Improvement of the Thermal Stability of LiNi[sub 0.8]Co[sub 0.2]O[sub 2] Cathode by a SiO[sub x] Protective Coating

Abstract

The surface of LiNi 0.8 Co 0.2 O 2 particles was protected by a thin layer of SiO x deposited via chemical vapor deposition ͑CVD͒. The aim was to enable lithium ions to intercalate into the cathode material through the coating layer while preventing the surface of the cathode to be directly in contact with the electrolyte media. The structure of LiNi 0.8 Co 0.2 O 2 is only slightly modified by the CVD process. The film deposited around the cathode particles was characterized. It consists of an amorphous layer of understoichiometric silicon dioxide SiO x (x Ͻ 2) which is 3-5 nm thick. The initial charge capacity of the starting material is not affected by the protective coating; nevertheless, the capacity fade is slightly increased upon cycling compared to the uncoated LiNi 0.8 Co 0.2 O 2 powder. The CVD process is very reproducible, and despite a small degradation of the electrochemical performance, the SiO x coating is efficient to decrease by 50% the exothermic reaction occurring at around 210°C in the charged state.

Reversible and High‐Capacity Nanostructured Electrode Materials for Li‐Ion Batteries

“…[112] On the other hand, MgO, SnO 2 , Al 2 O 3 , ZnO, ZrO 2 , and TiO 2 coatings on layered LiCoO 2 and LiNi 1Àx M x O 2 via the sol-gel method have been intensively investigated. [112][113][114][115][116][117][118][119][120][121][122][123][124][125][126][127] Among these coating materials, ZrO 2 coating exhibits the best capacity retention at >4.5 V cycling and hightemperature storage at 90 8C. [128] This finding can be supported with the ZrO 2 coating on spinel LiMn 2 O 4 , which shows the lowest capacity fading at 55 8C cycling among the various coating materials.…”

Effects of Co3(PO4)2 coatings on LiNi0.8Co0.16Al0.04O2 cathodes during application of high current

“…16 Al 0.04 O 2 used as starting material and reference samples were purchased from Sumitomo Chemical. (NH 4 ) 2 HPO 4 (0.45 g) and Co(NO 3 ) 2 Á 6H 2 O (1.5 g) were dissolved in distilled water for the coating solution.…”

Surface‐Initiated Growth of Thin Oxide Coatings for Li–Sulfur Battery Cathodes

“…However, these conventional sol-gel methods can be diffi cult to control, and utilizing them to produce an ultra-thin, homogenous coating on carbon (in contrast to lithium metal oxides) at low temperatures is challenging. Another effi cient way to generate homogeneous thin layers is chemical vapour deposition (CVD), which has been used to deposit SiO x layers on Li[Ni 0.8 Co 0.2 ]O 2 at high temperatures, [ 20 ] or a related atomic layer deposition (ALD) method, a gas-phase synthesis using repetitive sequential reactions to control the thickness of the layers. [ 21 ] This method includes several steps; i) purging a reactant gas and carrier gas on the functionalized surface at high temperature ( > 100 ° C), ii) reaction of reactants and the functional group on the surface, iii) eliminating (by evacuation) all un-reacted reactants and byproducts, iv) functionalizing the surface again, v) repeating the processes in (i-iv).…”