Enhanced high temperature cycling performance of LiMn2O4/graphite cells with methylene methanedisulfonate（MMDS） as electrolyte additive and its acting mechanism

The effects of methylene methanedisulfonate(MMDS) on the high-temperature(~50℃) cycle performance of LiMn_2O_4/graphite cells are investigated.By addition of 2 wt%MMDS into a routine electrolyte,the high-temperature cycling performance of LiMn204/graphite cells can be significantly improved.The analysis of differential capacity curves and energy-dispersive X-ray spectrometry(EDX) indicates that MMDS decomposed on both cathode and anode.The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells.It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMn_2O_4 material,while the capacity fading of cell with 2 wt%MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.     

Enhanced high temperature cycling performance of LiMn2O4/graphite cells with methylene methanedisulfonate (MMDS) as electrolyte additive and its acting mechanism

The effects of methylene methanedisulfonate(MMDS) on the high-temperature(~50℃) cycle performance of LiMn_2O_4/graphite cells are investigated.By addition of 2 wt%MMDS into a routine electrolyte,the high-temperature cycling performance of LiMn204/graphite cells can be significantly improved.The analysis of differential capacity curves and energy-dispersive X-ray spectrometry(EDX) indicates that MMDS decomposed on both cathode and anode.The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells.It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMn_2O_4 material,while the capacity fading of cell with 2 wt%MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.     

High capacity lithium-manganese-nickel-oxide composite cathodes with low irreversible capacity loss and good cycle life for lithium ion batteries

We report a method to eliminate the irreversible capacity of 0.4Li_2MnO_3·0.6LiNi_(0.5)Mn_(0.5)O_2(Li_(1.17)Ni_(0.25)Mn_(0.583)O_2) by decreasing lithium content to yield integrated layered-spinel structures.XRD patterns,High-resolution TEM image and electrochemical cycling of the materials in lithium cells revealed features consistent with the presence of spinel phase within the materials.When discharged to about 2.8 V,the spinel phase of LiM_2O_4(M=Ni,Mn) can transform to rock-salt phase of Li_2M_2O_4(M=Ni,Mn) during which the tetravalent manganese ions are reduced to an oxidation state of 3.0.So the spinel phase can act as a host to insert back the extracted lithium ions(from the layered matrix) that could not embed back into the layered lattice to eliminate the irreversible capacity loss and increase the discharge capacity.Their electrochemical properties at room temperature showed a high capacity(about 275 mAh g~(-1) at 0.1 C) and exhibited good cycling performance.     

Electrochemical Performance of Li_4Ti_5O_(12) Prepared by Different Methods

A series of Li4Ti5O12 materials were prepared by three different methods： solvothermal, sol-gel, and solid-state reaction methods. Phase composition, morphology, and particle sizes of the samples were studied by powder X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Electrochemical properties of the samples were investigated by charge-discharge tests. It is demonstrated that both sol-gel and solid-state reaction methods provided good control over the chemical composition and microstructure of the active material, in which sol-gel method yielded a fine Li4Ti5O12 spinel having an initial specific capacity of 146 mAh g-1 and low capacity fade during cycling. Comparatively, the solid-state method is simple and promising to prepare Li4Ti5O12 for commercial applications.     

Electrochemical properties of niobium and phosphate doped spherical Li-rich spinel LiMn2O4 synthesized by ion implantation method

Spherical Li-rich lithium manganese oxide(LMO) spinel material was synthesized by an ion implanted method assisted by polyalcohol doped with Niobium and Phosphate simultaneously.The material was characterized by scanning electron microscopy,X-ray diffraction and BET specific surface area analysis.The electrochemical performances were investigated with galvanostatic techniques and cyclic voltammetry.The synthesis process was investigated with TG/DSC.The results show that the lithium ion can be immersed into the pore of manganese dioxide at a low temperature with the ion implanted method.The prepared materials have a higher discharge capacity and better crystallization than those prepared by solid phase method.The doped Nb can improve the capacity of the Li-rich LMO spinel and reinforce the crystal growth along(111) and(400) planes.The crystal grains show circular and smooth morphology,which makes the specific surface area greatly decreased.Phosphate-doped LMO spinel exhibits good high-rate capacity and structure stability.The prepared Li_(1.09)Mn_(1.87)Nb_(0.031)O_(3.99)(PO_4)_(0.021)delivers a discharge capacity of 119mAhg~(-1) at 0.2C(1C=148mAg~(-1)) and 112.8 mAhg~(-1) at 10 C,the discharge capacity retention reaches 98% at 1 ℃ after 50 cycles at 25 ℃ and 94% at 55 ℃.     

