Lithium-reactive Co-3(PO4)(2) nanoparticle coating on high-capacity LiNi0.8Co0.16Al0.04O2 cathode material for lithium rechargeable batteries

Metal ion dissolution from high-capacity LiNi0.8 Co0.16 Al0.04 O2 cathode material during storage at 90°C was completely blocked by a lithium-reactive Co3 (PO4) 2 nanoparticle coating. As opposed to conventional coating methods, in which the coating material did not react with LiOH and Li2 CO3 impurities dissolved from the cathode, the Co3 (PO4) 2 coating material reacted with such impurities during annealing to form an olivine LiCoPO4 phase on the bulk surface. Electrochemical properties of the optimized sample, annealed at 700°C for 5 h, demonstrated a 30% enhancement of the cycle life, compared to a bare sample without a loss in the first discharge capacity. Storage tests of the 4.3 V charged electrode at 90°C after 7 days showed that the bare sample was transformed into the spinel phase with a Fd3m space group, whereas the Co3 (PO4) 2 -coated sample remained as a layered hexagonal phase with an R 3- m space group.close333

Synthesis and electrochemical properties of lithium-electroactive surface-stabilized silicon quantum dots

Highly lithium-electroactive Si quantum dots (n-Si), coated with an amorphous carbon layer, were prepared by of butyl-capped Si annealing at 700 or 900 ??C. The ordering of the carbon layer structure increased with increasing annealing temperature while the thickness decreased to 1 from 2 nm due to the increased ordering of carbon. n-Si, annealed at 900 ??C, had the same particle size (5 nm) as n-Si annealed at 700 ??C. In contrast to Si nanocrystals with an average particle size of 30 nm that had a first charge capacity of 225 mAh/g with a very small coulombic efficiency of 4%, n-Si that annealed at 900 ??C possessed a first charge capacity of 1257 mAh/g with a significantly enhanced coulombic efficiency of 71%. This improvement was due to the uniform distribution of n-Si with a carbon layer that prohibited n-Si aggregation during cycling.close192

Sn0.9Si0.1/carbon core-shell nanoparticles for high-density lithium storage materials

Sn0.9Si0.1 core/carbon shell nanoparticles, with the sizes of 16 and 10 nm, were prepared by annealing as-prepared butyl-capped Sn0.9Si0.1 particles with an average particle size of 1 ??m. Even though as-prepared samples were severely encapsulated by butyl terminators, annealing led to pulverization of the bulky particles into core - shell nanoparticles with a shell thickness dependent on the annealing temperature. The core Sn0.9Si0.1 size was estimated to be constant at 6 nm, and the carbon shell thickness decreased from 10 to 4 nm with increasing annealing temperature from 600 to 700??C, respectively. In addition, the carbon shell was found to be more ordered at 700??C than at 600??C. Sn0.9Si0.1 core/carbon shell nanoparticles exhibited excellent lithium storage ability at a high current rate, resulting in a value of 964 mA??h/g at a rate of 0.3 C (1 C = 1200 mA/g), and demonstrated good capacity retention after 50 cycles.close363

Structural changes of bare and AIPO(4)-coated LixCoO2 (x = 0.24 and 0.1) upon thermal annealing >= 200 degrees C

Structural changes of bare and AIPO(4)-coated LiCoO2 with a coating thickness of 20 and 200 nm are investigated at x = 0.24 and 0. 1 after thermal annealing at 200, 300, and 400 degrees C using XRD and Co K-edge XANES (X-ray absorption near-edge structure) and EXAFS (extended X-ray absorption fine structure). Both the bare and coated cathodes exhibit faster phase transformation into spinel phases at lower annealing temperatures as x in LixCoO2 is decreased. Bare LixCoO2 cathodes exhibit phase transitions from LixCo2O4 to Co3O4 spinel as the annealing temperature is increased and the x is value decreased, which suggests a possible reaction according to (1/2)LixCo2O4 -> xLi(2)CO(3) + (1/3)Co3O4 + (2/3)O-2. However, the coated cathodes sustain a Li(x)Co(2)O(4)phase even at 400 degrees C and x=0.1. This indicates that the AIPO(4) coating layer suppresses the Li,C0204 phase decomposition into Co3O4.close4

Effect of capping agents in tin nanoparticles on electrochemical cycling

Tin particles that were prepared using three different capping agents, hydrobenzamide, citrate, and polyvinyl pyrrolidone (PVP) exhibited different particle sizes. The hydrobenzamide-capped Sn had the smallest particle size (∼50 nm) and uniform distribution while the citrate and PVP-capped Sn had particle sizes of ∼100 and ∼300 nm, respectively, with severe particle aggregation. However, there was no SnO2 or SnO detected on the particle surfaces. The cycling results using coin-type half cells confirmed that the hydrobenzamide-capped Sn had the highest charge capacity of 994 mAh/g between 1.5 and 0 V and the best capacity retention. In contrast, the citrate and PVP-capped Sn showed severe capacity decay. Further analysis using cycled electrodes showed that the hydrobenzamide-capped Sn showed the least particle agglomeration and growth, compared with the others. From Fourier transform magnitude (FT) of Sn LIII-edge energy dispersive X-ray analysis spectra, these facts could be supported by the strong coordination formed as a result of chemical bonding between the nitrogen of the hydrobenzamide capping agent effectively inhibiting the particle growth during cycling.close202

