Areal power density is one of the core indicators determining how large areas a microbattery need to occupy when integrated directly with microelectronic devices for the Internet of Things. Unfortunately, the low power density of microbatteries hinders their applications, because microelectronic devices only provide finite areas for integration. Herein, we show that sputtered iron oxysulfide (FeO x S y ) thin films subjected to in situ plasma pretreatment display ultrahigh power density. This in situ plasma pretreatment can be regarded as a universal interface optimization strategy for suppressing mechanical degradation upon extended cycling. The synergistic effects of high structural integrity (robust interfacial adhesiveness and stress-relieving islands), perfect electrochemical reversibility, and near-surface charge exchanges (pseudocapacitive lithium storage mechanism) result in extremely high power density and stable cycling performance. The pretreated FeO x S y thin films can output an areal power density as high as 14.6 mW cm −2 and a considerable volumetric energy density of 291 μW h cm −2 μm −1 . Such a highpower density constitutes a new state-of-the-art level for sputtered thin-film materials with comparative areal capacity. This work provides an efficient and simple pretreatment method for achieving ultrahigh-power and stable thin-film electrodes for microbatteries.

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Lithium-sulfur (Li–S) system coupled with thin-film solid electrolyte as a novel high-energy micro-battery has enormous potential for complementing embedded energy harvesters to enable the autonomy of the Internet of Things microdevice. However, the volatility in high vacuum and intrinsic sluggish kinetics of S hinder researchers from empirically integrating it into all-solid-state thin-film batteries, leading to inexperience in fabricating all-solid-state thin-film Li–S batteries (TFLSBs). Herein, for the first time, TFLSBs have been successfully constructed by stacking vertical graphene nanosheets-Li2S (VGs-Li2S) composite thin-film cathode, lithium-phosphorous-oxynitride (LiPON) thin-film solid electrolyte, and Li metal anode. Fundamentally eliminating Li-polysulfide shuttle effect and maintaining a stable VGs-Li2S/LiPON interface upon prolonged cycles have been well identified by employing the solid-state Li–S system with an “unlimited Li” reservoir, which exhibits excellent long-term cycling stability with a capacity retention of 81% for 3,000 cycles, and an exceptional high temperature tolerance up to 60 °C. More impressively, VGs-Li2S-based TFLSBs with evaporated-Li thin-film anode also demonstrate outstanding cycling performance over 500 cycles with a high Coulombic efficiency of 99.71%. Collectively, this study presents a new development strategy for secure and high-performance rechargeable all-solid-state thin-film batteries.