• Journal of Powder Materials
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• v.23 no.4
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• pp.287-296
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• 2016

$Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders have been synthesized in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH using $NH_4OH$ as a chelating agent. The co-precipitation temperature is varied in the range of $30-80^{\circ}C$. Calcination of the prepared precursors with $Li_2CO_3$ for 8 h at $1000^{\circ}C$ in air results in Li $Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ powders. Two kinds of obtained powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analyzer, and tap density measurements. The co-precipitation temperature does not differentiate the XRD patterns of precursors as well as their final powders. Precursor powders are spherical and dense, consisting of numerous acicular or flaky primary particles. The precursors obtained at 70 and $80^{\circ}C$ possess bigger primary particles having more irregular shapes than those at lower temperatures. This is related to the lower tap density measured for the former. The final powders show a similar tendency in terms of primary particle shape and tap density. Electrochemical characterization shows that the initial charge/discharge capacities and cycle life of final powders from the precursors obtained at 70 and $80^{\circ}C$ are inferior to those at $50^{\circ}C$. It is concluded that the optimum co-precipitation temperature is around $50^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.45 no.2
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• pp.112-118
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• 2008

To prepare the high-capacity cathode material with improved electrochemical performances, nanoparticles of $C0_3(PO_4)_2$ were coated on the powder surface of $Li[Co_{0.1}Ni_{0.15}Li_{0.2}Mn_{0.55}]O_2$, which was already synthesized by simple combustion method. The coated powders after the heat treatment at >$700^{\circ}C$ surely showed well-structured crystalline property with nanoscale surface coating layer, which was consisted of $LiCOPO_4$ phase formed from the reaction bwtween $CO_3(PO_4)_2$ and lithium impurities. In addition, cycle performance was particularly improved by the $CO_3(PO_4)_2$-coating for the cathode material for lithium rechargeable batteries.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2571-2576
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• 2011

Surface film formation on $Li(Ni_{1/3}Co_{1/3}Mn_{1/3})O_2$ cathodes upon oxidation of electrolyte during electrochemical cycling was investigated. Information on the important factors for film formation on the cathode can facilitate the design of additives that improve the properties of the cathode. Pyrazole is added to the electrolyte because it is readily oxidized to form a surface film on the cathode. The results of differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR) showed that the active material played a dominant role in the interfacial film formation with the electrolyte. Carbon black played a negligible role in the surface film formation.

• Journal of the Korean Electrochemical Society
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• v.9 no.2
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• pp.64-69
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• 2006

Cathode materials of Al-doped $Li(Ni_{1/3}Co_{1/3}Mn_{1/3-x}Al_x)O_2$ (x=0.0, 0.005, 0.01 0.05) for lithium ion batteries were synthesized with ultra-sonic spray pyrolysis method and single-step heat treatment. No secondary phases were found in all synthesized powders. The intensity ratio of $I_{003}\;to\;I_{104}$, however, slightly decreased and the particle size increased with the Al contents. The cells with bare, 0.5 and 1.0 at% Al-doped powders showed the initial discharge capacities of 182, 180 and $184mAhg^{-1}$ in a voltage range of $3.0\sim4.5V$ at 1C rate, and the capacity retentions of 81, 77 and 78% at the end of 30 cycles, respectively. But in the voltage range of $3.0\sim4.6V$, the Al-doping significantly enhanced the cycle stability. For example, the discharge capacity after 50 cycles was maintained to 70% in the 0.5 at% Al-doped sample compared to only 30% in no doped sample. The improvement of the cycle stability was thought to be due to $Mn^{3+}$ ion decrease as the Al doping from the XPS analysis results.

• Journal of Hydrogen and New Energy
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• v.24 no.2
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• pp.160-171
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• 2013

$LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ powder for cathode materials in lithium rechargeable batteries was treated by atmospheric plasma containing hydrogen to investigate the relationship between charge/discharge performance and physical/chemical changes of materials. Hydrogen plasma at atmosphere pressure was irradiated on the surface of active materials, and the change for their crystal structure, surface morphology, and chemical composition were observed by XRD, SEM-EDS and titration method, respectively. The crystal structure and surface morphology of $H_2$ plasma-treated powders were not changed but their chemical compositions were slightly varied. For charge/discharge test, $H_2$ plasma affected initial capacity and rate capability of active materials but continuous cycling was not subject to plasma treatment. Therefore, it was observed that $H_2$ plasma treatment affected the surface of materials and caused the change of chemical composition.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.237-245
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• 2021

Atomic layer deposition (ALD) enhances the stability of cathode materials via surface modification. Previous studies have demonstrated that an Ni-rich cathode, such as LiNi_0.8Co_0.1Mn_0.1O₂, is a promising candidate owing to its high capacity, but is limited by poor cycle stability. In this study, to enhance the stability of the Ni-rich cathode, synthesized LiNi_0.8Co_0.1Mn_0.1O₂ was coated with Al₂O₃ using ALD. Thus, the surface-modified cathode exhibited enhanced stability by protecting the interface from Ni-O formation during the cycling process. The coated LiNi_0.8Co_0.1Mn_0.1O₂ exhibited a capacity of 176 mAh g^-1 at 1 C and retained up to 72% of the initial capacity after 100 cycles within a range of 2.8-4.3 V (vs Li/Li⁺. In contrast, pristine LiNi_0.8Co_0.1Mn_0.1O₂ presented only 58% of capacity retention after 100 cycles with an initial capacity of 173 mAh g^-1. Improved cyclability may be a result of the ALD coating, which physically protects the electrode by modifying the interface, and prevents degradation by resisting side reactions that result in capacity decay. The electrochemical impedance spectra and structural and morphological analysis performed using electron microscopy and X-ray techniques establish the surface enhancement resulting from the aforementioned strategy.

