High-temperature Energy Storage Research Articles

Magnetic-assisted alignment of nanofibers in a polymer nanocomposite for high-temperature capacitive energy storage applications.

Flexible polymer-based dielectrics with high energy storage characteristics over a wide temperature range are crucial for advanced electrical and electronic systems. However, the intrinsic low dielectric constant and drastically degraded breakdown strength hinder the development of polymer-based dielectrics at elevated temperatures. Here, we propose a magnetic-assisted approach for fabricating a polyethyleneimine (PEI)-based nanocomposite with precisely aligned nanofibers within the polymer matrix, and with Al2O3 deposition layers applied on the surface. The resulting polymer nanocomposite exhibits simultaneously increased dielectric constant and enhanced breakdown strength at high temperatures compared to pristine PEI. The enhanced dielectric constant is contributed by the depolarization effect of out-of-plane orientated nanofibers in composite films, while the surficial Al2O3 layers, with a wide bandgap, effectively prevent charge injection and transport at the electrode/dielectric interface. The optimally aligned composite films exhibit a significantly enhanced discharged energy density of 6.5 J cm-3 at 150 °C, with approximately 41% and 132% enhancement compared to random films and pristine PEI films, respectively. Additionally, a metalized multilayer polymer-based capacitor utilizing this composite film produces a high capacitance of 88 nF, while demonstrating excellent cyclability and flexibility at 150 °C. This work offers an effective strategy for developing polymer-based composite dielectrics with superior capacitive performance at elevated temperatures and demonstrates the potential of fabricating high-quality flexible capacitors.

Sandwich-structured polymer dielectrics exhibiting significantly improved capacitive performance at high temperatures by roll-to-roll physical vapor deposition

Electrostatic capacitors with ultrahigh power density are the key components in modern electrical and electronic systems. Polymers are preferred dielectrics for high-voltage electrostatic capacitors, however, unable to meet the ever-growing high-temperature requirements in emerging applications, such as electric vehicles, and photovoltaic power generation. In this work, sandwich-structured Polyphenylene sulfide (PPS) films with Al2O3 as the coating layer have been prepared by using roll-to-roll magnetron sputtering. The incorporation of Al2O3 coating layers enhances the potential barrier height at the electrode/dielectric interface, thereby impeding charge injection from electrodes and suppressing high-temperature electrical conduction. Consequently, the sandwich-structured PPS films demonstrate significantly improved breakdown strengths and enhanced capacitive performance at elevated temperatures compared to neat PPS films. The roll-to-roll magnetron sputtering process employed in fabricating these sandwich-structured dielectric films is highly compatible with large-scale capacitor film production. Thus, sandwich-structured PPS films hold promise in addressing the challenge of scalable fabrication of high-performance, high-quality polymer films required for high-temperature capacitive energy storage.

Dipole Orientation Engineering in Crosslinking Polymer Blends for High-Temperature Energy Storage Applications.

Polymer dielectrics that perform efficiently under harsh electrification conditions are critical elements of advanced electronic and power systems. However, developing polymer dielectrics capable of reliably withstanding harsh temperatures and electric fields remains a fundamental challenge, requiring a delicate balance in dielectric constant (K), breakdown strength (Eb), and thermal parameters. Here, amide crosslinking networks into cyano polymers is introduced, forming asymmetric dipole pairs with differing dipole moments. This strategy weakens the original electrostatic interactions between dipoles, thereby reducing the dipole orientation barriers of cyano groups, achieving dipole activation while suppressing polarization losses. The resulting styrene-acrylonitrile/crosslinking styrene-maleic anhydride (SAN/CSMA) blends exhibit a K of 4.35 and an Eb of 670 MV m-1 simultaneously at 120°C, and ultrahigh discharged energy densities (Ue) with 90% efficiency of 8.6 and 7.4 J cm-3 at 120 and 150°C are achieved, respectively, more than ten times that of the original dielectric at the same conditions. The SAN/CSMA blends show excellent cyclic stability in harsh conditions. Combining the results with SAN/CSMA and ABS (acrylonitrile-butadiene-styrene copolymer)/CSMA blends, it is demonstrated that this novel strategy can meet the demands of high-performing dielectric polymers at elevated temperatures.

Silicon Carbide Nanowire Based Integrated Electrode for High Temperature Supercapacitors.

Silicon carbide (SiC) single crystals have great prospects for high-temperature energy storage due to their robust structural stability, ultrahigh power output, and superior temperature stability. However, energy density is an essential challenge for SiC-based devices. Herein, a facile two-step strategy is proposed for the large-scale synthesis of a unique architecture of SiC nanowires incorporating MnO2 for enhanced supercapacitors (SCs), arising from the synergy effect between the SiC nanowires as a highly conductive skeleton and the MnO2 with numerous active sites. The SiC@MnO2 integrated electrode-based SCs with ionic liquid (IL) electrolytes were assembled and delivered outstanding energy and power density, as well as a great lifespan at 150 °C. This impressive work offers a novel avenue for the practical application of SiC-based electrochemical energy storage devices with high energy density under high temperatures.