High performance TiP2O7 nanoporous microsphere as anode material for aqueous lithium-ion batteries

This work developed a facile way to mass-produce a carbon-coated TiP_2O_7 nanoporous microsphere(TPO-NMS) as anode material for aqueous lithium-ion batteries via solid-phase synthesis combined with spray drying method. TiP_2O_7 shows great prospect as anode for aqueous rechargeable lithium-ion batteries(ALIBs) in view of its appropriate intercalation potential of-0.6 V(vs. SCE) before hydrogen evolution in aqueous electrolytes. The resulting sample presents the morphology of secondary microspheres(ca. 20 μm) aggregated by carbon-coated primary nanoparticles(100 nm), in which the primary nanoparticles with uniform carbon coating and sophisticated pore structure greatly improve its electrochemical performance. Consequently, TPONMS delivers a reversible capacity of 90 mA h/g at 0.1 A/g, and displays enhanced rate performance and good cycling stability with capacity retention of 90% after 500 cycles at 0.2 A/g. A full cell containing TPO-NMS anode and LiMn_2O_4 cathode delivers a specific energy density of 63 W h/kg calculated on the total mass of anode and cathode. It also shows good rate capacity with56% capacity maintained at 10 A/g rate(vs. 0.1 A/g), as well as long cycle life with the capacity retention of 82% after 1000 cycles at 0.5 A/g.     

Synthesis and characterization of phosphate-modified LiMn2O4 cathode materials for Li-ion battery

<正>LiMn_2O_4 spinel cathode materials were modified with 2 wt.%Li-M-PO_4(M=Co,Ni,Mn) by polyol synthesis method.The phosphate surface-modified LiMn_2O_4 cathode materials were physically characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDS).The charge-discharge test showed that the cycling and rate capacities of LiMn_2O_4 cathode materials were significantly enhanced by stabilizing the electrode surface with phosphate.     

Preparation of polypyrrole-coated CuFe_2O_4 and their improved electrochemical performance as lithium-ion anodes

CuFe_2O_4 network,prepared via the electrostatic spray deposition technique,with high reversible capacity and long cycle lifetime for lithium ion battery anode material has been reported.The reversible capacity can be further enhanced by coating high electronic conductive polypyrrole(PPy).At the current density of 100mA·g~(-1).Li/CuFe_2O_4 electrode delivers a reversible capacity of 842.9 mAh·g~(-1) while the reversible capacity of Li/PPy-coated CuFe_2O_4 electrode increases up to 1106.7 mAh-g~'.A high capacity of 640.7 mAhg"1 for the Li/PPy-coated CuFe_2O_4electrode is maintained in contrast of 398.9 mAh·g~(-1) for CuFe_2O_4 electrode after 60 cycles,which demonstrates good electrochemical performance of the composite due to the increase of electronic conductivity.The electrochemical impedance spectroscopy(EIS) further reveals that the Li/PPy-coated CuFe_2O_4 electrode has a lower charge transfer resistance than the Li/CuFe2C4 electrode.     

Preparation of polypyrrole-coated CuFe2O4 and their improved electrochemical performance as lithium-ion anodes

CuFe_2O_4 network,prepared via the electrostatic spray deposition technique,with high reversible capacity and long cycle lifetime for lithium ion battery anode material has been reported.The reversible capacity can be further enhanced by coating high electronic conductive polypyrrole(PPy).At the current density of 100mA·g~(-1).Li/CuFe_2O_4 electrode delivers a reversible capacity of 842.9 mAh·g~(-1) while the reversible capacity of Li/PPy-coated CuFe_2O_4 electrode increases up to 1106.7 mAh-g~'.A high capacity of 640.7 mAhg"1 for the Li/PPy-coated CuFe_2O_4electrode is maintained in contrast of 398.9 mAh·g~(-1) for CuFe_2O_4 electrode after 60 cycles,which demonstrates good electrochemical performance of the composite due to the increase of electronic conductivity.The electrochemical impedance spectroscopy(EIS) further reveals that the Li/PPy-coated CuFe_2O_4 electrode has a lower charge transfer resistance than the Li/CuFe2C4 electrode.     

Synthesis of carbon-coated Li4Ti5O12 and its electrochemical performance as anode material for lithium-ion battery

Carbon-coated Li_4Ti_5O_(12) sample was synthesized by a sol-gel method. The Li_4Ti_5O_(12) powders were obtained by calcinations of the gels at 750, 800, 850,900 ℃ at N_2 atmosphere. The structure, morphology and electrochemical properties of the materials were characterized by SEM, XRD and charge and discharge. The final product sintered at 850 ℃ demonstrates excellent performance with a specific capacity of 163.5 mAh/g after 100 cycles at 1C. Furthermore, the discharge specific capacity of the sample can retain 80 mAh/g at 10C.     

