Search

Abstract Poly(vinylidene fluoride- co -hexafluoropropylene) (P(VDF-HFP))-based composite polymer electrolytes (CPEs) doped with different amounts of CaTiO 3 inorganic fillers are prepared by phase inversion. With adding the CaTiO 3 fillers into the P(VDF-HFP) polymer matrix, the CPE membranes show more abundant and uniform micro-pore structure with lower crystallinity, better thermal stability and mechanical strength. The characterization results show that the ionic conductivity at room temperature and electrochemical working window of the CPE doped with 5 wt% CaTiO 3 fillers (CPE-5) can be up to about 3.557 mS cm−1 and 5.1 V, respectively. The interfacial resistance of the Li/CPE-5/Li simulated cell can quickly stabilize at 750 Ω after 5 days storage, and the assembled LiCoO 2 /CPE-5/Li coin cell shows excellent rate and cycle performance. Moreover, the CPE-5 membrane can still well maintain the original micro-pore structure after 100 cycles at 1.0 C without visible cracks. Those results suggest that the as-fabricated CPE doped with 5 wt% CaTiO 3 inorganic fillers may become a promising polymer electrolyte for the lithium ion battery Graphical abstract Cycling performance and coulombic efficiency plots of the LiCoO 2 /CPE-5/Li battery after 100 cycles at 1.0 C (The insert are the SEM images and digital photographs of the CPE-5 before and after cycle). Unlabelled Image Highlights • P(VDF-HFP)-based CPE membranes doped with different amounts of CaTiO 3 ceramics are fabricated by phase inversion. • The electrolyte uptake and ionic conductivity of the CPE-5 can be up to 187.4% and 3.557 mS cm−1. • The Li/CPE-5/Li simulated cell possesses good interfacial stability. • The assembled LiCoO 2 /CPE-5/Li battery shows good rate and cycle performance. [ABSTRACT FROM AUTHOR]

Designing heteroatom doped metal oxides and modifying them with carbonaceous materials can grant metal oxides with good Li + storage performance because of the improved structure stability and enhanced electric conductivity. Herein, monodispersed Cr-doped SnO 2 quantum dots fixed by graphene nanosheets and carbon layers (C/Cr-SnO 2 /G) were successfully assembled, which showed excellent cyclic stability, high reversible capacity and remarkable rate capability for Li + storage. According to the characteristics results, 3.8 wt% Cr were uniformly incorporated into SnO 2 lattice in form of Cr 3 + , resulting the decrease of SnO 2 diameters. The C/Cr-SnO 2 /G electrodes displayed an excellent reversible capacity of 672 mA h g − 1 after 200 cycles at 100 mA g − 1 without apparent capacity fading throughout the test, and still retained a stable specific capacity of 296 mA h g − 1 even at 5 A g − 1 . The enhanced electrochemical performances of C/Cr-SnO 2 /G can be related to incorporation of Cr into lattice of SnO 2 and the double structure protections by graphene nanosheets and carbon layers, which can easily obtain quantum dots structure, increase the conductivity, and keep the structure stability. [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]

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: 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]

Abstract: Micrometric LiMn2O4 particles are mechano-chemically modified by ball-milling to obtain a mixture of nano- and micro-scale particles. This mixture is tested as a potential active cathode material for rapid-charge Li ion batteries, and also as a model system for studying the detailed kinetics of Li intercalation/de-intercalation in such electrodes. Ragone plots recorded using galvanostatic measurements indicate enhanced power delivery characteristics of the ball-milled LiMn2O4 compared to its unprocessed counterpart. The processed material also exhibits improved resistance against electrolyte reactions and surface film formation. Due to these advantageous electrochemical attributes, the ball-milled LiMn2O4 serves as an adequately suited system for exploring certain fundamental aspects of Li intercalation in this material. Scan rate dependent slow scan cyclic voltammetry helps to identify the kinetic and diffusion controlled features of Li transport in mechano-chemically processed LiMn2O4. Electrochemical impedance spectroscopy substantiates these findings further and provides detailed kinetic parameters, including voltage dependent charge transfer resistance and diffusion coefficient of Li transport. [Copyright &y& Elsevier]

