Improvement of Cyclability of Li-Ion Batteries Using C-Coated Si Nanopowder Electrode Fabricated from Si Swarf with Limitation of Delithiation Capacity

Abstract

We have fabricated Si nanopowder from Si swarf using the simple ball milling method, and applied to Li-ion battery electrodes. Limitation of the delithiation capacity after deep lithiation at 0.01 V is the most effective to achieve a constant high capacity for long cycles. The delithiation capacity keeps constant at 1500 mAh/g until the 290th cycle, and it slightly decreases to 1480 mAh/g at the 300th cycle. However, without limitation of the lithiation and delithiation capacities in the voltage range between 1.5 and 0.01 V, the delithiation capacity monotonically decreases with the cycle number, and it becomes 950 mAh/g at the 300th cycle. With limitation of the lithiation capacity at 1500 mAh/g after deep delithiation at 1.5 V, the delithiation capacity keeps 1470 mAh/g until the 137th cycle, and then decreases monotonically with the cycles to 860 mAh/g at the 300th cycle. With limitation of the delithiation capacity, the overvoltage estimated from the lithiation and delithiation curves is the lowest, and peeling-off of Si nanopowder from the Si electrode is suppressed because of limited size changes of Si nanopowder during lithiation and delithiation of Si nanopowder.

Morphological Changes of Silicon Nanoparticles and the Influence of Cutoff Potentials in Silicon-Graphite Electrodes

“…for delithiation-limited SiG electrode cycling (0.01-0.65 V; marine symbols), only a comparatively small capacity fade upon cycling is observed. In this case, ∼15% (∼0.25 mAh cm −2 ) of active lithium remain in the silicon, which according to Kimura et al 42 reduces the formation of electronically insulated silicon particles. We would like to stress that although the capacity contribution from graphite is likely smaller for the lithiation-limited electrode (0.05-1.25 V; blue symbols), a similar behavior was also reported in the literature for silicon-based electrodes which did not contain any graphite.…”

“…We would like to stress that although the capacity contribution from graphite is likely smaller for the lithiation-limited electrode (0.05-1.25 V; blue symbols), a similar behavior was also reported in the literature for silicon-based electrodes which did not contain any graphite. 40,42 Next, we wanted to understand whether the improved cycling stability at the delithiation-limited cutoff potential results really from an improved electrode integrity and decreased overpotential or results just from a reduced lithium immobilization in poorly connected silicon particles due to the deliberate incomplete lithiation. Hence, the delithiation capacity of the intermediate cycles which were performed similarly for all electrodes in the full potential range with a deep delithiation (0.01-2.0 V vs. Li + /Li) at very low C-rates is summarized in Table I.…”

“…Based on our previous work, 39 where we differentiated two distinct degradation phenomena occurring in silicon-graphite electrodes, namely (i) the roughening of the silicon particles upon repeated (de-)lithiation which leads to increased irreversible capacity losses (furtheron described as silicon particle degradation), and (ii) the decay in the reversible capacity which mainly originates from increased interparticle contact resistances between the silicon particles (furtheron described as electrode degradation), we now focus on the underlying morphological changes of the silicon particles and of the electrode structure that occur upon repeated (de-)lithiation. Inspired by recent publications of the groups of Aurbach, 40 Abraham, 41 and Kobayashi,42 who independently reported a significant difference in the cycling stability of silicon-based electrodes depending on a capacity or potential limitation either during lithiation or delithiation, we extend our analysis of the different degradation phenonema by two cutoff potentiallimited cycling protocols. While it is widely accepted in the literature 8 that limiting the capacity of silicon reduces its degradation and irreversible capacity loss, the differences between limiting either the lower or the upper cutoff potential still require further understanding.…”

The Role of Balancing Nanostructured Silicon Anodes and NMC Cathodes in Lithium-Ion Full-Cells with High Volumetric Energy Density

“…In several works, a similar limitation of the capacity of silicon electrodes is applied and the electrode stability in half-cells could be significantly improved. 76 Nevertheless, the higher anode mass has to be taken into account which decreases the energy density. In addition, as it can be seen from the voltage profiles of the NMC cathode and Si anode derived from the half-cell tests in Fig.…”

Si Swarf Wrapped by Graphite Sheets for Li-Ion Battery Electrodes with Improved Overvoltage and Cyclability

“…4,5 We have investigated the reaction mechanisms of Si swarf electrodes. [6][7][8] Si swarf is a flakeshaped nano-Si material generated with nearly half the weight of a Si ingot for solar cells during the slicing process. 0.1 million tons of Si swarf are generated per year over the world from Si ingots that are produced with processes at 1000 °C ∼ 1800 °C from silica.…”