Surface Characterization of Electrodes from High Power Lithium-Ion Batteries

Abstract

X-ray photoelectron spectroscopy and scanning electron microscopy were used to study electrode samples obtained from 18650-type lithium-ion cells subjected to accelerated calendar-life testing at temperatures ranging from 25 to 70°C and at states-of-charge from 40 to 80%. The cells contained LiNi0.8Co0.2O2 -based positive electrodes (cathodes), graphite-based negative electrodes (anodes), and a 1 M LiPF6 ethylene carbonate:diethyl carbonate (1:1) electrolyte. The results from electrochemically treated samples showed surface film formation on both electrodes. The positive electrode laminate surfaces contained a mixture of organic species that included polycarbonates, and LiF, LixPFy -type and LixPFyOz -type compounds. The same surface compounds were observed regardless of test temperature, test duration, and state-of-charge. On the negative electrode laminates lithium alkyl carbonates false(ROCO2normalLifalse) and Li2CO3 were found in addition to the above-mentioned compounds. Decomposition of lithium alkyl carbonates to Li2CO3 occurred on negative electrodes stored at elevated temperature. Initial depth-profiling results suggest that the surface layer thickness is greater on positive electrode samples from cells stored at high temperature than on samples from cells stored at room temperature. This observation is significant because positive electrode impedance, and more specifically, charge-transfer resistance at the electrode/electrolyte interface, has been shown to be the main contributor to impedance rise in these cells. © 2002 The Electrochemical Society. All rights reserved.

Elucidation of the surface characteristics and electrochemistry of high-performance LiNiO2

“…As can be seen in Figure 4 (a), the main feature of the O1s XPS regions for all three samples is one strong peak around 531.5 eV, which is associated with Li 2 CO 3 on the surfaces. 19,20 The presence of surface Li 2 CO 3 is also supported by the following observations: (1) the Li1s peak located at 55.5 eV in Figure 4 (b), (2) the C1s peak around 290 eV in the XPS ( Figure S1). 19,20 Close examination of the XPS spectra shows the presence of a small peak with very low intensity at 529.5 eV in the solution_2exLi and solid_10exLi samples (Figure 4 (a)) which can be ascribed to O in oxide, in this case the lattice of the active material.…”

“…19,20 The presence of surface Li 2 CO 3 is also supported by the following observations: (1) the Li1s peak located at 55.5 eV in Figure 4 (b), (2) the C1s peak around 290 eV in the XPS ( Figure S1). 19,20 Close examination of the XPS spectra shows the presence of a small peak with very low intensity at 529.5 eV in the solution_2exLi and solid_10exLi samples (Figure 4 (a)) which can be ascribed to O in oxide, in this case the lattice of the active material. 19,20 The low intensity of the oxide peak indicate that the reaction layer at the surface is a few nm (The O1s XPS was recorded at 670eV, resulting in a very surface sensitive mean free path of less than 1nm).…”

“…19,20 Close examination of the XPS spectra shows the presence of a small peak with very low intensity at 529.5 eV in the solution_2exLi and solid_10exLi samples (Figure 4 (a)) which can be ascribed to O in oxide, in this case the lattice of the active material. 19,20 The low intensity of the oxide peak indicate that the reaction layer at the surface is a few nm (The O1s XPS was recorded at 670eV, resulting in a very surface sensitive mean free path of less than 1nm). The peak is almost invisible in the XPS spectra of solution_10exLi sample (Figure 4 (a)).…”

Synthesis and Properties of Nanoparticle Li[Li0.2Mn0.54Ni0.13CO0.13]O2Cathode Material by Coprecipitation Method with Non-aqueous Medium

“…However, the poor high rate capability of LIB withdraws its further use in high power applications [2,3]. Now commercial LIB mostly rely on lithium transition metal oxide, such as LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 [4][5][6].…”

“…The widely adoption choice of solid state or water medium coprecipitation method can give uniform, homogeneous and phase-pure oxide products, but the large particles with the size of micrometer withdraw its use in nanoparticle production [7,8]. In order to prepare nanosized particles for lithium metal oxide, we tried the used coprecipitation method with nonaqueous medium, and the pure Li [ 2 and MnCl 2 are dissolved in ethanol with the mole ratio of 1.9: 0.54:0.13:0.13. The total mole concentration is 1M.…”