Cross-linked aluminum dioxybenzene coating for stabilization of silicon electrodes

Highlights: • New polymeric hybrid inorganic–organic coating covalently bonded to silicon particles via molecular layer deposition. • Resolved the chemistry of the hybrid coating during crosslinking reactions. • High performance and high-rate-capable lithium-ion Si anode enabled by this robust, conductive surface coating. Progress toward a commercially viable silicon anode for lithium-ion batteries has been impeded by silicon's rapid capacity fade caused by large volumetric expansion and unstable solid-electrolyte interphases. This study focuses on developing unique coating chemistries to stabilize the surface of silicon (Si) electrodes via molecular layer deposition (MLD), as well as to accommodate volume changes during electrochemical reactions. A new reaction precursor – an aromatic organic diol, hydroquinone – combined with trimethylaluminum, has led to a robust, elastic, conductive surface coating composed of aluminum dioxybenzene. We studied the chemical and physical properties of this surface coating using X-ray absorption spectroscopy, electrochemical impedance, and nanoindentation. The flexibility of the coating enables the accommodation of volumetric changes and maintenance of the mechanical integrity of the Si electrodes. By applying this robust and conductive trimethylaluminum-hydroquinone coating, we demonstrate a Si anode that is reversible and capable of high performance and high rate, achieving over 200 cycles with capacities of nearly 1500 mAh g⁻¹. This research elucidates the significance of surface modification for high-energy battery materials with large volume changes, and also provides a platform for a new design of electrode surface coatings, with the aim of achieving durable, high energy density lithium-ion batteries.