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Abstract This work is focused on applying structural concepts and basic chemical principles to model two N -heterocyclic lithium salts, based on trifluoromethyl substituted pyrazolide anions. An easily upscalable preparation method without difficult purification steps was also developed. In a comparative study, the physicochemical properties of the two new lithium salts were investigated, particularly the effect of an additional BF 3 -group at the nitrogen atom. In comparison to non-substituted lithium pyrazolide, the BF 3 -addition led to a strong improvement of thermal and electrochemical stability, ionic conductivity, as well as better C-rate and cycling performance. Furthermore, the anodic stability of Al current collectors was investigated and compared to commercial lithium salts, namely LiPF 6 and lithium bis((trifluoromethyl)sulfonyl)imide (LiTFSI). Possible mechanisms that lead to the presented improvements are discussed. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Cathode materials LiMn 0.5 Fe 0.5 PO 4 /C and LiMnPO 4 /C were synthesized by a high-energy ball-milling assisted sol-gel method. The LiMn 0.5 Fe 0.5 PO 4 consists of nanorods and nanoparticles homogeneously wrapped with highly ordering carbon. The increased Néel-temperature and decreased effective magnetic moment of LiMn 0.5 Fe 0.5 PO 4 /C revealed the microstructure differences from LiMnPO 4 /C. Meanwhile, tiny amount of ferromagnetic impurities is detected in LiMn 0.5 Fe 0.5 PO 4 /C by magnetic tests. The synergetic effects of Fe substitution and carbon coating remarkably improve rate capacity and cyclic stability of LiMn 0.5 Fe 0.5 PO 4 /C. This solid solution delivers initial discharge capacities of 128.6 mAh g −1 and 116.3 mAh g −1 and capacity retentions of 93.5% and 90.3% after 100 cycles at 1C and 2C respectively, significantly better than LiMnPO 4 /C. [ABSTRACT FROM AUTHOR]

Pristine and yttrium-doped LiNi 0.5- x Y x Mn 1.5 O 4 spinel powders ( x = 0, 0.005, 0.01, 0.02, 0.04) were synthesized by a facile solid-state method. The effect of yttrium doping content on the electrochemical properties of LiNi 0.5- x Y x Mn 1.5 O 4 was investigated by using half-cells paired with lithium metal and full-cells paired with graphite. XRD and FT-IR analysis shows that the cation disordering degree (Mn 3+ content) first increase ( x ≤ 0.02) and then decrease with Y doping content and the Y doping can effectively inhibit the formation of Li x Ni 1- x O impurity phase. Electrochemical results show that in half-cells, the LiNi 0.5-x Y x Mn 1.5 O 4 cathode material with appropriate Y doping ( x = 0.01) exhibits optimal rate capability and cycling stability, due to higher phase purity, enlarged lattice parameter, higher disordering degree, higher structural stability by introducing Y O bond, lower charge transfer resistance and higher lithium ion diffusion coefficient, although the 0.2C discharge capacity is slightly lower than pristine LiNi 0.5 Mn 1.5 O 4 . Atomic Absorption Spectroscopy result shows that appropriate Y doping can effectively decrease the transition metal dissolution to certain extent, despite of higher Mn 3+ content. All above factors lead to the improved cycling performance of Y-doped electrode in half-cells paired with metallic Li at elevated temperature (55 °C) and in full-cells paired with graphite at room temperature. [ABSTRACT FROM AUTHOR]

New self-supported poly(vinylidene fluoride)/poly (vinyl chloride-co-vinyl acetate) (PVdF/P(VC-VAc)) blended polymer membranes are prepared via a phase inversion method, and then their electrochemical performances, immersed in the liquid electrolyte as the polymer electrolyte for lithium-ion batteries (LIBs), are evaluated. The Fourier transform infrared spectroscopy analysis, the differential scanning calorimeter test and the X-ray diffraction measurement demonstrate that homogeneous PVdF/P(VC-VAc) polymer composites can form at all blend compositions and the crystallinity degree of the blended polymers decreases as the P(VC-VAc) content increases. Specifically, when the proportion of PVdF/P(VC-VAc) is 70:30 (wt%), membranes with a rich surface and internal porous structure can be acquired. The ionic conductivity of the polymer electrolyte achieves a maximum value of 3.57 mS cm-1 at room temperature, and favourable electrochemical performances of LIBs can be obtained. LiNi0.5Mn1.5O4/Li cells with the as-prepared polymer electrolyte exhibit a higher initial discharge capacity of 131.0 mAh g-1 and superior cycle stability with a capacity retention of 96.1% at 0.2 C after 200 cycles compared to cells based on pure PVdF and P(VC-VAc) membranes. This can be attributed to the superior compatibility of the electrolyte with the electrodes. The results also indicate this electrolyte has promising applications in high-voltage LIBs. [ABSTRACT FROM AUTHOR]

We have studied the effect of final annealing temperature on the formation of lithium zinc titanate, its electrical conductivity, and its electrochemical performance. LiZnTiO has been shown to form in a wide range of annealing temperatures, from 673 to 1073 K. Its particle size increases systematically with increasing annealing temperature, whereas its conductivity decreases. The highest electrochemical capacity at low currents is offered by the materials annealed at 773 and 873 K, and the highest cycling stability is offered by the material prepared at 873 K. [ABSTRACT FROM AUTHOR]

Si doping at high voltage spinel LiNi 0.5 Mn 1.5 O 4 are presented as an effective strategy to greatly increase the electrochemical performance. Well-crystallized LiNi 0.5 Mn 1.5-x Si x O 4 (x = 0.05, 0.10, 0.15, 0.20) with homogeneous Si distribution are successfully synthesized through solid-state reaction. Structural and electrochemical characteristics are investigated through FESEM, XRD, FTIR, Raman spectroscopy, cyclic voltammetry and galvanostatic charge/discharge testing. It can be demonstrated that Si doping significantly improves the electrochemical performance. LiNi 0.5 Mn 1.35 Si 0.15 O 4 exhibits reversible capacities of 123 mAh/g after the 100th cycle at 0.5C and LiNi 0.5 Mn 1.35 Si 0.15 O 4 as well as LiNi 0.5 Mn 1.3 Si 0.2 O 4 show superior electrochemical stability over the pristine LiNi 0.5 Mn 1.5 O 4 material. Since the Si-O bond exhibits high dissociation energy of 798 kJ/mol (298 K), which is far beyond of the dissociation energies of the Mn-O or Ni-O bonds, the excellent electrochemical performance might be associated with an increased structural and chemical stability caused by incorporation of Si into the Oxygen-rich crystal lattice. [ABSTRACT FROM AUTHOR]