Abstract: A series of monoclinic Li3V2(PO4)3 cathode materials were prepared by H2 reduction (LVP-H2) and carbothermal reduction (LVP-CTR) methods. LVP-H2 showed a primary particle size of about 1 μm, which was much larger than the LVP-CTR samples. A uniform surface carbon layer was observed for the LVP-CTR samples by transmission electron microscope. This carbon layer not only limited the particle growth of the materials but also enhanced the material''s electronic conductivity by five orders of magnitude. The LVP-CTR samples exhibited much better electrochemical performance than LVP-H2. The good electrochemical performance of LVP-CTR was attributed to its nano particle size, high electronic conductivity, as well as the surface carbon layer which limited the vanadium dissolution in electrolyte. [Copyright &y& Elsevier]

Abstract: A series of spinel oxy-fluorides with the formula LiMn1.8Li0.1Ni0.1O4− η F η have been synthesized by both the conventional high-temperature (800 °C) firing method with LiF and a low temperature (450 °C) firing process with NH4HF2. Interestingly, the samples obtained by the high temperature (800 °C) procedure show no fluorine in the sample as revealed by the chemical analysis data, but an increase in lattice parameter and capacity values was observed due to a decrease in lithium content caused by the volatilization of LiF during the high temperature (800 °C) firing process. In contrast, the low-temperature fluorine doping approach was successful in incorporating fluorine into the spinel lattice, and the sample LiMn1.8Li0.1Ni0.1O3.85F0.15 exhibits a significant increase in discharge capacity compared to the oxide analog. [Copyright &y& Elsevier]

Abstract: Binary conductive additives (BCA), formed by sonication of mesoporous carbon (MC) and acetylene black (AB), were used as conductive additives to improve the electrochemical performance of a LiCoO2 composite cathode. The electrochemical performance of the LiCoO2 composite cathode dispersed with BCA was investigated. The results showed that the electrochemical performance (including the discharge capacity, the discharge voltage and the total internal resistance) of a BCA loaded LiCoO2 composite cathode was better than that of a cathode loaded with AB. The possible mechanism is that the MC in BCA can adsorb and retain electrolyte solution, which allows an intimate contact between the lithium ions and the cathode active material LiCoO2 due to its large mesopore specific surface area. A simplified model was also proposed. [Copyright &y& Elsevier]

Abstract: Layered LiNi0.5Mn0.5− x Al x O2 (x =0, 0.02, 0.05, 0.08, and 0.1) series cathode materials for lithium-ion batteries were synthesized by a combination technique of co-precipitation and solid-state reaction, and the structural, morphological, and electrochemical properties were examined by XRD, FT-IR, XPS, SEM, CV, EIS, and charge–discharge tests. It is proven that the aliovalent substitution of Al for Mn promoted the formation of LiNi0.5Mn0.5− x Al x O2 structures and induced an increase in the average oxidation number of Ni, thereby leading to the shrinkage of the lattice volume. Among the LiNi0.5Mn0.5− x Al x O2 materials, the material with x =0.05 shows the best cyclability and rate ability, with discharge capacities of 219, 169, 155, and 129 mAh g−1 at 10, 100, 200, and 400 mA g−1 current density respectively. Cycled under 40 mA g−1 in 2.8–4.6 V, LiNi0. 5Mn0.45Al0.05O2 shows the highest discharge capacity of about 199 mAh g−1 for the first cycle, and 179 mAh g−1 after 40 cycles, with a capacity retention of 90%. EIS analyses of the electrode materials at pristine state and state after first charge to 4.6 V indicate that the observed higher current rate capability of LiNi0. 5Mn0.45Al0.05O2 can be understood due to the better charge transfer kinetics. [Copyright &y& Elsevier]

Abstract: Nanosized silver particles were uniformly distributed on the surface of silicon particles by electroless deposition (ED) and high-energy mechanical milling (HEMM) methods, respectively. The HEMM-prepared Si/Ag composite with 10 wt.% silver exhibited a high first coulombic efficiency of 83.4% and a large capacity of ca. 800 mA h g−1 over 30 cycles as a result of conductivity enhancement. It was suggested that electric contact between silicon particles played a significant role in improving the cyclability of silicon electrode. [Copyright &y& Elsevier]