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We report on an effective approach to speed up the measurement of thermodynamic characterization curves (entropy of reaction Δ r S ( x )) of rechargeable batteries, in particular commercial 18650 lithium ion cells. We propose and demonstrate a measurement and data processing protocol that reduces the time required to record entropy profiles from time scales of weeks to time scales of hours – without loss in accuracy. For time consuming studies such as investigations on ageing of battery cells, entropy profile measurements thus become as feasible as conventional electrochemical characterisation techniques like dV/dQ or cyclic voltammetry. We demonstrate this at the examples of two ageing protocols applied to a commercial high power and a commercial high energy cell, respectively: (i) accelerated calendric aging by storing cells at 100% state of charge at 60 °C and (ii) continuous cycling with a 1C current at 25 °C. [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]

NiCr 2 O 4 is successfully prepared via hydrothermal pretreatment and subsequent sintering, which shows excellent electrochemical performance as a new anode material for lithium ion batteries with natural graphite adding and sodium alginate binder. At a specific current of 70 mA g −1 , it delivers charge and discharge capacities of 465.5 and 919.8 mAh g −1 in the initial cycle, which gradually increases along with cycle number owing to an electrochemical reconstruction in cycling. After 100 cycles, the charge and discharge capacities are 582.9 and 592.5 mAh g −1 , respectively. Furthermore, it is testified that natural graphite adding can effectively improve the electronic conductivity of the NiCr 2 O 4 electrode, and an appropriate amount of natural graphite is beneficial to improve the specific capacity and cycle stability of the electrode owing to a coordinated electrochemical reconstruction between NiCr 2 O 4 and natural graphite in cycling. [ABSTRACT FROM AUTHOR]

MoO 3 -coated Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 cathode materials were synthesized via using co-precipitation method and wet coating process, and their crystal structure and particle morphology were analyzed and observed by XRD, SEM and TEM. The electrochemical properties of these materials were investigated and analyzed by using charge-discharge tests and electrochemical impedance spectroscopy. The results showed that the surface coating on Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 cathode was composed of α-MoO 3 and Li 2 MoO 4 , and the electrochemical properties were improved after coated with MoO 3 thin films. The initial coulombic efficiencies increased from 71.2% to 79.3% when the MoO 3 content increased to 5 wt.%. Particularly, the 3 wt.% MoO 3 -coated Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 showed the highest capacity retention of 90.8% after 100 cycles, and possessed the excellent rate discharge performance. The electrochemical impedance spectroscopy (EIS) and cyclic voltammetric results demonstrated that the layered MoO 3 coating could restrain the increment of the charge transfer resistance and stabilize the active material structure during cyclic process. [ABSTRACT FROM AUTHOR]

We report a simple microwave-assisted method to fabricate high-quality two-dimensional (2D) ultrathin NiCo 2 O 4 nanosheets with a geometrically graphene-like architecture. The unique large-area nanostructures represent an ultrahigh surface atomic ratio with almost all active elements exposed outside for surface-dependent electrochemical reaction processes. Experimental results reveal that the as-synthesized ultrathin NiCo 2 O 4 nanosheets show excellent electrochemical performances for lithium storage application. The ultrathin NiCo 2 O 4 nanosheets could deliver a high first discharge capacity (1287.1 mAh g −1 ) with initial Coulombic efficiency of 80.0% at 200 mA g −1 current density. The reversible lithium storage capacity still retains at 804.8 mAh g −1 in the 100th cycle, suggesting a good cycling stability. The excellent electrochemical properties of the as-synthesized NiCo 2 O 4 nanosheets could be ascribed to the unique ultrathin 2D architecture, which could offer large exposed active surface with more lithium-insertion channels and significantly reduce lithium ion diffusion distance. The cost-efficient synthesis and excellent lithium storage properties make the 2D NiCo 2 O 4 nanosheets as a promising anode material for high-performance lithium ion batteries. [ABSTRACT FROM AUTHOR]

The peanut shells derived porous hard carbons (PSDHCs) by pyrolysis have been investigated as anodes of lithium/sodium batteries (LIBs/NIBs). Directly from the starting peanut shells, 600°C is found to be the favorable pyrolysis temperature for preparation of the PSDHC sample (PSDHC-600) with the best electrochemical performances for LIB applications. Furthermore, from the activated peanut shells in KOH solution, the produced PSDHC-600A by pyrolysis at 600°C is observed to offer greatly enhanced Li + /Na + ion storages. For LIB applications, PSDHC-600A delivers a retained capacity of 474 mAhg −1 after 400 cycles at 1 Ag −1 , larger than 314 mAhg −1 of PSDHC-600. At a high current rate of 5 Ag −1 , PSDHC-600A sustains over 10000 cycles with no obvious sign of fade in capacity, and a capacity of 310 mAhg −1 is still retained. For NIB applications, a capacity of 193 mAh g −1 is retained after 400 cycles at 0.25 Ag −1 , higher than 130 mAhg −1 of PSDHC-600. Even at 1 Ag −1 , PSDHC-600A can be stably cycled over 3000 cycles, and a capacity of 129 mAhg −1 is still retained. In comparison to PSDHC-600, the enhanced electrochemical properties of PSDHC-600A can be attributed to the finer porous structure with the increased percentage of nanoscale pores of diameter less than 2 nm and the larger specific surface area. [ABSTRACT FROM AUTHOR]