Surface and bulk structure investigation of fully delithiated bare and AIPO(4)-coated LixCoO2 (x=0) cathode materials annealed between 200 and 400 degrees C

The surface and bulk structure of the fully delithiated bare and AlPO4-coated LixCoO2 cathode materials (x = 0) between 200 and 400 ??C were investigated using high resolution XRD, XAS (X-ray absorption spectroscopy), TEM, and solid-state NMR. Bare and coated CoO2 cathodes showed different phase transformation between 200 and 400 ??C. The bare samples exhibited only the O1-CoO2 phase in the fully delithiated state, but the CoO2 phase was converted to the Co3O4 phase at higher temperatures. On the other hand, the AlPO4-coated LixCoO2 at x = 0 showed a mixture of phases including the major O1-type CoO2 and minor Co3O4 spinel phases in the fully delithiated state. When annealing temperatures increased from 200 to 400 ??C, the bare samples showed a slow phase transition to Co3O4 and were completely transformed into the thermally stable Co3O4 spinel phase at 400 ??C. The coated samples, however, were completely transformed into the spinel phase alone at 200 ??C. We believe that the AlPO4 coating layer accelerated the phase transition to the spinel phase at lower temperatures. TEM and XAS results showed that structural damages were mainly confined to the cathode particle surface, and this phenomenon was only observed in the bare samples.close3

Amorphous carbon-coated tin anode material for lithium secondary battery

The use of amorphous carbon-coated tin particles as an alternative material to ensure the dimensional integrity during Sn alloy/dealloy was highlighted. Inductively coupled plasma mass spectroscopy (ICP_MS) analysis of the Sn in the coated carbon showed that Sn wt% was 80, and the remaining 20 wt% was estimated to be carbon. It was indicated that most hydroxyl groups in glucose were removed during the hydrothermal reaction. It was found that an almost uniform amorphous carbon coating on the tin nanoparticles was prepared from aqueous glucose solutions using a hydrothermal method at 180??C, which facilitated enhanced dimensional stability during Li alloying/dealloying.close14914

Comparison of structural changes in fully delithiated Li-x[Ni1/3Co1/3Mn1/3]O-2 and Li-x[Ni0.33Co0.33Mn0.30Mg0.04]O1.96F0.04 cathodes (x=0) upon thermal annealing

This study compared the structural changes in Lix [Ni13 Co13 Mn13] O2 and Lix [Ni0.33 Co0.33 Mn0.3 Mg0.04] O1.96 F0.04 cathodes (x=0) occurring after full delithiation and subsequent heat-treatment at 200, 300, and 400°C using X-ray diffraction (XRD), transmission electron microscopy, and X-ray absorption spectra (XAS). In both cathodes, XRD patterns at x=0 showed a layered O3 -type structure (CdCl2), but subsequent thermal annealing led to a similar structure decomposition to a Co3 O4 -type spinel and possible new O3- Ni13 Mn13 O2+δ -type layered phases. However, the XAS spectra clearly showed that the Lix [Ni0.33 Co0.33 Mn0.3 Mg0.04] O1.96 F0.04 exhibited much improved structural stability, showing a suppression of the phase decomposition to spinel Co3 O4, as evidenced by a decrease in the FT peak intensity of corner-shared CoO6 octahedra at ∼3.2 Å.close2

Monomer-capped tin metal nanoparticles for anode materials in lithium secondary batteries

The preparation of the size-controlled monomer-capped amorphous and crystalline tin nanoparticles using new capping agents, 2,4,6-tri(2-pyridyl)-1, 3,5-triazine and 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine, was reported. It was observed that TT-capped Sn electrodes of the after cycling showed good adhesion on the current collector while the DT-capped sample was severely separated from the current collector. It was also observed that TT-capped tin nanoparticles reduced the formation of surface cracks induced from the volume change in the LixSny phase. In terms of the irreversible capacity, the monomer-capped Sn was comparable to the commercially used graphite anode materials.close434

Structural characterization of the surface-modified LixNi0.9Co0.1O2 cathode materials by MPO4 coating (M = Al, Ce, SrH, and Fe) for Li-ion cells

Structural characterization of surface-modified Lix Ni0.9 Co0.1 O2 cathodes (x=0.3 and 0.15) using an MP O4 coating (M=Al, Ce, SrH, and Fe) were investigated for their potential applications to Li-ion cells. MP O4 nanoparticles that were precipitated from metal nitrate and (N H4) 2 HP O4 in water at pH=10 were coated on the cathodes via mixing and heat treatment at 700??C. The CeP O4 and SrHP O4 -coated Li0.3 Ni0.9 Co0.1 O2 cathodes heat treated at 300??C were mainly made up of the rock-salt phase (Fm3m), while AlP O4 and FeP O4 -coated cathodes showed disordered [Li1-x (Ni,Co)x] 3b [(Ni,Co)y] 3a O2 -type hexagonal structure (R 3- m) with a cation mixing. However, when the x value decreased from 0.3 to 0.15, bare and coated cathodes which had a spinel (Fd3m) or hexagonal structure (R 3- m) at x=0.3 were transformed into a NiO-type rock-salt structure. AlP O4 -coated sample exhibited lowest degree of oxygen generation after 300??C annealing at x=0.15, indicating the highest thermal stability among the bare and coated cathodes.close444