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Solid-state batteries (SSBs) have recently been revived to increase the energy density and eliminate safety concerns associated with conventional Li-ion batteries with flammable liquid electrolytes. To achieve large-scale, low-cost production of SSBs as soon as possible, it would be advantageous to modify the mature manufacturing platform, involving slurry casting and roll-to-roll technologies, used for conventional Li-ion batteries for application to SSBs. However, the manufacturing of SSBs depends on the development of suitable solid electrolytes. Inorganic–polymer composite electrolytes combine the advantages of inorganic and polymer solid electrolytes, making them particularly suitable for the mass production of SSBs. In this Review, we discuss the properties of solid electrolytes comprising inorganic–polymer composites and outline the design of composite electrolytes for realizing high-performance devices. We also assess the challenges of integrating the composite electrolytes into batteries, which will enable the mass production of SSBs. Inorganic–polymer composites have emerged as viable solid electrolytes for the mass production of solid-state batteries. In this Review, we examine the properties and design of inorganic–polymer composite electrolytes, discuss the processing technologies for multilayer and multiphase composite structures, and outline the challenges of integrating composite electrolytes into solid-state batteries.

Dielectric capacitors with ultrahigh power densities are fundamental energy storage components in electrical and electronic systems. However, a long-standing challenge is improving their energy densities. We report dielectrics with ultrahigh energy densities designed with polymorphic nanodomains. Guided by phase-field simulations, we conceived and synthesized lead-free BiFeO₃-BaTiO₃-SrTiO₃ solid-solution films to realize the coexistence of rhombohedral and tetragonal nanodomains embedded in a cubic matrix. We obtained minimized hysteresis while maintaining high polarization and achieved a high energy density of 112 joules per cubic centimeter with a high energy efficiency of ~80%. This approach should be generalizable for designing high-performance dielectrics and other functional materials that benefit from nanoscale domain structure manipulation.

Understanding the breakdown mechanisms of polymer-based dielectrics is critical to achieving high-density energy storage. Here a comprehensive phase-field model is developed to investigate the electric, thermal, and mechanical effects in the breakdown process of polymer-based dielectrics. High-throughput simulations are performed for the P(VDF-HFP)-based nanocomposites filled with nanoparticles of different properties. Machine learning is conducted on the database from the high-throughput simulations to produce an analytical expression for the breakdown strength, which is verified by targeted experimental measurements and can be used to semiquantitatively predict the breakdown strength of the P(VDF-HFP)-based nanocomposites. The present work provides fundamental insights to the breakdown mechanisms of polymer nanocomposite dielectrics and establishes a powerful theoretical framework of materials design for optimizing their breakdown strength and thus maximizing their energy storage by screening suitable nanofillers. It can potentially be extended to optimize the performances of other types of materials such as thermoelectrics and solid electrolytes. Polymer dielectrics are promising for high-density energy storage but dielectric breakdown is poorly understood. Here, a phase-field model is developed to investigate electric, thermal, and mechanical effects in the breakdown process for a range of polymer dielectrics, and analytical expression for breakdown strength is provided by machine learning.

All‐solid‐state lithium batteries have emerged as a priority candidate for the next generation of safe and energy‐dense energy storage devices surpassing state‐of‐art lithium‐ion batteries. Among multitudinous solid‐state batteries based on solid electrolytes (SEs), sulfide SEs have attracted burgeoning scrutiny due to their superior ionic conductivity and outstanding formability. However, from the perspective of their practical applications concerning cell integration and production, it is still extremely challenging to constructing compatible electrolyte/electrode interfaces and developing available scale processing technologies. This review presents a critical overview of the current underlying understanding of interfacial issues and analyzes the main processing challenges faced by sulfide‐based all‐solid‐state batteries from the aspects of cost‐effective and energy‐dense design. Besides, the corresponding approaches involving interface engineering and processing protocols for addressing these issues and challenges are summarized. Fundamental and engineering perspectives on future development avenues toward practical application of high energy, safety, and long‐life sulfide‐based all‐solid‐state batteries are ultimately provided. Sulfide‐based all‐solid‐state lithium batteries have emerged as a priority candidate for the next generation of energy‐dense and safe energy storage devices. This review presents a critical overview of the current underlying understanding of interfacial issues and analyzes the main processing challenges faced by sulfide‐based all‐solid‐state batteries. The corresponding approaches involving interface engineering and processing protocols are highlighted. Fundamental and engineering perspectives on future development avenues toward their practical application are also presented.

