doping spinel LiMn_(2-x)RE_xO_4 (RE=La, Ce, Nd) cathode materials for lithium ion batteries were synthesized by the solid-state reaction method. The structure characteristics of these produced samples were investigated by XRD, SEM, and particle size distribution analysis. According to the microstructure and charge-discharge testing, the effect of doping rare earth on stabilizing the spinel structure was analyzed. Through a series of doping experiments, it is shown that when the doping content x within the range of 0.01～0.02 the cycle performance of the materials is greatly improved. The discharge capacity of the sample LiMn_(1.98)La_(0.02)O_4, LiMn_(1.98)Ce_(0.02)O_4 and LiMn_(1.98)Nd_(0.02)O_4 remain 119.1, 114.2 and 117.5 mAh·g^(-1) after 50 cycles.

Review on Heteroatom Doping Carbonaceous Materials Toward Electrocatalytic Carbon Dioxide Reduction

Carbon dioxide(CO_(2))reduction into chemicals or fuels by electrocatalysis can eff ectively reduce greenhouse gas emissions and alleviate the energy crisis.Currently,CO_(2)electrocatalytic reduction(CO_(2)RR)has been considered as an ideal way to achieve“carbon neutrality.”In CO_(2)RR,the characteristics and properties of catalysts directly determine the reaction activity and selectivity of the catalytic process.Much attention has been paid to carbon-based catalysts because of their diversity,low cost,high availability,and high throughput.However,electrically neutral carbon atoms have no catalytic activity.Incorpo-rating heteroatoms has become an eff ective strategy to control the catalytic activity of carbon-based materials.The doped carbon-based catalysts reported at present show excellent catalytic performance and application potential in CO_(2)RR.Based on the type and quantity of heteroatoms doped into carbon-based catalysts,this review summarizes the performances and catalytic mechanisms of carbon-based materials doped with a single atom(including metal and without metal)and multi atoms(including metal and without metal)in CO_(2)RR and reveals prospects for developing CO_(2)electroreduction in the future.

Doping tuned anomalous Hall effect in the van der Waals magnetic topological phases Mn(Sb_(1-x)Bi_(x))_(4)Te_(7)

The van der Waals(vdW)MnSb4Te7is a newly synthesized antiferromagnetic(AFM)topological insulator hosting a robust axion insulator state irrelative to the specific spin structure.However,the intrinsic hole doped character of MnSb_4Te_7makes the Fermi level far away from the Dirac point of about 180 meV,which is unfavorable for the exploration of exotic topological properties such as the quantum anomalous Hall effect(QAHE).To shift up the Fermi level close to the Dirac point,the strategy of partially replacing Sb with Bi as Mn(Sb_(1-x)Bi_(x))_(4)Te_(7)was tried and the magnetotransport properties,in particular,the anomalous Hall effect,were measured and analyzed.Through the electron doping,the anomalous Hall conductanceσAH changes from negative to positive between x=0.3 and 0.5,indicative of a possible topological transition.Besides,a charge neutrality point(CNP)also appears between x=0.6 and 0.7.The results would be instructive for further understanding the interplay between nontrivial topological states and the magnetism,as well as for the exploration of exotic topological properties.

Engineered nitrogen doping on VO_(2)(B)enables fast and reversible zinc-ion storage capability for aqueous zinc-ion batteries

Vanadium-based compounds with high theoretical capacities and relatively stable crystal structures are potential cathodes for aqueous zinc-ion batteries(AZIBs).Nevertheless,their low electronic conductivity and sluggish zinc-ion diffusion kinetics in the crystal lattice are greatly obstructing their practical application.Herein,a general and simple nitrogen doping strategy is proposed to construct nitrogen-doped VO_(2)(B)nanobelts(denoted as VO_(2)-N)by the ammonia heat treatment.Compared with pure VO_(2)(B),VO_(2)-N shows an expanded lattice,reduced grain size,and disordered structure,which facilitates ion transport,provides additional ion storage sites,and improves structural durability,thus presenting much-enhanced zinc-ion storage performance.Density functional theory calculations demonstrate that nitrogen doping in VO_(2)(B)improves its electronic properties and reduces the zinc-ion diffusion barrier.The optimal VO_(2)-N400 electrode exhibits a high specific capacity of 373.7 mA h g^(-1)after 100 cycles at 0.1 A g^(-1)and stable cycling performance after 2000 cycles at 5 A g^(-1).The zinc-ion storage mechanism of VO_(2)-N is identified as a typical intercalation/de-intercalation process.