Silver with a high theoretical capacity for lithium storage is an attractive alloy based anode for Li-ion batteries, but large volume changes associated with AgLi x alloy formation leads to electrode cracking, pulverization and rapid capacity fading. A buffer matrix, like the electrospun hollow carbon nanofibers, can reduce this problem to a great extent. Herein, we demonstrate the facile synthesis of a free-standing, binder free Ag-C hybrid electrode through co-axial electrospinning, where well dispersed Ag nanoparticles are embedded in hollow carbon nanofibers. Using this approach, the long cycle life of carbon is complemented with the high lithium storage capacity of Ag, resulting in a high performance anode. The Ag-C composite electrode delivers a capacity of 739 mAh g −1 (>conventional graphite anodes) at 50 mA g −1 , with ∼85% capacity retention after 100 cycles. In addition, the Ag-C composite nanofibers are highly porous and exhibit a large accessible surface area (∼726.9 m 2 g −1 ) with an average pore diameter of ∼6.07 nm. The encapsulation of Ag in the hollow interiors not only provides additional lithium storage sites but also enhances the electronic conductivity, which combined with the reduced lithium diffusion path lengths in the nanofibers result in faster charge-discharge kinetics and hence a high rate performance. [ABSTRACT FROM AUTHOR]

A series of anatase TiO 2 nanowires (TiO 2 -NWs) and Ag-modified TiO 2 nanowires (TiO 2 @Ag-NWs) film electrodes with hierarchical 3D nano-network structure are successfully synthesized via a facile hydrothermal process followed by the traditional silver mirror reaction. Successful modification of silver nanoparticles onto the TiO 2 -NWs surface is confirmed by X-ray diffraction, scanning electron microscope, transmission electron microscopy with energy-dispersive X-ray analysis, and inductively coupled plasma technique. The electrochemical performances of the TiO 2 -NWs and TiO 2 @Ag-NWs film electrodes are also investigated in this work. Compared with the pristine TiO 2 -NWs, the TiO 2 @Ag-NWs nanomaterial exhibits a higher rate capability and better reversibility. At charge/discharge rates of 50, 100, 200, 400, 800, 1600 and 3350 mA/g, the discharge capacities of the TiO 2 @Ag-NWs electrodes are 237, 219, 198, 179, 159, 139 and 120 mAh/g, respectively. After 120 cycles at 200 mA/g, its capacity retention was as high as 99.1% with little capacity fading. [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]

Nanocrystalline lithium iron silicate/carbon (Li 2 FeSiO 4 /C) composites were successfully prepared by impregnation of a commercial porous carbon using ethanolic solutions of the different metallic precursors, followed by thermal annealing at 600 °C. The effects of Li 2 FeSiO 4 loading content on the structure and organization of the Li 2 FeSiO 4 /C composites at the nanoscale were investigated. Through optimization of the synthesis conditions, small Li 2 FeSiO 4 nanocrystals (4–12 nm) are formed and well dispersed in the porous conductive carbon. The electrochemical performances of these composites were tested as positive electrodes for lithium-ion batteries. The Li 2 FeSiO 4 /C composite with the lowest Li 2 FeSiO 4 loading exhibits the best rate capability with a significant capacity contribution from carbon. It was found that the presence of carbon delays the lowering of the Fe 3+ /Fe 2+ redox voltage usually reported for Li 2 FeSiO 4 (from 3.1/3.0 to 2.8/2.7 V vs. Li + /Li), due to a stabilization effect of the initial Li 2 FeSiO 4 crystal structure. For the Li 2 FeSiO 4 /C composite (81/19 weight ratio), a discharge capacity of 81 mAh g −1 can be achieved at 55 °C for a charge/discharge rate of 2C, with 86% capacity retention after 500 cycles, showing the positive effect of the porous carbon addition for long term cycling stability. [ABSTRACT FROM AUTHOR]

