High Power Density Research Articles

Ultrahigh energy storage performance in BNT-based binary ceramic via relaxor design and grain engineering

Dielectric capacitors attract much attention for advanced electronic systems owing to their ultra-fast discharge rate and high power density. However, the low energy storage density (Wrec) and efficiency (η) severely limit their applications. Herein, Bi0.5Na0.5TiO3-K0.5Na0.5NbO3 binary ceramic is developed to obtain excellent energy storage performance with strong relaxor behavior, together with large polarization and distorted lattice calculated by first-principles calculations. The atomic-scale local structure analysis of 0.75Bi0.5Na0.5TiO3–0.25K0.5Na0.5NbO3 ceramic reveals distorted polarization distribution and small polar nanoregion related with the enhanced relaxation and low hysteresis. Finite element analysis demonstrates ultrafine grain and increased grain boundary density following hot-pressing sintering are crucial factors in significantly enhancing the breakdown strength (Eb). As a result, ultrahigh Wrec of 12.39 J/cm3 and η of 87.1 % are achieved at a superhigh Eb of 713 kV/cm. Encouragingly, excellent performance of temperature, frequency and fatigue stability at 400 kV/cm are obtained, and high power density of ∼ 306 MW/cm3 as well as fast discharge speed of ∼ 23.3 ns are also realized. This work proposes a simple binary design with strong relaxor behavior, and highlights the potential of grain engineering to achieve outstanding energy storage performance with great stability and excellent charge-discharge property for pulse power devices.

In situ construction of metal organic framework derived FeNiCoSe@NiV-LDH polymetallic heterostructures for high energy density hybrid supercapacitor electrode materials

Metal-organic framework (MOF) derivatives as supercapacitor electrodes are limited by their poor conductivity and capacitance properties. Therefore, it is crucial to improve the performance by constructing a rational structure. Here, MIL-88A is converted into a unique hollow heterostructure FeNiCoSe@NiV layered double hydroxide (FeNiCoSe@NiV-LDH, simplified as FNCS@NVL) by a simple ion-exchange combined with co-precipitation technique. The Ni-Co ratio is modulated by an intermediate optimization strategy. Owing to the multi-metal sites and the unique structure, the designed FNCS@NVL shows excellent electrochemical properties as expected. It exhibits excellent specific capacity (1964.4 F·g−1 at 1 A·g−1) and capacitance retention (82.1 % at 10,000 cycles) at three-electrode setup. In addition, the hybrid supercapacitor (HSC) assembled by FNCS@NVL as the positive electrode and activated carbon as the negative electrode also exhibits a high energy density of 71.9 W h·kg−1 at a power density of 800.01 W·kg−1. These results demonstrate that the designed FNCS@NVL complex is an excellent energy storage material and further validate the great potential of polymetallic materials in energy storage. It provides a unique idea for constructing supercapacitors with high energy density and power density.

Graphene benefits penta-nitrogen coordinated iron and catalytic stability of oxygen reduction reaction

Metal-nitrogen-carbon catalytic material, generally thought as a promising low-cost electrocatalyst of oxygen reduction reaction (ORR), surfers from long-term catalytic durability for fuel cell and metal-air battery. Here, we describe an approach of synthesizing electrochemically exfoliated graphene supported penta-nitrogen coordinated iron exhibiting encouraging ORR catalytic activity and durability. The synthesized catalyst exhibits high half-wave potentials in alkaline medium (E1/2 0.940 V) enabling high-performance zinc-air battery and in acidic condition for durable fuel cell with a high peak power density (630 mW cm−2). The current density of a proton exchange membrane fuel cell loading the catalyst as cathode tends to decay little after initial hours under H2-air measurement, remarkably inhibiting commonly decline tendency of iron–nitrogen-carbon catalysts. DFT calculation combined with extensive experimental investigations demonstrate that penta-nitrogen coordinated iron supported by graphene is thermodynamically stable, and thus benefits the catalytic stability of ORR.