Research on cathode material of Li-ion battery by yttrium doping

Modification of LiFePO4, LiMn2O4 and Li1＋xV3O8 by doping yttrium was investigated. The influences of doping Y on structure, morphology and electrochemical performance of cathode materials were investigated systematically. The results indicated that the mechanisms of Y doping in three cathode materials were different, so the influences on the material performance were different. The crystal structure of the three materials was not changed by Y doping. However, the crystal parameters were influenced. The crystal parameters of LiMn2O4 became smaller, and the interlayer distance of （100） crystal plane of Li1-xV3O8 was lengthened after Y doping. The grain size of Y-doped LiFePO4 became smaller and grain morphology became more regular than that of undoped LiFePO4. It indicated that Y doping had no influence on crystal particle and morphology of LiMn2O4. The morphology of Li1＋xV3O8 became irregular and its size became larger with the increase of Y. For LiFePOaand Li1＋xV3O8, both the initial discharge capacities and the cyclic performance were improved by Y doping. For LiMn2O4, the cyclic performance became better and the initial discharge capacities declined with increasing Y doping.

Influence of Sb_2O_3 doping on the properties of KBT-NBT-BT lead-free piezoelectric ceramics

0.144（K0.5Bi0.5）TiO3-0.85（Na0.5Bi0.5）TiO3-0.006BaTiO3（KBT-NBT-BT） lead-free piezoelectric ceramics were prepared using a conventional solid state method.The influence of Sb2O3 doping on the crystal phase,surface microstructure and properties of the KBT-NBT-BT lead-free piezoelectric ceramics were investigated using X-ray diffraction（XRD）,scanning electron microscope（SEM） and other analytical methods.The results show that all compositions are of pure perovskite structure solid states.Sb2O3 doping does not influence the microstructure of KBT-NBT-BT lead-free piezoelectric ceramics obviously in the Sb2O3 doping range of 0.1-0.5 wt.%.Sb2O3 functions as a donor when doped small amount,while functions as a acceptor when doped large amount.The piezoelectric strain constant（d33） increases first and then decreases;the dielectric constant（ε33^T/ε0） and the dielectric loss（tanδ） decrease continuously when the amount of Sb2O3 dopant increases.When the doping amount of Sb2O3 is 0.1 wt.%,the KBT-NBT-BT piezoelectric ceramics with good comprehensive properties are obtained,whose d33,ε33^T/ε0 and tanδ are 147 pC/N,1510 and 4.2%,respectively.

Efficient doping modulation of monolayer WS_2 for optoelectronic applications

Transition metal dichalcogenides(TMDCs) belong to a subgroup of two-dimensional(2 D) materials which usually possess thickness-dependent band structures and semiconducting properties. Therefore, for TMDCs to be widely used in electronic and optoelectronic applications, two critical issues need to be addressed, which are thickness-controllable fabrication and doping modulation of TMDCs. In this work, we successfully obtained monolayer WS2 and achieved its efficient doping by chemical vapor deposition and chemical doping, respectively. The n-and p-type dopings of the monolayer WS2 were achieved by drop coating electron donor and acceptor solutions of triphenylphosphine(PPh3) and gold chloride(AuCl_3), respectively, on the surface, which donates and captures electrons to/from the WS2 surface through charge transfer, respectively. Both doping effects were investigated in terms of the electrical properties of the fabricated field effect transistors. After chemical doping, the calculated mobility and density of electrons/holes are around 74.6/39.5 cm^2 · V^(-1) ·s^(-1)and 1.0 x 10^(12)/4.2 x 10^(11) cm^(-2), respectively. Moreover, we fabricated a lateral WS2 p-n homojunction consisting of nondoped n-type and p-doped p-type regions, which showed great potential for photodetection with a response time of 1.5 s and responsivity of 5.8 A/W at V_G = 0 V and V_D = 1 V under 532 nm light illumination.

