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.