Li 2 FeSiO 4 was synthesized through Sol–Gel method and the effect of calcination temperature, time and chelating agent concentration were investigated. Appropriate calcination temperature above 550 °C was determined by TG/DTA analysis. Afterward, the dried gel powder was calcined at each temperature of 650 °C, 700 °C and 750 °C for 1, 2 and 3 h. XRD studies illustrated the most appropriate calcination temperature of 700 °C for 1 h. To compare the effect of chelating agent concentration, citric acid with molar ratio of 1/3, 2/3 and 1 were used which 1/3 was determined as the best concentration. FE-SEM observation showed that mean grain is size lower than 100 nm. By using this material, a three electrodes test cell was assembled and its electrochemical properties were investigated. The results showed high charge capacity which could be achieved at current density of 0.05C. [ABSTRACT FROM AUTHOR]

Introducing the Mg ion into host lattice is applied to improving the electrochemical performance of LiNi 0.6 Co 0.2 Mn 0.2 O 2 . The effect of Mg substitution for Co on the structure, morphology, electrochemical properties and Li + diffusion coefficients are investigated in details. Rietveld refinement results reveal that Mg is incorporated into the bulk lattice, which results in reduced cation mixing and expand c -lattice parameter. All Mg-doped sample exhibit better cycle and rate performances, although the Mg substitution for Co led to decreasing a part of capacity. The Li diffusion coefficients obtained by galvanostatic intermittent titration technique (GITT) are increased with increases of Mg content. [ABSTRACT FROM AUTHOR]

Electrochemical performance of the 18650 lithium-ion batteries consisting lithium-rich layered oxides 0.5Li 2 MnO 3 ·0.5LiMn 0.33 Ni 0.33 Co 0.33 O 2 cathode material and soft carbon anode is investigated in detail. The cathode is synthesized by a spray drying process and the properties are studied by various methods, while the soft carbon is commercial available. The assembled batteries can exhibit excellent cyclic performance with a capacity retention of 90.2% even after 600 cycles in the voltage ranges of 2.0-4.5 V (at 1C-rate). Moreover, they can also deliver excellent rate capabilities as the discharge capacity under 40C is nearly equal to 83.9% of that under 1C (voltage range is in 2.0-4.5 V). Furthermore, in order to evaluate the mechanism of the superior performance exhibited by the full cells, cells after 300 cycles are disassembled in a glove box to assess the changes on the active materials by using a series of technique methods, including a scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), High-resolution transmission electron microscope (TEM) and selected area electron diffraction (SAED). [ABSTRACT FROM AUTHOR]

The present study reports on the direct synthesis of LiFePO 4 nanoparticles and graphene nanosheets to form a composite cathode (LFP/GNs) in a one-step microwave-assisted polyol reaction. The polyol reaction induced by microwave irradiation for a few minutes produces nanocrystalline LFP and graphene nanosheets simultaneously from lithium, iron and phosphorus and carbon (5 wt% of graphite oxide) sources, respectively, used as starting precursors. Powder X-ray diffraction (XRD), electron microscopy, and atomic force microscopy (AFM) studies on microwave-reacted sample obtained using just graphite oxide confirms the formation of graphene nanosheets separately. Whereas, electron microscopy studies on the LFP/GNs composite reveals that olivine nanoparticles of average sizes ranging between 5 and 20 nm are well-dispersed on the graphene nanosheets. Electrochemical measurements reveal that the LiFePO 4 /GNs nanocomposite cathodes registered enhanced discharge capacities (79 and 108 mAh g −1 for the as-prepared and annealed composite cathodes, respectively) at 32 C rates with good capacity retention capabilities. The AC impedance measurements confirm that the enhanced cathode properties of the LFP/GNs nanocomposite are ascribed to the improved electronic conductivity of the graphene nanosheets and the nano-sized particles. The slightly better electrochemical properties of the annealed LFP/GNs are attributed to its higher crystallinity. [ABSTRACT FROM AUTHOR]

Li 3 V 2 (PO 4 ) 3 /C (LVP/C) cathode materials for lithium ion batteries have been successfully synthesized via carbon thermal reduction method using pitch as both a new carbon source and a reduction agent. The influences of different carbon sources (pitch, Super P, KS15 and Vulcan-XC72) and heat treatments between 650 and 950 °C on the LVP/C materials have also been investigated. The structural and electrochemical properties of the samples are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM) and high resolution transmission electron microscopy (HRTEM) as well as charge-discharge experiments. The LVP/C synthesized with pitch have smooth surface with uniform residue carbon distribution and presents the best electrochemical performance. In addition, the oxidation of carbon has been discussed. The results indicate that carbons obtained from four carbon sources are tended to be oxidized to CO 2 than CO. Electrochemical tests show the LVP/C-750 °C exhibits the highest discharge capacity and the most excellent capacity retention. Spherical LVP/C particles are obtained using the spray drying method. The spray drying-LVP/C composite deliver higher discharge capacity than those of LVP/C composites obtained by carbon thermal reduction method or by drying with oven. [ABSTRACT FROM AUTHOR]

A series of lithium borate added electrolyte compounds, x Li 3 BO 3 -(1− x )Li 3.5 Si 0.5 P 0.5 O 4 (0 ≤ x ≤ 0.2), are synthesized and characterized. This so-called LISICON electrolyte system is analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), solid state nuclear magnetic resonance (ss-NMR), electrochemical impedance spectra (EIS), and direct current (DC) polarization methods. From 11 B MAS NMR spectra, it is demonstrated that a small fraction of boron exists in the form of BO 4 , while its majority settles at grain boundaries in the form of BO 3 , indicating that lithium borate glasses play a role as sintering assistant. This prominently increases the relative density of samples, and is beneficial to the ionic conductivity. Further results show that the electrical conduction of lithium borate added LISICONs is dominated by Li + ions, with a transference number of t Li + ≥ 0.996 and a corresponding ionic conductivity of about 6.5 × 10 −6 S cm −1 at room temperature, almost two times that of pristine Li 3.5 Si 0.5 P 0.5 O 4 . [ABSTRACT FROM AUTHOR]

