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The interfacial instabilities, including side reactions due to electrolyte decompositions and Cobalt (Co) dissolutions, are the main detrimental processes at LiCoO2 cathode when a high-voltage window (>4.2 V) is applied. Nevertheless, cycling the cathode with a voltage above 4.2 V would deliver an increased gravimetric capacity, which is desired for high power battery operation. To address these drawbacks, we demonstrate a synergistic approach by manufacturing the three-dimensional high-temperature LiCoO2 electrodes (3D HT-LCO) using laser-microstructuring, laser-annealing and subsequent coating with polymerized C60 thin films (C60@3D HT-LCO) by plasma-assisted thermal evaporation. The C60@3D HT-LCO cathode delivers higher initial discharge capacity compared to its theoretical value, i.e. 175 mA h g−1 at 0.1 C with cut-off voltage of 3.0–4.5 V. This cathode combines the advantages of the 3D electrode architecture and an advanced C60 coating/passivation concept leading to an improved electrochemical performance, due to an increased active surface area, a decreased charge transfer resistance, a prevented Co dissolution into the electrolyte and a suppressed side reaction and electrolyte decomposition. This work provides a novel solution for other cathode materials having similar concerns in high potential regimes for application in lithium-ion microbatteries.

Due to the excellent theoretical capacity, silicon-based electrodes have been extensively studied to develop high energy-density lithium-ion batteries (LIBs). Nevertheless, the large volume expansion and unfavorable interface seriously hamper its application, and the underlying physics behind are still unclear. In this work, using in-situ environment scanning electron microscopy (ESEM), the morphological evolution of composite silicon-graphite electrodes with different ionic liquids as electrolytes are compared in the range of 20 °C–60 °C. Surprisingly, combining the microstructure and surface reaction products from transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS), it finds out that the fully reaction of lithium-silicon does not generate huge volume expansion, while the side reaction between graphite and electrolyte decomposition products causes dramatic volume expansion and hinders the further lithiation of silicon. On the other hand, the electrolyte which is capable of rapidly releasing F− to form LiF-rich solid electrolyte interphase (SEI) is favorable to maintain the structure integrity and cycling performance. This work casts new understanding from the perspective of intrinsic reaction between electrode and ionic liquid electrolyte, which suggests that the practical application of silicon-based electrodes with appropriate electrolyte is a promising route for high energy-density LIBs.

Practical application of silicon anodes for lithium-ion batteries has been mainly hindered because of their low electrical conductivity and large volume change (ca. 300%) occurring during the lithiation and delithiation processes. Thus, the surface engineering of active particles (material design) and the modification of electrode structure (electrode design) of silicon are necessary to alleviate these critical limiting factors. Silicon/carbon core–shell particles (Si@C, material design) are prepared by the thermal decomposition and subsequent three-dimensional (3D) electrode structures (electrode design) with a channel width of 15 μm are incorporated using the laser ablation process. The electrochemical characteristics of 3D Si@C used as the anode material for lithium-ion batteries are investigated to identify the effects of material and electrode design. By the introduction of a carbon coating and the laser structuring, an enhanced performance of Si anode materials exhibiting high specific capacity (>1200 mAh g −1 over 300 cycles), good rate capability (1170 mAh g −1 at 8 A g −1 ), and stable cycling is achieved. The morphology of the core–shell active material combined with 3D channel architecture can minimize the volume expansion by utilizing the void space during the repeated cycling.

Porous LiMn 2 O 4 thick-film cathodes for Li-ion microbatteries are realized by laser-printing. The porous structure of the printed composite cathode consisting of active powder, binder, carbon black and graphite enables ionic and electronic transport through 50–60 μm thick electrodes due to its high intrinsic active surface area. In order to further improve the cycle stability and capacity retention of the laser-printed thick-film cathodes for discharging rates up to 1 C, laser-printed thick films are first calendered in a press and then structured using ultrafast femtosecond-laser radiation in order to form three-dimensional (3D) cathode architectures. It is shown that calendered/laser structured cathodes in the form of rectangular 3D grids exhibit discharge capacity retention of 68% at a 1 C rate, while calendered but unstructured cathodes retain only about 45% of their initial capacity at the same discharge rate. Overall, the improved discharge capacity retention and reduced degradation during later cycles can be attributed to the combination of increased electrical contact with shortened Li-ion pathways.