Doping effect on thermoelectric properties of nonstoichiometric AgSbTe_2 compounds

Nonstoichiometric ternary thermoelectric materials Ag0.84Sb1.15M0.01Te2.16 （M=Ce, Yb, Cu） were prepared by a direct melt-quench and hot press process. The carrier concentration of all the samples increased after doping. Thermoelectric properties, namely electrical con-ductivity, Seebeck coefficient, and thermal conductivity, were measured from 300 to 673 K. The phase transition occurring at about 418 K representing the phase transition from b-Ag2Te to a-Ag2Te influenced the electrical transport properties. The electrical conductivities of Ce and Yb doped samples increased after doping from 1.9×104 to 2.5×104 and 2.3×104 S·m-1, respectively, at 673 K. Also, at room temperature, the Seebeck coefficient of the Ce doped sample relatively increased corresponding to the high carrier concentration due to the changes in the band structure. However, all the thermal conductivities increased after doping at low temperature. Because of the higher thermal conductivity, the dimensionless figure of merit ZT of these doped samples has not been improved.

Effects of Dysprosium Oxide Doping on Microstructure and Properties of Barium Titanate Ceramic

Different amounts of dysprosium oxide were incorporated into barium titanate powders synthesized by hydrothermal method. Relations of substitution behaviors and lattice parameters with solid-solubility were studied. Furthermore, the influences of dysprosium oxide doping fraction on grain size and dielectric properties of barium titanate ceramic, including dielectric constant and breakdown electric field strength , were investigated via scanning electron microscope, X-ray diffraction and electric property tester. The results show that dysprosium oxide can restrain abnormal grain growth during sintering and that fine-grained and high density of barium titanate ceramic can result in excellent dielectric properties. As mass fraction of dysprosium oxide is 0.6%, the lattice parameters of grain increase to the maximum because of the lowest vacancy concentration. The electric property parameters are cited as following： dielectric constant （25 ℃ ） reaches 4100, the change in relative dielectric constant with temperature is - 10% to 10% within the range of - 15 - 100 ℃, breakdown electric field strength （alternating current） achieves 3.2 kV·mm^-1, which can be used in manufacturing high voltage ceramic capacitors

Transport Property of La_(0.67-x)Sm_xSr_(0.33)MnO_3 at Heavy Samarium Doping (0.40≤x≤0.60)

The influence of heavy samarion （Sm） doping （0.40≤x≤0.60） on magnetic and electric properties of La0.67-xSmxSr0.33MnO3 was investigated by measuring the magnetization-temperature （M - T） curves, magnetization-magnetic density （ M - H） curves, resistivity-temperature （ρ- T） curves and magnetoresistivity-temperature （ MR - T） curves of the samples under different temperatures. It is found that, form from long-range ferromagnetic order to spin-cluster glass with the increase of Sm doping amount, the samples transstate and anti-ferromagnetic state; and when x = 0.60, the transport property becomes abnormal under magnetic background; and the magnetic structure changes and extra magnetic coupling induced by doping leads to colossal magnetoresistance effect. The transport mechanism of metallic conduction at low temperature is mainly electron-magneton interaction and can be fitted by the formula ρ = ρ0 ＋ AT^4.5, and the insulatorlike transport mechanism on high temperature range is mainly the function of variable-range hopping and can be fitted by the formula ρ = ρ0exp（T0/T）^1/4. In the formulas above, p is resistivity, T is temperature, and A, ρ0, T0 are constants.