Thermoelectric materials can realize direct conversion between heat and electricity, showing excellent potential for waste heat recovery. Cu 2 Se is a typical superionic conductor thermoelectric material having extraordinary ZT values, but its superionic feature causes poor service stability and low mobility. Here, we reported a fast preparation method of self-propagating high-temperature synthesis to realize in situ compositing of BiCuSeO and Cu 2 Se to optimize the service stability. Additionally, using the interface design by introducing graphene in these composites, the carrier mobility could be obviously enhanced, and the strong phonon scatterings could lead to lower lattice thermal conductivity. Ultimately, the Cu 2 Se-BiCuSeO-graphene composites presented excellent thermoelectric properties with a ZT max value of ~2.82 at 1000 K and a ZT ave value of ~1.73 from 473 K to 1000 K. This work provides a facile and effective strategy to largely improve the performance of Cu 2 Se-based thermoelectric materials, which could be further adopted in other thermoelectric systems. Here, the authors devise a synthesis strategy to optimize the stability and thermoelectric performance of Cu 2 Se-based materials. They obtain a maximum ZT value of ~2.82 at 1000 K on Cu 2 Se-BiCuSeO-graphene composites.

Conductive Ti3C2Tx MXenes have been widely investigated for the construction of flexible and highly‐sensitive pressure sensors. Although the inevitable oxidation of solution‐processed MXene has been recognized, the effect of the irreversible oxidation of MXene on its electrical conductivity and sensing properties is yet to be understood. Herein, we construct a highly‐sensitive and degradable piezoresistive pressure sensor by coating Ti3C2Tx MXene flakes with different degrees of in situ oxidation onto paper substrates using the dipping‐drying method. In situ oxidation can tune the intrinsic resistance and expand the interlayer distance of MXene nanosheets. The partially oxidized MXene‐based piezoresistive pressure sensor exhibits a high sensitivity of 28.43 kPa−1, which is greater than those of pristine MXene, over‐oxidized MXene, and state‐of‐the‐art paper‐based pressure sensors. Additionally, these sensors exhibit a short response time of 98.3 ms, good durability over 5000 measurement cycles, and a low force detection limit of 0.8 Pa. Moreover, MXene‐based sensing elements are easily degraded and environmentally friendly. The MXene‐based pressure sensor shows promise for practical applications in tracking body movements, sports coaching, remote health monitoring, and human–computer interactions. The highly‐sensitive and degradable piezoresistive pressure sensor was constructed by coating Ti3C2Tx MXene flakes with different degrees of in situ oxidation onto paper substrates using the dipping‐drying method. In situ oxidation tunes the intrinsic resistance and expand the interlayer distance of MXene nanosheets, which regulates the sensitivity of the sensor. It is found that the partially oxidized MXene based pressure sensor demonstrates remarkably higher sensitivity (28.43 kPa−1) than those of pristine MXene, over‐oxidized MXene, and state‐of‐the‐art paper‐based pressure sensors.

With the increasing popularity of smart wearable devices, flexible pressure sensors are highly desired in various complex application scenarios. A great challenge for existing flexible pressure sensors is to maintain high sensitivity over a wide temperature range, which is critical for their applications in harsh environments. Herein, a flexible piezoresistive sensor made of polyetherimide (PEI) fibrous network evenly covered with MXene nanosheets is reported to construct conductive pathways, showing ultrahigh sensitivity over a wide temperature range from −5 °C (sensitivity of 80 kPa−1) to 150 °C (20 kPa−1), low detection limit of 9 Pa, fast response time of 163 ms, outstanding durability over 10 000 cycles at room temperature, 2000 cycles at 100 °C and 500 cycles at −5 °C. The pressure sensor can monitor various human activities in real‐time, apply to human–machine interaction, and measure pressure distribution. It also can sensitively respond to external mechanical stimuli at 150 °C and extremely low temperature (in liquid nitrogen). Moreover, the fibrous network exhibits an excellent Joule heating performance, which can reach 78 °C at an applied voltage of 12 V. Thus, the piezoresistive sensor has considerable potential for wearable garments and personal heating applications in harsh temperature conditions. A highly‐sensitive piezoresistive sensor based on 3D MXene/polyetherimide network is proposed. The sensor exhibits ultrahigh sensitivity in a wide temperature range from 80 kPa−1 at −5 °C to 20 kPa−1 at 150 °C, low detection limit of 9 Pa, outstanding durability over 10 000 cycles at room temperature, 2000 cycles at 100 °C and 500 cycles at −5 °C.