A convenient chitosan-assisted hydrothermal and postannealing strategy was successfully developed to fabricate 2D ultrathin MoS 2 /graphene heterostructures. The resultant heterostructures were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and nitrogen adsorption-desorption. It was found that the ultrathin MoS 2 nanosheets were of few-layered structures (3–4 layers) and were well anchored on the large flexible graphene flakes to form heterostructures, which had more uniform mesoporosity and larger surface area than the pristine MoS 2 . As a result, the obtained MoS 2 /graphene heterostructure electrode exhibited superior electrochemical lithium-storage performances such as high reversible specific capacity (∼1100 mAh g −1 ), excellent cyclic stability and significantly enhanced rate capability. The prominent electrochemical performance could be attributed to the robust 2D mesoporous heterostructures composed of ultrathin few-layered MoS 2 nanosheets and highly conductive graphene as well as the resultant positive synergistic effect between them. [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]

Used LiCoO material was renovated by means of ultrasound radiation under hydrothermal conditions. The optimal reaction condition for renovation process was obtained: temperature 120 °C, ultrasonic power 999 W, and ultrasonic method 'work 5 s-stop 2 s' and ultrasonic radiation time 10 h. The XRD, SEM, ICP-AES analysis, and charge-discharge test showed that the renovated LiCoO had a high degree of crystallinity, a fine-layered structure, good dispersion of particles, and improved electrochemical cycle performance. The first-time charge capacity and discharge capacity of renovated LiCoO were 132.6 and 131.5 mAh/g, respectively. The first-time charge and discharge efficiency was 99.2 %. After 20 cycles, the discharge capacity retention rate was 98.1 % which reaches or approaches the electrochemical properties of commercial batteries. [ABSTRACT FROM AUTHOR]

A facile method to synthesize graphene-like MoS 2 nanowall/graphene sheet (GL-MoS 2 nanowall/GNS) composites has been developed through a solvothermal method, and followed by annealing at 400 °C under Ar. The characterization results indicate that the thin flaky wall type GL-MoS 2 nanowall was supported well on the crumpled graphene flakes with good dispersion. The as-obtained nanowall-nanosheet hybrids are more robust and still retain the reversible capacity of 700 mA h g −1 after 100 cycles at a charge–discharge rate of 500 mA g −1 . The outstanding performance in electrochemistry is attributed to both the robust nanocomposite structure and the synergistic interactions between graphene and GL-MoS 2 nanowall, which makes it an efficient stable lithium storage material. [ABSTRACT FROM AUTHOR]

CoV 2 O 6 /natural graphite electrode with sodium alginate binder is prepared, which shows excellent electrochemical performance as anode for Li-ion batteries. It exhibits initial discharge and charge capacity of 902 and 638 mAh g −1 at a specific current of 110 mA g −1 . After 100 cycles, the discharge and charge capacity maintain of 669 and 665 mAh g −1 , respectively. The charge/discharge mechanism of CoV 2 O 6 is also studied, suggesting a structure variation in discharging, which involves the initial formation of LiV 2 O 5 and Co 3 V 2 O 8 , the subsequent transition from Co 3 V 2 O 8 to Li x V 2 O 5 and CoO, and the later reduction of CoO into Co. The structure variation of Co 3 V 2 O 8 accompanies by an amorphization process, which maintains in the subsequent discharging and charging process. [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 dense instead of porous gel polymer electrolyte for lithium ion batteries is reported for the first time. Its host is a renewable and environment friendly polymer, hydroxyethyl cellulose (HEC). The preparation of HEC membrane is very simple. The membrane is stable up to 280 °C, much higher than the melting points of those commercial separators based on polyolefin. The evaporation temperature of the organic electrolyte in the prepared gel polymer electrolytes is up to 75 °C. In addition, the gel polymer electrolyte shows good electrochemical performance including high ionic conductivity at room temperature, and a high lithium ion transference number. When tested as separator and electrolyte, a LiFePO 4 positive electrode displays satisfactory electrochemical properties including high discharge capacity and stable cycling. These results indicate a very promising direction for a low cost and renewable gel polymer electrolyte for lithium ion batteries. [ABSTRACT FROM AUTHOR]

Carbon-coated LiMnSiO powders were synthesized by a citric acid-assisted sol-gel process, and their physical and electrochemical properties were characterized to assess their suitability as a cathode material in lithium-rechargeable batteries. Carbon was coated onto the LiMnSiO particles through the carbonization of polymeric materials that were caused by the addition of citric acid during the sol-gel process. The particle size and electrical conductivity of the LiMnSiO powders were found to be changed by varying the amount of citric acid added during the sol-gel process. XRD analysis showed that the quantity of impurities in LiMnSiO was decreased during the sol-gel process. The carbon coating led to an increase in conductivity and mean particle size by creating an electrical and physical connection between the particles. The discharge capacity of LiMnSiO with over 5 % carbon coating was significantly increased to ~125 mAh g compared to just ~3 mAh g for noncoated material. [ABSTRACT FROM AUTHOR]