Exploring higher-order harmonic eddy current in soft magnetic composites

Electric motors, as the key building blocks of electric vehicles require high power density to enable driving over long distances with minimal power loss. In this regard, considerable research efforts have focused on searching for new magnetic materials, with soft magnetic composites (SMCs) considered promising. However, the eddy currents generated in SMCs are the primary contributors to power loss owing to their induced magnetic field reduction, harmonics that can distort the power waveform, and overheating. While eddy currents have been sufficiently investigated at the macroscopic level, information on their microscopic characteristics and contributions, particularly those depending on harmonic orders, has remained elusive. Here, we propose a systematic way to explore in detail the harmonics of eddy currents in two model systems including a power inductor and iron powder disk, using the atomic force microscopy based technique, so called multidimensional magnetic force microscopy (MMFM). Using MMFM, we show key effects of harmonics related to eddy currents by unveiling each contribution toward magnetic signals. In particular, the MMFM images show local variations in the nth harmonic of the eddy current signals within the spatially mapped magnetic features. These results show the proposed approach is effective to explore the harmonics of eddy currents, offering fundamental insight for development of highly efficient electric motors.

Simultaneous improvements in energy density and thermal conductivity of PAN polymer nanocomposites enabled by core-shell structure BZCT@BNNS nanofibers

If the heat generated by electronic devices in high-power applications cannot be dissipated in a timely manner, it will not only affect the use of the equipment but also reduce its service life. Therefore, there is an urgent need to develop thin films of dielectric nanocomposites with high thermal conductivity, high energy storage, and excellent flexibility and electrical insulation performance. In this study, we reported the successful preparation of BZCT nanofibers (BZCT NFs) and core-shell structures BZCT@BNNS nanofibers using electrospinning and coaxial electrospinning techniques, respectively, and there were used to composite with polyacrylonitrile (PAN) polymer matrix to prepare BZCT NFs/PAN and BZCT@BNNS/PAN dielectric nanocomposites thin film. Research has found that when the shell thickness of BNNS is 15 nm and BZCT@BNNS (15 nm) volume fraction is 20 vol%, the comprehensive performance of the dielectric nanocomposites is the best, with thermal conductivity and energy storage performance of 3.36 W m−1K−1 and 12.23 J/cm3, respectively. Therefore, the nanocomposites thin film can be used as a potential high-performance dielectric material for thermal management applications in high-power density electronic devices.

Novel synthesis of B-doped Ti3C2Tx thin sheets via BF3 Lewis acid etching: Structural insights and Supercapacitor applications

The rising demand for energy storage spurs research on supercapacitor materials, valued for high-power density and long-term cycling, vital in industries. Among two-dimensional materials, MXene, with a general formula of Mn+1XnTx, where M represents early transition metals, X indicates C and/or N, Tx represents functionalized surface groups, and n = 1, 2, or 3, stands out as an ideal candidate for energy storage applications. Here, for the first time, we report the use of a Lewis acid, boron trifluoride (BF3), as an electron-deficient etchant in a sulfuric acid (H2SO4) solution for etching aluminum from the model system Ti3AlC2 MAX (M: transition metals, A: Al, X: carbon.), resulting in the formation of B-doped Ti3C2Tx MXene. Ex-Situ electrochemical X-ray diffraction (XRD) analysis showed reversible (002) plane changes in B-doped Ti3C2Tx MXene, from 5.72° to 7.0°, indicating ions intercalation and deintercalation, a first-time demonstration of significant ion transportation. Such fundamental insight determines that the specific capacitance of B-doped Ti3C2Tx MXene has found to be 396 F/g at current density of 1 A/g. This research introduces a novel synthesis approach aimed at understanding microstructural transformations of B-doped Ti3C2Tx MXene during electrochemical processes. This contributes to the advancement of MXene-based materials for future electrochemical applications.

P-Block anion compressed d/p band center of bifunctional oxygen electrocatalysts for durable aqueous Zn–air batteries

Robust bifunctional electrocatalysts that accelerate the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are vital for rechargeable aqueous Zn–air batteries (AZABs). In this study, a three-dimensional foam-like N-doped carbon frameworks (NCFs) catalyst with abundant NCoTe2 active sites (CoTe2@NCFs) was successfully constructed using the carbon dots (CDs)-assisted strategy as the efficient bifunctional ORR/OER catalyst. In situ Raman spectra were used to monitor the formation of Co-OOH, which confirmed the dynamic change in oxygen intermediates on the surface of the CoTe2@NCFs catalyst. Both theoretical calculations and experimental results demonstrate that the integrated Te element in the p-block results in a reduction in the difference between d/p band centers (Δεd-p), which effectively enhances the rapid adsorption/desorption capability of *OOH/*OH, thereby improving the ORR/OER performance. Impressively, the CoTe2@NCFs catalyst shows excellent bifunctional oxygen catalytic performance (ΔE = 0.66 V). Moreover, the assembled CoTe2@NCFs-based rechargeable AZABs exhibit a high peak power density of 177.8 mW cm−2, substantial specific capacity of 793.4 mAh g−1, and excellent long-term cycling durability over 1000 cycles. The compressed d/p-band synergistic center provides novel insights into the design of bifunctional oxygen electrocatalysts for efficient energy storage and conversion devices.

