Lithium-ion batteries (LIBs) and electrical double-layer capacitors (EDLCs) are widely used in commercial energy storage systems, but each has inherent limitations. To overcome these limitations, the lithium-ion capacitor (LIC) has emerged as a hybrid energy storage device, combining the benefits of LIBs and EDLCs. However, the introduction of active lithium into LICs poses challenges due to lithium's reactivity and instability. In this study, we propose a dual wet chemical prelithiation strategy to enhance LIC performance. By wet chemically prelithiating both the activated carbon cathodes and hard carbon anodes, significant improvements are achieved compared to traditional prelithiation methods. The dual prelithiation approach outperforms electrochemical prelithiation in terms of energy storage performance, cycle life, and process simplification. LICs with dual wet chemically prelithiated electrodes demonstrate the highest energy density and retain a substantial portion of reversible capacity even at high discharge rates. The strategy exhibits fast kinetics and wide operational stability. In contrast, LICs with metallic lithium anodes or electrochemically prelithiated hard carbon anodes exhibit inferior performance and limited cycle life. The dual wet chemical prelithiation strategy represents a breakthrough in LIC technology, offering superior performance, cycle stability, and scalability. It holds promise for alkali-ion energy storage systems and drives advancements in electrochemical energy storage technology.
This investigation explores the differentiated electrochemical behavior of silicon (Si) anodes in lithium-ion batteries (LIBs) under different operating protocols defined by specific voltage windows and capacity control strategies. Our investigation reveals distinctive responses of the Si anode to different state of charge (SoC) ranges, translating delivered capacity into significant variations in cycle life. While predominantly mostly lithiated Si anodes at 0.01-0.32 V subjected to voltage-controlled operation with an SoC between 75% and 100% exhibit poor cycle life, a similar situation with predominantly mostly delithiated anodes at 0.23-1.5 V and an SoC of 0%-25% also results in inferior cycle performance. Conversely, predominantly partially lithiated Si anodes at 0.01-0.5V under voltage-controlled conditions with an SoC range of 65%-100% show superior cycle life performance. However, predominantly partially delithiated Si anodes at 0.1-1.5 V, voltage controlled with an SoC of 0%-40%, lead to a cycle life with obvious degradation. Likewise, Si anodes subjected to full lithiation followed by delithiation at 1200 mA h g-1, controlled by delithiation capacity, demonstrate excellent cycle life within a SoC range of 65%-100%. On the contrary, full delithiation followed by lithiation at 1200 mA h g-1 results in less favorable cycle life within an SoC range of 0%-35%. In short, maintaining the lithiation state at a higher level, i.e. a high SoC, throughout the cycle allows Si anodes to maintain low impedance, resulting in outstanding cycle performance. These results provide important insights into tailoring operating parameters to optimize Si anode cycle performance in LIBs.
Following a rigorous semester of hard work, we gathered at Sheraton to indulge in a delightful afternoon tea and extend heartfelt blessings to our new graduates for a bright and prosperous future ahead.