A lithium ion battery consists of numerous electrochemical cell units. Thermal and electrical behaviors of these local cell units have great influence on the battery's performance and safety. To study the relationship between the cell units and the battery cell, a pseudo 3D (three-dimensional) model was developed for a prismatic LiFePO 4 battery by coupling the mass, charge, and energy conservations, as well as the cell electrochemical kinetics. The model treated the battery with current collecting tabs as 3D and the local cell units as 1D. Both electrochemical and thermal characteristics of the battery were studied by using this simplified model during the discharge process. A uniformity index characterizing the SOC (state of charge) distributions among 1D cell units was also introduced. This index was used to investigate the effects of the tab placement on the uniformity of the battery cell. The placement of the positive and negative current collecting tabs on the prismatic battery was found to have a significant effect on the distributions of its potential and local reaction rates, which therefore affect the heat generation rate, and thus the temperature distribution within the battery. [ABSTRACT FROM AUTHOR]

Spinel LiMnO and multidoped spinel LiMnCoCrNiFeO were synthesized by the glycine-nitrate method and coated with lithium borosilicate (LBS) in order to enhance the electrochemical performance at room temperature. The structure and electrochemical performance of all samples were characterized by inductively coupled plasma-mass spectrometer (ICP-MS), X-ray diffraction (XRD), differential thermal analysis/thermogravimetry (DTA/TG), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and galvanostatic charge-discharge measurements. The XRD analysis shows that the samples exhibit a pure spinel phase. The SEM results indicated that LBS particles had encapsulated the surface of the undoped and multidoped LiMnO without causing any structural change. The charge-discharge tests showed that LiMnCoCrNiFeO displays better cycling performance than the pristine LiMnO at room temperature. However, in the same conditions, LBS-coated LiMnCoCrNiFeO and LiMn O have better cycling performance than uncoated samples. The results suggest that multidoped and LBS-coated LiMnO could develop into a promising cathode material for lithium ion batteries. [ABSTRACT FROM AUTHOR]

V 2 O 3 /C composites were synthesized by oxygen corrosive and carbon coating process by the one-pot hydrothermal method. The uniform carbon coating and bridged pores significantly improved its electrochemical performance. It delivers more than two times the capacity of V 2 O 3 and an impressive capacity of 283 mAh g −1 @ 25 A g −1 . [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]

Porous LiMn 0.6 Fe 0.4 PO 4 (LMFP) is synthesized by a modified sol–gel process. Highly conductive LMFP due to uniform dispersion of carbon throughout LMFP particles are achieved by the addition of sucrose as an additional carbon source. The LMFP obtained has a high specific surface area with a uniform, porous, and web-like nano-sized carbon layer on the surface. The initial discharge capacity and energy density of the LMFP cathode is 152 mAh g −1 and 570 Wh kg −1 , respectively, at 0.1C current rate. The combined effect of high porosity and high electrical conductivity lead to fast lithium ion diffusion and enhance initial capacity compared to materials prepared by the general sol–gel method. However, with conventional electrolyte (1M LiPF 6 in EC/DMC) poor cycle performance is observed due to HF attack. To improve the cycle stability we add tris (trimethylsily) phosphite (TMSP) as an additive in the electrolyte which dramatically improves cycle stability and rate-capability. [ABSTRACT FROM AUTHOR]

α-MoO nanobelts were synthesized by simple hydrothermal method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Cyclic voltammogram (CV) and galvanostatic charge/discharge testing techniques were employed to evaluate electrochemical behaviors of α-MoO materials. Results showed that α-MoO nanobelts with about 80 nm in diameter and 5-12 μm in length were grown in the orthorhombic system. Electrochemical characterisation confirmed that in lithium ion insertion/extraction process, the first intercalation of lithium ion in α-MoO at about 2.8 V was irreversible, corresponding to LiMoO (0 < x ≤ 0.25) and the parent MoO materials coexisting, the second lithium ion inter-calation was reversible at the potential range of 2.2-2.4 V followed by LiMoO (0.25 < x ≤ 0.5), and below 1.0 V the mechanism of lithium ion storage changed from lithium ion intercalation reaction into lithium alloying reaction. The α-MoO nanobelts showed better electrochemical performance, 319 mA h g initial discharge capacity, around 52% capacity retention after 20 cycles than that of α-MoO bulk. [ABSTRACT FROM AUTHOR]

A low cost and facile way was developed to prepare high performance Fe 2 O 3 /natural graphite electrode for lithium ion batteries. For the purpose of reducing the cost and improving the feasibility of large-scale fabrication, commercial ferric oxide and natural graphite were adopted as raw materials and mechanical milling was adopted as preparation method in material fabrication process, and water soluble sodium alginate was adopted as binder in electrode preparation procedure. The Fe 2 O 3 /natural graphite electrode delivers initial discharge and charge capacity of 943.8 and 691.4 mAh g -1 at a specific current of 72 mA g -1 , maintaining of 687.6 and 679.3 mAh g -1 after 100 cycles. After 60 cycles at various specific currents from 104 to 3470 mA g -1 , the discharge and charge capacity of the Fe 2 O 3 /natural graphite electrode can restore well when lowering the specific current to 104 mA g -1 . A novel electrochemical reconstruction between Fe 2 O 3 and natural graphite was observed for the electrode after cycling, which results in the formation of an integrated architecture with good combination between Fe 2 O 3 and natural graphite, being responsible for the good electrochemical performance. [ABSTRACT FROM AUTHOR]