Layered-spinel composite cathode material Li 1.1 Ni 0.25 Mn 0.75 O 2.3 has been synthesized and cooled by different methods (naturally cooled within the furnace and cooled in liquid nitrogen). The effect of cooling methods on physical and electrochemical properties are discussed using the characterizations of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), charge/discharge, cyclic and rate tests. The layered-spinel composite structure has been detected in Li 1.1 Ni 0.25 Mn 0.75 O 2.3 electrodes from the XRD patterns and TEM images. XPS results show that the content of Mn 3+ in the Li 1.1 Ni 0.25 Mn 0.75 O 2.3 cooled in liquid nitrogen is more than that of Li 1.1 Ni 0.25 Mn 0.75 O 2.3 cooled with furnace. The electrochemical performance results show that the Li 1.1 Ni 0.25 Mn 0.75 O 2.3 cooled in liquid nitrogen has higher initial discharge capacity, coulomb efficiency, better cyclic and rate performance compared with Li 1.1 Ni 0.25 Mn 0.75 O 2.3 cooled with furnace. EIS results show that the charge transfer resistance ( R ct ) of Li 1.1 Ni 0.25 Mn 0.75 O 2.3 cooled in liquid nitrogen is lower than that of Li 1.1 Ni 0.25 Mn 0.75 O 2.3 cooled with furnace. The improved cyclic and rate performances of Li 1.1 Ni 0.25 Mn 0.75 O 2.3 cooled in liquid nitrogen cathode are attributed to the lower R ct and more content of Mn 3+ . [ABSTRACT FROM AUTHOR]

We designed a novel aqueous rechargeable lithium battery with LiFePO 4 /C (LFP) and LiMn 2 O 4 /C (LMO) as the anode and cathode, respectively; then investigated the battery in Li 2 SO 4 aqueous electrolyte. We also studied the electrochemical behavior of LFP in aqueous electrolyte using cyclic voltammetry (CV). The material exhibited excellent electrochemical performance in the aqueous electrolyte, including good oxidation/reduction reversibility and cycling stability; almost no decays were observable after 200CV cycles. The diffusion coefficients of Li ions through the interface between the liquid electrolyte and the solid LiFePO 4 in terms of intercalation and deintercalation were 1.22 × 10 −14 and 9.97 × 10 −15 cm 2 /s, respectively. The material could be completely intercalated/deintercalated with Li ions in the aqueous electrolyte, indicating the excellent performance of LFP in an aqueous solution. Further, an aqueous rechargeable lithium battery (ARLB), which we fabricated using LFP as the anode and LMO as the cathode, also exhibited quite good performance in aqueous Li 2 SO 4 solution: after 1,000 charge–discharge cycles at 2 C, the capacity loss was less than 30%, indicating that this type of ARLB has excellent cycling stability and may be promising for future research and application. [ABSTRACT FROM AUTHOR]

Solid solution cathode materials 0.6Li[Li 1/3 Mn 2/3 ]O 2 -0.4Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 with different morphologies were synthesized by electrospinning and coprecipitation method respectively. The field-emission scanning electron microscope images verified the successful formation of nanofibers for electrospinning and nanoparticles for coprecipitation and the nanofibers showed larger specific surface area according to the Brurauer Emmerr Teller procedure. The X-ray powder diffraction patterns and the corresponding lattice parameter refinements showed that both samples can be indexed to hexagonal α-NaFeO 2 layered structure with space group of R-3m. And the material prepared by electrostatic spinning method has a tight atomic arrangement in the layer yet the different dimensions do not influence the intercalation and deintercalation of lithium ion through the interlayer. The discharge capacity of nanofibers electrode is 302.3 mAh g −1 at 0.05 C and the initial columbic efficiency is 76.2%, which are higher than 282.7 mAh g −1 and 68.2% of the nanoparticles electrode. The nanofibers electrode also presented better cycleability and rate capability, especially performed capacity of 126.6 mAh g −1 at 5 C, much higher than that of 109.4 mAh g −1 for nanoparticles electrode. The step-by-step cyclic voltammetry revealed that the nanofibers electrode performs higher discharge voltage platform and enhanced discharge energy density. The excellent electrochemical performance of nanofibers electrode is ascribed to the better conductivity and superior lithium ion diffusion ability according to the electrochemical impedance spectrum measurement. [ABSTRACT FROM AUTHOR]

LiNi 0.5 Co 0.2 Mn 0.3 O 2 is successfully coated with Li 2 ZrO 3 through a simple sol–gel method. The formation of a uniform Li 2 ZrO 3 coating layer on the surface of the bare sample is confirmed by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectrometer (EDS). Similar discharge capacities are delivered by both bare and Li 2 ZrO 3 -coated samples. However, the capacity retention of Li 2 ZrO 3 -coated sample is much higher than that of the bare one at 1 C after 100 charge–discharge cycles under a high cutoff voltage of 4.6 V. Meanwhile, the rate performances of Li 2 ZrO 3 -coated sample are dramatically enhanced especially at high rates. Furthermore, the increase of impedance during charge–discharge process is suppressed by Li 2 ZrO 3 coating layer. [ABSTRACT FROM AUTHOR]

The Li3V2(PO4)3/C cathode materials for lithium ion batteries are synthesised by sol-gel method using three different compounds (citric acid, glycine and oxalic acid) as the chelating agents. The effects of chelating agents on the physical properties and electrochemical performances of the Li3V2(PO4)3/C composites are investigated by thermogravimetric analysis, infrared spectrometry, X-ray diffraction, scanning electron microscopy and various electrochemical techniques. The results show that the electrochemical properties of Li3V2(PO4)3/C prepared using citric acid as chelating agent are better. In the voltage range of 3.0-4.3 V (versus Li+/Li), the citric acid chelated Li3V2(PO4)3 displays large reversible capacity with an initial discharge capacity of 126.7 mAh g− 1 at 0.5°C, and 91.3% of the initial discharge capacity is retained after 50 charge-discharge cycling. [ABSTRACT FROM AUTHOR]

A novel 2Li 3 V 2 (PO 4 ) 3 ·LiV 3 O 8 composite with short rod and thin plate shapes is synthesized through sol–gel method followed by hydrothermal and solid–state reaction. LiV 3 O 8 is used as an additive to improve the capacity of Li 3 V 2 (PO 4 ) 3 . In the composite cathode, active impurity phase Li 0.3 V 2 O 5 is also present, which has little impact on the whole electrochemical properties. The 2Li 3 V 2 (PO 4 ) 3 ·LiV 3 O 8 composite delivers a high initial capacity of 162.8 mAh g −1 at a current density of 100 mA g −1 in the voltage range of 2.0–4.3 V. Furthermore, the composite with high crystallinity also shows high electrochemical reversibility and good rate capability. The diffusion coefficient of Li ions in the composite is in the range of 10 −11 –10 −9 cm 2 s −1 obtained from galvanostatic intermittent titration technique. [ABSTRACT FROM AUTHOR]

