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LiNiO2 cathode material for lithium‐ion batteries has the advantages of high specific capacity, abundant resources, and low cost, but it suffers from difficulties in preparation, structural instability, and serious capacity decay. In this work, highly pure and layered structural LiNi0.95AlaTi0.05‐aO2 (a=0, 0.025, 0.05) cathode materials were synthesized by a simply sol‐gel method. The cation mixing of Ni2+ and Li+, structural deterioration, irreversible conversion between H2 and H3 phases and unstable surface and CEI (Cathode‐electrolyte interface) film can be effectively suppressed by co‐doping with Al3+ and Ti4+. A preferred LiNi0.95Al0.025Ti0.025O2 sample provides a discharge specific capacity of 223 mAh g−1 at 0.1 C and 148.32 mAh g−1 at 5 C, a capacity retention of 72.7 % after 300 cycles at 1 C and a Li+ diffusion coefficient of about 2.0×10−9 cm2 s−1. [ABSTRACT FROM AUTHOR]

The full-concentrationgradient LiNi0.9Co0.083Mn0.017O2 (CG-LNCM), consisting of core Ni-rich LiNi0.93Co0.07O2, transition zone LiNi1−x−yCoxMnyO2, and outmost shell LiNi1/3Co1/3Mn1/3O2 was prepared by a facile co-precipitation method and high-temperature calcination. CG-LNCM was then investigated with an X-ray diffractometer, ascanning electron microscope, a transmission electron microscope, and electrochemical measurements. The results demonstrate that CG-LNCM has a lower cation mixing of Li+ and Ni2+ and larger Li+ diffusion coefficients than concentration-constant LiNi0.9Co0.083Mn0.017O2 (CC-LNCM). CG-LNCM presents a higher capacity and a better rate of capability and cyclability than CC-LNCM. CG-LNCM and CC-LNCM show initial discharge capacities of 221.2 and 212.5 mAh g−1 at 0.2C (40 mA g−1) with corresponding residual discharge capacities of 177.3 and 156.1 mAh g−1 after 80 cycles, respectively. Even at high current rates of 2C and 5C, CG-LNCM exhibits high discharge capacities of 165.1 and 149.1 mAh g−1 after 100 cycles, respectively, while the residual discharge capacities of CC-LNCM are as low as 148.8 and 117.9 mAh g−1 at 2C and 5C after 100 cycles, respectively. The significantly improved electrochemical performance of CG-LNCM is attributed to its concentration-gradient microstructure and the composition distribution of concentration-gradient LiNi0.9Co0.083Mn0.017O2. The special concentration-gradient design and the facile synthesis are favorable for massive manufacturing of high-performance Ni-rich ternary cathode materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: A novel Li3V2(PO4)3/C nanofibers composite has been first prepared by a facile and environmentally friendly electrospinning method using NH4VO3, CH3COOLi, poly (4-vinyl) pyridine (PVP) and citric acid aqueous solution as raw materials. The composite is investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and electrochemical tests. The Li3V2(PO4)3/C nanofibers composite exhibits excellent cycle performance and good rate capability in the voltage range of 3.0–4.8 V. The composite displays a high discharge capacity of 190 mAh g−1 (close to theoretical capacity of 197 mAh g−1) at 0.1 C (19.7 mA g−1). Even at a high-rate of 20 C, the composite presents the discharge capacity of 132 mAh g−1 and good cycle performance. The outstanding electrochemical performance is attributed to the particular morphology and microstructure of Li3V2(PO4)3/C nanofibers composite that dispersive Li3V2(PO4)3 nanofibers and carbon nanofibers aggregate to form nanofibers composite with mesopores and large surface area. [Copyright &y& Elsevier]

Abstract: The cycle performance of spinel LiMn2O4 at 25 and 55°C is improved by LaF3 modification via a chemical deposition method. The physical and electrochemical performances of pristine and LaF3-coated LiMn2O4 cathode materials are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical measurements. The coated LiMn2O4 with 2.92wt% LaF3 (LaF3-3-LMO) displays capacity retentions of 90.1% and 84.2% at 25 and 55°C, respectively, after 100 cycles, much higher than those of pristine LiMn2O4, 72.7% and 54.8%. The concentration of manganese dissolved from LaF3-3-LMO in electrolyte is much lower than that from pristine LiMn2O4. The analysis of AC impedance indicates that the charge transfer resistance (R ct) and the increase of R ct for LaF3-3-LMO during cycling are much lower than those for pristine LiMn2O4. The significantly improved electrochemical performance of the LaF3-coated LiMn2O4 can be attributed to the reduction of manganese dissolution in electrolyte and charge transfer resistance with the help of LaF3 coating. [Copyright &y& Elsevier]

