Fabrication of LiCoO2 thin films on flexible stainless steel substrate for lithium ion batteries (original) (raw)
Related papers
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.
Synthesis of LiCoO2 thin films by sol/gel process
Journal of Power Sources, 2010
LiCoO 2 thin films were synthesized by sol/gel process using acrylic acid (AA) as chelating agent. The gel formulation was optimized by varying solvent (ethylene glycol or water) and precursors molar ratios (Li, Co, AA) in order to obtain a dense film for positive electrode of lithium batteries. The gel was deposited by spin-coating technique on an Au/TiO 2 /SiN/SiO 2 /Si substrate. Thin films were deposited by either single or multistep process to enhance the density of the thin film and then calcined during 5 h at 800 • C to obtain the R-3m phase (HT-LiCoO 2 ).
Ceramics International, 2010
Nanometric-sized LiCoO 2 powders were obtained from a novel sol-gel method, in which the gels were synthesized by the polymerization of citric acid and hydroxypropyl cellulose. Molar ratios of citric acid to metal ions were varied, and the resulting effects on the properties of powders were studied using Fourier transfer infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicate that with a molar ratio of citric acid/metal ions = 1, the resin contains a number of bidentate ligand fractions and higher portion of C-C-O structure, which makes it possible to synthesize the low temperature phase of LiCoO 2 at a temperature as low as 300 8C. The powder calcined at 600 8C exhibits a pure high temperature phase of LiCoO 2 (HT-LiCoO 2 ) with a particle size of about 40-60 nm and a specific surface area of 25.24 m 2 /g. The electrode prepared at 600 8C exhibits a better HT-LiCoO 2 structure and demonstrates a higher first run charge/discharge capacities at 186 and 168 mAh/g, respectively.
Chemistry of Materials, 2015
Both the origin and mechanism of the improvement in the electrochemical performances of post-thermal treated LiCoO 2 as a cathode material for lithium ion batteries are investigated through high-quality characterization. X-ray diffraction and transmission electron microscopy measurements revealed that the high temperature sintering results in Li deficiency and the consequent formation of spinel Li x Co 2 O 4. The slow quenching allows the two phases of LiCoO 2 and Li x Co 2 O 4 to intermix, whereas the post-thermal treatment at 800 °C results in the separation of the spinel phase at the surface of LiCoO 2. The post-thermal treated material exhibits a much better cell performance for the cycling capacity and charge rate capability than the slowly quenched material. From the conductive atomic force microscopy measurement and electrochemical impedance spectroscopy experiment, it is shown that the high electrical conductivity of the effective coating layer of the post-thermal treated LiCoO 2 performs a role in enhancing the charge transfer activity of the active material.
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.
In situ electrochemical surface modification for high-voltage LiCoO2 in lithium ion batteries
Journal of Power Sources, 2019
High-voltage LiCoO 2 has been revisited to improve the energy density of lithium ion batteries. LiCoO 2 can deliver the reversible capacity of about 200 mA h g −1 when the upper cutoff voltage increases to 4.55 V (vs. Li/ Li +). However, the high upper cutoff voltage causes the severe failures of LiCoO 2 such as structural degradation, electrolyte decomposition, and Co dissolution. Various surface-modified LiCoO 2 materials have been introduced to suppress electrolyte decomposition and Co dissolution, thereby leading to the improved electrochemical performance. Most of the coated LiCoO 2 materials are obtained through a conventional coating process such as sol-gel synthesis, which is complex and high-cost. In this paper, the in situ electrochemical coating method is introduced as a simple and low-cost coating process, where the electrolyte additive of Mg salts is electrochemically decomposed to form a MgF 2-based coating layer on the LiCoO 2 surface. LiCoO 2 electrochemically coated with MgF 2 suppresses Co dissolution in electrolytes, resulting in excellent electrochemical performance such as high reversible capacity of 198 mA h g −1 and stable cycle performance over 100 cycles in the voltage range between 3 and 4.55 V (vs. Li/Li +) at 45°C. The formation mechanism of MgF 2 is also demonstrated through ex situ XPS and XANES analyses.
Solid State Ionics, 2003
Thermal decomposition of freeze-dried salt precursors leads to the formation of low-temperature (LT) modification of LiCoO 2 at 350 -450 jC. The conversion rate of LT into high-temperature (HT) modification at 850 jC depends greatly on the anion composition of salt precursors and correlates quite well with the appearance of second step at thermogravimetric curves of their thermal decomposition related to the solid-state reaction between Li 2 CO 3 and Co 3 O 4 . Relationship between the appearance of Co 3 O 4 and preferential formation of LT/HT polymorphs at reduced temperatures is discussed. The consecutive formation of LT and HT modifications during solid-state reaction between Li 2 CO 3 and Co 3 O 4 at T>800 jC was observed. LiCoO 2 cathode materials with the domination of LT polymorph demonstrated a better initial discharge capacity while a greater amount of HT modification is accompanied by better reversibility of charge -discharge processes. D
Atomic Layer Deposition of LiCoO2 Thin-Film Electrodes for All-Solid-State Li-Ion Micro-Batteries
Journal of the Electrochemical Society, 2013
DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
A simple mechano-thermal coating process for improved lithium battery cathode materials
Journal of Power Sources, 2004
A simple, economical and convenient mechano-thermal coating procedure for the production of LiCoO 2 with improved cycling performance is described. The coating material was pre-formed nanoparticulate fumed silica. TEM studies with a 1.0 wt.% silica-coated cathode suggested that the silica species partially diffused into the bulk of the cathode material. XRD studies showed a diminished lattice parameter c upon coating, indicating that a substitutional compound of the LiSi y Co 1−y O 2+0.5y type might have formed upon calcination. SEM images, R-factor values from XRD studies and electrochemical studies showed that a coating level of 1.0 wt.% gave an optimal performance in capacity and cyclability. SEM images showed that above this level, the excess silica formed spherules, which got glued to the coated cathode particles. Galvanostatic cycling studies showed that at a coating level of 1.0 wt.%, cyclability improved three and nine times for two commercial LiCoO 2 samples.
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.