LiFePO 4 /graphene active material (LFP/G) was successfully synthesized via a simple, low raw material cost and environment friendly hydrothermal method at 170 °C. LFP/G composite was prepared in a template-free method using graphene nano-sheets as a conductive additive (3.0 wt.%) without any carbon coating. Results indicated the presence of LFP crystallites of the olivine phase, which are randomly anchored on the surface of graphene. Electrochemical characteristics of the LFP/G modified electrode show well-defined peaks, smaller peak potential separation and higher cycling stability compared to those of the pristine LFP obtained in the absence of graphene. LFP/G delivered an initial discharge capacity of 157 mA h g −1 at 0.2 C and 114 mA h g −1 at 5 C and the values were compared to those of LFP (the capacities reach up to 120 mA h g −1 at 0.1 C and 50 mA h g −1 at 5 C). The electrochemical enhancement of LFP/G could be mainly ascribed to synergetic effects of bridging graphene nanosheets and creating an interconnected conducting network of cross-linking between neighboring crystallites. Such network would enhance the stability of the cathode composite and buffer spaces to accommodate the volume pulsation during charge/discharge cycling. [ABSTRACT FROM AUTHOR]

A ferrocene-assisted calcination process (FACP) has been applied during the preparation of LiFe 0.6 Mn 0.4 PO 4 /C cathode material. Ferrocene works as a promoter to improve the quality of the coated carbon layers. The influence of ferrocene on the property of carbon layers and electrochemical performance of LiFe 0.6 Mn 0.4 PO 4 /C has been investigated systematically. The LiFe 0.6 Mn 0.4 PO 4 /C with FACP presents more uniformly and tightly coated carbon layers with higher graphitization degree than the sample without FACP. High-quality carbon layers can greatly enhance the electrochemical performance of cathode materials. The LiFe 0.6 Mn 0.4 PO 4 /C with FACP behaves higher discharge capacities (163.6 and 120.7 mAh g −1 at 0.2C and 20C, respectively) than the LiFe 0.6 Mn 0.4 PO 4 /C without FACP (158.4 and 111.5 mAh g −1 at the same rates). Furthermore, the LiFe 0.6 Mn 0.4 PO 4 /C with FACP exhibits excellent cycling performance even at 60 °C, still delivering capacity retention above 96% after 100 cycles at 3C, while the retention of the controlled sample is only 70% after 75 cycles. The cycling performance of the LiFe 0.6 Mn 0.4 PO 4 /C with FACP at high temperature is largely improved. [ABSTRACT FROM AUTHOR]

Compared with thermally exfoliated graphene oxide (TEGO) prepared at high temperature of 800 °C and a long time of 12 h, microwave exfoliated graphene oxide (MEGO) is successfully synthesized at 800 W for 2 min benefiting from “inert and instant heating” of microwave irradiation and employed to optimize electrochemical performance of LiFePO 4 . The as-obtained LiFePO 4 /MEGO exhibits overwhelming superiorities to LiFePO 4 /TEGO, particularly in high-rate performance. Although LiFePO 4 /MEGO delivers the similar specific capacity of 158.1 mAh · g −1 as well as the LiFePO 4 /TEGO at the rate of 0.1 C, the LiFePO 4 /MEGO performs smaller polarization of 53.3 mV resulting in better specific energy of 518.1 Wh · kg −1 and energy efficiency of 89.8%. Even at the high rate of 10 C and 20 C, the LiFePO 4 /MEGO delivers excellent specific energy of 300.3 Wh · kg −1 and 229.7 Wh · kg −1 (with corresponding specific capacity of 104.3 mAh · g −1 and 87.3 mAh · g −1 respectively), much better than those of the LiFePO 4 /TEGO. After 2000 cycles, the LiFePO 4 /MEGO still performs excellent rate capabilities with 91.2% and 83.8% retention respectively. [ABSTRACT FROM AUTHOR]

LiNi 1/3 Co 1/3 Mn 1/3 O 2 one-dimensional (1D) hierarchical microrods assembled with nanoparticles have been successfully prepared through post-heat treatment of MC 2 O 4 · x H 2 O (M = Ni, Co, Mn) microrod precursor which was obtained via stepwise co-precipitation. The CoC 2 O 4 ·2H 2 O microrod crystallites formed in the first step can effectively template the subsequent formation of manganese, cobalt and nickel oxalates on the initial CoC 2 O 4 ·2H 2 O microrods during the second step co-precipitation, without assistance of any surfactants. The LiNi 1/3 Co 1/3 Mn 1/3 O 2 1D hierarchical microrods with pores and voids as cathode material for lithium ion batteries exhibit superior initial coulombic efficiency, reversible capacity, rate capability and cycling stability to the LiNi 1/3 Co 1/3 Mn 1/3 O 2 microsized particles. They deliver high specific discharge capacities of 163.3 and 104.9 mAh g −1 at rates of 0.1 and 20 C, respectively. At 0.5 C, they achieve a discharge capacity of 152.2 mAh g −1 with a capacity retention of 89.5% after 160 cycles. The excellent electrochemical performance can be attributed to the novel hierarchical microrod structure with much porous and void space, which shortens the diffusion path of electron and lithium ion, and benefits for their transfer. In addition, this unique structure provides not only appropriate contact area between electrode and electrolyte, but also good accommodation for the strain relaxation during charge and discharge. [ABSTRACT FROM AUTHOR]

Spherical layered Li 1+x Ni 0.5 Mn 0.5 O 2+δ (x = 0, 0.1 and 0.2) materials are synthesized by rheological phase reaction method. X-ray diffraction patterns reveal that the prepared materials have the α-NaFeO 2 structure with R-3m space group. The materials with different lithium contents show distinct differences in structure, particle morphology, electrochemical property and safety characteristics. When x = 0.1 and 0.2, excess lithium resides in the transition metal layer to form Li 2 MnO 3 -like structure. With lithium content increasing from 1.0 to 1.2, the initial discharge capacity and Coulombic efficiency are decreased, while capacity maintenance is improved. Mn ions are electrochemically activated in the charge–discharge process and has a contribution to the capacity when cycling in a voltage window of 2.5–4.5 V for x = 0.2, leading to a high discharge capacity of near 200 mAh g −1 and the excellent cycling performance (with no capacity decay after 100 cycles) at 20 mA g −1 . Electrochemical impedance spectroscopy shows that the appropriate excess of lithium can decrease charge transfer resistance obviously in the initial several cycles. The differential scanning calorimetric indicates that the generated heat of Li 1+x Ni 0.5 Mn 0.5 O 2+δ is increased with the increase of x. [ABSTRACT FROM AUTHOR]