Microstructure and mechanical properties of low cost co-free high strength steel fabricated by plasma arc-based directed energy deposition

Arc-based directed energy deposition (DED) is characterized by high efficiency and excellent manufacturing flexibility, making it a promising choice for fabricating large structural components. High power density plasma arc-based directed energy deposition (PA-DED) was employed to fabricate high strength steel (HSS) component with a new Co-free welding wire. The microstructure and mechanical properties of the component were investigated in detail. The results showed that the matrix microstructure consisted mainly of martensite and ferrite. Austenite was observed in the bottom and middle samples, and the bottom sample exhibited the highest austenite content. All the samples in different regions exhibited a pronounced {100} 〈001〉 cube texture. The vertical samples had worse tensile properties than horizontal samples, which would be contributed to the interlayer bands and preferred orientation. The horizontal-middle samples demonstrated the highest tensile strength (UTS: 1207.8 ± 14 MPa, EL: 15.91 ± 1.03%). All deposited samples showed strong plastic deformation characteristics, illustrating that the new Co-free HSS components manufactured by PA-DED might replace conventional high-alloy HSS components for industrial applications.

Modelling and optimization of planar transformers for high power density step-down DC–DC converters

Modelling and optimization of planar transformers for high power density step-down DC–DC converters

Surface degradation of epoxy resin exposed to corona discharge under bipolar square wave field: From phenomenon to the insights

The unavoidable corona discharge induced by distorted field is detrimental to the safety of power equipment, especially the equipment with high voltage magnitude and high frequency. In this paper, the degradation morphology, residual components, lifetime of endurance, partial discharge characteristics, and evolution of surface traps of epoxy insulation under bipolar square wave field is investigated. The results show that degraded zone exhibits as three layers with round pits and channel-like ravines on the surface of epoxy resin exposed to corona discharge. It is demonstrated that more oxygen element during corona discharge while more carbon element during breakdown appeared, and nano-Al2O3 fillers migrates to the discharged zone. The maximum temperature and number of emitted phonons increase with voltage amplitude and frequency in power law and exponential form, respectively, corresponding to the fitting function of endurance lifetime. The emitted light is concentrated on the near ultraviolet (UV) and infrared ray (IR) band, indicating the energy pooling and thermal effect of corona discharge, which interprets the distinct degradation behavior of samples under sinusoidal and bipolar square wave voltage. The effect of space charge and thermal conductivity should be considered simultaneously in the degradation of epoxy insulation under bipolar square wave field due to polarity reversal and high frequency, which is proved by the disparate behavior of EP/nano-Al2O3 composites resistance to corona discharge and the breakdown moment at falling edge of bipolar square wave voltage. This work may contribute to the advancement of resistance to corona discharge degradation in equipment with high power density, high voltage amplitude and high frequency.

Engineering Partially Oxidized Gold via Oleylamine Modifier as a High-Performance Anode Catalyst in a Direct Borohydride Fuel Cell.

Direct borohydride fuel cell (DBFC) is considered a promising energy storage device due to its high theoretical cell voltage and energy density. For DBFC, an Au catalyst has been used as an anode for achieving an ideal eight-electron reaction. However, the poor activity of the Au catalyst for borohydride oxidation reaction (BOR) limits its large-scale application because of the weak BH4- adsorption. We found, by density functional theory calculations, that the adsorption of BH4- on the oxidized Au surface is stronger than that on the metallic Au surface, which can promote the process of the oxidation of BH4- to *BH3 during the BOR. Here, we reported an oleylamine-modified partially oxidized Au supported on carbon powder (AuC-OLA) with a stable oxidation state. The obtained catalyst delivered a high peak power density of 143 mW/cm2, which is 2 times higher than that of a commercial 40% AuC (Pretemek). The in situ Fourier transform infrared studies showed that the activity of AuC-OLA for BOR is ascribed to the enhanced adsorption for BH4- on the partially oxidized Au surface. These findings will promote the reasonable design of efficient Au electrocatalysts for DBFCs.

