Abstract
Silicon (Si) has been well recognized as a promising candidate to replace graphite because of its earth abundance and high‐capacity storage, but its large volume changes upon lithiation/delithiation and the consequential material fracturing, loss of electrical contact, and over‐consumption of the electrolyte prevent its full application. As a countermeasure for rapid capacity decay, a composite electrode of graphite and Si has been adopted by accommodating Si nanoparticles in a graphite matrix. Such an approach, which involves two materials that interact electrochemically with lithium in the electrode, necessitates an analytical methodology to determine the individual electrochemical behavior of each active material. In this work, a methodology comprising differential plots and integral calculus is established to analyze the complicated interplay among the two active batteries and investigate the failure mechanism underlying capacity fade in the blend electrode. To address performance deficiencies identified by this methodology, an aluminum alkoxide (alucone) surface‐modification strategy is demonstrated to stabilize the structure and electrochemical performance of the graphite‐Si composite electrode. The integrated approach established in this work is of great importance to the design and diagnostics of a multi‐component composite electrode, which is expected to be high interest to other next‐generation battery system.
Highlights
Developing sustainable, inexpensive, and high-energy-density Li-ion batteries (LIBs) is vital to realize electrified transportation and deepen the penetration of renewable energy.[1]
With this artificial interphase layer, we demonstrate highly reversible graphite and Si (G–Si) electrodes with a specific capacity of ≈810 mAh g−1 (2 mAh cm−2) for hundreds of charge–discharge cycles
It is noteworthy that the G–Si composite electrode fails to deliver the capacity of 308 mAh g−1, which should be achieved by the graphite component alone
Summary
Developing sustainable, inexpensive, and high-energy-density Li-ion batteries (LIBs) is vital to realize electrified transportation and deepen the penetration of renewable energy.[1]. To alleviate mechanical instabilities and simultaneously improve energy density of Si anodes, composite electrodes comprising graphite and Si (G–Si) at various ratios have increasingly been investigated.[23–26]. A surface modification enabled by a molecular layer deposition (MLD) technique, recently demonstrated in our research group,[27–33] has been applied on the G–Si composite electrodes to stabilize the surface of the Si component. With this artificial interphase layer, we demonstrate highly reversible G–Si electrodes with a specific capacity of ≈810 mAh g−1 (2 mAh cm−2) for hundreds of charge–discharge cycles
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