Abstract: Nd-doped Li3V2−xNdx(PO4)3/C (x=0, 0.01, 0.02, 0.04, 0.06 and 0.08) cathode materials are successfully and fast synthesized by a microwave solid-state route. The effects of Nd-doping on the structure and electrochemical properties of Li3V2(PO4)3/C are investigated. Compared with the X-ray diffraction (XRD) pattern of the undoped sample, these Nd-doped samples have no extra reflections, which indicate that Nd enters the structure of the Li3V2(PO4)3/C cathode. Scanning electron microscope (SEM) images show that Nd-substitution in Li3V2(PO4)3/C has regular and uniform particles. According to the results of charge/discharge measurements at 0.1C rate, the initial capacities of the Nd-doped samples are all higher than that of the undoped sample which is 140mAhg−1. Among all the doped samples, Li3V1.96Nd0.04(PO4)3/C shows the best rate capability and cycling stability. The initial discharge capacity of Li3V1.96Nd0.04(PO4)3/C is 157mAhg−1 with the capacity retention ratio of 92.5% after 50cycles at 0.1C. Especially, it still shows a high discharge capacity of 126mAhg−1 even at a higher rate of 5.0C. Electrochemical impedance spectroscopy (EIS) reveals that the charge transfer resistance of as-prepared samples is reduced through Nd-substitution and its reversibility is enhanced as proved by the cyclic voltammograms (CV). The improved electrochemical properties of Nd-doped Li3V2(PO4)3/C can be attributed to the optimizing particle size and structural stability due to the proper amount of Nd-doping in V sites. [Copyright &y& Elsevier]

Abstract: Olivine structured LiFePO4/C cathode was synthesized via a freeze-drying route and followed by microwave heating with two kinds of carbon sources: PEG-4000 (organic) and Super p (inorganic). XRD patterns indicate that the as-prepared sample has an olivine structure and carbon modification does not affect the structure of the sample. Image of SEM shows a uniform and optimized particles size, which greatly improves the electrochemical properties. TEM result reveals the amorphous carbon around the surface of the particles. At a low rate of 0.1C, the LiFePO4/C sample presents a high discharge capacity of 157.8mAhg−1 which is near the theoretical capacity (170mAhg−1), and it still attains to 149.1mAhg−1 after 200 cycles. It also exhibits an excellent rate capacity with high discharge capacities of 143.2mAhg−1, 137.5mAhg−1, 123.7mAhg−1 and 101.6mAhg−1 at 0.5C, 1.0C, 2.0C and 5.0C, respectively. EIS results indicate that the charge transfer resistance of LiFePO4 decreases greatly after carbon coating. [Copyright &y& Elsevier]

Abstract: With an aim to broaden the understanding of the factors that govern electrochemical performance of lithium-rich layered oxide, the influences of insufficient lithium on reversible capacity, cyclic stability and rate capability of the oxide as cathode of lithium ion battery are investigated in this study. Various concentrations of lithium precursor are introduced to synthesize a target composition Li[Li0.13Ni0.30Ni0.57]O2, and the resulting products are characterized with inductively coupled plasma spectrum, scanning electron microscope, X-ray diffraction, Raman spectroscopy, and electrochemical measurements. The results indicate that the lithium content in the resulting oxide decreases with reducing the concentration of lithium precursor from 10wt%-excess lithium to stoichiometric lithium, due to insufficient compensation for lithium volatilization during synthesis process at high temperature. However, all these oxides still exhibit typically structural and electrochemical characteristics of lithium-rich layered oxides. Interestingly, with decreasing the Li content in the oxide, its reversible capacity increases due to relatively higher content of active transition-metal ions, while the cyclic stability degrades severely because of structural instability induced by higher content of Mn3+ ions and deeper lithium extraction. [Copyright &y& Elsevier]

Solvothermal approach is used to synthesize LiMn0.9Fe0.1PO4 (LMFP) nanomaterial for Li-ion batteries (LIBs). Experimental parameters such as feeding sequences, reaction time and reaction temperature are discussed and the obtained LMFP are characterized by XRD, SEM and TEM. To understand the formation of LMFP, a reaction mechanism is proposed. The proposed mechanism indicates that the suitable concentration of MLi (M = Fe, Mn) antisite defect can improve the electrochemical performance of the material. The charge–discharge data of obtained LMFP shows that the LiMn0.9Fe0.1PO4 material synthesized at 180 °C for 4 h and then sintering with sucrose at 650 °C for 5 h under argon protection has the highest discharge capacity, which is 149.2 mAh g−1 at 0.1C rate. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous hydrated iron (III) phosphate has been synthesized by a coordinate precipitation method from equimolecular Fe(NO3)3 and (NH4)2HPO4 solutions at an elevated temperature. Hydrated iron (III) phosphate samples and the corresponding LiFePO4/C products were characterized by XRD and SEM. The electrochemical behavior was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The LiFePO4/C fabricated from as-synthesized FePO4 delivered discharge capacities of 162.5, 147.3, 133.0, 114.7, 97.2, 91.3 and 88.5mAhg−1 at rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C and 4C with satisfactory capacity retention, respectively. [Copyright &y& Elsevier]

Abstract: LiAlO2-coated LiNi1/3Mn1/3Co1/3O2 powders were prepared by a sol–gel method associated with ultra-sonication, and the obtained LiAlO2-coated LiNi1/3Mn1/3Co1/3O2 was investigated as positive electrode materials for all-solid-state batteries with sulfide-based solid electrolytes. All-solid-state lithium batteries were assembled with the obtained LiAlO2-coated LiNi1/3Mn1/3Co1/3O2 powders and with amorphous Li3PS4 as solid electrolytes. The charge–discharge cycle performance of the all-solid-state cells was improved by the LiAlO2-coating on LiNi1/3Mn1/3Co1/3O2 powders. The LiAlO2 coating was effective in suppressing an increasing of the interfacial resistance between the LiNi1/3Mn1/3Co1/3O2 electrode material and the sulfide based solid electrolyte, Li3PS4, during charge–discharge cycling. The battery with the 1.0mol% LiAlO2-coated LiNi1/3Mn1/3Co1/3O2 showed an initial discharge capacity of 134 mAhg−1 and the battery retained the capacity more than 124 mAhg −1 even after 400 charge–discharge cycles at a current density of 11 mAg −1 at room temperature. [Copyright &y& Elsevier]

Highlights: [•] To improve the electrochemistry of LiMn2O4 by partial substitution of Li by Na. [•] Na-substitution can improve the cycling stability. [•] A new, low-cost method to improve its electrode properties due to low-cost of Na resource. [ABSTRACT FROM AUTHOR]

Abstract: The structure and electrochemical properties of epitaxial thin film LiNi0.5Mn1.5O4 electrodes are investigated for lithium ion secondary batteries applications. The orientation and thickness of the LiNi0.5Mn1.5O4 films are controlled by changing the substrate orientation and the pulse laser deposition time, respectively. The lattice parameters of the films increase with film thickness and the manganese valence decreases without any change in the nickel valence. Regardless of their orientation, all the films exhibit reversible capacities of 80–130 mAh g−1. The dependence of the discharge capacity on film thickness indicates a nanosize effect. The electrochemical properties of the high voltage spinel system are significantly dependent on their electronic properties, lattice orientations, and film thicknesses of the electrodes. [Copyright &y& Elsevier]