L2A Cdus Performance and Considerations for Server Rooms Upgrade with Conventional Air Conditioning

Abstract As web-based AI applications are growing rapidly, server rooms face escalating computational demands, prompting enterprises to either upgrade their facilities or outsource to co-located sites. This growth strains conventional HVAC systems, which struggle to handle the substantial thermal load, often resulting in hotspots. Liquid-to-Air (L2A) Coolant Distribution Units (CDUs) emerge as a solution, efficiently cooling servers by circulating liquid coolant through cooling loops mounted on each server board. In this study, the performance of a 24-kW L2A CDU is evaluated across various scenarios, emphasizing cooling effect, stability, and reliability. Experimental tests involve a rack with three thermal test vehicles (TTVs), monitoring both liquid coolant and air sides for analysis. Tests are conducted in a limited air-conditioned environment, resembling upgraded server rooms with conventional AC systems. The study also assesses the impact of high-power density cooling units on the server room environment, measuring noise, air velocity, and ambient temperature against ASHRAE standards for human comfort. Recommendations for optimal practices and potential system improvements are included in the research, addressing the growing need for efficient cooling solutions amidst escalating computational demands.

Diamond/cubic boron nitride (111) heterojunction interface: Rational regulation of high two-dimonsional electron gas

Wide-bandgap diamond exhibits excellent physical and chemical properties, making it an ideal substrate material for developing high-temperature and high-power semiconductor devices and broadening its application prospects in the field of microelectronics and optoelectronic devices. However, because of the Fermi pinning effect, it is difficult to achieve n-type diamond with excellent transport properties. Cubic boron nitride (cBN) has similar structural properties and a smaller lattice mismatch with diamond. Thus, making the two-dimensional electron gas of the diamond/cBN heterojunction provides a new idea to solve the problem of diamond n-incorporation difficulty and small bandgap regulation range. The diamond/cBN heterojunction is applied to study the law of influence factors on the heterojunction band structure, band alignment, and polarization strength. Further, a regulation mechanism for two-dimensional electron gas density is established at heterojunction interfaces, which can help solve the core difficulties of diamond n-type doping, small bandgap regulation range, and high impedance, providing a theoretical basis for realizing diamond power devices with high power density and low power consumption.

Design and optimization of 30 kW CLLLC resonant converter for vehicle‐to‐grid applications

AbstractThe CLLLC resonant converter is a promising technology for electric vehicles and microgrids due to its ability to operate bidirectionally. This article presents a design of a bidirectional CLLLC resonant converter that is applied in the vehicle‐to‐grid (V2G). The battery side of the converter uses a two‐channel parallel structure to enhance its efficiency and reliability. In contrast, the DC‐bus side uses a transformer series structure to obtain the benefits of passive current sharing on the secondary side and reduce the transformer turns ratio. By utilizing the proposed design method, the converter can achieve a wide input and output voltage range, high efficiency, and high power density. The article analyzes the working principle of the converter and explains the design process, which includes the transformer turns ratio, magnetizing inductance, and resonance parameters. Finally, an experimental prototype is produced to verify the theory's validity and the design's feasibility. The prototype has a DC‐bus side voltage of 660–860 V, a battery side voltage of 250–500 V, and a maximum power output of 30 kW. The peak efficiency of the prototype is 98.2%, and its power density can reach up to 8 kW/L.

