• Korean Journal of Materials Research
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• v.20 no.11
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• pp.592-599
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• 2010

A porous nickel-tin nano-dendritic electrode, for use as the anode in a rechargeable lithium battery, has been prepared by using an electrochemical deposition process. The adjustment of the complexing agent content in the deposition bath enabled the nickel-tin alloys to have specific stoichiometries while the amount of acid, as a dynamic template for micro-porous structure, was limited to a certain amount to prevent its undesirable side reaction with the complexing agent. The ratios of nickel to tin in the electro-deposits were nearly identical to the ratios of nickel ion to tin ion in the deposition bath; the particle changed from spherical to dendritic shape according to the tin content in the deposits. The nickel to tin ratio and the dendritic structure were quite uniform throughout the thickness of the deposits. The resulting nickel-tin alloy was reversibly lithiated and delithiated as an anode in rechargeable lithium battery. Furthermore, the resulting anode showed much more stable cycling performance up to 50 cycles, as compared to that resulting from dense electro-deposit with the same atomic composition and from tin electrodeposit with a similar porous structure. From the results, it is expected that highly-porous nickel-tin alloys presented in this work could provide a promising option for the high performance anode materials for rechargeable lithium batteries.

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.31-35
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• 2007

In this review article, we are going to explain the recent development of lithium secondary batteries for a cellular phone. There are three kinds of rechargeable batteries for cellular phones such as nickel-cadmium, nickel-metal hydride, and lithium ion or lithium ion polymer. The lithium secondary battery is one of the most excellent battery in the point of view of energy density. It means very small and light one among same capacity batteries is the lithium secondary battery. The market volume of lithium secondary batteries increases steeply about 15% annually. The trend of R&D is focused on novel cathode materials including $LiFePO_4$, novel anode materials such as lithium titanate, silicon, and tin, elecrolytes, and safety insurance.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.14-17
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• 1998

Mesophase pitch-based carbon fibers(MPCF) have been investigated as an anode active material for lithium ion secondary battery. Graphitized MPCF gives high discharge capacity and good Ah efficiency. MPCF/Li cell shows an initial discharge capacity of 300 mAh/g and Ah efficiency above $90\%$ at a current density of 25 mA/g at $0\~1$ V. Cylindrical lithium ion secondary battery was fabricated using mixed carbon anode and $LiCoO_2$, cathode. In order to improve the cyclability of lithiun ion secondary battery, other carbons were added to the MPCF up to $10wt\%$. The cycle performance of lithium ion secondary battery using mixed carbons was superior to those using graphitized MPCF.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.598-598
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• 2012

Rechargeable lithium-ion batteries have been considered the most attractive power sources for mobile electronic devices. Although graphite is widely used as the anode material for commercial lithium-ion batteries, it cannot fulfill the requirement for higher storage capacity because of its insufficient theoretical capacity of 372 mAh/g. For the sake of replacing graphite, Sn-based materials have been extensively investigated as anode materials because they can have much higher theoretical capacities (994 mAh/g for Sn, 875 mAh/g for SnO, 783 mAh/g for $SnO_2$). However, these materials generate huge volume expansion and shrinkage during $Li^+$ intercalation and de-intercalation and result in the pulverization and cracking of the contact between anode materials and current collector. Therefore, there have been significant efforts of avoiding these drawbacks by using nanostructures. In this study, we present the CVD growth of SnO branched nanostructures on Cu current collector without any binder, using a combinatorial system of the vapor transport method and resistance heating technique. The growth mechanism of SnO branched nanostructures is introduced. The SnO nanostructures are evaluated as an anode for lithium-ion battery. Remarkably, they exhibited very high discharge capacities, over 520mAh/g and good coulombic efficiency up to 50 cylces.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.3025-3032
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• 2012

Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT@C) have been fabricated by a two step polymerization method. Silicon nanoparticles-carbon nanotubes (Si-CNT) nanohybrids were prepared with a wet-type beadsmill method. A polymer, which is easily removable by a thermal treatment (intermediate polymer) was polymerized on the outer surfaces of Si-CNT nanocomposites. Subsequently, another polymer, which can be carbonized by thermal heating (carbon precursor polymer) was incorporated onto the surfaces of pre-existing polymer layer. In this way, polymer precursor spheres containing Si-CNT nanohybrids were produced using a two step polymerization. The intermediate polymer must disappear during carbonization resulting in the formation of an internal free space. The carbon precursor polymer should transform to carbon shell to encapsulate remaining Si-CNT nanocomposites. Therefore, hollow carbon microcapsules containing Si-CNT nanocomposites could be obtained (Si-CNT@C). The successful fabrication was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These final materials were employed for anode performance improvement in lithium ion battery. The cyclic performances of these Si-CNT@C microcapsules were measured with a lithium battery half cell tests.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.337-342
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• 2018