Study on Performance of La Doping LiLa_xMn_(2-x)O_4 Spinel

To improve the cycling performance and the properties at high rates of spinel LiMn_2O_4 cathode material, La-doped LiLa_xMn_ 2-xO_4 spinel was synthesized by high temperature solid-phase reaction. XRD measurement showed that the spinel structure was retained after La-doping. The performance was measured with the prepared material as cathode active material, MCMB as anode active material and 1 mol·L -1 LiPF_6-EC+DEC+DMC as electrolyte. Results showed that the cycling performance and the properties at high rates of the cathode material were greatly improved by La-doping. The reduction of LiLa_ 0.1Mn_ 0.9O_4 was under 10% of the initial capacity after 900 charge and discharge cycles. SEM analysis of the electrode before and after charge-discharge cycles showed that the morphology of the electrode changed little. The discharge capacity at 2C was about 97% of the capacity at 0.1C. The electrochemical impedance spectroscopy (EIS) of LiLa_xMn_ 1-xO_4 consists of one depressed semicircle and a straight line, which showed that the rate-determining step of the electrode was the diffusion of Li+ in the cathode material.

Controlling the electronic structure of SnO_2 nanowires by Mo-doping

Mo-doped SnO2 （MTO） nanowires are synthesized by an in-situ doping chemical vapour deposition method. Raman scattering spectra indicate that the lattice symmetry of MTO nanowires lowers with the increase of Mo doping, which implies that Mo ions do enter into the lattice of SnO2 nanowire. Ultraviolet-visible diffuse reflectance spectra show that the band gap of MTO nanowires decreases with the increase of Mo concentration. The photoluminescence emission of SnO2 nanowires around 580~nm at room temperature can also be controlled accurately by Mo-doping, and it is extremely sensitive to Mo ions and will disappear when the atomic ratio reaches 0.46%.

Effects of Co^(2+)Doping on the Crystal Structure and Electrochemical Performance of LiFePO_4

Co2＋-doped LiFePO4/C composite material was prepared by solid-state synthesis method using Fe2O3,Li2CO3 and NH4H2PO4 as the starting materials.The structures and elec-trochemical performance of samples were studied by XRD,SEM and constant current charge-discharge method.The results showed that the Co2＋ doping did not change the crystal structure of LiFePO4.The unit cell volume changed with the increase of Co2＋,and reached the maximum at x = 0.04.The LiFe0.96Co0.04PO4/C sample proved the best electrochemical properties.Its initial discharge capacity was 138.5 mA·h /g at 1 C rate.After 30 cycles,the capacity remained 127.7 mA·h /g,and the capacity retention rate was 92.2%.

Thermoelectric Properties of the CuGaTe_2 Crystal from First-principles Calculations:the Role of Doping and Temperature

The thermoelectric properties of CuGaTe2 crystal are investigated by using the first-principles method and semi-classical Boltzmann theory. We find that the electronic structure of CuGaTe2 is favorable for p-type doping. The transport coefficients can be tuned by doping and changing the work temperature to yield an optimized thermoelectric performance. The optimal doping concentration is 2 × 10^20 cm^-3, in which the maximum ZT value can reach 1.65 at 900 K. The results suggest CuGaTe2 might find promising applications as good thermoelectric materials, particularly at high temperature.

Effect of Lithium Doping on the Properties L-Citrulline Oxalate Monohydrate Nonlinear Optical Crystals

Single crystals of pure and Li+ doped L-citrulline oxalate (LCO) crystals are grown successfully by slow evaporation technique. The effect of lithium doping on crystal properties has been studied. The samples are characterized by X-ray powder diffraction, TGA, FTIR, Raman and UV-Vis spectroscopic techniques. The presence of lithium in Li+ doped LCO crystals is estimated using AES. The thermal stability and the optical transparency region are found to be enhanced for the doped samples. The second harmonic generation efficiency of the doped crystal has improved considerably compared to pure L-citrulline oxalate. Lithium doping can hence be considered as a simple and advantageous technique to improve the thermal, optical and non linear optical (NLO) properties of the LCO single crystals.