Improved high temperature energy storage density and efficiency of polyimide nanocomposites via hindering charge and molecular motions

Electric vehicles and renewable energy consumption have huge demands for high-performance polymer dielectric capacitors. However, the resistivity and breakdown strength of existing polymer dielectrics deteriorate significantly at high temperatures, reducing the energy storage density and charge-discharge efficiency of capacitors below service requirements. The charge transport and molecular chain motion characteristics in linear polymers determine their conductivity, breakdown, and energy storage properties, but the quantitative relationship between them is not clear. An in-situ polymerization method was used to prepare polyimide/Al2O3 nanocomposites (PI/Al2O3 PNCs). Experimental results show that the resistivity, breakdown strength, energy storage density, and charge-discharge efficiency of PNCs increase initially and then decrease with increasing doping content, peaking at 3 wt%. The discharged energy density of PI/Al2O3-3 wt% PNCs at 180°C is 207.52 % higher than pure PI. A conductance-breakdown-energy storage co-simulation model based on charge transport and molecular chain displacement was used to simulate the voltage-current, breakdown, and energy storage characteristics of PNCs. The simulation results are consistent with the experiments. Comparative studies between simulation and experiments show that the independent interface zone between nanofillers and PI hinders charge transport and molecular chain movement, reducing electric field distortion and molecular chain spacing, thereby improving high-temperature breakdown and energy storage performance of PNCs.

Scalable polyolefin-based all-organic dielectrics with superior high-temperature capacitive energy storage performance

Polymer dielectrics capable of efficient and stable operation at elevated temperatures (>150 °C) are urgently needed to meet the stringent requirements of capacitive energy storage in harsh environments. However, the current leading commercially available polymer dielectric, biaxially oriented polypropylene (BOPP), can only sustain continuous operation at temperatures below 85 °C due to its limited thermal stability and significant increase in electrical conduction at high temperatures. Here, we present an all-organic polymer composite comprising nonpolar polyolefin and organic semiconductor that demonstrates superior dielectric and capacitive energy storage performance at 150 °C. Notably, the dielectric properties of the polymer composite remain stable across a broad temperature range, exhibiting an ultralow dissipation factor at elevated temperatures. Benefiting from the deep trap energy levels introduced by the organic semiconductor, the composite film achieves one order of magnitude reduction in electrical conductivity. As a result, the composite film attains discharged energy densities of 7.1 J/cm3 and 5.5 J/cm3 with a charge-discharge efficiency of 90 % at 25 °C and 150 °C, respectively. Furthermore, the composite film maintains stable capacitive performance over extended charge-discharge cycles (50,000 cycles) in harsh environments (500 MV/m and 150 °C), along with excellent breakdown self-healing capability. These remarkable performances, coupled with the potential for large-scale production using commercially available raw materials, highlight the practically viability of the composite film for high-temperature capacitive energy storage applications.

Polyimide-coated MgO nanoparticles improves high-temperature energy storage performance in polyetherimide-based nanocomposite films

Enhancing the energy storage capacity of dielectric polymers can be achieved by the introduction of inorganic nanoparticles. However, the difference in surface energy often influences the interfacial compatibility of nanoparticles with polymers, consequently limiting their comprehensive dielectric properties. Here, the magnesium oxide (MgO) nanoparticles were coated with polyimide (PI) shells via in-situ polymerization, which is beneficial to improve the scattered particles in the polyether imide (PEI) matrix. The PI buffer shell is tightly bound to the PEI matrix through automatic electrostatic interaction making the defects decrease, together with the increased dielectric permittivity (εr) attributed to MgO, significantly enhancing the discharged energy density (Udis) and storage efficiency (η) of the PI@MgO/PEI nanocomposite films in harsh conditions. Thus, the maximal Udis of the PI@MgO/PEI nanocomposites is 4.33 J/cm3 at 150 °C, twice that of the pristine PEI. Even if an η exceeds 90 %, the Udis of 3.83 J/cm3 of 1 vol%-PI@MgO/PEI at 500 MV/m and 150 °C is better than that of the most advanced dielectric polymers.

High-temperature capacitive energy storage in polymer nanocomposites through nanoconfinement

Polymeric-based dielectric materials hold great potential as energy storage media in electrostatic capacitors. However, the inferior thermal resistance of polymers leads to severely degraded dielectric energy storage capabilities at elevated temperatures, limiting their applications in harsh environments. Here we present a flexible laminated polymer nanocomposite where the polymer component is confined at the nanoscale, achieving improved thermal-mechanical-electrical stability within the resulting nanocomposite. The nanolaminate, consisting of nanoconfined polyetherimide (PEI) polymer sandwiched between solid Al2O3 layers, exhibits a high energy density of 18.9 J/cm3 with a high energy efficiency of ~ 91% at elevated temperature of 200°C. Our work demonstrates that nanoconfinement of PEI polymer results in reduced diffusion coefficient and constrained thermal dynamics, leading to a remarkable increase of 37°C in glass-transition temperature compared to bulk PEI polymer. The combined effects of nanoconfinement and interfacial trapping within the nanolaminates synergistically contribute to improved electrical breakdown strength and enhanced energy storage performance across temperature range up to 250°C. By utilizing the flexible ultrathin nanolaminate on curved surfaces such as thin metal wires, we introduce an innovative concept that enables the creation of a highly efficient and compact metal-wired capacitor, achieving substantial capacitance despite the minimal device volume.