Using a high pressure homonizer, we report on the electrochemical performance of $Li_4Ti_5O_{12}(LTO)$ particles manufactured as anode active material for lithium ion battery. High-pressure synthesis processing is performed under conditions in which the mole fraction of Li/Ti is 0.9, the synthesis pressure is 2,000 bar and the numbers of passings-through are 5, 7 and 10. The observed X-ray diffraction patterns show that pure LTO is manufactured when the number of passings-through is 10. It is found from scanning electron microscopy analysis that the average size of synthesized particles decreases as the number of passings-through increases. $LiCoO_2-based$ active cathode materials are used to fabricate several coin half/full cells and their battery characteristics such as lifetime, rate capability and charge transfer resistance are then estimated, revealing quite good electrochemical performance of the LTO particles as an effective anode active material for lithium secondary batteries.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.6
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• pp.421-428
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• 2021

Lithium-ion secondary batteries exhibit advantageous characteristics such as high voltage, high energy density, and long life, allowing them to be widely used in both military and daily life. However, the lithium-ion secondary battery does have its limitation; for example, the output power and capacity are readily decreased due to the increased internal impedance during discharging at a lower temperature (-32℃, military requirement). Also, during charging at a lower temperature, lithium dendrite growth is accelerated at the anode, thereby decreasing the battery capacity and life as well. This paper describes a study that involves increasing the internal temperature of lithium-ion secondary battery by energy circulation operation in a low-temperature environment. The energy circulation operation allows the lithium-ion secondary battery to alternately charge and discharge, while the internal resistance of lithium-ion battery acts as a heating element to raise its own temperature. Therefore, the energy circulation operation method and device were newly designed based on the electrochemical impedance spectroscopy of the lithium-ion secondary battery to mediate the battery performance at a lower temperature. Through the energy circulation operation of lithium ion secondary battery, as a result of the heat generated from internal resistance in an extremely low-temperature environment, the temperature of the lithium-ion secondary battery increased by more than 20℃ within 10 minutes and showed a 75% discharging capacity compared with that at room temperature.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.90-99
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• 2022

Owing to the rising concern of global warming, lithium-ion batteries have gained immense attention over the past few years for the development of highly efficient electrochemical energy conversion and storage systems. In this study, alpha-phase VOPO₄·2H₂O with nanosheet morphology was prepared via a facile hydrothermal method for application in high-performance lithium-ion batteries. The X-ray diffraction and scanning electron microscopy (SEM) analyses indicated that the obtained sample had an alpha-2 (αII) phase, and the nanosheet morphology of the sample was confirmed using SEM. The lithium-ion battery with VOPO₄·2H₂O as the anode exhibited excellent long-term cycle life and a high capacity of 256.7 mAh g^-1 at room temperature. Prelithiation effectively improved the specific capacity of pristine VOPO₄·2H₂O. The underlying electrochemical mechanisms were investigated by carrying out AC impedance, rate capability, and other instrumental analyses.

• Journal of the Korean Chemical Society
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• v.67 no.6
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• pp.429-440
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• 2023

1,1-Dialkyl-2,5-bis(trimethylsilylethynyl)-3,4-diphenylsiloles (R=Et, i-Pr, n-Hex; 3a-c) were prepared and utilized as anode active materials for lithium-ion batteries; 3a was also used as a filler for the solid-state electrolytes (SSE). Siloles 3a-c were prepared by substitution reactions in which the two bromine groups of 1,1-dialkyl-2,5-dibromo-3,4-diphe- nylsiloles, used as precursors, were substituted with trimethylsilylacetylene in the presence of palladium chloride, copper iodide, and triphenylphosphine in diisopropylamine. Among siloles 3a-c, 3a had the best electrochemical properties as an anode material for lithium-ion batteries, including an initial capacity of 758 mAhg^-1 (0.1 A/g), which was reduced to 547 mAhg^-1 and then increased to 1,225 mAhg^-1 at 500 cycles. A 3a-composite polymer electrolyte (3a-CPE) was prepared using silole 3a as an additive at concentrations of 1, 2, 3, and 4 wt.%. The 2 wt.% 3a-CPE composite afforded an excellent ionic conductivity of 1.09 × 10^-3 Scm^-1 at 60℃, indicating that silole 3a has potential applicability as an anode active material for lithium-ion batteries, and can also be used as an additive for the SSE of lithium-ion batteries.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.128.2-128.2
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• 2007