Sn-doped Li-rich layered oxides of Li1.2Mn0.54-xNi0.13Co0.13SnxO2 have been synthesized via a sol-gel method, and their microstructure and electrochemical performance have been studied. The addition of Sn4+ ions has no distinct influence on the crystal structure of the materials. After doped with an appropriate amount of Sn4+, the electrochemical performance of Li1.2Mn0.54-xNi0.13Co0.13SnxO2 cathode materials is significantly enhanced. The optimal electrochemical performance is obtained at x = 0.01. The Li1.2Mn0.53Ni0.13Co0.13Sn0.01O2 electrode delivers a high initial discharge capacity of 268.9 mAh g?1 with an initial coulombic efficiency of 76.5% and a reversible capacity of 199.8 mAh g?1 at 0.1 C with capacity retention of 75.2% after 100 cycles. In addition, the Li1.2Mn0.53Ni0.13Co0.13Sn0.01O2 electrode exhibits the superior rate capability with discharge capacities of 239.8, 198.6, 164.4, 133.4, and 88.8 mAh g?1 at 0.2, 0.5, 1, 2, and 5 C, respectively, which are much higher than those of Li1.2Mn0.54Ni0.13Co0.13O2 (196.2, 153.5, 117.5, 92.7, and 43.8 mAh g?1 at 0.2, 0.5, 1, 2, and 5 C, respectively). The substitution of Sn4+ for Mn4+ enlarges the Li+ diffusion channels due to its larger ionic radius compared to Mn4+ and enhances the structural stability of Li-rich oxides, leading to the improved electrochemical performance in the Sn-doped Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials. 相似文献
As a promising Li-ion battery cathode active material, lithium-rich manganese-based layer-structured oxides suffer from inferior cycle performance and poor rate capability. Herein, Nb-doped Li1.2Mn0.54Ni0.13Co0.13O2 is prepared by a sol-gel method, and the effects of Nb doping on its electrochemical performance are investigated. It is concluded that the Nb-doped Li1.2Mn0.54Ni0.13Co0.13O2, has a good layered structure along c-axis independent on the amount of Nb dopant and little cationic mixing. Nb doping for Li1.2Mn0.54Ni0.13Co0.13O2 has no obvious influence on its morphology. It is found that Nb doping can enhance the electrochemical activity of Li1.2Mn0.54Ni0.13Co0.13O2, such as improved rate performance and cycle performance under high rate conditions. Li1.2Mn0.54Ni0.13Co0.13O2 doped with 0.015 Nb shows the best cycle performance under the high rate with the capacity maintenance of 95.4% after 100 cycles under 5 C rate, which is higher than that of the undoped one by 10.5%.
A porous, hollow, microspherical composite of Li2MnO3 and LiMn1/3Co1/3Ni1/3O2 (composition: Li1.2Mn0.53Ni0.13Co0.13O2) was prepared using hollow MnO2 as the sacrificial template. The resulting composite was found to be mesoporous; its pores were about 20 nm in diameter. It also delivered a reversible discharge capacity value of 220 mAh g?1 at a specific current of 25 mA g?1 with excellent cycling stability and a high rate capability. A discharge capacity of 100 mAh g?1 was obtained for this composite at a specific current of 1000 mA g?1. The high rate capability of this hollow microspherical composite can be attributed to its porous nature.
LiNi1-x-yCoxMnyO2 (NCM) with excessive lithium is known to exhibit high rate capability and charge–discharge cycling durability. However, the practical usage of NCM is difficult, because the positive electrode slurry is unstable and battery cells swell due to the alkaline residual lithium compound generated on the surface of NCM particles. To reduce the residual lithium compound, ammonium metatungstate (AMT) added to NCM is studied, and the effect is investigated by scanning electron microscopy, aberration-corrected scanning transmission electron microscopy, X-ray diffractometry, synchrotron X-ray diffractometry, and several electrochemical measurements. It is found that the AMT modification reduces the amount of alkaline residual lithium compound and improves the rate capability due to the ~1-nm-thick W-rich layer generated on the NCM surface.