A series of Li 2 Fe 1- x V x SiO 4 /C ( x = 0.00, 0.03, 0.05 and 0.07) composites have been synthesized via a refluxing-assisted solid-state reaction. XRD results confirm the monoclinic structure with space group P2 1 for Li 2 Fe 1- x V x SiO 4 /C compounds. TEM and Raman spectroscopy demonstrate V-doping can increase the graphitization degree of residual carbon. XPS confirms that V-incorporation does not change the divalent state of Fe, and the oxidation state of V in V-doped Li 2 FeSiO 4 /C is +3. Combined Ar-ion sputtering with XPS, it is found that V has been successfully doped into the crystal lattice of Li 2 FeSiO 4 . Electrochemical tests show that LFS/C-5 V delivers the highest initial discharge capacity of 220.4 mAh g −1 and the biggest Li-ion diffusion coefficient of 1.60 × 10 −11 cm 2 s −1 . In addition, the density functional theory (DFT) calculations predict that V-doping decreases the electronic band gap of Li 2 FeSiO 4 , thus leads to significant improvement in the electrical conductivity of Li 2 FeSiO 4 . The enhanced electrochemical performance can be attributed to the increased electronic conductivity, the decreased charge transfer impedance, and the improved Li-ion diffusion coefficient. Our results clarified the nature of V doping into Li 2 FeSiO 4 and demonstrated that V-doping is a promising approach to improve the electrochemical performance of Li 2 FeSiO 4 . [ABSTRACT FROM AUTHOR]

A series of RuO 2 modified LiNi 0.5 Mn 1.5 O 4 materials are successfully prepared by the precipitation method. X-ray photoelectron spectroscopy confirms the presence of Ru 4+ in the materials. Scanning electron microscope and high resolution transmission electron microscope show that RuO 2 covers the surface of LiNi 0.5 Mn 1.5 O 4 particles. The amounts of RuO 2 in the materials are determined to be 1.6 wt.%, 2.0 wt.% and 3.0 wt.%, respectively. The electrochemical kinetics of the materials is studied by cyclic voltammetry and electrochemical impedance spectroscopy. The results show that RuO 2 modification decreases the polarization of the electrode, prevents the side reactions of the electrode and the electrolyte, and improves the charge transfer reactions at the electrode interface, all of which are beneficial for the electrochemical properties of LiNi 0.5 Mn 1.5 O 4 . In all samples tested, the one containing 2.0 wt.% of RuO 2 exhibits superior electrochemical performance. It shows discharge capacities of 131.7 mAh g −1 (room temperature) and 129.7 mAh g −1 (60 °C) at the 0.5 C rate with the corresponding capacity retention of 97.7% and 97.2% after 100 cycles. In addition, the material delivers high discharge capacities of 104.5 mAh g −1 at the 5 C rate and 66.1 mAh g −1 at the 10 C rate, demonstrating its excellent rate capability. [ABSTRACT FROM AUTHOR]

Hierarchical assembly of hollow microstructures is of great scientificity and practical value. In this paper, a hydrothermal synthesis of Li 4 Ti 5 O 12 hollow microspheres assembled by nanosheets is introduced. Transmission electron microscopy (TEM) image shows that such Li 4 Ti 5 O 12 microspheres, with sizes of 2 μm in diameter, are composed of a hollow inner cavity and thin outer shell assembled by nanosheets. A possible growth mechanism of the structure is further expounded. The Li 4 Ti 5 O 12 hollow microspheres calcinated at 700 °C display extremely good electrochemical performance, including high capacity (147.3 mA h g −1 at 3 C), excellent cyclic stability (95.0% capacity retention after 100 cycles at 3 C) and remarkable rate capability (131.3 mA h g −1 at 20 C). [ABSTRACT FROM AUTHOR]