Abstract: The composites of monoclinic Li3−x Na x V2(PO4)3 (x =0, 0.03, 0.05 and 0.07) and carbon are prepared by a sol–gel method. The composites are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical measurements. XRD results show that the cell volumes of the monoclinic Na-doped Li3V2(PO4)3 samples are larger than that of Li3V2(PO4)3. All Na-doped composites exhibit better electrochemical performance than that of pristine one and the Li2.95Na0.05V2(PO4)3/C composite displays highest capacity and best cycle performance. The Li2.95Na0.05V2(PO4)3/C composite presents initial capacities of 187 and 173.1mAhg−1 at 0.2C and 1C between 3.0 and 4.8V, respectively, much higher than that 175.5mAhg−1 (0.2C) and 153.4mAhg−1 (1C) of Li3V2(PO4)3/C composite. The capacity retentions of Li2.95Na0.05V2(PO4)3/C are 95.3% and 91% at 0.2C and 1C after 30 cycles, respectively, while the capacity retentions of Li3V2(PO4)3/C are 90.4% and 87% at 0.2C and 1C after 30 cycles, respectively. The rapid Li+ diffusion due to the doping of Na+ is responsible for the good electrochemical performance of Na-doped Li3V2(PO4)3 cathode materials. [Copyright &y& Elsevier]

LiNiCoMnO cathode materials for the application of lithium ion batteries were synthesized by carbonate co-precipitation routine using different ammonium salt as a complexant. The structures and morphologies of the precursor [NiCoMn]CO and LiNiCoMnO were investigated through X-ray diffraction, scanning electron microscope, and transmission electron microscopy. The electrochemical properties of LiNiCoMnO were examined using charge/discharge cycling and cyclic voltammogram tests. The results revealed that the microscopic structures, particle size distribution, and the morphology properties of the precursor and electrochemical performance of LiNiCoMnO were primarily dependent on the complexant. Among all as-prepared LiNiCoMnO cathode materials, the sample prepared from NaCO-NHHCO routine using NHHCO as the complexant showed the smallest irreversible capacity of 19.5 mAh g and highest discharge capacity of 178.4 mAh g at the first cycle as well as stable cycling performance (98.7% of the initial capacity was retained after 50 cycles) at 0.1 C (20 mA g) in the voltage range of 2.5-4.4 V vs. Li/Li. Moreover, it delivered high discharge capacity of over 135 mAh g at 5 C (1,000 mA g). [ABSTRACT FROM AUTHOR]

Abstract: A carbon coated Li3V2(PO4)3 cathode material for lithium ion batteries was synthesized by a sol–gel method using V2O5, H2O2, NH4H2PO4, LiOH and citric acid as starting materials, and its physicochemical properties were investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), transmission electron microscope (TEM), and electrochemical methods. The sample prepared displays a monoclinic structure with a space group of P21/n, and its surface is covered with a rough and porous carbon layer. In the voltage range of 3.0–4.3V, the Li3V2(PO4)3 electrode displays a large reversible capacity, good rate capability and excellent cyclic stability at both 25 and 55°C. The largest reversible capacity of 130mAhg−1 was obtained at 0.1C and 55°C, nearly equivalent to the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133mAhg−1). It was found that the increase in total carbon content can improve the discharge performance of the Li3V2(PO4)3 electrode. In the voltage range of 3.0–4.8V, the extraction and reinsertion of the third lithium ion in the carbon coated Li3V2(PO4)3 host are almost reversible, exhibiting a reversible capacity of 177mAhg−1 and good cyclic performance. The reasons for the excellent electrochemical performance of the carbon coated Li3V2(PO4)3 cathode material were also discussed. [Copyright &y& Elsevier]

[Display omitted] • Na 4 P 2 O 7 was investigated as a new coating for Na 4 MnV(PO 4) 3 first in this manuscript. • Na 4 P 2 O 7 decorated Na 4 MnV(PO 4) 3 /C (NMVP-SP) was prepared by a facile sol–gel method. • The optimal NMVP-SP has much better electrochemical performance than Na 4 MnV(PO 4) 3 /C. • The optimal NMVP-SP owns higher capacity, better rate capability and cyclability. Na 4 P 2 O 7 decorated Na 4 MnV(PO 4) 3 /C (NMVP-SP) composites were prepared by a simple sol–gel method combined with high-temperature calcination in inert atmosphere. As a cathode material for sodium-ion batteries, the optimal NMVP-SP presents much higher capacity, better rate capability and cyclability than Na 4 MnV(PO 4) 3 /C, which is attributed to Na 4 P 2 O 7 coating that has good ionic conductivity and inhibits the manganese dissolution from Na 4 MnV(PO 4) 3 in electrolyte. [ABSTRACT FROM AUTHOR]