Layered Li-rich transition metal oxides are considered among the most promising cathode materials for high energy density lithium-ion batteries. It was studied how the method and conditions of synthesis of Li-rich oxides Li1.2Mn0.54Ni0.13Co0.13O2 affect their electrochemical properties. Coprecipitation methods and modified Pechini process were used. It was shown that it is necessary to carefully choose the synthesis conditions when using the modified Pechini method because of their significant effect on the morphology of Li-rich oxides. Samples were obtained with high electrochemical characteristics: capacity discharge of 260–270 mAh/g (16 mA/g) and 60–70 mAh/g (988 mA/g) within the voltage range of 2.5–4.8 V. 相似文献
Layered transition metal oxide LiNixCoyMnzO2 cathode materials with different Li amount were successfully synthesized via co-precipitation method. Monodispersed Li[Ni0.5Co0.2Mn0.3]O2 and Li-rich Li1.1[Ni0.5Co0.2Mn0.3]O2 spherical agglomeration consisted of secondary particles, which is favorable for the higher tap-density of materials, can be easily obtained. The pouch-typed cells with obtained materials were assembled to investigate electrochemical performance at level of full-cell. The results show that the assembled pouch-typed full-cells with Li-rich sample present higher capacity, better rate capability and cycle life. 相似文献
Nano-structured spinel Li2Mn4O9 powder was prepared via a combustion method with hydrated lithium acetate (LiAc·2H2O), manganese acetate (MnAc2·4H2O), and oxalic acid (C2H2O4·2H2O) as raw materials, followed by calcination of the precursor at 300 °C. The sample was characterized by X-ray diffraction,
scanning electron microscope, and energy-dispersive X-ray spectroscopy techniques. Electrochemical performance of the nano-Li2Mn4O9 material was studied using cyclic voltammetry, ac impedance, and galvanostatic charge/discharge methods in 2 mol L−1 LiNO3 aqueous electrolyte. The results indicated that the nano-Li2Mn4O9 material exhibited excellent electrochemical performance in terms of specific capacity, cycle life, and charge/discharge
stability, as evidenced by the charge/discharge results. For example, specific capacitance of the single Li2Mn4O9 electrode reached 407 F g−1 at the scan rates of 5 mV s−1. The capacitor, which is composed of activated carbon negative electrode and Li2Mn4O9 positive electrode, also exhibits an excellent cycling performance in potential range of 0–1.6 V and keeps over 98% of the
maximum capacitance even after 4,000 cycles. 相似文献
Vanadium pentoxide (V2O5) nanofibers (NFs) with a thin carbon layer of 3–5 nm, which wrapped on V2O5 nanoparticles, and integrated multiwalled carbon nanotubes (MWCNTs) have been fabricated via simple electrospinning followed by carbonization process and post-sintering treatment. The obtained composite displays a NF structure with V2O5 nanoparticles connected to each other, and good electrochemical performance: delivering initial capacity of 320 mAh g?1 (between 2.0 and 4.0 V vs. Li/Li+), good cycling stability (223 mAh g?1 after 50 cycles), and good rate performance (~?150 mAh g?1 at 2 A g?1). This can attribute to the carbon wrapped on the V2O5 nanoparticles which can not only enhance the electric conductivity to decrease the impendence of the cathode materials but also maintain the structural stability to protect the nanostructure from the corruption of electrolyte and the strain stress due to the Li-ion intercalation/deintercalation during the charge/discharge process. And, the added MWCNTs play the role of framework of the unique V2O5 coated by carbon layer and composited with MWCNT NFs (V2O5/C@MWCNT NFs) to ensure the material is more stable. 相似文献
LiNi0.8Co0.2O2 and Ca-doped LiNi0.8Co0.2O2 cathode materials have been synthesized via a rheological phase reaction method. X-ray diffraction studies show that the
Ca-doped material, and also the discharged electrode, maintains a hexagonal structure even when cycled in the range of 3.0–4.35 V
(vs Li+/Li) after 100 cycles. Electrochemical tests show that Ca doping significantly improves the reversible capacity and cyclability.
The improvement is attributed to the formation of defects caused by the partial occupancy of Ca2+ ions in lithium lattice sites, which reduce the resistance and thus improve the electrochemical properties. 相似文献
A series of the mixed transition metal compounds, Li[(Ni1/3Co1/3Mn1/3)1–x-yAlxBy]O2-zFz (x = 0, 0.02, y = 0, 0.02, z = 0, 0.02), were synthesized via coprecipitation followed by a high-temperature heat-treatment. XRD patterns revealed that
this material has a typical α-NaFeO2 type layered structure with R3-m space group. Rietveld refinement explained that cation mixing within the Li(Ni1/3Co1/3Mn1/3)O2 could be absolutely diminished by Al-doping. Al, B and F doped compounds showed both improved physical and electrochemical
properties, high tap-density, and delivered a reversible capacity of 190 mAh/g with excellent capacity retention even when
the electrodes were cycled between 3.0 and 4.7 V. 相似文献