Thiophene derivatives (THs) are examined as novel functional additives for improving the cycling performance of high-voltage LiCoO 2 . Our investigation reveals that 2,2′-Bithiophene (2TH) and 2,2′:5′,2′′-Terthiophene (3TH) can be electrochemically polymerize prior to the electrolyte solvent decomposition to form a protective layer of conducting polymer film on the cathode surface, which blocks off severe electrolyte decomposition at high voltages and, therefore, improves the cycling stability of high voltage LiCoO 2 cathode. After 100 cycles at a high cutoff voltage of 4.4 V, the discharge capacity retention is 50% in the base electrolyte, in contrast, the LiCoO 2 cathode cycled in the electrolyte containing 0.1 wt% 3TH displays a high capacity retention of 84.8% at 0.25 C rate. This work demonstrates that these thiophene derivatives have considerable potential as functional additives for the applications in high-voltage lithium-ion batteries. [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 LiMn 2 O 4 nanoparticles were successfully prepared via solution combustion synthesis by controlling calcinating temperature. XRD results indicate that high purity LiMn 2 O 4 can be fabricated by calcinating the precursor above 600 °C. SEM results reflect that LiMn 2 O 4 calcinated lower than 600 °C are composed of nanoparticles about 100 nm. Therefore, LiMn 2 O 4 calcinated at 600 °C possess high purity and nanoparticles, which ensure the most excellent electrochemical performance among the precursor as well as LiMn 2 O 4 calcinated at 500 °C, 600 °C and 700 °C. LiMn 2 O 4 calcinated at 600 °C even can deliver a capacity of 103.8 mA h g −1 at 10 C, which is the 83.6% of the capacity at 0.2 C. It also displays excellent capacity retention ratio of 95.1% for 100 cycles at constant current rate of 1 C. [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]

The formation of the solid electrolyte interface (SEI) layer on the surface of the anode electrode of a lithium ion battery prevents further electrolyte decomposition reaction. However, at certain battery operating conditions, the SEI breakdown leading to more electrolyte decomposition reactions that form several species on the anode electrode surface. This paper focuses on the effect of battery potential and charge rate on the decomposition side reaction on the anode electrode of a lithium ion polymer battery, as a result of the breakdown of the SEI layer. The results from this study indicate that raising the state of charge (SOC) increases the rate of the electrolyte decomposition side reaction that resulted in formation of a thick deposit layer at the electrolyte/electrolyte interface. This deposit layer contains lithium that can no longer participate in the reversible electrochemical reaction. In addition, at high cycling potential and charge rates the amount of lithium in the graphite after complete cell discharge increased due to the entrapment of lithium in the graphite. The amount of irreversible capacity loss for the batteries cycled at high potential and current correlates with the amount of trapped lithium in the graphite and the growth of the deposit layer thickness at the electrode/electrolyte interface. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive model coupling the effects of hydrostatic stress, surface/interface stress, phase transformation and the structure of electrodes. First, the governing equation of moving phase interface with hydrostatic stress is established. Under the effect of hydrostatic stress, phase transformation process is much faster, which means phase transformation time is overestimated in previous publications. Then, a cross-scale analysis is presented to investigate the size effect owing to hydrostatic stress, surface stress and interface stress separately, which concludes that the effect of hydrostatic stress is significant for the stress field in microelectrode particles, whereas that of surface/interface stress is highlighted in nano-ones. Finally, an electrochemical variable 'efficiency' (ratio of effective capacity over total capacity) is defined. The advantages of hollow structure electrodes on stress and efficiency are analysed. The present model is helpful for the material and structure design of electrodes of lithium ion batteries. [ABSTRACT FROM AUTHOR]

Lithium transportation across the interface of LiMn 2 O 4 /LiPF 6 -based electrolyte was studied by 6/7 Li solid-state NMR with 6 Li-enriched LiPF 6 . For almost stoichiometric LiMn 2 O 4 , we show that exchange of lithium ions occurs across an electrolyte/electrode interface just by immersing LiMn 2 O 4 powder into LiPF 6 -based electrolyte, while such transportation is suppressed in Li-excess LiMn 2 O 4 . The exchange was approximated by the 1st-order reaction, and the rate was estimated from the 6 Li/ 7 Li intensities to be 0.024 min −1 at room temperature. The lithium ions penetrated into the surface of a LiMn 2 O 4 particle reach to the core with a time scale of a few hours at room temperature. The suppression of the exchange in Li-excess LiMn 2 O 4 was ascribed to the presence of excess amount of Mn 4+ . [ABSTRACT FROM AUTHOR]

High performance hybrid phase Li 2 NaV 2 (PO 4 ) 3 (H-LNVP) composite consist of rhombohedral Li 3 V 2 (PO 4 ) 3 (60.9%), rhombohedral Na 3 V 2 (PO 4 ) 3 (31.6%) and monoclinic Li 3 V 2 (PO 4 ) 3 (7.5%) is successfully synthesized via a sol-gel method. The rhombohedral phase Li 2 NaV 2 (PO 4 ) 3 (R-LNVP) is also obtained for comparison. The H-LNVP delivers better electrochemical performance, higher Li + diffusion coefficient and more stable structure than that of R-LNVP duo to the existence of small amount monoclinic Li 3 V 2 (PO 4 ) 3 . For the synthesised H-LNVP, there are 123.3 mAh g -1 that can be delivered at 0.5 C rate as cathode and 128.4 mAh g -1 that can be delivered at 0.2 Crate as anode. On this basis, a LNVP||LNVP lithium ion full cell is fabricated, with an output output potential of ∼2.48 V and a specific discharge capacity of 99.3 mA h g −1 . [ABSTRACT FROM AUTHOR]

