SnO2-coated LiCoO2 cathode material for high-voltage applications in lithium-ion batteries (original) (raw)
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Improvement of electrochemical stability of LiCoO< sub> 2 cathode by a nano-crystalline coating
Journal of power sources, 2004
A nano-crystalline MgO coating was formed on the surface of LiCoO 2 particle via a sol-gel method. MgO coating can improve the cycling stability of LiCoO 2 significantly. After the 40th cycle a discharge capacity of more than 120 mAh/g was remained for 1 mol% MgO-coated LiCoO 2 , while only 13 mAh/g for pristine LiCoO 2 when both charged up to 4.7 V. During heat treatment and charge/discharge process, Mg 2+ in coatings will diffuse into LiO 2 -layers of LiCoO 2 , which does not cause any detectable shift in X-ray diffractometer (XRD) peak positions, but does impact the XRD peak intensity due to the aberrance of (0 0 3) plane. Mg 2+ ions existing in LiO 2 -layers will stabilize the lattice structure of LiCoO 2 , hence improve the cycling performance of LiCoO 2 cathode. More MgO coating on LiCoO 2 is detrimental to the electrochemical properties of LiCoO 2 cathode, probably due to the electrochemical inactivity of MgO particles.
Electrochimica Acta, 2018
Herein, the influence of the dopant concentration and the effect of varying the amount of the carbon coating for the electrochemical properties of Co-doped SnO 2 as lithium-ion anode material are presented. Pure SnO 2 and three different doping ratios of Co-doped SnO 2 (Sn 0.95 Co 0.05 O 2 , Sn 0.90 Co 0.10 O 2 , and Sn 0.85 Co 0.15 O 2) were synthesized and characterized regarding their structure, morphology, and electrochemical behavior. The results reveal that the Co content has a significant impact on the specific capacity and cycling stability, rendering Sn 0.90 Co 0.10 O 2 as the sample with the best electrochemical performance among these three dopant ratios. The impact of the carbon coating content was explored for two different concentrations, i.e., 16 wt% (Sn 0.90 Co 0.10 O 2-C16%) and 50 wt% (Sn 0.90 Co 0.10 O 2-C50%), reflecting that the carbon coating as such and concerning the eventual amount has a significant influence on the cycling stability, coulombic efficiency, and rate capability.
Journal of Power Sources, 2008
Lithium-ion battery a b s t r a c t LiCoO 2 particles were coated with various wt.% of lanthanum aluminum garnets (3LaAlO 3 :Al 2 O 3 ) by an in situ sol-gel process, followed by calcination at 1123 K for 12 h in air. X-ray diffraction (XRD) patterns confirmed the formation of a 3LaAlO 3 :Al 2 O 3 compound and the in situ sol-gel process synthesized 3LaAlO 3 :Al 2 O 3 -coated LiCoO 2 was a single-phase hexagonal ␣-NaFeO 2 -type structure of the core material without any modification. Scanning electron microscope (SEM) images revealed a modification of the surface of the cathode particles. Transmission electron microscope (TEM) images exposed that the surface of the core material was coated with a uniform compact layer of 3LaAlO 3 :Al 2 O 3 , which had an average thickness of 40 nm. Galvanostatic cycling studies demonstrated that the 1.0 wt.% 3LaAlO 3 :Al 2 O 3 -coated LiCoO 2 cathode showed excellent cycle stability of 182 cycles, which was much higher than the 38 cycles sustained by the pristine LiCoO 2 cathode material when it was charged at 4.4 V.
Journal of The Electrochemical Society, 2010
Ultrathin atomic layer deposition ͑ALD͒ coatings enhance the performance of lithium-ion batteries ͑LIBs͒. Previous studies have demonstrated that LiCoO 2 cathode powders coated with metal oxides with thicknesses of ϳ100 to 1000 Å grown using wet chemical techniques improved LIB performance. In this study, LiCoO 2 powders were coated with conformal Al 2 O 3 ALD films with thicknesses of only ϳ3 to 4 Å established using two ALD cycles. The coated LiCoO 2 powders exhibited a capacity retention of 89% after 120 charge-discharge cycles in the 3.3-4.5 V ͑vs Li/Li + ͒ range. In contrast, the bare LiCoO 2 powders displayed only a 45% capacity retention. Al 2 O 3 ALD films coated directly on the composite electrode also produced improved capacity retention. This dramatic improvement may result from the ultrathin Al 2 O 3 ALD film acting to minimize Co dissolution or reduce surface electrolyte reactions. Similar experiments with ultrathin ZnO ALD films did not display enhanced performance.
Electrochimica Acta, 2017
Careful modulation of surficial and interfacial properties of electrode materials is a critical factor for determining overall electrochemical characteristics. Recent studies have indicated that metal oxide nanocoating layer (such as titanium (IV) oxide (TiO 2)) on metal oxide anodes (such as tin (IV) oxide (SnO 2)) exhibited superior electrochemical properties, but fundamental research on the effect and role of TiO 2 layer thickness has been limited. Here we have successfully conducted in-depth study on how the thickness of TiO 2 overlayer on SnO 2 can have significant influence in the overall parameters of electrochemistry. It is revealed that TiO 2 overlayer with 12 nm shows good cycle retention (75.8%) even after 80 cycles and retains capacity of 438.3 mAh g À1 even at high current density (5000 mA g À1). Surprisingly, it was further discovered that TiO 2 layer not only alleviates the volume expansion but also helps to facilitate Li ion transport compared with SnO 2. The improvements in both ionic and electrical conductivity of TiO 2 layer are main factors in better cycle retention and rate capabilities. Finally, in situ transmission electron microscopy analysis was adopted to observe the growth dynamics of solid electrolyte interphase layer on TiO 2 @SnO 2 , which demonstrates that TiO 2 overlayer results in homogeneous and thinner interphase layer compared with SnO 2 NTs.