LiNi 1/3 Co 1/3 Mn 1/3 O 2 (LNCM) cathode material with high specific capacity has been received extensive attention in power batteries. However, the poor cycle performance and serious safety issues limit its application prospect. In this paper, the technology of surfactant-assisted hydrothermal synthesis combined with vanadium pentoxide (V 2 O 5) coating is applied in LNCM cathode material. Firstly, the Ni 1/3 Co 1/3 Mn 1/3 CO 3 precursor with good dispersibility and uniform morphology is synthesized by surfactant-assisted hydrothermal reaction. Secondly, the precursor is uniformly mixed with the lithium salt and ammonium metavanadate in the solution. Experienced drying and sintering processes, the LNCM cathode material uniformly coated with V 2 O 5 is achieved. The electrochemical test results show that the discharge specific capacity of LNCM cathode material coated with 2 wt% V 2 O 5 reaches 101.7 mAh ·g−1 at 10 C, and the capacity retention rate has 89.12% after 100 cycles at 0.5 C. Both of the novel synthetic method and the coating effect of V 2 O 5 reduce electrolyte side reaction on the LNCM cathode material, and accelerate Li+ diffusion rate, then further derive more desirable electrochemical properties. Image 108684 • The in-situ coating strategy by the soft template action of the surfactant has been designed to prepare V 2 O 5 coated LiNi 1/3 Co 1/3 Mn 1/3 O 2. • The V 2 O 5 coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 exhibits better rate and cycle performance. • The coating of V 2 O 5 cuts down the migration resistance of lithium ions at the electrolyte-electrode interface, and effectively improves the Li+ diffusion rate. [ABSTRACT FROM AUTHOR]

The full concentration-gradient Na 0.65 Ni 0.16 Co 0.14 Mn 0.7 O 2 (CG-NCM), in which the composition varies gradiently from core Na 0.65 Ni 0.01 Co 0.01 Mn 0.98 O 2 to shell Na 0.65 Ni 0.31 Co 0.27 Mn 0.42 O 2 , was prepared by a co-precipitation method plus high-temperature calcination, and was investigated by XRD, SEM, TEM and electrochemical measurements. Benefiting from the special concentration-gradient core-shell structure, CG-NCM possesses higher diffusion coefficients of Na+ and the consequently better rate capability and cyclability than concentration-constant Na 0.65 Ni 0.16 Co 0.14 Mn 0.7 O 2 (CC-NCM). Galvanostatically cycled at 30 mA g−1 between 1.5 and 4.1 V (vs Na+/Na), CC-NCM and CG-NCM have initial discharge capacities of 168.5 and 162.5 mA h g−1, and the capacity retentions of 11.5 % and 51.4 % after 100 cycles, respectively. CG-NCM presents high initial discharge capacities of 144.5, 138.2 and 121.8 mA h g−1 at 75, 300 and 750 mA g−1, respectively, and exhibits capacity retentions of 70.6 %, 73.2 % and 76.9 % after 100 cycles, respectively. However, CC-NCM shows initial discharge capacities of 149.5, 136.5 and 107.3 mA h g−1 at 75, 300 and 750 mA g−1, respectively, and the matching capacity retentions are as low as 49.8 %, 52.3 % and 53.9 %, respectively. The results indicate that the construction of concentration-gradient oxide electrode materials is an effective strategy for improvement of the electrochemical performance of oxides cathodes. • Concentration-gradient Ni 0.16 Co 0.14 Mn 0.7 (OH) 2 (CG-NCMH) prepared by co-precipitation. • Full concentration-gradient Na 0.65 Ni 0.16 Co 0.14 Mn 0.7 O 2 (CG-NCM) is target product. • CG-NCM was obtained by high-temperature sintering mixture of CH 3 COONa and CG-NCMH. • CG-NCM is of Na 0.65 Ni 0.01 Co 0.01 Mn 0.98 O 2 core and Na 0.65 Ni 0.31 Co 0.27 Mn 0.42 O 2 shell. • CG-NCM is superior to concentration-constant NCM in electrochemical performance. [ABSTRACT FROM AUTHOR]

