Abstract
Carbon coated Si (Si/C) composites with a high Si content of 81 wt% are synthesized by one-pot carbonization of the mixture containing commercial Si particles and polyvinylidene fluoride (PVDF) at an optimized temperature. The Si/C electrodes deliver a high cyclic capacity of 2003 mA h g-1 at 0.5 A g-1 after 50 cycles and an enhanced rate capability of ~750 mA h g-1 at 4 A g-1 for over 200 cycles. The effect of ultrathin carbon coating on lithiation mechanisms of Si particles is evaluated using the in-situ transmission electron microscopy (TEM). It is revealed that the carbon-coated Si particles undergo an isotropic to anisotropic transition during the initial lithiation, whereas such transition is not observed for the uncoated Si particle. The lithiation rate of Si/C is 3-4.5 times faster than that of uncoated Si with the same diameter, a testament to high rate capacities of Si/C in real batteries. The flexible, amorphous carbon coating favorably alters the damage mode of Si particles from pulverization by multiple cracking to fracture by a single crack. The above findings offer fundamental understanding and practical guideline for designing carbon coatings of Si-based electrodes with much enhanced electrochemical performance.
Original language | British English |
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Pages (from-to) | 45-54 |
Number of pages | 10 |
Journal | Energy Storage Materials |
Volume | 3 |
DOIs | |
State | Published - 1 Apr 2016 |
Keywords
- Carbon coating
- in-situ TEM
- Li-ion batteries
- Silicon particles