Spinel LiNi0.5Mn1.5O4 cathode material is a promising candidate for next-generation rechargeable lithium-ion batteries. In this work, BiFeO3-coated LiNi0.5Mn1.5O4 materials were prepared via a wet chemical method and the structure, morphology, and electrochemical performance of the materials were studied. The coating of BiFeO3 has no significant impact on the crystal structure of LiNi0.5Mn1.5O4. All BiFeO3-coated LiNi0.5Mn1.5O4 materials exhibit cubic spinel structure with space group of Fd3m. Thin BiFeO3 layers were successfully coated on the surface of LiNi0.5Mn1.5O4 particles. The coating of 1.0 wt% BiFeO3 on the surface of LiNi0.5Mn1.5O4 exhibits a considerable enhancement in specific capacity, cyclic stability, and rate performance. The initial discharge capacity of 118.5 mAh g?1 is obtained for 1.0 wt% BiFeO3-coated LiNi0.5Mn1.5O4 with very high capacity retention of 89.11% at 0.1 C after 100 cycles. Meanwhile, 1.0 wt% BiFeO3-coated LiNi0.5Mn1.5O4 electrode shows excellent rate performance with discharge capacities of 117.5, 110.2, 85.8, and 74.8 mAh g?1 at 1, 2, 5, and 10 C, respectively, which is higher than that of LiNi0.5Mn1.5O4 (97.3, 90, 77.5, and 60.9 mAh g?1, respectively). The surface coating of BiFeO3 effectively decreases charge transfer resistance and inhibits side reactions between active materials and electrolyte and thus induces the improved electrochemical performance of LiNi0.5Mn1.5O4 materials. 相似文献
LiNi0.5Mn1.5O4 cathode materials were successfully prepared by sol–gel method with two different Li sources. The effect of both lithium
acetate and lithium hydroxide on physical and electrochemical performances of LiNi0.5Mn1.5O4 was investigated by scanning electron microscopy, Fourier transform infrared, X-ray diffraction, and electrochemical method.
The structure of both samples is confirmed as typical cubic spinel with Fd3m space group, whichever lithium salt is adopted. The grain size of LiNi0.5Mn1.5O4 powder and its electrochemical behaviors are strongly affected by Li sources. For the samples prepared with lithium acetate,
more spinel nucleation should form during the precalcination process, which was stimulated by the heat released from the combustion
of extra organic acetate group. Therefore, the particle size of the obtained powder presents smaller average and wider distribution,
which facilitates the initial discharge capacity and deteriorates the cycling performance. More seriously, there exists cation
replacement of Li sites by transition metal elements, which causes channel block for Li ion transference and deteriorates
the rate capability. The compound obtained with lithium hydroxide exhibits better electrochemical responses in terms of both
cycling and rate properties due to higher crystallinity, moderate particle size, narrow size distribution and lower transition
cation substitute content. 相似文献
The Li(Ni0.33Co0.33Mn0.33)O2 (LNCMO) cathode material is prepared by poly(vinyl pyrrolidone) (PVP)-assisted sol-gel/hydrothermal and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly (ethylene glycol) (Pluronic-P123)-assisted hydrothermal methods. The compound prepared by PVP-assisted hydrothermal method shows a comparatively higher electrical conductivity of ~2?×?10?5 S cm?1 and exhibits a discharge capacity of 152 mAh g?1 in the voltage range of 2.5 to 4.4 V, for a C-rate of 0.2 C, whereas the compounds prepared by P123-assisted hydrothermal method and PVP-assisted sol-gel method show a total electrical conductivity in the order of 10?6 S cm?1 and result in poor electrochemical performance. The structural and electrical properties of LNCMO (active material) and its electrochemical performance are correlated. The difference in percentage of ionic and electronic conductivity contribution to the total electrical conductivity is compared by transference number studies. The cation disorder is found to be the limiting factor for the lithium ion diffusion as determined from ionic conductivity values. 相似文献
LiMn2O4 is one of the most promising cathode materials due to its high abundance and low cost. However, the practical application of LiMn2O4 is greatly limited owing to its low volumetric energy density. Therefore, increasing its energy density is an urgent problem to be resolved. Herein, using the simple and mass production preferred solid-state reaction, surficial Nb-doped LiMn2O4 composed of the truncated octahedral or spherical-like primary particles are successfully synthesized. Auger electron spectroscopy (AES) and X-ray diffraction (XRD) characterizations confirm that most of Nb5+ enrich in the surficial layer of the particles to form a LiMn2-xNbxO4 phase. This kind of doping can increase the specific discharge capacity of LiMn2O4 materials. Contrast with the pristine LiMn2O4, the discharge capacity of LiMn1.99Nb0.01O4-based 18650R-type battery increases from 1497 to 1705 mAh with the volumetric energy density increasing by ~?13.9%, benefiting from the joint increments of the specific discharge capacity from 119.5 to 123.7 mAh g?1 and the compacted density from 2.81 to 3.10 g cm?3. Furthermore, the capacity retention after 500 cycles at 1 C (1500 mA) is also improved by 17.1%.