Abstract: LiVO3 materials are synthesized by combustion method with oxalic acid as fuel. Owing to its relatively low crystallization and small particle size, the LiVO3 calcined at 450 °C for 2 h displays optimal electrochemical performances, delivering a high discharge capacity of 298.4 mAh g−1 and 262.5 mAh g−1 between 1.0 and 3.5 V at a current density of 50 mA g−1 and 500 mA g−1 respectively, and exhibiting good cyclic stability. In this work, the chemical diffusion coefficient of Li+ (D Li+) in the LiVO3 electrode is determined by electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). The value calculated by EIS is in the range of 10−9–10−8 cm2 s−1, while it calculated by GITT is 10−9.5–10−8 cm2 s−1. [Copyright &y& Elsevier]

Abstract: Li-excess Li[Li0.18Ni0.15Co0.15Mn0.52]O2 layered cathode material is prepared by the sol-gel method. The material is aged in a LiPF6 based electrolyte and then is subjected to a series of structural and electrochemical analyses. X-ray diffraction shows that aging in electrolyte does not change the C2/m ordering of the material crystal lattice. But the surface of the material is etched by the electrolyte which is confirmed by transmission electron microscope and Raman scattering. This causes dissolution of some transition metal elements (especially Ni and Co) and formation of a spinel-like surface layer. Also, some by-products resulted from the electrolyte decomposition are detected on the surface of the material. Electrochemical impedance spectroscopy shows that aging in electrolyte severely hinders the electrochemical kinetics of the material. Cyclic voltammetry indicates that the aged sample has large electrode polarization which prevents the oxygen loss process and the activation of Mn4+ ions. As a result, the discharge capacity of the aged sample continuously increases from 134 mAh g−1 to 215 mAh g−1 in the initial several cycles. [Copyright &y& Elsevier]

Abstract: LiMn2O4/LiNi0.5Mn1.5O4 composite with LiMn2O4 substrate and LiNi0.5Mn1.5O4 surface layer is proposed and prepared through sol–gel method. The resulting samples have been characterized by XRD and SEM measurements, in terms of which the impurity-free phase, uniform particle morphology have been proved. Charge–discharge test, XPS measurement combining with TEM observation confirm the existence of LiNi0.5Mn1.5O4 surface layer. Comparing with the bare LiMn2O4, the LiNi0.5Mn1.5O4-coated LiMn2O4 phase presents significantly improved cycling stability, especially at 60°C. Additionally, the rate capability and thermal safety of LiMn2O4 are greatly enhanced after being coated by LiNi0.5Mn1.5O4. ICP-AES measurement, structural analysis, and impedance experiment indicate that the improved electrochemical property of LiNi0.5Mn1.5O4-coated LiMn2O4 should be attributed to the alleviated dissolution loss of manganese, strengthened structural stability, and improved SEI property. [Copyright &y& Elsevier]

Abstract: Morphology-controlled LiMn0.9Fe0.1PO4 nanoplatelets as high performance cathode material for lithium ion batteries have been synthesized via a simple ascorbic acid-assisted solvothermal process in water-ethanol solvent. The phase structure and morphology of the products were characterized by XRD, SEM and TEM. The results reveal that decreasing the crystallite size along b-axis direction and increasing the surface area of (010) plane can shorten Li+ diffusion path and increase the electrode reaction activity. The LiMn0.9Fe0.1PO4 nanoplatelet holds the high capacity of 145 mA h g−1, 134 mA h g−1, 119 mA h g−1, 97 mA h g−1 and 68 mA h g−1 at 0.1 C, 0.5 C, 1 C, 5 C and 10 C respectively, and it can retain 75% of the initial reversible capacity even after 100 cycles at 10 C rate. [Copyright &y& Elsevier]

Abstract: Cube-like and plate-like Li[Li0.2Mn0.54Ni0.13Co0.13]O2 particles are obtained after treated in LiCl and KCl molten salts at 800 °C, respectively, comparing to the ball-like original particles calcined in air. The oxide treated in KCl molten salt with large specific area of 17.05 m2 g−1 delivers high discharge capacities of 254.1 mAh g−1 and 168.5 mAh g−1 at current densities of 200 mA g−1 and 2000 mA g−1, respectively. In addition, enhanced cycle stability with capacity retention of 94.9% after 80 cycles at charge–discharge current densities of 200 mA g−1 is obtained for the oxide treated in LiCl molten salt with sacrifice of a little capacity. Such electrochemical performance change is proved to be independent of Li+ diffusion coefficient. It appears that the treatment in molten salts can effectively reform the electrochemical performances of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode materials for various applications. [Copyright &y& Elsevier]

Abstract: Rechargeable lithium-ion batteries (LIBs) are currently accepted to be one of the most suitable energy storage resources in portable electronic devices because of their high gravimetric and volumetric energy density. To understand the behavior of Li+ ions on electrochemical lithium extraction/insertion process, we performed in situ 7Li nuclear magnetic resonance (NMR) measurements for LiCoO2 cathode in a plastic cell battery, and the spectral evolutions of the 7Li NMR signal of Li x CoO2 (0≤ x ≤1) were well investigated. Very narrow solid solution region of Li x CoO2 (∼0.99≤ x <1) was explicitly defined from the large intensity reduction of LiCoO2 signal at ∼0ppm, which is related to the localized nature of the electronic spin of paramagnetic Co4+ ion formed at the very early delithiation stage. With further decreasing the signal intensity of LiCoO2, a Knight-shifted signal corresponding to an electrically conductive Li x CoO2 phase emerged at x =0.97, which then monotonously decreased in intensity for x <0.75 in accordance with the electrochemical lithium de-intercalation from Li x CoO2. These observations acquired in situ fully confirm the earlier studies obtained in ex situ measurements, although the present study offers more quantitative information. Moreover, it was shown that the peak position of the NMR shift for Li x CoO2 moved as a function of lithium content, which behavior is analogous to the change in its c lattice parameter. Also, the growth and consumption of dendritic/mossy metallic lithium on the counter electrode was clearly observed during the charge/discharge cycles. [Copyright &y& Elsevier]

Highlights: [•] Cation-incorporated Li3V2(PO4)3/C have been systematically investigated. [•] Cation incorporation in Li3V2(PO4)3 does not change the monoclinic structure but form solid solution. [•] Fe-incorporation shows the best electrochemical performance whereas Ni-incorporation shows the poorest performance. [•] A clear profile of cation incorporation with Fe, Co, Ni, Mn ions in Li3V2(PO4)3/C is obtained. [ABSTRACT FROM AUTHOR]