Ultrathin 3 V Spinel Clothed Layered Lithium-Rich Oxides as Heterostructured Cathode for High-Energy and High-Power Li-ion Batteries

In an attempt to overcome the drawbacks of high-capacity layered lithium-rich cathodes xLi2MnO3·(1–x)LiMO2(0-1 and maintains 259.8 mAh g^-1 after 80 cycles at 0.1 C rate.Meanwhile,it delivers outstanding rate discharge capacities of 229.4 mAh g^-1 at 1 C,216.8 mAh g^-1 at 2 C and 184.4 mAh g^-1 at 5 C as well as alleviated voltage fade.It is believed the ultrathin clothing spinel layer plays a vital role in the modification of the materials kinetics,and structural and electrochemical stability of the heterostructured cathode.     

Synthesis of iron oxide cubes/reduced graphene oxide composite and its enhanced lithium storage performance

Fe₃O₄ is considered as a promising electrode material for lithium-ion batteries(LIBs) due to its low cost and high theoretical capacity(928 mAh/g).Nevertheless,the huge volume expansion and poor conductivity seriously hamper its practical applications.In this study,we use a facile hydrothermal reaction together with a post heat treatment to construct the three-dimensional heterostructured composite(Fe₃O₄/rGO) inwhich reduced graphene oxide sheets wraped the Fe₃O₄ submicron cubes as the conductive network.The electric conduction and electrode kinetics of lithium ion insertion/extraction reaction of the composite is enhanced due to the assist of conductive rGO,and thus the Listorage performance is obviously improved.The composite exhibits a reversible charge capacity of772.1 mAh/g at the current density of 0.1 A/g,and the capacity retention reaches 70.3% after400 cycles at0.5 A/g,demonstrating obviously higher specific capacity and rate capability over the Fe₃O₄ submicron cubes without rGO,and much superior cycling stability to the parent Fe_2 O_3 submicron cubes without rGO.On the other hand,as a synergic conductive carbon support,the flexible rGO plays an important role in buffering the large volume change during the repeated discharge/charge cycling.     

N-doped coaxial CNTs@a-Fe_2O_3@C nanofibers as anode material for high performance lithium ion battery

N-doped coaxial CNTs@α-Fe_2O_3@C nanofibers have been successfully synthesized according to a facile solvothermal/hydrothermal method.The obtained CNTs@α-Fe_2O_3@C nanofibers composites exhibited special three-dimensional(3-D)network structure,which endows they promising candidate for anode materials of lithium ion battery.The coaxial property of CNTs@α-Fe_2O_3@C nanofibers could significantly improve the cycling and rate performance owing to the acceleration of charge/electron transfer,improvement of conductivity,maintaining of structural integrity and inhibiting the aggregation.Theα-Fe_2O_3nanoparticles with small size and high percentage of N-doped amount could further improve the electrochemical performance.As for the CNT@α-Fe_2O_3@C nanofibers,the capacity presented a high value of1255.4 mAh/g at 0.1 C,and retained at 1213.4 mAh/g after 60 cycles.Even at high rate of 5 C,the capacity still exhibited as high as 319 mAh/g.The results indicated that the synthesized N-doped coaxial CNTs@α-Fe_2O_3@C nanofibers exhibited high cycling and rate performance.     

Exploring high-voltage fluorinated carbonate electrolytes for LiNi_(0.5)Mn_(1.5)O_4 cathode in Li-ion batteries

Ethyl-(2,2,2-trifluoroethyl)carbonate(ETFEC)is investigated as a solvent component in high-voltage electrolytes for LiNi_(0.5)Mn_(1.5)O_4 (LNMO).Our results show that the self-discharge behavior and the high temperature cycle performance can be significantly improved by the addition of 10% ETFEC into the normal carbonate electrolytes,e.g.,the capacity retention improved from 65.3% to 77.1% after 200 cycles at 60℃.The main reason can be ascribed to the high stability of ETFEC which prevents large oxidation of the electrolyte on the cathode surface.In addition,we also explore the feasibility of electrolytes using single fluoriated-solvents with and without additives.Our results show that the cycle performance of LNMO material can be greatly improved in 1 MLiPF_6+ pure ETFEC-solvent system with 2 wt% ethylene carbonate(EC)or ethylene sulfate(DTD).The capacity retention of the LNMO materials is 93% after 300 cycles,even better than that of carbonate-based electrolytes.It is shown that the additives are oxidized on the surface of LNMO particles and contribute to the formation of cathode/electrolyte interphase(CEI)films.This composite CEI film plays a crucial role in suppressing the serious decomposition of the electrolyte at high voltage.     

Optimization of Al3+ Doping on the Microstructure and Electrochemical Performance of Spinel LiMn2O4

A series of spinel Li Al_xMn_2-xO₄ (x≤0.1) cathode materials was synthesized by controlled crystallization and solid state route with micro-spherical Mn₃O₄ as the precursor.X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the crystal structure of the synthetic material and the microscopic morphology of the particles.It was found that Al³⁺doping did not change the spinel structure of the synthesized...     

