Highly Durable Sn-Ni Alloy Anode Pretreated in Vinylene Carbonate-Containing Electrolyte for Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) are promising energy storage devices for electric vehicles because they rank between LIBs and EDLCs in terms of energy and power density. In a previous work, an LIC with a Sn-Ni alloy anode was proven to be superior in terms of energy and power density compared to that with a graphite anode. To improve the cycle durability at a practical level, the effect of vinylene carbonate (VC), which positively affects LIBs, was investigated. VC demonstrates a positive effect during the pre-treatment process, but also a negative effect during charge-discharge cycling. The difference between these effects is discussed in terms of the potential and morphology changes of the anode, revealing that the VC forms a polymer-like solid electrolyte interphase during the pre-treatment process, suppressing the deactivation of Sn caused by crack growth and peeling off during charge-discharge cycling. In contrast, VC continuously decomposes during charge-discharge cycling while consuming pre-treated lithium. Finally, an excellent cycle durability (10,000 cycles with a capacity retention of 72.3%) is here demonstrated for the first time for the LIC with a high volumetric energy density of 38.9 Wh L −1 at 120 W L −1 .