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An existence of a new, stable oligomer state of the solid film is reported, which is produced under electrochemical conditions. In this state, a formal charge exchanged in the redox process is about one-half of electron per oligomer molecule. The procedure, which allows controlling precisely the amount of oligomer on the electrode surface, is proposed that together with the coulometric evaluation of the electric charge provides the number of electrons involved in a redox process. This is demonstrated for a case of α-monochloro-substituted regioregular sexi (3-octylthiophene) oligomer (6OTCl). The electrochemical results are discussed together with UV–Vis–NIR spectroelectrochemical data obtained for both solution and solid phase that support the proposed interpretation.

LiMnPO4 has been attracting attention for high energy density (701 Wh kg−1) and excellent safety. However, LiMnPO4 suffers from the cycling instability coming from the fragile solid electrolyte interface, besides the Jahn-Teller effect of Mn3+, the poor electrical conductivity and the sluggish ionic conductivity. The substitution of cation with less ionic radius for Mn2+ is conducive to stabilize the solid-electrolyte interface and retard the erosion from electrolyte; therefore, the gradient Co-doped LiMn0.98Co0.02PO4 was synthesized with 25.93 (mol) % Co on the surface by the secondary solvothermal method, and the permeated depth reaches more than 20 nm because of the coprecipitation and cation exchange of Co2+ and Mn2+. LiMn0.98Co0.02PO4/Li cell that demonstrates the cycling performance is remarkably enhanced with 87% capacity retention after 380 cycles at room temperature, even 87% after 100 cycles at 60 °C. Meanwhile, the preferential growth along the a–c plane results in the highly [010]-oriented LiMnPO4 by the solvothermal, which afford more channels for Li+ migration by exposing more reaction sites, and the infrared spectrum also reflects the less Mn2+-Li+ antisite defects in the crystal. So the samples show the superior rate performance as well.

We have developed a new method to describe a fading model integrated with a parasitic reaction of rechargeable Li-ion batteries in the present work. In our work, the Li-ion battery reactions and the parasitic reaction are incorporated into one model. A new governing equation and a new field variable are presented in the new model to characterize the parasitic reaction and the relationship to the battery fading. Due to the new variations, the parameters that are changed with the battery’s aging are able to be calculated and updated automatically in the model. The parasitic reaction is assumed to obey a Tafel equation. The simulating results show that the distribution of overpotential of the parasitic reaction as function of x shapes, a figure close to a “V,” suggests the nonuniform distribution of the parasitic current. The parasitic reaction’s equilibrium potential is proved to be one of most important factors that determine the rate of the reaction. In addition, the cutoff charging state of charge (SOC) has a large influence on the parameters related to the rate of the parasitic reaction. Therefore, controlling the charging SOC can be seen as an effective method to protect the battery from aging.

Lithium–sulfur (Li–S) battery is considered as a promising option for electrochemical energy storage applications because of its low-cost and high theoretical capacity. However, the practical application of Li–S battery is still hindered due to the poor electrical conductivity of S cathode and the high dissolution/shuttling of polysulfides in electrolyte. Herein, we report a novel physical and chemical entrapment strategy to address these two problems by designing a sulfur–MnO2@graphene (S–MnO2@GN) ternary hybrid material structure. The MnO2 particles with size of ~ 10 nm are anchored tightly on the wrinkled and twisted GN sheets to form a highly efficient sulfur host. Benefiting from the synergistic effects of GN and MnO2 in both improving the electronic conductivity and hindering polysulfides by physical and chemical adsorptions, this unique S–MnO2@GN composite exhibits excellent electrochemical performances. Reversible specific capacities of 1416, 1114, and 421 mA h g−1 are achieved at rates of 0.1, 0.2, and 3.2 C, respectively. After a 100 cycle stability test, S–MnO2@GN composite cathode could still maintain a reversible capacity of 825 mA h g−1.

High-voltage LiNi0.5Mn1.5O4 with a spinel structure is considered as important cathode materials for high-energy density Li-ion batteries (LIBs). In this study, we investigate the size, structure, and the electrochemical performance of LiNi0.5Mn1.5O4 electrodes prepared by using two different-sized Mn3O4 nanocrystal precursors under different calcination conditions. As the calcination temperature rises, the particle sizes of the acquired LiNi0.5Mn1.5O4 cathode materials can vary from ~ 100 nm to ~ 1 µm, and the morphology changes from nano round shape to truncated octahedral shape. The content of Mn3+ is closely related to the calcination temperature and is affected by the size of Mn precursor. It is found that the LiNi0.5Mn1.5O4 sample prepared by using 50-nm-sized Mn3O4 nanocrystals under a calcination temperature of 800 C exhibits good cycling performance with a capacity retention ratio of 96.1% at 1 C after 200 cycles, while the LiNi0.5Mn1.5O4 sample prepared by using 7-nm-sized Mn3O4 nanocrystals under a calcination temperature of 800 °C shows an excellent rate performance with a capacity retention ratio of 98% after 500 cycles at 10 C. The results show that the size of Mn3O4 precursor is an important parameter that governs the final size and electrochemical performances of LiNi0.5Mn1.5O4 cathode materials.

In this work, the poly(styrene-vynil pyridine) block copolymer was used as a porous pattern to study the electrodeposition of gold inside the pores, as a new method to obtain gold nanoparticles. The porous pattern left by the copolymer film onto a conductive glass surface was characterized by atomic force microscopy (AFM), evidencing pores of 30 nm diameter. After the electrodeposition, 30 nm diameter gold nanoparticles were obtained and they were characterized by cyclic voltammetry (CV) and AFM, and then used to study the adsorption of glucose oxidase enzyme. The adsorption process of glucose oxidase on gold nanowires was investigated by CV and electrochemical impedance spectroscopy. The morphological and capacitance results indicate that the block copolymer–gold nanoparticle composite seems to be a good candidate to design biosensors and immunosensors.