Effect of doping elements on catalytic performance of CeO_2-ZrO_2 solid solutions

CeZr, CeYZr, LaCeZr, LaCePrZr, LaCePrYZr, and LaCePr solid solutions were prepared via the coprecipitation method, and characterized by means of X-Ray Diffraction （XRD） and Brunauer-Emmett-Teller （BET） techniques. The oxygen storage capacity （OSC） of the solid solutions was evaluated by the pulse technique and the catalytic activity was assessed using a 4-channel catalysis device. It was seen that the solid solutions presented cubic structure. The specific surface area and thermal stability could be enhanced by doping Y into the solid solutions. Doping a small amount of La had a positive effect on the thermal durability while doping a large amount of La decreased the specific surface area and the thermal stability. LaCePrZr and LaCePrYZr solid solutions synthesized using Baotou rare earth mineral residue enriched with LaCePr after Nd extraction presented a certain higher value in specific surface area and thermal stability, thereby enabling to be used as economic catalysts for automobile exhaust purification. Coating Al2O3 or SiO2 layer on the surface of ceria-zirconia solid solutions increased the specific surface area and thermal resistance.

Influence of Ti^(4+) doping on electrochemical properties of LiFePO_4/C cathode material for lithium-ion batteries

To improve the performance of LiFePO4, single phase Li1-4xTixFePO4/C (x=0, 0.005, 0.010, 0.015) cathodes were synthesized by solid-state method. A certain content of glucose was used as carbon precursor and content of carbon in every final product was about 3.5%. The samples were characterized by X-ray diffraction(XRD), scanning electron microscopy observations(SEM), charge/discharge test, carbon analysis and electrochemical impedance spectroscopy(EIS). The results indicate that the prepared samples have ordered olivine structure and doping of the low concentration Ti^(4+) does not affect the structure of the samples. The electrochemical capabilities evaluated by charge-discharge test show that the sample with 1% Ti^(4+) (molar fraction) has good electrochemical performance delivering about an initial specific capacity of 146.7 mA·h/g at 0.3C rate. Electrochemical impedance spectroscopy measurement results show that the charge transfer resistance of the sample could be decreased greatly by doping an appropriate amount Ti^(4+).

Preparation and effects of W-doping on electrochemical properties of spinel Li_4Ti_5O_(12) as anode material for lithium ion battery

W-doped Li4Ti5O12 in the form of Li4Ti4.95W0.05O12 was firstly synthesized via solid state reaction. X-ray diffraction (XRD) and scanning electron microscope (SEM) were employed to characterize the structure and morphology of Li4Ti4.95W0.05O12 . W-doping does not change the phase composition and particle morphology, while remarkably improves its cycling stability at high charge/discharge rate. Li4Ti4.95W0.05O12 exhibits an excellent rate capability with a reversible capacity of 131.2 mA·h/g at 10C and even 118.6 mA·h/g at 20C. The substitution of W for Ti site can enhance the electronic conductivity of Li4Ti5O12 via the generation of mixing Ti4+/Ti3+ , which indicates that Li4Ti4.95W0.05O12 is promising as a high rate anode for the lithium-ion batteries.

Preparation and property of spinel LiMn_2O_4 material by co-doping anti-electricity ions

LiMn2-xMxO4-yFy(x=0.05; y=0.05; M=Al, Co, Cr and Mg, separately), as the cathode material, was synthesized by the method of high temperature solid-state reaction in laboratory. The results of charge-discharge test show that the properties of LiMn1.95M0.05O3.95F0.05(M= Al, Mg) are obviously superior to those of LiMn2O4. Through the condition experiments on sintering temperature, it is found that the materials present the integrate crystal structure and favorable cycle performance at 800 ℃. The research on the effects of different Mg2+ sources on the properties of LiMn2-xMgxO4-yFy shows that, with Mg(OH)2 and LiF as the reagents respectively offering Mg2+ and F?, LiMn1.95Mg0.05O3.95F0.05 synthesized has integrate crystal structure and its capacity hardly fades. The results of cyclic voltammetry indicate that the shape of two couples of redox peaks of the material synthesized by co-doping anti-electricity ions is more integrate and symmetrical than that of pure spinel LiMn2O4, which reveals that the co-doping material possesses preferable electrochemical reversibility.