Graphite As an Anode in Lithium-Ion Batteries
Graphite is the perfect anode material for lithium-ion batteries (LIBs) with its incomparable balance of low cost, high energy density, and long cycle life. It is also a key element in advanced LIBs for electric vehicles and grid-scale energy storage applications.
The development of highly efficient battery cells has led to a new generation of advanced LIBs featuring high energy densities and a range of different anode materials. These include graphite-based negative electrodes or silicon-based composite anodes containing silicon monoxide (SiO), which exhibit superior capacity performance while delivering higher cyclability than pure graphite.
However, incorporating SiO into stable graphite anode degrades not only cycle life but also calendar life of LIBs, while little is known about its aging mechanisms. In this study, we investigate the thermal instability of graphite/SiO composite anode and reveal that SiO accelerates not only the loss of stored lithium but also facilitates the lithium de-intercalation from graphite.
Stable graphite anode consists of fully lithiated and charged graphite particles, which have a rigid SEI preventing the leakage of electrons from the active material to the electrolyte. This mechanism is crucial to the rate capability of the graphite anode.
In a typical electrolyte, the cation-exchange capacity (CEC) of the anode increases in step with charging until it reaches a peak value, which is the maximum induced CEC. Once the charge is discharged, the cation-exchange capacity of the anode decreases again, and this process is referred to as self-discharge.
