Softening of thermoelectric generators facilitates conformal contact with arbitrary-shaped heat sources, which offers an opportunity to realize self-powered wearable applications. However, existing wearable thermoelectric devices inevitably exhibit reduced thermoelectric conversion efficiency due to the parasitic heat loss in high-thermal-impedance polymer substrates and poor thermal contact arising from rigid interconnects. Here, we propose compliant thermoelectric generators with intrinsically stretchable interconnects and soft heat conductors that achieve high thermoelectric performance and unprecedented conformability simultaneously. The silver-nanowire-based soft electrodes interconnect bismuth-telluride-based thermoelectric legs, effectively absorbing strain energy, which allows our thermoelectric generators to conform perfectly to curved surfaces. Metal particles magnetically self-assembled in elastomeric substrates form soft heat conductors that significantly enhance the heat transfer to the thermoelectric legs, thereby maximizing energy conversion efficiency on three-dimensional heat sources. Moreover, automated additive manufacturing paves the way for realizing self-powered wearable applications comprising hundreds of thermoelectric legs with high customizability under ambient conditions.

Skin-like health care patches (SHPs) are next-generation health care gadgets that will enable seamless monitoring of biological signals in daily life. Skin-conformable sensors and a stretchable display are critical for the development of standalone SHPs that provide real-time information while alleviating privacy concerns related to wireless data transmission. However, the production of stretchable wearable displays with sufficient pixels to display this information remains challenging. Here, we report a standalone organic SHP that provides real-time heart rate information. The 15-μm-thick SHP comprises a stretchable organic light-emitting diode display and stretchable organic photoplethysmography (PPG) heart rate sensor on all-elastomer substrate and operates stably under 30% strain using a combination of stress relief layers and deformable micro-cracked interconnects that reduce the mechanical stress on the active optoelectronic components. This approach provides a rational strategy for high-resolution stretchable displays, enabling the production of ideal platforms for next-generation wearable health care electronics.

Formation of a glue-nanofiller layer between grains, consisting of a middle-temperature spinel-like Lix CoO2 phase, reinforces the strength of the incoherent interfacial binding between anisotropically oriented grains by enhancing the face-to-face adhesion strength. The cathode treated with the glue-layer exhibits steady cycling performance at both room-temperature and 60 °C. These results represent a step forward in advanced lithium-ion batteries via simple cathode coating.

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along the grain boundaries. [12][13][14][15] Consequently, such structural instability causes rapid capacity fading and poor electrochemical performance, which are ascribed to the deteriorated ionic and electronic conduction. To date, many surface treatment and morphology control technologies have been suggested to prevent capacity fading and structure degradation during cycling. [3] For the surface treatment of nickel-based layered cathodes, this concept is considered as a very simple and viable way by introducing additional layers consisting of polymer, [16] metal phosphate, [17,18] metal fluoride, [19,20] metal oxide, [21,22] or core shell [23][24][25] on the surface of the secondary particle clusters. The point that is often overlooked, however, is that these approaches do not fully prevent the fundamental issues related to the grain boundaries among the primary particles. In this context, a novel concept of full concentration-gradient of manganeserich phase with long rod-shaped primary particles was reported and demon strated good structural stability. [26][27][28][29][30] More recently, Cho and co-workers introduced two approaches for the grain boundary coating including the nanoscale surface treatment by cobalt-rich cation mixing layer [31] and spinel-like Li x CoO 2 layer as a glue-nanofiller [32] for highly stable active materials, where an improved structural and thermal stability was achieved by suppressing the phase transition from layered to rock-salt phase of primary particles. However, these kinds of surface treatment methods accompanied a multistep coprecipitation process [29,30] or were carried out after coprecipitation process of active materials by using additional chemicals for surface coatings, [31][32][33] which can cause the increase of the process time and capital cost.Herein, we report a highly stable LiNi 0.6 Co 0.2 Mn 0.2 O 2 cathode with a TM concentration gradient in primary particles and inner pores in secondary particles via a simple, one-step coprecipitation method by exploiting polymeric-beads as a sacrificial template without any surface coating reagents. The prepared sample retains the self-induced TM concentration gradient with reduced nickel oxidation state in the primary particles, which significantly improved the structural stability by suppressing the evolution of microcracks in cathode particles at a high voltage cutoff of 4.45 V and even at a high temperature of 60 °C. Additionally, the internal pores in the secondary particles successfully provided a buffer effect against the volume change of the primary particles.The synthesis process for polystyrene beads (PSBs) incorporated LiNi 0.6 Co 0.2 Mn 0.2 O 2 , denoted as a PSB-NCM, is simple and highly scalable. Briefly, the cathode precursor, PSB-Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 , was synthesized by the coprecipitation To meet the demand of electric vehicles and electrical energy storage systems, lithium-ion batteries with high energy density, high rate capability, and thermal stability have been required. [1][2][3] Among the man...

The ability to image pressure distribution over complex three-dimensional surfaces would significantly augment the potential applications of electronic skin. However, existing methods show poor spatial and temporal fidelity due to their limited pixel density, low sensitivity, or low conformability. Here, we report an ultraflexible and transparent electroluminescent skin that autonomously displays super-resolution images of pressure distribution in real time. The device comprises a transparent pressure-sensing film with a solution-processable cellulose/ nanowire nanohybrid network featuring ultrahigh sensor sensitivity (>5000 kPa −1 ) and a fast response time (<1 ms), and a quantum dot-based electroluminescent film. The two ultrathin films conform to each contact object and transduce spatial pressure into conductivity distribution in a continuous domain, resulting in super-resolution (>1000 dpi) pressure imaging without the need for pixel structures. Our approach provides a new framework for visualizing accurate stimulus distribution with potential applications in skin prosthesis, robotics, and advanced human-machine interfaces.

By the combination of the inkjet printing of PEDOT:PSS transfer template and selective transfer of silver nanowires (AgNW), AgNWs of customizable transparency can be patterned with high degree of freedom, without need of high equipment cost and complicated process. The AgNW‐transferred PEDOT:PSS transparent electrodes exhibit both great figure of merit and easily tunable optoelectronic properties. With maintaining the advantages and overcoming the issues of the AgNWs, the method developed by Yongtaek Hong and co‐workers in article number 2000042 can be applied to various flexible electronics.

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