Abstract: LiNi1/3Co1/3Mn1/3O2 (LNCM) with a well-ordered layered structure, confirmed by X-ray diffraction, was synthesized by the chemical-wet synthesis incorporated with (i) a pulse microwave-assisted heating of LNCM precursors and (ii) a carbon coating technique. The microwave irradiation periods (i.e., 5–20min) and amount of carbon additive (i.e., glucose content: 0.1–0.75%) served as key factors in modifying as-prepared LNCM powders. The electrochemical performance of as-prepared LNCM cathodes was well characterized by cyclic voltammetry and charge–discharge cycling at 0.1–5C. Both appropriate microwave heating and carbon coating significantly improve discharge capacity, rate capability, and cycling stability of LNCM cathodes. This improved performance can be attributed to the facts that an appropriate microwave heating of LNCM precursors induces low cation mixing of the layered lattices and the carbon coating enables the creation of outer circuit of charge-transfer pathway, preventing cathode corrosion from direct contact to the electrolyte. The C-coated LNCM cathode shows the increased capacity retention from 70.2 to 93.3% after 50 cycles at 1C. On the basis of the experimental results, both the microwave heating and the carbon coating provide a feasible potential way to improve the electrochemical performance of LNCM cathode, benefiting the development of Li-ion batteries. [Copyright &y& Elsevier]

Abstract: Lithium-rich layered cathode Li1.2Mn0.54Ni0.13Co0.13O2 is synthesized by a co-precipitation method followed by high-temperature treatment and surface coated with different amount of amorphous FePO4. The microstructure and electrochemical performance of the as-prepared cathode materials are investigated systematically. It is demonstrated that the Li1.2Mn0.54Ni0.13Co0.13O2 particles are uniformly coated with amorphous FePO4. With proper amount of amorphous FePO4 coating layer, significant improvements in discharge capacity, initial Coulombic efficiency, rate capability, cycle performance, and thermal stability are achieved at room temperature. Specifically, the 3 wt.% FePO4-coated cathode exhibits the highest discharge specific capacities (271.7 mAh g−1 at C/20), improved initial Coulombic efficiency (85.1%), and best cyclability (discharge capacity of 202.6 mAh g−1 at C/2 after 100 cycles), while the 1 wt.% FePO4-coated cathode displays the best rate capability (194.3 mAh g−1 at 1 C rate and 167.9 mAh g−1 at 2 C rate). The charge–discharge curves and electrochemical impedance spectra reveal that the improved electrochemical performances are due to the suppression of both the oxygen vacancy elimination at the end of the first charge and side reactions of the cathode with the electrolyte, as well as the decrease in charge transfer polarization by the FePO4 coating layer. [Copyright &y& Elsevier]

Abstract: Carbon coated LiMn0.5Fe0.5PO4 solid solution materials (LiMn0.5Fe0.5PO4/C) are synthesized by rheological phase reaction with stearic acid as carbon source, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET and TG/DTG. The results show that well-crystallized olivine structure LiMn0.5Fe0.5PO4 nanoplatelets with no obvious impurity phase are obtained. The as-synthesized materials are served as cathode of lithium ion battery and investigated by galvanostatic charge/discharge tests. The results demonstrate that, in comparison with the LMFP materials of different Mn:Fe ratio (LiMn0.2Fe0.8PO4/C and LiMn0.8Fe0.2PO4/C) synthesized by the same route of rheological phase reaction, the LiMn0.5Fe0.5PO4/C exhibit excellent rate specific capability, and can deliver discharge capacity of 138, 99, 80, 72, 67 and 55 mAh g−1 at respectively 0.1, 1, 5, 10, 15 and 20C rates. Moreover, the electrode possesses good cycle stability. A specific capacity of 100 mAh g−1 at 1C after 300 cycles of charge–discharge at room temperature is reached, which represents 95% of capacity retention. The significantly improved electrochemical performances of the LiMn0.5Fe0.5PO4/C cathode are attributed to the uniformly distributed particles and the enhancement of conductivity that is originated from the surface coating of carbon on primary particles. [Copyright &y& Elsevier]

Abstract: A brand new method for synthesizing Mn(PO3(OH))·3H2O is attained in this paper. During this process, pure flake-like Mn(PO3(OH))·3H2O precipitate is prepared using C2H5OH as initiator. Besides that, LiMn0.5Fe0.5PO4/C is successfully synthesized from the Mn(PO3(OH))·3H2O precursor at 650 °C for the first time. Thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) are applied in the characterization of the Mn(PO3(OH))·3H2O precursor and LiMn0.5Fe0.5PO4/C. High-resolution transmission electron microscopy (HRTEM) is also used to investigate the morphology of LiMn0.5Fe0.5PO4/C. X-ray photoelectron spectroscopy (XPS) and galvanostatic charge and discharge test are employed to characterize the Mn(PO3(OH))·3H2O precursor and LiMn0.5Fe0.5PO4 material, respectively. The as-prepared LiMn0.5Fe0.5PO4/C material exhibited a reversible capacity of 131 mAh g−1 at 0.05 C. It can be confirmed that the incorporation of Fe into LiMnPO4 can significantly improve the electrochemical properties for improving the conductivity of the material and facilitating the Li+ diffusion. In addition, a capacity of 120 mAh g−1 is still delivered at 0.05 C rate with a capacity retention of about 91% after 25 cycles, and reversible capacity can reach 105 mAh g−1 at 1 C. [Copyright &y& Elsevier]

Abstract: Li-rich layered oxide Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is synthesized by combustion reaction using alcohol as both solvent and fuel. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the oxide synthesized at 800 °C exhibits perfect crystallinity and lattice ordering, and has particle sizes of 50–150 nm. The layered oxide delivers an initial discharge capacity of 290.1 mAh g−1 at a current density of 20 mA g−1 after activation, and exhibits improved rate capability with high discharge capacities of 238.6 and 165.0 mAh g−1 at current densities of 200 and 2000 mA g−1 in the voltage range of 2.0–4.8 V, respectively. Low Li-ion diffusion coefficient of 1.07 × 10−14−1.01 × 10−16 cm2 s−1 is calculated by galvanostatic intermittent titration technique (GITT) during the initial discharge process, indicating that the improved rate capability is mainly attributed to the small particle sizes of the Li-rich oxide. [Copyright &y& Elsevier]

