Anode interphase engineering for high-performance next-generation batteries
Abstract
Lithium (Li) and Silicon (Si) have been considered as promising anode materials for the next-generation batteries due to high theoretical capacity (3860 mAh g-1 for Li and 3580 mAh g-1 for Si). However, they both face great challenges that obstruct their practical application, such as unstable solid-electrolyte interphase (SEI) and large volume change. Moreover, Li also suffers from the uncontrollable dendrite growth, whereas Si suffers from slow reaction kinetics. This thesis mainly focuses on the interphase engineering to tackle the challenges of Li and Si anode materials.
First, organic polyurea (PU) coating is deposited on Li by molecular layer deposition (MLD) as a protective film. The post-cycling investigation revealed that PU can suppress dendrite growth and stabilize SEI. This work demonstrates MLD thin film technology as an effective strategy for interphase engineering on anode material. Secondly, the following study shows that the mechanical property of MLD PU film can be tuned by inorganic aluminum crosslinker. The stiffness of PU is improved by the incorporation of crosslinker, and the cycling stability of Li is improved significantly owing to the enhanced mechanical property. Thirdly, the accurate control on the gradient distribution of inorganic component for the nano-scale thin film is achieved by MLD for the first time. The inorganic lithiophilic zinc sites can facilitate the Li nucleation on the inner side, while organic insulating PU on the top can confine Li deposition underneath. Owing to the elaborate design of ‘gradient coating’, the protected Li exhibits long cycling over 1500 hours in the next-generation Li-O2 battery. Both studies on mechanical property and gradient of inorganic component reveal the role of MLD thin film for Li and provide deep insight on the design of interphase engineering. Finally, the MLD PU strategy is extended to Si/C composite electrode to tackle the volume change and unstable SEI. The flexible PU film can enable a stable performance of Si/C anode with a high areal capacity over 3 mAh cm-2. The excellent cycling performance enabled by MLD strategy in this work contributes great potential to break through the bottleneck of energy density for Lithium-ion batteries (LIBs).