Improved electrochemical performance of LiCoO 2 surface treated with Li 4Ti 5O 12
Journal of Power Sources, 2007
The LiCoO 2 cathode material was surface treated with the Li 4 Ti 5 O 12 particles by a simple mechano-thermal process, followed by calcination at 723 K for 10 h in air. The X-ray diffractometer (XRD) patterns showed a single-phase hexagonal ␣-NaFeO 2 -type structure for the surface treated LiCoO 2 without any structure modification and new phase formation. The transmission electron microscope (TEM) image exposed a uniform layer Li 4 Ti 5 O 12 particulate over the surface of the LiCoO 2 particles that had an average thickness of ∼20 nm. The electrochemical performance studies indicated that a 1.0 wt.% Li 4 Ti 5 O 12 coated LiCoO 2 sample heated at 723 K for 10 h in air exhibited an initial discharge capacity of 171 mAh g −1 and excellent cycle stability of about 148 cycles for a cut-off voltage of 80% when cycled between 2.75 and 4.40 V. The differential capacity plots for LiCoO 2 surface treated with Li 4 Ti 5 O 12 confirmed that the enhanced performance can be attributed to slower impedance growth and increased resistance to Co dissolution into the electrolyte during the (de)intercalation processes.
LiCoO 2 thin film cathodes grown by sol–gel method
Journal of Electroceramics, 2009
Lithiated layered transitional metal oxide materials of the LiMO2 type and especially LiCoO2 presents interesting specific properties as high energy density, long cycle life and constant discharging properties in a wide range of working conditions as well as a good safety. These properties made these materials excellent candidates as active compounds for high capacity cathode materials for rechargeable lithium batteries. LiCoO2 is the most common lithium storage material for lithium rechargeable batteries, used widely to power portable electronic devices. Operation of lithium rechargeable batteries is dependent on reversible lithium insertion and extraction processes into and from the host materials of lithium storage. In this study, LiCoO2 thin films were prepared by the sol–gel spin coating technique using metal acetate and citric acid as starting materials. Citric acid acts as a chelating agent, which promotes the preliminary reaction between lithium and cobalt and suppresses the precipitation of acetates. The sol–gel method is well known as one of promising thin-film preparation methods, which has good advantages such as low fabrication cost, relatively easy stoichiometry control, high deposition rate and also known as a low-temperature synthesis method for various ceramics. In addition, the crystal phases involved in the thin film can also be controlled by changing the chemical compositions of the sol. The crystallinity, microstructure and electrochemical properties of final films are also studied by XRD, SEM, AFM and galvanostatic charge/discharge cycling test. Films heat-treated under appropriate conditions exhibit high capacity and good crystallinity so those films are considered to be candidates as cathodes for thin-film micro batteries.
Enhanced electrochemical performance and thermal stability of La 2O 3-coated LiCoO 2
Electrochimica Acta, 2006
An enhanced electrochemical performance LiCoO 2 cathode was synthesized by coating with various wt.% of La 2 O 3 to the LiCoO 2 particle surfaces by a polymeric method, followed by calcination at 923 K for 4 h in air. The surface-coated materials were characterized by XRD, TGA, SEM, TEM, BET and XPS/ESCA techniques. XRD patterns of La 2 O 3 -coated LiCoO 2 revealed that the coating did not affect the crystal structure, ␣-NaFeO 2 , of the cathode material compared to pristine LiCoO 2 . TEM images showed a compact coating layer on the surface of the core material that had an average thickness of about ∼15 nm. XPS data illustrated that the presence of two different environmental O 1s ions corresponds to the surface-coated La 2 O 3 and core material. The electrochemical performance of the coated materials by galvanostatic cycling studies suggest that 2.0 wt.% coated La 2 O 3 on LiCoO 2 improved cycle stability (284 cycles) by a factor of ∼7 times over the pristine LiCoO 2 cathode material and also demonstrated excellent cell cycle stability when charged at high voltages (4.4, 4.5 and 4.6 V). Impedance spectroscopy demonstrated that the enhanced performance of the coated materials is attributed to slower impedance growth during the charge-discharge processes. The DSC curve revealed that the exothermic peak corresponding to the release of oxygen at ∼464 K was significantly smaller for the La 2 O 3 -coated cathode material and recognized its high thermal stability.
O 2 cathode surface for lithium ion batteries
2018
Lithium-manganese-rich cathode material Li1.2Mn0.54Ni0.13Co0.13O2 is prepared by combustion method, and then coated with nano-sized LiFePO4 and nano-sized Al2O3 particles via a wet chemical process. The as-prepared Li1.2Mn0.54Ni0.13Co0.13O2, LiFePO4-coated Li1.2Mn0.54Ni0.13Co0.13O2 and Al2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The scanning electron microscopy shows the agglomeration of the materials and their nanoparticle size which ranges between 80 100 nm. The transmission electron microscopy confirmed that LiFePO4 forms a rough mat-like surface and Al2O3 remain as islandic particles on the surface of the Li1.2Mn0.54Ni0.13Co0.13O2 material. The Li1.2Mn0.54Ni0.13Co0.13O2 coated with LiFePO4 and Li1.2Mn0.54Ni0.13Co0.13O2 coated with Al2O3 exhibits improved electrochemical performance. The initial discharge capacity is enhanced to 267 mAhg after the LiFePO4 coating and 285 mAhg aft...