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Abstract Lithium‐ion batteries are indispensable power sources for a wide range of modern electronic devices. However, battery lifespan remains a critical limitation, directly affecting the sustainability and user experience. Conventional battery failure analysis in controlled lab settings may not capture the complex interactions and environmental factors encountered in real‐world, in‐device operating conditions. This study analyzes the failure of commercial wireless earbud batteries as a model system within their intended usage context. Through multiscale and multimodal characterizations, the degradations from the material level to the device level are correlated, elucidating a failure pattern that is closely tied to the specific device configuration and operating conditions. The findings indicate that the ultimate failure mode is determined by the interplay of battery materials, cell structural design, and the in‐device microenvironment, such as temperature gradients and their fluctuations. This holistic, in‐device perspective on environmental influences provides critical insights for battery integration design, enhancing the reliability of modern electronics. 

Hydrated vanadates are promising layered cathodes for aqueous zinc-ion batteries owing to their specific capacity as high as 400 mA h g −1 ; however, the structural instability causes serious cycling degradation through repeated intercalation/deintercalation reactions. This study reveals the chemically inserted Mn( ii ) cations act as structural pillars, expand the interplanar spacing, connect the adjacent layers and partially reduce pentavalent vanadium cations to tetravalent. The expanded interplanar spacing to 12.9 Å reduces electrostatic interactions, and transition metal cations collectively promote and catalyze fast and more zinc ion intercalation at higher discharge current densities with much enhanced reversibility and cycling stability. Manganese expanded hydrated vanadate (MnVO) delivers a specific capacity of 415 mA h g −1 at a current density of 50 mA g −1 and 260 mA h g −1 at 4 A g −1 with a capacity retention of 92% over 2000 cycles. The energy efficiency increases from 41% for hydrated vanadium pentoxide (VOH) to 70% for MnVO at 4 A g −1 and the open circuit voltage remains at 85% of the cutoff voltage in the MnVO battery on the shelf after 50 days. Expanded hydrated vanadate with other transition metal cations for high-performance aqueous zinc-ion batteries is also obtained, suggesting it is a general strategy for exploiting high-performance cathodes for multi-valent ion batteries. 

Generating oxygen vacancies (Vö) in vanadium pentoxide (V 2 O 5 ) has been demonstrated as an effective approach to tailor its electrochemical properties. The present study investigates three different kinds of conductive polymer (CP = PPy, PEDOT, and PANI) coated V 2 O 5 nanofibers with Vö generated at the interface during the polymerization process. Surface Vö form a local electric field and promote the charge transfer kinetics of the resulting Vö-V 2 O 5 /CP nanocables, and the accompanying V 4+ and V 3+ ions may also catalyze the redox reactions and improve the supercapacitor performance. The differences and similarities of three different CP coatings have been compared and discussed, and are dependent on their polymerization conditions and coating thickness. The distribution of Vö in the surface layer and in the bulk has been elaborated and the corresponding effects on the electrochemical properties and supercapacitor performance have also been investigated. Vö-V 2 O 5 /CP can deliver a high capacity of up to 614 F g −1 at a current rate of 0.5 A g −1 and supercapacitors with Vö-V 2 O 5 /CP demonstrated excellent cycling stability over 15 000 cycles at a rate of 10 A g −1 .