Structure optimization design approach of friction pairs for low-temperature rise wet brake in hydraulic motor

Cam-lobe radial-piston hydraulic motors are widely used in large heavy-duty machinery as direct-drive components of hydraulic systems. Due to their extremely high output torque and power density, the wet brake equipped with the hydraulic motors are necessary to achieve ultra-high braking torque in a compact space. However, due to a large number of internal friction pairs and small fit clearance between multiple friction pairs in wet brake, the rotation of the friction pairs in non-braking state will cause large friction torque loss and obvious temperature rise, thereby leading to the thermal failure of wet brake. How to optimize the structure of friction pairs to reduce the temperature rise of wet brake in non-braking state is a persistent challenge. Existing structure optimization design approaches of friction pairs in brakes mainly focus on the structure of each friction pair, which ignore the effect of fit clearance between the friction pairs on the temperature rise of brakes. Nevertheless, the fit clearance between friction pairs is an important factor that affect the temperature rise. For that, this study proposes a two-step structure optimization design approach of friction pairs for low-temperature rise wet brake in hydraculic motor, which simultaneously considers the fit clearance between the friction pairs and the structure of each friction pair. In this approach, the design process could be divided into two steps: firstly, the influence of fit clearance between multiple friction pairs on the temperature rise of wet brake in non-braking state is analyzed and optimized by the temperature rise theoretical model; secondly, in order to further reduce the temperature rise of wet brake, the oil groove structure of each friction plate are introduced and optimized by fluid-solid-thermal coupling simulation method. By this approach, the low-temperature rise structure of friction pairs with the optimized fit clearance between multiple friction pairs and oil grooves of each friction plate. Finally, a series of experiments are conducted to verify the effectiveness of the design approach. The result show that the temperature rise of wet brake could be effectively reduced 12 % by optimizing the structure of wet brake, demonstrating that the structure optimization design approach could provide a theoretical guidance to design low-temperature rise wet brake for large torque hydraulic motors.

CO2-regulated, ultrahigh-concentration aqueous electrolytes for high energy and power of supercapacitors

Aqueous supercapacitors are recognized for their high power density, ultralong cycle life, and reliable safety. However, their widespread applications are impeded by low energy density arising from the narrow electrochemical stability windows of aqueous electrolytes. Although the use of high-concentration aqueous electrolytes can mitigate this issue, sluggish ion diffusion within these electrolytes results in decreased capacitance and power performance of supercapacitors. Herein, we propose the simultaneous achievement of high energy and power density of supercapacitors using carbon dioxide (CO2)-regulated high-concentration aqueous electrolytes. The introduction of CO2 enables greater capacitance in sodium perchlorate (NaClO4)-containing electrolyte than sodium nitrate (NaNO3)- and sodium bis (fluorosulfonyl)imide (NaFSI)-containing electrolytes. This is attributed to the increased H+ concentration and the unique interaction between CO2 and ClO4−, leading to a denser counter-ion arrangement on the electrode surface. Notably, the CO2-regulation strategy is effective in a nearly-saturated 17 mol kg−1 NaClO4 electrolyte, showing an increase in energy density of up to 27.8 %, while maintaining a high 2.2 V operating voltage and a long >20 000 cycle life of supercapacitors. This study offers a distinct insight into the regulation of high-concentration aqueous electrolytes for comprehensive enhancement of supercapacitor performance.

Harnessing the Trade‐Off between CoFe/Fe3C Interfacial Junction with Unparalleled Potential Gap of 0.58 V for Reversible Oxygen Electrocatalysis: Application toward Liquid and Solid‐State Zn‐Air Batteries

AbstractEffective integration of multiple active moieties and strategic engineering of coordinated interfacial junctions are crucial for optimizing the reaction kinetics and intrinsic activities of heterogeneous electrocatalysts. Herein, a simple integrated heterostructure of biphasic Co0.7Fe0.3/Fe3C embedded on in situ grown N‐doped carbon sheets is constructed. Rationally designed CoFe/Fe3C‐T2 owns more accessible active sites and interfacial junction effects, cooperatively boosting the electron and mass transfer, needed for multifunctional electrocatalysis. Leveraging the synergistic effect of dual active sites, CoFe/Fe3C‐T2 demonstrates outstanding oxygen electrocatalytic activity in alkaline medium with an ultra‐low potential gap of 0.58 V, surpassing the recently available state‐of‐the‐art catalysts. Moreover, CoFe/Fe3C‐T2 air‐electrode achieves a high peak power density of 249 mW cm−2, a large specific capacity of 808 mAh g−1 and excellent cycling stability for aqueous Zn‐air batteries. Remarkably, the solid‐state flexible ZAB also exhibits satisfactory performance, showcasing an open‐circuit voltage of 1.43 V and a peak power density of 66 mW cm−2. These outstanding results push this catalyst to the top of the list of non‐noble metal‐based electrode materials. This work offers a viable method for using the active‐site‐uniting strategy to create double‐active‐site catalysts, which may find real‐time applications in energy conversion/storage devices.

