In recent years, both silicon thin films and nickel-rich layered oxides have received much attention as promising anode or cathode materials for next generation lithium ion batteries, respectively. In this work, full cells containing Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 (NCM811) as cathode in combination with amorphous columnar silicon thin films as anode are evaluated in coin cells and 3-electrode cells with varying capacity balancing. Full cells with area capacity ratios of negative to positive electrodes (n/p-ratio) reaching from 1.15 : 1 to 2.70 : 1 are studied. The cells with a high n/p-ratio (2.00 : 1 and 2.70 : 1) show significantly lower specific capacity of 115 mA h g NCM −1 after 50 cycles of galvanostatic cycling in comparison to 130 mA h g NCM −1 for a cell with a n/p-ratio of 1.15 : 1. One reason for this phenomenon is the decline of the initial coulombic efficiency with increasing n/p-ratios. Secondly, through only partial utilization of the silicon anode by using high n/p-ratios, the anode potential is increased at the end of charge. This leads to a higher cathode potential and therefore a faster degradation of the cell. In summary, for designing high performance NCM811/Si full cells, high n/p-ratios should be avoided.
We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm2, a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging.
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