Abstract: The dynamic structural change of graphite during the electrochemical lithium intercalation at 1/3C was identified by an in situ high energy synchrotron XRD. Thanks to the fast data collecting detector and high energy X-ray beam of this characterization technique, the detailed structure change of graphite was monitored. Under a high current density, the voltage plateaus in discharge curve and superlattice peaks in XRD patterns were not observed. These results indicated that the dynamic lithium intercalation behavior was remarkably different from that described by the classical staging mechanism. Instead, a Li-riched phase as well as a series of intermediate phases for the x value in Li x C6 being larger than 0.5 were identified. This dynamic phenomenon was considered to be synergistically affected by the driving force of the intercalation reaction, van der Waals force between graphene layers and repulsive interaction between the intercalated Li specie. Basing on the experimental results, a dynamic mechanism was proposed. [Copyright &y& Elsevier]

Abstract: A new alkoxide-based sol containing lithium isopropoxide, vanadylisopropoxide, di-n-butyl-phosphate, acetic-acid and polyvinylpyrrolidone, was used for the synthesis of monoclinic α-Li3V2(PO4)3/C composites by sol-gel and electrospinning techniques. The precursor mixture was highly soluble in organic solvents and thereby suitable for different synthesis techniques like sol-gel electrospinning or conventional sol-gel synthesis, to generate α-Li3V2(PO4)3/C nanocomposites with zero- and one-dimensionality. Electrospinning resulted in well-defined nanofibers and conventional sol-gel synthesis in polydisperse, isotropic nanoparticles. Phase composition and morphology in the composite nanostructures was examined by XRD, TGA, FT-IR, Raman, SEM and HR-TEM analysis. Comparative constant-current and cyclovoltammetric measurements of α-Li3V2(PO4)3/C composite applied as conventional film electrodes (nanoparticles and nanofibers) and self-supporting nanofiber electrodes revealed the influence of electrode texturing on the electrochemical performances. The nanofibrous self-supported electrodes showed superior cycling stability giving an initial discharge capacity of 124mAhg−1 at 0.2°C with retention of 95% after 50 cycles with rate variation in a voltage range of 3–4.3V. [Copyright &y& Elsevier]

Abstract: An electro-active LiCoO2 layer is coated onto the surface of LiNi0.8Co0.15Al0.05O2 powders via a molten salt method. The effect of calcination temperature, calcination time, flux content and coating amount on the electrochemical properties of the sample is investigated. The X-ray diffraction (XRD) analyses show that the LiCoO2 coating does not change the structure of LiNi0.8Co0.15Al0.05O2. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) measurements indicate that a uniform layer LiCoO2 particulate is coated on the surface of the LiNi0.8Co0.15Al0.05O2 particles. The electrochemical performance studies demonstrate that the 3.0wt.% LiCoO2-coated LiNi0.8Co0.15Al0.05O2 powders sintered at 800°C for 4h at weight ratio of KCl/LiNi0.8Co0.15Al0.05O2 =2 exhibit the best electrochemical properties, with an initial discharge capacity of 196.2mAhg−1 and capacity retention of 98.7% after 50cycles when cycled at a current density of 0.2C between 2.8 and 4.3V. Besides, these powders also show better rate capability and high-temperature performance than LiNi0.8Co0.15Al0.05O2. [Copyright &y& Elsevier]

Abstract: Spherical Li3V2(PO4)3/C (LVP/C) composites are successfully synthesized via two different spray-drying processes. XRD results reveal that some impurities, such as Na3V2(PO4)3, Li2NaV2(PO4)3 and Li4(P2O7), appear when sodium salt of carboxy methyl cellulose (CMC) acts as carbon source. SEM images show two different morphologies: solid spherical particles for LVP/C(A) prepared by adding CMC after pre-sintering, and hollow for LVP/C(B) prepared by adding CMC before pre-sintering. Compared to LVP/C(B), LVP(A) presents higher tap density and better electrochemical performance at any C-rate. Remarkably, another charge/discharge plateaus or anodic/cathodic peaks around 3.85V are detected for both LVP/C(A) and LVP/C(B) electrodes, which is attributed to the formation of Li3−x Na x V2(PO4)3 or some other electrochemically active composites containing Na+. CMC addition sequence has a significant influence on morphology of Li3V2(PO4)3. Furthermore, acting as carbon source and Na dopant, CMC shows a notable effect on electrochemical behavior of Li3V2(PO4)3 cathode material. [Copyright &y& Elsevier]

Abstract: Three techniques, i.e., pyrolysis of sucrose, spray of acetylene black, and propane vapor deposition, are adopted to coat carbon onto the surface of LiCoPO4 particles, and their effects are compared. The LiCoPO4/C composites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS). The results show that the coating techniques determine the property of carbon films formed on the surface of LiCoPO4 particles, which further affect the performance of LiCoPO4. A complete and homogeneous carbon layer is the key to a high electrochemical activity and stable cycle performance. Among these LiCoPO4/C composites, the material processed via the deposition technique shows a more uniform carbon layer than that of the others, thus it exhibits a large reversible capacity of 130 mA h g−1 with favorable cyclability and rate capability in the voltage range of 3.0–5.0 V. [Copyright &y& Elsevier]

Abstract: The Li x Ni0.23Co0.12Mn0.65O2 electrode system with various compositions (x =1.19, 1.33, 1.46, 1.58) was synthesized from a metal oxide precursor synthesized by co-precipitation method. The XRD patterns of the prepared powders revealed a hexagonal α-NaFeO2 structure (space group: R-3m, 166) and the existence of a Li2MnO3 phase in the composite structure. In particular, the low Li content sample shows a three integrated structure (spinel, Li2MnO3, LiMO2) for a Li/Metal(Ni/Co/Mn) mol ratio of 1.2. Scanning electron microscopy showed that all the synthesized samples contained spherical agglomerates with a size of 8–10μm. Among the samples tested, Li1.46Ni0.23Co0.12Mn0.65O2 shows relatively high charge and discharge capacity for the first cycle is 287, 192.9mAhg−1, respectively. Also, charge transfer resistance was also significantly improved compare with other samples. [Copyright &y& Elsevier]

Abstract: The carbon-coated monoclinic Li3V2(PO4)3/C composite was prepared via rheological phase method with EDTA (ethylene diamine tetraacetic acid), a new type of carbon source. XRD patterns demonstrate the pure monoclinic structure of the sample. The images of SEM show the uniform and optimized particles size, which greatly improves the electrochemical performance. The TEM test shows the amorphous carbon around the surface of the particles. In the potential range of 3.0–4.3V, the initial discharge capacity is 129.1mAh/g at 0.1C which is almost near the theoretical capacity, and it keeps so fairly stable that a discharge capacity of more than 125mAh/g can still be held after 50 galvanostatical cycles. It also exhibits an excellent rate capability with high discharge capacities of more than 108mAh/g at 2C after 100cycles. [Copyright &y& Elsevier]