• Journal of Electrochemical Science and Technology
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• v.2 no.2
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• pp.97-102
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• 2011

Different amounts of excess lithium in the range of x = 0~0.3 were added to $Li_{1+x}[Mn_{0.720}Ni_{0.175}Co_{0.105}]O_2$ cathode materials synthesized using the co-precipitation method to investigate its microstructure and electrochemical properties. Pure layered structure without impurities was confirmed in the XRD pattern analysis and increasing peak intensity of $Li_2MnO_3$ was observed along with the addition of over 0.2 mol Li. The initial discharge capacity of the stoichiometric composition was determined to be 246 mAh/g, while the discharge capacity of the addition of 0.1 mol Li was obtained to be 241 mAh/g, which was not significantly different from that of the stoichiometric composition. However, the discharge capacities decreased dramatically after the addition of 0.2 and 0.3 mol Li to 162 mAh/g and 146 mAh/g, respectively. In the rate capability test, the active $Li_{1+x}[Mn_{0.720}Ni_{0.175}Co_{0.105}]O_2$ cathode material of the stoichiometric composition showed a dramatic decrease in its discharge capacity with increasing C-rate, as evidenced by the result that the discharge capacity at 5C was 13% compared with 0.1C. On the other hand, the discharge capacity of compositions containing excess lithium was improved at higher current rates. The cycling test showed that the composition containing an excess of 0.1 mol Li had the most outstanding capacity retention.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3233-3237
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• 2010

A $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_2$ cathode was modified by coating with Li-La-Ti-O, and the effect of the coating thickness on their electrochemical properties was studied. The thickness of the coating on the surface of $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_2$ was increased by increasing the wt % of the coating material. The rate capability of the Li-La-Ti-O-coated electrode was superior to that of the pristine sample. 1- and 2-wt %-coated samples showed considerable improvement in capacity retention at high C rates. However, the rate capability of a 5-wt %-coated sample decreased. All the coated samples showed a high discharge capacity and slightly improved cyclic performance under a high cut-off voltage (4.8 V) condition. Results of a storage test confirmed that the Li-La-Ti-O coating layer was effective in suppressing the dissolution of the transition metals as it offered protection from the attack of the acidic electrolyte. In particular, the 2- and 5-wt %-coated samples showed a better protection effect than the 1-wt %-coated sample.

• Journal of Powder Materials
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• v.23 no.2
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• pp.136-142
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• 2016

As precursors of cathode materials for lithium ion batteries, $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders are prepared in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH in the presence of $NH_4OH$ in air or nitrogen ambient. Calcination of the precursors with $Li_2CO_3$ for 8 h at $1,000^{\circ}C$ in air produces dense spherical cathode materials. The precursors and final powders are characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analysis, tap density measurement, and thermal gravimetric analysis. The precursor powders obtained in air or nitrogen ambient show XRD patterns identified as $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$. Regardless of the atmosphere, the final powders exhibit the XRD patterns of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ (NCM). The precursor powders obtained in air have larger particle size and lower tap density than those obtained in nitrogen ambient. NCM powders show similar tendencies in terms of particle size and tap density. Electrochemical characterization is performed after fabricating a coin cell using NCM as the cathode and Li metal as the anode. The NCM powders from the precursors obtained in air and those from the precursors obtained in nitrogen have similar initial charge/discharge capacities and cycle life. In conclusion, the powders co-precipitated in air can be utilized as precursor materials, replacing those synthesized in the presence of nitrogen injection, which is the usual industrial practice.

• Journal of Electrochemical Science and Technology
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• v.15 no.1
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• pp.168-177
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• 2024

Ni-rich cathode is one of the promising candidates for high-energy lithium-ion battery applications. Due to its specific capacity, easy industrialization, and good circulation ability, Ni-rich cathode materials have been widely used for lithium-ion batteries. However, due to the limitation of the co-precipitation method, including sewage pollution, and the instability of the long production cycles, developing a new efficient and environmentally friendly synthetic approach is critical. In this study, the Ni_0.91Co_0.06Mn_0.03CO₃ precursor powder was successfully synthesized by an efficient spray-drying method using carbonate compounds as a raw material. This Ni_0.91Co_0.06Mn_0.03CO₃ precursor was calcined by mixing with LiOH·H₂O (5 wt% excess) at 480℃ for 5 hours and then sintered at two different temperatures (780℃/800℃) for 15 hours under an oxygen atmosphere to complete the cathode active material preparation, which is a key component of lithium-ion batteries. As a result, LiNi_0.91Co_0.06Mn_0.03O₂ cathode active material powders were obtained successfully via a simple sintering process on the Ni_0.91Co_0.06Mn_0.03CO₃ precursor powder. Furthermore, the obtained LiNi_0.91Co_0.06Mn_0.03O₂ cathode active material powders were characterized. Overall, the material sintered at 780℃ shows superior electrochemical performance by delivering a discharge capacity of 190.76 mAh/g at 1^st cycle (0.1 C) and excellent capacity retention of 66.80% even after 50 cycles.