In Li-ion batteries, the solid electrolyte interface (SEI) plays a crucial role in transferring Li ions into active materials through an electrochemical driving force. SEI is a composite layer containing of inorganic and organic components, which are fabricated by the salt degradation products and partial or complete reduction products of the solvent of the electrolyte at the battery's initial charge-discharge cycle. The chemical properties of SEI and the electrochemical driving force must be mutually optimized so as to strengthen its integrity, while minimizing irreversible SEI formation; thereby suppressing the decomposition at high temperatures. In this study, we investigated a new method of creating the SEI, i.e. the forward and reverse differential-pulse (FRDP) method, which balances the reaction kinetics of SEI formation. Furthermore, the use of the FRDP method also creates a SEI with a modified kinetic reaction route that affects battery performance. Here, we present data from the first charge-discharge and cycle performance at a high rate and a high temperature, obtained using scanning electron microscopy, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and Li + -diffusion kinetics analysis. Our findings indicate that the use of the FRDP method for generating the SEI results in a 58% reduction in the SEI's ionic diffusion activation energy and a 4.5% increase in battery capacity at room temperature, while increasing battery performance at 60 °C stability compared to batteries in which the SEI is formed using the constant-current method. [ABSTRACT FROM AUTHOR]

Tris(trimethylsilyl) phosphite (TMSPi) is reported as an effective electrolyte additive for high voltage layered lithium nickel cobalt manganese oxide cathode of lithium ion battery. Charge/discharge tests demonstrate that the cyclic stability and rate capability of LiNi 1/3 Co 1/3 Mn 1/3 O 2 can be improved significantly by adding 0.5wt% TMSPi into a standard electrolyte, 1.0 M LiPF 6 in ethylene carbonate/dimethyl carbonate (1/2, in volume). The capacity retention of LiNi 1/3 Co 1/3 Mn 1/3 O 2 is improved from 75.2% to 91.2% after 100 cycles at 0.5 C rate (1C = 160 mA g− 1 ), while its discharge capacity at 5 C is enhanced from 122.4 mAh g− 1 to 134.4 mAh g− 1 . This improvement can be ascribed to the suppression of electrolyte decomposition and transition metal ion dissolution by TMSPi, due to the preferential oxidation of TMSPi to electrolyte and the formation of a protective solid electrolyte interphase on LiNi 1/3 Co 1/3 Mn 1/3 O 2 , which are confirmed by electrochemical measurements and surface characterizations. [ABSTRACT FROM AUTHOR]

Li 3 VO 4 nanoparticles with mean size about 100 nm are uniformly deposited on the surface of natural graphite via a quasi sol gel method. The electrochemical performance of the Li 3 VO 4 /natural graphite composite as anode for lithium ion batteries is studied via galvanostatic battery testing, which shows excellent cycle stability and rate capability. At a specific current of 156 mA g −1 , it delivers discharge and charge capacity of 579 and 427 mAh g −1 in the initial cycle, which maintain of 469 and 468 mAh g −1 after 100 cycles. After 60 cycles at various specific currents from 234 to 11,719 mA g −1 , the discharge capacity can restore to 450 mAh g −1 when reverting the discharge/charge current to 234 mA g −1 . It is demonstrated that natural graphite has important effect on the electrochemcial performance of the composite electrode, and an appropriate amount of natural graphite is beneficial to reduce the charge transfer resistance and maintain stable charge transfer process in cycling. [ABSTRACT FROM AUTHOR]

The Li4Ti5O12/G/CNTs hybrid material was synthesized via a facile rheological phase reaction route. For comparison, the Li4Ti5O12/G hybrid material was also prepared using the similar rheological phase method. The results showed that the Li4Ti5O12/G/CNTs had better rate capability and cycling performance than that of the Li4Ti5O12/G. At 0.2 C, the initial discharge capacity of the Li4Ti5O12/G/CNTs was 172 mA h/g, and even at the high rate of 5.0 C and 10.0 C, it could still remain at 150 mA h/g and 144 mA h/g, respectively. Moreover, only less than 6% discharge capacity loss over 100 cycles at 10.0 C was observed. The outstanding electrochemical performances make it a promising anode material for high rate lithium ion batteries. [ABSTRACT FROM AUTHOR]

