Super high capacity of silicon carbon anode over 6500 mAh g-1 for lithium battery

Abstract

As silicon is approaching its theoretical limit for the anode materials in lithium battery, searching for a higher limit is indispensable. Herein, we demonstrate the possible of achieving ultrahigh capacity over 6500 mAh g-1 in silicon-carbon composites. Considering the numerous defects inside the silicon nanostructures, it is deduced the formation of quasi-Bose Einstein condensation should be possible, which can lead to the low viscosity flow of lithium-ions through the anode. At a charge-discharge rate of 0.1C (0.42 A g-1), the initial discharge specific capacity reaches 6694.21 mAh g-1, with a Coulomb efficiency (CE) of 74.71%, significantly exceeding the theoretical capacity limit of silicon. Further optimization of the anode material ratio results in improved cycling stability, with a discharge specific capacity of 5542.98 mAh g-1 and a CE of 85.25% at 0.1C. When the initial discharge capacity is 4043.01 mAh g-1, the CE rises to 86.13%. By training a multilayer perceptron with material parameters as inputs and subsequently optimizing it using a constrained genetic algorithm, an initial discharge specific capacity of up to 7789.55 mAh g-1 can be achieved theoretically. This study demonstrates that silicon-carbon composites have great potential to significantly enhance the energy density of lithium-ion batteries.