Developing high-performance film dielectrics for capacitive energy storage has been a great challenge for modern electrical devices. Despite good results obtained in lead titanate-based dielectrics, lead-free alternatives are strongly desirable due to environmental concerns. Here we demonstrate that giant energy densities of ~70 J cm −3 , together with high efficiency as well as excellent cycling and thermal stability, can be achieved in lead-free bismuth ferrite-strontium titanate solid-solution films through domain engineering. It is revealed that the incorporation of strontium titanate transforms the ferroelectric micro-domains of bismuth ferrite into highly-dynamic polar nano-regions, resulting in a ferroelectric to relaxor-ferroelectric transition with concurrently improved energy density and efficiency. Additionally, the introduction of strontium titanate greatly improves the electrical insulation and breakdown strength of the films by suppressing the formation of oxygen vacancies. This work opens up a feasible and propagable route, i.e., domain engineering, to systematically develop new lead-free dielectrics for energy storage. Dielectrics with high capacitive energy storage density are essential for modern electrical devices and pulsed power systems. Here, the authors realised superior energy storage performance in lead-free bismuth ferrite-based relaxor ferroelectric films through domain engineering.

Oxide-based ceramics could be promising thermoelectric materials because of their thermal and chemical stability at high temperature. However, their mediocre electrical conductivity or high thermal conductivity is still a challenge for the use in commercial devices. Here, we report significantly suppressed thermal conductivity in SrTiO 3 -based thermoelectric ceramics via high-entropy strategy for the first time, and optimized electrical conductivity by defect engineering. In high-entropy (Ca 0.2 Sr 0.2 Ba 0.2 Pb 0.2 La 0.2 )TiO 3 bulks, the minimum thermal conductivity can be 1.17 W/(m·K) at 923 K, which should be ascribed to the large lattice distortion and the huge mass fluctuation effect. The power factor can reach about 295 μW/(m·K 2 ) by inducing oxygen vacancies. Finally, the ZT value of 0.2 can be realized at 873 K in this bulk sample. This approach proposed a new concept of high entropy into thermoelectric oxides, which could be generalized for designing high-performance thermoelectric oxides with low thermal conductivity.

Space-charge layers are frequently believed responsible for the large resistance of different interfaces in all-solid-state Li batteries. However, such propositions are based on the presumed existence of a Li-deficient space-charge layer with insufficient charge carriers, instead of a comprehensive investigation on the atomic configuration and its ion transport behavior. Consequently, the real influence of space-charge layers remains elusive. Here, we clarify the role of space-charge layers in Li 0.33 La 0.56 TiO 3 , a prototype solid electrolyte with large grain-boundary resistance, through a combined experimental and computational study at the atomic scale. In contrast to previous speculations, we do not observe the Li-deficient space-charge layers commonly believed to result in large resistance. Instead, the actual space-charge layers are Li-excess; accommodating the additional Li + at the 3c interstitials, such space-charge layers allow for rather efficient ion transport. With the space-charge layers excluded from the potential bottlenecks, we identify the Li-depleted grain-boundary cores as the major cause for the large grain-boundary resistance in Li 0.33 La 0.56 TiO 3 . Space-charge layers are believed to profoundly influence the interfaces in all-solid-state Li batteries. Here, the authors provide atomic scale insights into this phenomenon, and discover that its impact could be fundamentally different from commonly believed.