Two-electron sulfonyl(trifluoromethanesulfonyl)imide-anthraquinone redox electrolytes for high-energy density supercapacitors

Organic redox electrolyte-enhanced electrochemical double layer capacitors (ORECs) are potentially better solution for combining both high power and energy density. The critical factor of ORECs is to develop high-performance organic redox electrolytes. Anthraquinone (AQ) derivatives are the promising organic redox electrolyte candidates because of their low redox potential and fast two-electron redox kinetics. Low solubility and poor longevity in aprotic solvents of charged AQ species are main issues for effective enhancement. Here we report two-electron redox ionic compounds by functionalizing AQ with a robustly electron-withdrawing sulfonyl(trifluoromethanesulfonyl)imide (AQSTFSI) anion and pairing counter monovalent cations for high-performance ORECs. The highly electron-conjugate substitute markedly stabilizes the radical and 2e−-charged forms of AQ by decentralizing the electron density of the CO heads, preventing the adverse reaction of electrophilic/nucleophilic attack, revealing by theoretical simulation. Also, the STFSI− substituent enables AQSTFSI-compounds significantly improved solubility, thermostability, and redox reversibility. Consequently, the AQSTFSI-K applied in OREC shows all-roundly superior performance containing 3.2 V cell voltage, specific energy of 58 Wh kg−1 with 1.8 times of corresponding electrochemical double layer capacitors (EDLCs), specific power over 8 kW kg−1, cycling stability over 12,000 cycles, low self-discharge, and wide working-temperature range. This molecular strategy grounded on electron density modulation of redox electrolyte structures provides valuable insights into the design for high-performance ORECs in practical applications.

One single-atom Mn doping strategy enabling two functions of oxygen reduction reaction and pseudocapacitive performance

Single-atom metal species as highly effective active sites are crucial for enhancing energy storage and conversion properties. However, achieving the simultaneous construction of single-atom sites and the regulation of matrix structures to enable their application in both energy storage and conversion remains a challenge. Here, we have successfully developed unique MnN2C2 active sites, atomically dispersed on N-doped mesoporous graphitic carbon sheets (MnSAs/NMC). This is accomplished through the strategic utilization of MnCl2 salt, which serves dual roles of a pore-forming agent and a template. The MnSAs/NMC catalyst demonstrates compelling electrocatalytic activity for the oxygen reduction reaction (ORR), with an impressive half-wave potential (E1/2 = 0.90 V), alongside superior capacitance reaching 444 F g-1 at 0.5 A g-1 for supercapacitors. Crucially, both experimental and theoretical simulations validate that the single-atom dispersed MnN2C2 optimizes the adsorption energy of reactants and intermediates in the ORR process and pseudocapacitive behavior, leading to excellent ORR activity and capacitive performance. Interestingly, MnSAs/NMC-based Zn-air batteries exhibit concurrently high-power density derived from capacitive property and high energy density enhanced by ORR process. This study presents a novel preparation method for single-atom catalysts, which paves the way for the commercial application of super energy storage and conversion devices.

Defect Engineering Realizes Superior Thermoelectric Performance of GeTe

AbstractGeTe has been considered as a promising mid‐temperature thermoelectric (TE) candidate, but its zT value is severely limited by the excessive hole concentration and high thermal conductivity. Here, it is demonstrated that the TE properties of GeTe can be significantly improve by defect engineering of Sb‐Pb and AgCuTe codoping. The Sb‐Pb codoping is adopted to optimize the carrier concentration and manipulate the rhombohedral lattice distortion, leading to valence band convergence and enhanced power factor. The AgCuTe alloying introduces multiscale phonon scattering centers including dislocations and nano‐precipitates to reduce the lattice thermal conductivity in GeTe. Consequently, a maximum zT of 2.3 at 773 K and an average zT of 1.43 (300–773 K) are obtained in (Ge0.84Sb0.06Pb0.1Te)0.99(AgCuTe)0.01. Moreover, the fabricated thermoelectric module exhibits a high output power density of 0.59 W cm–2 and an energy conversion efficiency of 7.9% at ΔT = 500 K, suggesting hierarchical defect engineering is an effective strategy to realize high‐performance GeTe‐based thermoelectric.