Highlights: [•] LNMO and LANMO hollow microspheres are synthesized by template method. [•] The as-synthesized hollow microspheres have particle-size of 2μm. [•] The hollow structure is responsible for improved electrochemical performance. [ABSTRACT FROM AUTHOR]

Ni-rich mixed metal oxides (LiNi0.80Co0.15Mn0.05O2) as a high capacity cathode material for lithium ion battery are synthesized in two different heat-treatment atmospheres of air and oxygen, respectively. A cell with LiNi0.80Co0.15Mn0.05O2 heat-treated in the oxygen atmosphere shows better electrochemical performance of initial (193.7 mAh/g) and retention (185.2 mAh/g) capacities than a cell with the cathode material heat-treated in the air atmosphere (initial capacity: 185.2 mAh/g and retention capacity: 172.0 mAh/g). In order to find the reasons of the different electrochemical performance, the samples have been characterized in detail by X-ray diffraction and scanning electron microscopy. The structural differences are revealed at the nanometer scale from the experimental works of scanning transmission electron microscopy images mapped with orientation and reliability indices and electron energy loss spectroscopy. The NiO phase of the rock salt structure is considerably developed on the surfaces of the materials in the less oxidative environment of the air atmosphere; this is related to the poor electrochemical performances. [ABSTRACT FROM AUTHOR]

Cobalt sulfide-carbon composite powders were prepared by sulfidation of precursor powders obtained by spray drying. The precursor powders were composed of large particles with dimensions of several tens of micrometers and a hollow morphology with a thin-walled structure. The XRD pattern of the powders sulfidated at 200°C showed Co9S8as the main phase and CoS as the minor phase. However, the XRD patterns of the powders sulfidated at 300 and 400°C showed CoS as the main phase and Co9S8, Co3S4, and CoS2as the minor phases. The primary particle sizes of the powders sulfidated at 200, 300, and 400°C were 80, 190, and 230nm, respectively. Ultrafine cobalt sulfide crystals, a few nanometers in size, were uniformly distributed across the cobalt sulfide-carbon composite sheet. Dot-mapping images revealed that the carbon component was uniformly distributed throughout the composite powder. The optimum sulfidation temperature to obtain the composite powders with superior electrochemical properties was 300°C. The initial discharge and charge capacities of the composite powders sulfidated at 300°C at a current density of 1000mAg−1were 1089 and 878mA h g−1, respectively. The discharge capacity of the composite powders sulfidated at 300°C became stable at around 790mA h g−1for up to 70 cycles. [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]

We have prepared two types TiO2(B)-carbon composites from Lepidocrocite-type compounds (K0.86Li0.26Ti1.72O4) heated at 700 and 900°C under presence of carbon nanotube (CNT) and glucose as carbon sources. The XRD data shows that it contains a single phase of TiO2(B) and the existence of carbon was confirmed by Raman spectra. TEM image confirms that TiO2(B) primary particles and carbon nanotube are scattered randomly and contact tightly in the composite. Carbon content in the composite was found to be 5 - 8% and CNT is the major carbonaceous material. The charge and discharge curves of TiO2(B)-carbon composite prepared from precursor heated at 700°C resemble with that of amorphous TiO2. The calculated discharge capacity of the composite is 323mAhg−1 at a cut off voltage of 0.9V, which is higher than that of bare TiO2(B). It is suggested that the electrochemical performance of this material is strongly influenced by both the operating temperature and cut off voltage. The discharge capacity can reach 198mAhg−1 at 4.5C rate at a cut off voltage 1.3V and the coulombic efficiency is over 99.8% after 10th cycles. [ABSTRACT FROM AUTHOR]

The influence of the vanadium substituted LiNi0.5Co0.2Mn0.3O2 (LNCM-532) cathode materials on the structure and electrochemical properties were investigated by means of X-ray diffraction, Rietveld refinement, scanning electron microscope, X-ray photoelectric spectroscopy, energy dispersive spectrometer, electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge/discharge tests. XRD, EDS, XPS results show that vanadium is successfully substituted for the transitional metal in LiNi0.5Co0.2Mn0.3O2 crystal lattice. Rietveld refinement results show that suitable vanadium substitution leads to low cation mixing. Electrochemical tests show that the discharge capacity of Li[Ni0.5Co0.2Mn0.3]0.97V0.03O2 at 5 C remains 72.2% of that at 0.1 C, while the capacity retention is only 58.9% for LiNi0.5Co0.2Mn0.3O2. LiNi0.5Co0.2Mn0.3O2 exhibits the capacity retention of 93.9% at 1 C after 50 cycles. After substituting, the capacity retention of Li[Ni0.5Co0.2Mn0.3]0.97V0.03O2 is increased to 96.3% at 1 C. EIS measurement indicates that vanadium substitution contributes to the better lithium ion diffusion and the lower charge transfer resistance. [ABSTRACT FROM AUTHOR]