LiNi0.80Co0.15Al0.05O2 (NCA) is explored to be applied in a hybrid Li+/Na+ battery for the first time. The cell is constructed with NCA as the positive electrode, sodium metal as the negative electrode, and 1 M NaClO4 solution as the electrolyte. It is found that during electrochemical cycling both Na+ and Li+ ions are reversibly intercalated into/de-intercalated from NCA crystal lattice. The detailed electrochemical process is systematically investigated by inductively coupled plasma-optical emission spectrometry, ex situ X-ray diffraction, scanning electron microscopy, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy. The NCA cathode can deliver initially a high capacity up to 174 mAh g?1 and 95% coulombic efficiency under 0.1 C (1 C?=?120 mA g?1) current rate between 1.5–4.1 V. It also shows excellent rate capability that reaches 92 mAh g?1 at 10 C. Furthermore, this hybrid battery displays superior long-term cycle life with a capacity retention of 81% after 300 cycles in the voltage range from 2.0 to 4.0 V, offering a promising application in energy storage. 相似文献
In this study, the effect of the sol-gel starting materials with different particle sizes on the sol-gel-synthesized spinel Li4Ti5O12 (LTO) was systematically investigated. The physical and electrochemical properties of the synthesized materials were characterized by X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller-specific surface area analyses, galvanostatic charge/discharge tests, cyclic voltammetry, and electrochemical impedance spectroscopy. It was found that the initial particle size of sol-gel starting material played a crucial role on the properties of as-prepared LTOs. The LTO synthesized with the relatively finer particle size of starting materials possessed relatively smaller particle size and larger specific surface area and therefore resulted in the superior electrochemical properties. The initial discharge capacity of the as-prepared LTO exhibited 168.2, 150.6, and 142.7 mAh g?1 at current densities of 1, 5, and 10 C, respectively, and up to 95, 95, and 90 % of the corresponding initial discharge capacity was retained after 50 cycles. 相似文献
Zn-doped LiNi0.8Co0.2O2 exhibits impressive electrochemical performance but suffers limited cycling stability due to the relative large size of irregular and bare particle which is prepared by conventional solid-state method usually requiring high calcination temperature and prolonged calcination time. Here, submicron LiNi0.8Co0.15Zn0.05O2 as cathode material for lithium-ion batteries is synthesized by a facile sol-gel method, which followed by coating Al2O3 layer of about 15 nm to enhance its electrochemistry performance. The as-prepared Al2O3-coated LiNi0.8Co0.15Zn0.05O2 cathode delivers a highly reversible capacity of 182 mA h g?1 and 94% capacity retention after 100 cycles at a current rate of 0.5 C, which is much superior to that of bare LiNi0.8Co0.15Zn0.05O2 cathode. The enhanced electrochemistry performance can be attributed to the Al2O3-coated protective layer, which prevents the direct contact between the LiNi0.8Co0.15Zn0.05O2 and electrolyte. The escalating trend of Li-ion diffusion coefficient estimated form electrochemical impedance spectroscopic (EIS) also indicate the enhanced structural stability of Al2O3-coated LiNi0.8Co0.15Zn0.05O2, which rationally illuminates the protection mechanism of the Al2O3-coated layer. 相似文献
Spherical Li[Ni1/3Co1/3Mn1/3]O2 cathode materials with different microstructure have been prepared by a continuous carbonate co-precipitation method using
LiOH⋅H2O, Li2CO3, CH3COOLi⋅2H2O and LiNO3 as lithium source. The effects of Li source on the physical and electrochemical properties of Li[Ni1/3Co1/3Mn1/3]O2 are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. The results
show that the morphology, tap density and high rate cycling performance of Li[Ni1/3Co1/3Mn1/3]O2 spherical particles are strongly affected by Li source. Among the four Li sources used in this study, LiOH⋅H2O is beneficial to enhance the tap density of Li[Ni1/3Co1/3Mn1/3]O2, and the tap density of as-prepared sample reaches 2.32 g cm−3. Meanwhile, Li2CO3 is preferable when preparing the Li[Ni1/3Co1/3Mn1/3]O2 with high rate cycling performance, upon extended cycling at 1 and 5C rates, 97.5% and 92% of the initial discharge capacity
can be maintained after 100 cycles. 相似文献
Natural graphite treated by mechanical activation can be directly applied to the preparation of Li3V2(PO4)3. The carbon-coated Li3V2(PO4)3 with monoclinic structure was successfully synthesized by using natural graphite as carbon source and reducing agent. The amount of activated graphite is optimized by X-ray diffraction, scanning electron microscope, transmission electron microscope, Raman spectrum, galvanostatic charge/discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy tests. Our results show that Li3V2(PO4)3 (LVP)-10G exhibits the highest initial discharge capacity of 189 mAh g?1 at 0.1 C and 162.9 mAh g?1 at 1 C in the voltage range of 3.0–4.8 V. Therefore, natural graphite is a promising carbon source for LVP cathode material in lithium ion batteries. 相似文献