Chong Seung Yoon

A Li[Li(0.19)Ni(0.16)Co(0.08)Mn(0.57)]O(2) cathode was coated with AlF(3) on the surface. The AlF(3)-coating enhanced the overall electrochemical characteristics of the electrode while overcoming the typical shortcomings of lithium-enriched cathodes. This improvement was attributed to the transformation of the initial electrode layer to a spinel phase, induced by the Li chemical leaching effect of the AlF(3) coating layer.

A series of single-crystal, Ni-rich Li[NixCoyMn1–x–y]O2 (NCM) cathodes (x = 0.7, 0.8, and 0.9) with particle diameters of ∼3 μm are systematically compared with polycrystalline cathodes with corresponding Ni contents. Despite their high resistance to microcracking, the electrochemical performances of single-crystal NCM cathodes, in terms of capacity and cycling stability, are inferior to those of polycrystalline NCM cathodes. In situ XRD and TEM analyses reveal that the lithium concentrations in

Abstract Boron‐doped Li[Ni 0.90 Co 0.05 Mn 0.05 ]O 2 cathodes are synthesized by adding B 2 O 3 during the lithiation of the hydroxide precursor. Density functional theory confirms that boron doping at a level as low as 1 mol% alters the surface energies to produce a highly textured microstructure that can partially relieve the intrinsic internal strain generated during the deep charging of Li[Ni 0.90 Co 0.05 Mn 0.05 ]O 2 . The 1 mol% B‐Li[Ni 0.90 Co 0.05 Mn 0.05 ]O 2 cathode thus delivers a dis

Ni-rich Li[Ni1–x–yCoxAly]O2 (NCA) cathodes (1 – x – y = 0.8, 0.88, and 0.95) are synthesized to investigate the capacity fading mechanism of Ni-rich NCA cathodes. The capacity retention and thermal property of the cathodes deteriorate as their discharge capacity increases when the Ni fraction is increased. The capacity fading correlates well with the anisotropic volume variations caused by the H2–H3 phase transition and the resulting extent of microcracking. Although all three cathodes start to

A spherical stoichiometric LiNiO2 particle, which was composed of compactly packed nanosized primary particles, was prepared and cycled at different cutoff voltages to explicitly demonstrate the effect of phase transitions during Li deintercalation/intercalation on the Li-ion intercalation stability of LiNiO2. The capacity retention was greatly improved by suppressing the H2 → H3 phase transition at 4.1 V, such that 95% of the initial capacity (164 mAh g–1) was retained after 100 cycles when cyc

A series of Ni-enriched Li[NixCoyAlz]O2 cathodes (x = 0.80–0.95) were synthesized and evaluated comprehensively to investigate the capacity fading mechanism. Capacity retention was shown to be strongly related to the extent of microcracking within the secondary particles. Moreover, the range and limit of the depth of discharge (DOD), which determined the extent of microcracking, critically affected the cycling stability such that the extremely Ni-rich Li[Ni0.95Co0.04Al0.01]O2 cathode cycled at a

Abstract Li[Ni 0.9 Co 0.1 ]O 2 (NC90), Li[Ni 0.9 Co 0.05 Mn 0.05 ]O 2 (NCM90), and Li[Ni 0.9 Mn 0.1 ]O 2 (NM90) cathodes are synthesized for the development of a Co‐free high‐energy‐density cathode. NM90 maintains better cycling stability than the two Co‐containing cathodes, particularly under harsh cycling conditions (a discharge capacity of 236 mAh g −1 with a capacity retention of 88% when cycled at 4.4 V under 30 °C and 93% retention when cycled at 4.3 V under 60 °C after 100 cycles). The re

Capacity degradation of highly Ni-enriched NCM cathodes is aggravated by the formation of the H3 phase in the delithiated state.

Electrochemical properties and structural and thermal stability of Li[Ni0.65Co0.13Mn0.22]O2 (FCG65), Li[Ni0.75Co0.08Mn0.17]O2 (TSFCG75), and Li[Ni0.85Co0.05Mn0.10]O2 (TSFCG85) with concentration gradients of Ni and Mn were evaluated to comprehensively demonstrate the effectiveness of compositional gradation for a wide range of Ni-rich Li[NixCoyMn1–x–y]O2 (NCM) cathodes. The discharge capacities of FCG65, TSFCG75, and TSFCG85 were 194.2, 206.8, and 222.2 mAh g–1, respectively with capacity retent

A series of Ni-rich Li[Ni_<i>x</i>Co_{(1-<i>x</i>)/2}Mn_{(1-<i>x</i>)/2}]O₂ (<i>x</i> = 0.9, 0.92, 0.94, 0.96, 0.98, and 1.0) (NCM) cathodes are prepared to study their capacity fading behaviors. The intrinsic trade-off between the capacity gain and compromised cycling stability is observed for layered cathodes with <i>x</i> ≥ 0.9. The initial specific capacities of LiNiO₂ and Li[Ni_0.9Co_0.05Mn_0.05]O₂ are

Ordered occupation of Ni ions in the Li ion layer (and vice versa) was observed in 0.4 mol % Zr-doped LiNiO2 with R3̅m structure. Although cation mixing is prevalent in LiNiO2 and in other Ni-rich layered cathodes, cation ordering (Li and Ni) has not been previously reported in the as-prepared or fully discharged states. First-principles calculations verified that low-level doping of LiNiO2 with Zr can energetically promote the observed cation ordering. Contrary to previous beliefs, antisite def

A self-passivating Li2ZrO3 layer with a thickness of 5–10 nm, which uniformly encapsulates the surfaces of LiNiO2 cathode particles, is spontaneously formed by introducing excess Zr (1.4 atom %). A thin layer of Li2ZrO3 on the surface is converted into a stable impedance-lowering solid–electrolyte interphase layer during subsequent cycles. The Zr-doped LiNiO2 cathode with an initial discharge capacity of 233 mA·h·g–1 exhibited significantly improved capacity retention (86% after 100 cycles) and

Abstract A Ni‐rich concentration‐gradient Li[Ni 0.865 Co 0.120 Al 0.015 ]O 2 (NCA) cathode is prepared with a Ni‐rich core to maximize the discharge capacity and a Co‐rich particle surface to provide structural and chemical stability. Compared to the conventional NCA cathode with a uniform composition, the gradient NCA cathode exhibits improved capacity retention and better thermal stability. Even more remarkably, the gradient NCA cathode maintains 90% of its initial capacity after 100 cycles wh