Silicon is being increasingly studied as the next-generation anode material for Li-ion batteries because of its ten times higher gravimetric capacity compared with the widely-used graphite. While nanoparticles and other nanostructured silicon materials often exhibit good cyclability, their volumetric capacity tends to be worse or similar than that of graphite. Furthermore, these materials are commonly complicated and expensive to produce. An effortless way to produce nanostructured silicon is electrochemical anodization. However, there is no systematic study how various material properties affect its performance in LIBs. In the present study, the effects of particle size, surface passivation and boron doping degree were evaluated for the mesoporous silicon with relatively low porosity of 50%. This porosity value was estimated to be the lowest value for the silicon material that still can accommodate the substantial volume change during the charge/discharge cycling. The optimal particle size was between 10–20 µm, the carbide layer enhanced the rate capability by improving the lithiation kinetics, and higher levels of boron doping were beneficial for obtaining higher specific capacity at lower rates. Comparison of pristine and cycled electrodes revealed the loss of electrical contact and electrolyte decay to be the major contributors to the capacity decay.

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In this study, various methods to study individual electrodes in polymer electrolyte membrane cells are reviewed and a novel reference electrode design is developed for a laboratory scale single cell polymer electrolyte membrane water electrolyser. The design uses an internal pseudo-reference electrode which is proven to enable galvanostatic electrochemical impedance spectroscopy studies. The setup is used to study the state-of-the-art electrode materials with high loadings in a start-stop cycling durability test. The cycled catalyst layers are characterized ex-situ with SEM, TEM and XRD. As a result, on the anode the mass transport resistance increases, the macro porosity increases and a structural change from amorphous IrO x toward crystalline IrO 2 is detected. On the cathode the platinum particle size increases and an intensifying corrosion phenomenon is detected. In overall, this degradation has still low effect on the full cell performance during the studied 1750 hours. However, there is a clear indication that if the start-stop cycling is further continued, the cell will experience a dramatic performance loss much sooner than when operating it in a constant current mode.

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Two new atomic/molecular layer deposition processes for depositing crystalline metal‐organic thin films, built from 1,4‐benzenedisulfonate (BDS) as the organic linker and Cu or Li as the metal node, are reported. The processes yield in‐situ crystalline but hydrated Cu‐BDS and Li‐BDS films; in the former case, the crystal structure is of a previously known metal‐organic‐framework‐like structure, while in the latter case not known from previous studies. Both hydrated materials can be readily dried to obtain the crystalline unhydrated phases. The stability and the ionic conductivity of the unhydrated Li‐BDS films were characterized to assess their applicability as a thin film solid polymer Li‐ion conductor.

Mesoporous thin films of PtCo, PtNi and PtCu are prepared by a single-step potentiostatic electrodeposition on a carbon substrate. Films are characterized by SEM, XRD, XRF and BET, and their activity for oxygen reduction reaction (ORR) is studied in an acidic three-electrode cell. The results are compared with both a commercial nanoparticle Pt/C catalyst and a Pt catalyst prepared using the same method. Additionally, the ORR activity of PtCo is studied in a fuel cell. The onset potential of ORR is found to be higher for all the electrodeposited catalysts compared to commercial Pt/C. The ORR activity of mesoporous Pt is found to be linearly dependent on the amount of deposited platinum within a platinum loading range of 0.1−0.5 mg cm −2. All the mesoporous catalysts exhibited higher mass activity towards ORR than commercial Pt/C. Of the studied catalysts, PtCo is found to have the highest durability. Similar results are obtained in fuel cell experiments as PtCo exhibits enhanced durability and activity towards ORR, peak powers being 60, 70 and 90 mW gPt −1 for commercial Pt/C, mesoporous Pt and mesoporous PtCo, respectively.

A high‐performing, lightweight, and flexible asymmetric supercapacitor (ASC) using NiCo‐layered double hydroxide (NiCo LDH) supported on 3D nitrogen‐doped graphene (NG) as a positive electrode and NG as a negative electrode is demonstrated. Highly conductive NG provides fast electron transfer and facilitates (dis)charging of NiCo LDH deposited on it. The composite electrode of NiCo LDH@NG exhibits a high specific capacitance of 1421 F g−1 at 2 A g−1. Moreover, the as‐obtained hybrid electrode shows an excellent rate capability with a specific capacitance of 1397 F g−1 at a high current density of 10 A g−1, which is about 98% of the capacitance obtained at 2 A g−1. The flexible ASC device shows a specific capacitance of 109 F g−1 at 0.5 A g−1 and a maximum energy density of 49 W h kg−1, which is comparable with or superior to previously reported electrodes based on nickel‐cobalt hydroxides. Furthermore, an excellent mechanical stability is obtained. Under repeated mechanical bendings, the ASC demonstrates high bending stability up to 450 bending cycles at a 90° angle. Hence, this flexible NiCo LDH@NG electrode that is free of binders and conductive agents shows superior performance and stability, and is a promising candidate for the future wearable energy storage devices.