It is still a great challenge to improve the diffusion dynamics of Na + throughout the Na 3 V 2 (PO 4 ) 3 , one of the most promising cathodes for sodium ion batteries. In this work, we present a facile doping strategy to tackle this problem by co-doping the Na + with K + and Ca 2+ . Na 3-3x K x Ca x V 2 (PO 4 ) 3 /C (x = 0, 0.05, 0.07 and 0.09) composites are prepared by a sol-gel method combined with freeze-drying and high-temperature calcination processes, and the composites are characterized by XRD, XPS, SEM, TEM and electrochemical measurements. The results indicate that co-substitution of K + and Ca 2+ for Na in Na 3 V 2 (PO 4 ) 3 enlarges the cell volume of Na 3 V 2 (PO 4 ) 3 and is beneficial for improving electrochemical performance. All co-doped Na 3 V 2 (PO 4 ) 3 /C composites have better electrochemical performance than the pristine Na 3 V 2 (PO 4 ) 3 /C composite. The optimal doping compositions are found to be Na 2.79 K 0.07 Ca 0.07 V 2 (PO 4 ) 3 /C, displaying reversible capacities of 110.2, 92.7 and 83.6 mAh·g -1 at the current densities of 0.1, 1, and 10C (1180 mA·g -1 ), respectively, in the voltage range of 2.5–4.0 V. The Na 2.79 K 0.07 Ca 0.07 V 2 (PO 4 ) 3 /C exhibits capacity retentions of 91% at 1C after 50 cycles and 83% at 10C after 150 cycles, while Na 3 V 2 (PO 4 ) 3 /C composite displays capacity retentions of 88.5% at 1C after 50 cycles and 26.5% at 10C after 150 cycles, respectively. The improved electrochemical performance of co-doped Na 3 V 2 (PO 4 ) 3 /C is ascribed to enhanced Na + diffusion after the co-substitution of K + and Ca 2+ for Na in Na 3 V 2 (PO 4 ) 3 /C. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new cobalt-free Ni-rich cathode material LiNi 0.9 Fe 0.05 Al 0.05 O 2 is reported first. • LiNi 0.9 Fe 0.05 Al 0.05 O 2 (NFA) was easily prepared by modified rheological phase method. • Electrochemical performance of NFA is comparable to other Ni-based ternary materials. • NFA has high discharge capacity of 195 mAh/g, better rate capability and cyclability. To develop high-energy density and inexpensive LIBs, it is exigent to hunt for inexpensive cathode materials with high capacity and operating voltage. Herein, cobalt-free Ni-based ternary material LiNi 0.9 Fe 0.05 Al 0.05 O 2 was prepared by a modified rheological phase reaction method. LiNi 0.9 Fe 0.05 Al 0.05 O 2 exhibits high discharge capacity of 195 mAh g−1 at 0.1C, better rate capability and cyclability. LiNi 0.9 Fe 0.05 Al 0.05 O 2 is competitive among Ni-based cathode materials based on the comprehensive consideration of cost and electrochemical performance. [ABSTRACT FROM AUTHOR]

LaF 3 -coated LiMn 2 O 4 composites were prepared by a simple co-precipitation method using pristine LiMn 2 O 4 , La(NO 3 ) 3 ·6H 2 O, NH 4 F and polyvinyl pyrrolidone (PVP) as raw materials and the physical and electrochemical properties of the composites were investigated. The results indicate that LaF 3 coating is beneficial to improving the electrochemical performance of LiMn 2 O 4 used as a cathode material for aqueous rechargeable lithium battery (ARLB) in 1 mol/L LiNO 3 solution. The optimal LaF 3 -coated LiMn 2 O 4 composite (L-3-LMO) containing 3 wt% LaF 3 exhibits much improved electrochemical performance as compared with the pristine LiMn 2 O 4 . When galvanostatically charged and discharged at 2 C (296 mA g −1 ), L-3-LMO displays initial discharge capacity of 118.4 mAh g −1 and capacity retention of 99.7% after 50 cycles, while the pristine LiMn 2 O 4 presents initial discharge capacity of 109.2 mAh g −1 and capacity retention of 89.4%. Even at high current density of 10 C, L-3-LMO delivers discharge capacity of 109.5 mAh g −1 and the capacity remains 107.9 mAh g −1 after 100 cycles, while the highest discharge capacity of pristine LiMn 2 O 4 is only 101.6 mAh g −1 and the capacity is as low as 86.3 mAh g −1 after 100 cycles. The effects of LaF 3 coating on Li + diffusion coefficient, dissolution of manganese ion of electroactive materials are also investigated. [ABSTRACT FROM AUTHOR]

