No abstract

Metal‐assisted chemical etching (MACE) provides a versatile way to synthesize silicon nanowires (SiNW) of different morphologies. MACE was used to synthesize oxide‐free porous and nonporous SiNW for use as anodes for lithium‐ion batteries. To improve their processing behavior, the SiNW were functionalized using acrylic acid. Differential capacity plots were used as a way to identify the degradation processes during cycling through tracking the formation of Li15Si4 and changes in polarization. The cycling performance between porous and nonporous SiNW differed regarding Coulombic efficiency and cycling stability. The differences were attributed to the porous hull and its ability to reduce the volume expansion, although not through its porous nature but the reduced uptake of Li ions.

Silicon based materials show highest capacity among state-of-the art anode materials for LIBs and next generation batteries. Silicon anodes attract wide attention due to high specific capacity of Si, i.e. 3590mAh/g for Li15Si4 phase at room temperature. As known, large volume changes and subsequent pulverization of brittle Si during cycling can be alleviated by using nano-sized Si particles [1]. However, the surrounding binder matrix still has to compensate large stress and strain induced by accumulated volume changes of the single particles. The works presented here focus on the challenges on the electrode level. Choice of binder is crucial to create a matrix that can accommodate mechanical stress and strain during prolonged charge/discharge cycles. For reliable comparison of the impact of active material/binder ensembles, equal properties of electrodes (loading, porosity) are very important and hence receive special attention. To investigate the impact of processing and electrode matrix in more detail, electrodes with high Si contents (60 to 80wt.%) and controlled, application-related loadings are produced. Characterization is carried out in laboratory sized pouch bag cells. Crucial parameters such as binder, processing, loading and voltage regime on available capacity and cycle life are discussed. Remaining reversible capacity of more than 1500mAh/gcoating (1875mAh/gSi) after 100 cycles at 0.5C is reported. Remaining electrode capacity is approx. 1.5mAh/cm² at this point. [1]: H. Wu, Y. Cui, Nano Today (2012) Figure 1

Aerosol Jet® Printing is investigated as deposition technique for silicon as anode material for lithium-ion batteries. Binder free structures with silicon particles were deposited and galvanostaticly cycled. The morphological changes of the electrode were examined with SEM, Raman spectroscopy and x-ray photon spectroscopy (XPS). The fast degradation is explained with the huge amount of side reactions building LiF and the low conductivity of the intrinsic silicon particles. The addition of conducting carbon did not affect cycling stability.