Change in Crystal Structure of LiNi0.8Co0.19Cu0.01O2 Cathode during Charge of Coin Cell Observed by Ex Situ Time-of-flight Neutron Diffraction

Abstract

In the present study, we performed a new ex situ analysis of the change in the crystal structure of a cathode containing the composite material in a coin cell during the chargedischarge cycle. Time-of-flight neutron powder diffraction with Rietveld refinement was used to analyze the crystal structure of LiNi 0.8 Co 0.19 Cu 0.01 O 2 produced by solid-phase synthesis, both for the powder and a cathode before and after charging. The powder and the cathode had similar crystal structure parameters before charging. The results obtained demonstrate that crystal structure analysis by neutron diffraction is possible for a cathode containing 8.5 mg of active material. The results also showed that it is possible to quantitatively determine the Li composition, Li/Ni cation mixing amount, (Ni,Co,Cu)O 6 octahedral distortion, and small quantities of the second phase component in the cathode before and after charging.LiCoO 2 is currently used in the cathodes of most commercially available lithium-ion batteries. However, a great deal of research has been devoted to finding a substitute for cobalt, which is both expensive and toxic.1 In our research, we have focused on a Li(Ni,Co)O 2 system in which Co is substituted by Ni in LiNiO 2 . With its relatively high capacitance and low Co content, this system is a promising replacement for LiCoO 2 . However, Li is volatile at high temperatures and Li loss and cation mixing tend to occur under calcination. This is because Ni 2+ has a similar radius (0.69 ¡) to Li + (0.76 ¡) and it thus tends to occupy the empty site, resulting in inferior battery performance.2 To resolve this problem, we synthesized a test material in which a portion of the (Ni, Co) is replaced by lowvalence Cu with the aim of reducing the Ni 2+ content to reduce cation mixing and thereby enhance the battery characteristics. To determine the amount of Li/Ni cation mixing, we have performed average structure analysis by neutron diffraction with Rietveld refinement.3 This analysis has mainly been performed on the powder form that has not been subjected to charge discharge cycling, but to determine the battery characteristics it is essential to determine changes in the crystal structure during the cycle. However, as the electrodes in coin cells contain relatively small amounts of active material, it has not been possible to perform structure analysis by neutron diffraction of samples subjected to chargedischarge.In the present study, we performed ex situ measurements of the change in the crystal structure of the cathode material subjected to a chargedischarge cycle in a coin cell fabricated for this purpose. The results of time-of-flight neutron diffraction analysis of the cathode, which is composed of solid-phasesynthesized LiNi 0.8 Co 0.19 Cu 0.01 O 2 as the active cathode material together with a conductor and a binder, before and after charging demonstrate that it is possible to determine the change in the crystal structure in an actual cathode containing 8.5 mg of active material.LiNi 0.8 Co 0.19 Cu 0.01 O 2 was synt...

Chemical delithiation and exfoliation ofLixCoO2

“…In any case, we could not attribute these deviations to a distortion of the hexagonal unit cell to monoclinic, which has been reported in at x =0.5 [11] for electrochemically de-lithiated samples. Further, we could not attribute them to a change in the Co-occupancy, to the occupation of tetrahedral sites or a partial Li-Co site exchange [31] (like 3a/3b in [32] ), or to the formation of de-lithiated materials like [33,34] [35] , CoO [36] or CoOOH. However, there is an additional small broadened peak for sample LCO8 occurring at a d -spacing of 453 pm, that is better visible in the X-ray data (see zoom Fig.…”

Investigation into properties of highly functional oxides using quantum beam and thermodynamic measurement

“…(LNCC). The raw data with the background (instrument and V peaks) excluded ("Raw-BKG") and the raw data when they were not excluded ("Raw") 32) Sample Data …”

Synthesis, Crystal Structure Analysis, and Electrochemical Properties of Rock-Salt Type MgxNiyCozO2 as a Cathode Material for Mg Rechargeable Batteries

“…Research and development aimed at breakthroughs for MRBs has been active in recent years, and it is necessary to search for a new cathode material capable of repetitive insertion and deinsertion of Mg 2+ . Layered rock salt-type LiNi 0.8 Co 0.2 O 2 has already been applied practically as a cathode material in Li-ion batteries, and the influence of the average/local structure on battery characteristics has been reported. , Here, we examine the rock-salt type Mg x Ni y Co z O 2 ( x + y + z ≤ 2.0), which is a novel composition regarded as Co-substituted MgNiO 2 with some vacancies. The purpose of this study was to synthesize and evaluate the electrochemical properties of Mg x Ni y Co z O 2 as a MRB cathode, and conduct a crystal/electronic structure analysis.…”

“…6,7 Here, we examine the rock-salt type Mg x Ni y Co z O 2 (x + y + z ≤ 2.0), which is a novel composition regarded as Co-substituted MgNiO 2 with some vacancies. The purpose of this study was to synthesize and evaluate the electrochemical properties of Mg x Ni y Co z O 2 as a MRB cathode, and conduct a crystal/electronic structure analysis.…”