Abstract: LiV3O8–Polypyrrole (LiV3O8–PPy) composite has been chemically synthesized by an oxidative polymerization of pyrrole monomer on the surface of LiV3O8 using ferric chloride as oxidizing agent. The electrochemical properties of LiV3O8–PPy composite were systematically investigated using a variety of electrochemical methods. The LiV3O8–PPy composite electrode exhibited better cycling behavior and superior rate capability as compared with the bare LiV3O8 electrode. Cyclic voltammetry corroborated the galvanostatic cycling tests, with the composite cathode material showing better reversibility than bare material. Finally, fitting the impedance results to an equivalent circuit indicated that the enhanced electrochemical performances of LiV3O8–PPy composite resulted from a facilitated kinetics of interfacial charge transfer in the presence of PPy. [Copyright &y& Elsevier]

LiNi 0.6 Mn 0.2 Co 0.2 O 2 is considered as a promising Ni-rich layered cathode material of lithium-ion batteries due to low cost and high capacity. However, it is generally prepared by complicated precursor methods. In this work, LiNi 0.6 Mn 0.2 Co 0.2 O 2 is synthesized by a solid-state method with manganese acetate as manganese source and an effective mixing way. The as-prepared samples are characterized by XRD, FESEM, XPS and electrochemical techniques. The results show that the synthesized LiNi 0.6 Mn 0.2 Co 0.2 O 2 cathode materials have an α-NaFeO 2 type structure with insignificant cation mixing, octahedral single crystal and quasi sphere morphology, smaller particle size and good dispersion, so that it displays an initial discharge capacity of 163.6 mAh g−1 with a coulombic efficiency of 85.6% at 0.1C, a capacity retention of 99.1% after 100 cycles at 0.5C and an excellent rate performance, and also an initial discharge capacity of 177.3 mAh g−1 with capacity retention of 94.6% after 155 cycles at 55 °C. • Octahedral single crystal and quasi sphere of LiNi 0.6 Mn 0.2 Co 0.2 O 2 is synthesized by solid-state reaction. • LiNi 0.6 Mn 0.2 Co 0.2 O 2 has high crystallinity layered structure and insignificant cation mixing. • LiNi 0.6 Mn 0.2 Co 0.2 O 2 shows excellent coulombic efficiency, cycle stability and rate performance. [ABSTRACT FROM AUTHOR]

Rb-doped K 3-x Rb x V 2 (PO 4) 3 /C (x = 0, 0.03, 0.05 and 0.07) composites for high-voltage cathode have been synthesized via a facile sol-gel process. The as-prepared materials have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical tests. SEM and TEM show that the Rb-doped K 3 V 2 (PO 4) 3 /C composites exhibit similar morphology and particle sizes to the undoped one. The electrochemical tests demonstrate that the Rb-doped composites with varied Rb contents deliver better electrochemical performance than the pristine K 3 V 2 (PO 4) 3 /C, where K 2.95 Rb 0.05 V 2 (PO 4) 3 /C performs the best. In the voltage range of 2.5–4.6 V (vs. K+/K) at 20 mA g−1, K 3 V 2 (PO 4) 3 /C and K 2.95 Rb 0.05 V 2 (PO 4) 3 /C display initial discharge capacities of 41.1 and 55.7 mAh g−1, respectively. The corresponding discharge capacities decrease to 32.1 and 52.6 mAh g−1 after 50 cycles, respectively. At a current density as high as 200 mA g−1, K 2.95 Rb 0.05 V 2 (PO 4) 3 /C still presents higher initial discharge capacity of 34.5 mAh g−1 with a capacity retention of 95.4% after 100 cycles, while K 3 V 2 (PO 4) 3 /C only shows the initial discharge of 21.1 mAh g−1 with the capacity retention of 85.7%. The improvement in electrochemical performance of Rb-doped K 3 V 2 (PO 4) 3 /C is attributed to the doping of Rb into K sites of K 3 V 2 (PO 4) 3 and this doping can increase the K+ diffusion coefficients in electroactive particles. The results imply that replacement of K+ by larger cations is also helpful to improve the electrochemical performance of other K-containing electrode materials for potassium-ion batteries. Image 1 • Carbon-coated K 3-x Rb x V 2 (PO 4) 3 cathode composites were prepared by a sol-gel route. • These Rb-doped composites have superior electrochemical performance to K 3 V 2 (PO 4) 3 /C. • K 2.95 Rb 0.05 V 2 (PO 4) 3 /C has the best electrochemical performance among doped samples. • K 2.95 Rb 0.05 V 2 (PO 4) 3 /C has 1.5 times higher capacity than K 3 V 2 (PO 4) 3 at 200 mA/g. • D K of K 2.95 Rb 0.05 V 2 (PO 4) 3 /C is over 10 times higher than that of K 3 V 2 (PO 4) 3 /C. [ABSTRACT FROM AUTHOR]