The electrochemical behaviors and lithium-storage mechanism of LiCoO2 in a broad voltage window (1.0−4.3 V) are studied by charge−discharge cycling, XRD, XPS, Raman, and HRTEM. It is found that the reduction mechanism of LiCoO2 with lithium is associated with the irreversible formation of metastable phase Li1+x CoII IIIO2−y and then the final products of Li2O and Co metal. During the charging process, the Li2O/Co mixture can be oxidized into CoO, and then the Li2O/CoO mixture can result in the formation of Co3O4 in the higher-voltage region. Li x CoO y is the final product when the active material is charged to 4.3 V. During the subsequent cycles, the lithium uptake/release reactions are related to the reversible conversion of Co ↔ CoO ↔ Co3O4 ↔ Li x CoO y .

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The surface physical and chemical behaviors of conductive additive acetylene black (AB) are studied after the samples are cycled at different working temperatures (−20, 20, and 60 °C). Working at low temperature (−20 °C), AB shows high polarization and poor electrochemical property. In addition, plenty of inorganic compounds are formed on the surface of AB. For comparison, the surface film on AB after being worked at 60 °C is comprised of an outer organic layer and an inner inorganic layer. Moreover, it consumes large electrical energy and results in irreversible trapped lithium for surface film formation. Furthermore, much more organic components can induce lower thermal stability of conductive additive. During repeated electrochemical cycles, the surface structure of AB experiences a series of changes of surface electrolyte decomposition products. It is found that the organic polymer in outer layer will decompose into other stable species, and partial surface fluorides in the inner layer will transform into other fluorides. The working temperature has a great effect on the final transformation products.

The flower‐like CuO–WO3–Bi2WO6 with p–n–n heterostructure was prepared via a simple two‐step approach, which was using hydrothermal method synthesising WO3–Bi2WO6 and subsequent CuO recombination through impregnation‐calcination technique. The products were characterised by X‐ray powder diffraction, energy dispersion spectroscopy, scanning electronic microscopy, transmission electron microscopy, nitrogen sorption measurements (BET), UV–vis diffuse reflectance spectra, photoluminescence (PL) emission spectra, photocurrent transient responses and EIS Nyquist plots. The photodegradation results of products under visible light irradiation revealed the order: CuO–WO3–Bi2WO6 (0.3:0.2:1) > CuO–WO3–Bi2WO6 (0.5:0.2:1) > CuO–WO3–Bi2WO6 (0.1:0.2:1) > CuO–Bi2WO6 > WO3–Bi2WO6 > Bi2WO6. The enhanced activity can be attributed to the p–n–n type heterojunction, which resulted in the cascade electron transfer from CuO to Bi2WO6 and then to WO3 through the interfacial potential gradient in the ternary hybrids conduction bands and improved separation rate of photogenerated charge carriers.