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All‐solid‐state thin film lithium batteries (TFBs) are proposed as the ideal power sources for microelectronic devices. However, the high‐temperature (>500 °C) annealing process of cathode films, such as LiCoO2 and LiMn2O4, restricts the on‐chip integration and potential applications of TFBs. Herein, tunnel structured LixMnO2 nanosheet arrays are fabricated as 3D cathode for TFBs by a facile electrolyte Li+ ion infusion method at very low temperature of 180 °C. Featuring an interesting tunnel intergrowth structure consisting of alternating 1 × 3 and 1 × 2 tunnels, the LixMnO2 cathode shows high specific capacity with good structural stability between 2.0 and 4.3 V (vs. Li+/Li). By utilizing the 3D LixMnO2 cathode, all‐solid‐state LixMnO2/LiPON/Li TFB (3DLMO‐TFB) has been successfully constructed with prominent advantages of greatly enriched cathode/electrolyte interface and shortened Li+ diffusion length in the 3D structure. Consequently, the 3DLMO‐TFB device exhibits large specific capacity (185 mAh g−1 at 50 mA g−1), good rate performance, and excellent cycle performance (81.3% capacity retention after 1000 cycles), outperforming the TFBs using spinel LiMn2O4 thin film cathodes fabricated at high temperature. Importantly, the low‐temperature preparation of high‐performance cathode film enables the fabrication of TFBs on various rigid and flexible substrates, which could greatly expand their potential applications in microelectronics.

Lumpectomy, also called breast-conserving surgery, has become the standard surgical treatment for early-stage breast cancer. However, accurately locating the tumor during a lumpectomy, especially when the lesion is small and nonpalpable, is a challenge. Such difficulty can lead to either incomplete tumor removal or prolonged surgical time, which result in high re-operation rates (~25%) and increased surgical costs. Here, we report a fiber optoacoustic guide (FOG) with augmented reality (AR) for sub-millimeter tumor localization and intuitive surgical guidance with minimal interference. The FOG is preoperatively implanted in the tumor. Under external pulsed light excitation, the FOG omnidirectionally broadcasts acoustic waves through the optoacoustic effect by a specially designed nano-composite layer at its tip. By capturing the acoustic wave, three ultrasound sensors on the breast skin triangulate the FOG tip’s position with 0.25-mm accuracy. An AR system with a tablet measures the coordinates of the ultrasound sensors and transforms the FOG tip’s position into visual feedback with <1-mm accuracy, thus aiding surgeons in directly visualizing the tumor location and performing fast and accurate tumor removal. We further show the use of a head-mounted display to visualize the same information in the surgeons’ first-person view and achieve hands-free guidance. Towards clinical application, a surgeon successfully deployed the FOG to excise a “pseudo tumor” in a female human cadaver. With the high-accuracy tumor localization by FOG and the intuitive surgical guidance by AR, the surgeon performed accurate and fast tumor removal, which will significantly reduce re-operation rates and shorten the surgery time.

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