Interfacial strain engineering induces fatigue-resistant, high-capacity photo-assisted lithium storage

Mechanical fatigue, rather than redox instability, often limits the lifetime of high-capacity battery electrodes, as repeated ion insertion induces microstrain, cracking, and interfacial failure. Here, we show that interfacial strain engineering can be used to mitigate this vulnerability, enabling improved cyclability and capacity in metal-ion systems. Using a multiphase TiO₂/K₂Ti₄O₉-reduced graphene oxide composite as a model platform, we demonstrate that interfacial strain arising from intimately coupled oxide–oxide and oxide–carbon interfaces enhances photo-assisted lithium storage and contributes to fatigue-resistant cycling behaviour. These strain-modulated interfaces promote charge separation, improve Li+ transport, and help to stabilise the electrode framework against repeated volume fluctuations. The photoelectrode delivers a light-enhanced capacity of ∼534 mAh g⁻¹ at 0.1C, exceeding the theoretical limit of TiO₂, and retains >86% of its capacity after 300 cycles at 1C. Operando Raman microscopy, together with ex situ and post-mortem analyses, shows that strain relaxation correlates with suppressed disorder accumulation and delayed interfacial degradation. These findings highlight interfacial strain engineering as a promising strategy for stabilising high-capacity electrodes in photo-assisted and broader battery chemistries limited by mechanically driven capacity fade.