Effect of initial precursor concentration on TiO2 thin film nanostructures prepared by PCVD system

TiO₂ thin film was prepared on Si substrate by plasma chemical vapor deposition（PCVD） system and the morphologies of TiO₂ thin film were controlled by adjusting the initial precursor concentration.As the initial titanium tetra-isopropoxide（TTIP） concentration increases in PCVD reactor,the shapes of TiO₂ particles generated in PCVD reactor change from the spherical small-sized particles around 20 nm and spherical large-sized particles around 60 nm to aggregate particles around 100 nm.The TiO₂ particles with different shapes deposit on the substrate and become the main building blocks of resulting TiO₂ thin film.We observed the TiO₂ thin film with smooth morphology at low initial TTIP concentration,granular morphology at medium initial TTIP concentration,and columnar morphology at high initial TTIP concentration.It is proposed that we can prepare the TiO₂ thin film with controlled morphologies in one-step process just by adjusting the initial precursor concentration in PCVD.     

Synthesis and Absorption Properties of Leaf-like Nd_2Cu_2O(4+δ) via a Coordination Complex Method with [NdCu(3,4-pdc)_2(OAc)(H_2O)_5]·6.5H_2O Precursor

Nd_2Cu_2O_(4+δ) nanosheets were synthesized via coordination complex method(CCM) by using [NdCu(3,4-pdc)_2(OAc)(H_2O)_5]·6.5 H_2O(1,3,4-pdc = 3,4-pyridinedicarboxylic acid) as the precursor. Compared to the particles prepared by SSM(simple solution method), Nd_2Cu_2O_(4+δ) prepared by CCM showed leaf-like morphology composed of nanosheets with an average thickness of 50～80 nm and a BET surface area up to 17.9 m~2/g. The Nd_2Cu_2O_(4+δ) samples exhibit selective adsorption towards malachite green(MG) with significant Qm(maximum adsorption capacity) values reaching up 1.55 g/g at room temperature, and the thermodynamic parameters of adsorption process were obtained. In addition, the properties of selective adsorption of the prepared samples were investigated by temperature change tests.     

Orthorhombic 3-LiV2O5 as Cathode Materials in Lithium Ion Batteries： Synthesis and Property

The rod-like and bundle-like v-LiV205 were synthesized via a simple solvothermal process- ing. The rod-like 7-LiV205 with diameter of 500-800 nm and the bundle-like architectures are composed of several of order-attached rods with diameter of 100-600 nm. ＂y-LiV205 were synthesized using LiOH.H20, NH4VO3, HNO3, C2H5OH without and with PVP as raw materials. At the same time, the actual formation mechanism of Y-LiV205 was also investigated. As the cathode materials for lithium ion batteries, the bundle-like Y-LiV205 prepared with PVP delivers a better electrochemical performance, which has an initial dis charge capacity of 269.3 mAh/g at a current density of 30 mA/g and is still able to achieve 228 mAh/g after the 20th cycle. The good electrochemical properties of the as-synthesized Y-LiV205 coupled with the simple, relatively low temperature, and low cost of the prepara tion method may make this material a promising candidate as a cathode material for lithium ion batteries.     

Restraining migration and dissolution of transition-metal-ions via functionalized separator for Li-rich Mn-based cathode with high-energy-density

Lithium-rich manganese-based materials(LRMs) are promising cathode for high-energy-density lithiumion batteries due to their high capacity,low toxicity,and low cost.However,LRMs suffer from serious voltage decay and capacity fade due to continual migration and dissolution of transition metal ions(TMs) during cycling process.Herein,a novel strategy is proposed to inhibit the TMs migration of LRMs through a modified separator by means of functionalized carbon coating layer,which depends on the che...     

Synthesis and Electrochemical Characterization of Gradient Composite LiNi1-yCoyO2 Used as Cathode Materials in Lithium-ion Battery

Gradient composites, LiNi1-yCoyO2, are synthesized from coated spherical Ni(OH)2 precursor. These composites could be applied as new cathode materials in lithium-ion batteries because they have low cobalt content (y≤0.2)and exhibit excellent properties during high-rate charge/discharge cycles. The initial discharge capacity of coated composite of LiNio.95Co0.05O2 is 186 mAh/g, and the decreasing rate of the capacity is 3.2% in 50 cycles at 1C rate. It has been verified by TEM and EDX experiments that a core-shell structure of the composite particles develops because of the cobalt enrichment near the surfaces, and the formation of the cobalt enrichment layer is sensitive to sintering temperature. High cobalt surface concentration may reduce the undesired reactions and stabilize the structure of the particles.