Significantly enhanced high-temperature energy storage performance for polymer composite films with gradient distribution of organic fillers

Film capacitors as one of the most important electronic devices are heading in large capacity, heightened integration and excellent extreme-condition tolerance, which faces the challenges in maintaining outstanding performance under harsh conditions of high temperature and large electric field. Nonetheless, polymer capacitive films, which are renowned for their exceptional thermal stability, experience an escalation in conduction losses at elevated temperatures, resulting in degradation of energy storage performance. This study presents the gradient distribution of organic fillers content in all-organic polymer capacitive films utilizing electrospinning technique, the significantly improved high-temperature energy storage performance has been achieved. Glucose (GLC), a weak polar molecule rich in hydroxyl groups, is blended with the most promising polyetherimide (PEI). Experimental and theoretical calculations confirm that the formed hydrogen bond between GLC and PEI acts as a trapping site for capturing carriers and suppressing conduction losses. Furthermore, the spatial distribution of organic fillers was designed on the basis of direct mixing. The results demonstrate that the gradient composite film introduces interlayer interfacial polarization, while the dielectric mismatch between adjacent layers increases the height of potential barriers for the charge carriers across the interfaces, thereby achieving a synergistic enhancement of dielectric response and insulation strength. The maximum discharge energy density of 6.52 J/cm3 with an efficiency of 85.6 % has been achieved at 150℃ for the modified capacitive films. This work establishes a decoupling relationship between permittivity and electric breakdown strength, offering insights for the advancement of polymer films with outstanding energy storage capabilities in extreme environments.

CFD virtual prototyping of a high temperature energy storage system

CFD virtual prototyping of a high temperature energy storage system

PYN-based antiferroelectric ceramics with superior energy storage performance within an ultra-wide temperature range

Antiferroelectric (AFE) ceramics are known for their rich field-induced phase transitions, which mainly contribute to their superior energy storage performance. However, the phase transitions instability caused by high temperature often limits its application scenarios. Developing AFE ceramics with high energy storage properties and wide application temperature ranges is challenging. Here, considering the B-site ordering characteristics of Pb(Yb0.5Nb0.5)O3, we propose a simple approach for introducing A-site distortion and adjusting B-site ordering to confront these challenges. In our Fe3+/Sr2+co-doping system, we realized an ultra-wide temperature range of 25–200 °C, within which the recoverable storage density was considerable: 8.48–13.39 J cm−3. In this interval, the discharge energy density could reach 6.15–9.67J cm−3, and the discharge current density and discharge power density were 755.09–1667.36 A cm−2 and 207.65–500.21 MW cm−3, respectively. The obtained high-temperature energy storage performance was superior to that of existing energy storage ceramics or polymer films. The introduction of A-site distortion improves the stability of AFE phase, the decrease in B-site ordering suppresses the remanent polarization and delays change in structural symmetry with temperature. This study forms a basis for further applications of dielectric capacitors and signifies the development of wide-temperature-range energy storage devices.

Improved Energy Density at High Temperatures of FPE Dielectrics by Extreme Low Loading of CQDs.

Electrostatic capacitors, with the advantages of high-power density, fast charging-discharging, and outstanding cyclic stability, have become important energy storage devices for modern power electronics. However, the insulation performance of the dielectrics in capacitors will significantly deteriorate under the conditions of high temperatures and electric fields, resulting in limited capacitive performance. In this paper, we report a method to improve the high-temperature energy storage performance of a polymer dielectric for capacitors by incorporating an extremely low loading of 0.5 wt% carbon quantum dots (CQDs) into a fluorene polyester (FPE) polymer. CQDs possess a high electron affinity energy, enabling them to capture migrating carriers and exhibit a unique Coulomb-blocking effect to scatter electrons, thereby restricting electron migration. As a result, the breakdown strength and energy storage properties of the CQD/FPE nanocomposites are significantly enhanced. For instance, the energy density of 0.5 wt% CQD/FPE nanocomposites at room temperature, with an efficiency (η) exceeding 90%, reached 9.6 J/cm3. At the discharge energy density of 0.5 wt%, the CQD/FPE nanocomposites remained at 4.53 J/cm3 with an efficiency (η) exceeding 90% at 150 °C, which surpasses lots of reported results.

Interface engineering of polymer composite films for high-temperature capacitive energy storage

Polymer film capacitors encounter challenges in harsh conditions of high temperatures and electric fields because of large conduction loss and degraded breakdown strength (Eb). Herein, an interface engineering strategy is proposed to fluorinate the interfaces between the polyetherimide (PEI) matrix and wide bandgap boron nitride nanosheets (BNNSs) fillers. The composite films exhibit high-performance capacitive energy storage with a remarkable energy density of 5.73 J/cm3 and an ultrahigh efficiency of 91.22 % in conditions of 575 kV/mm and 150 °C. By adopting interfacial fluorination, the band structure of BNNSs is tailored to achieve a type II band alignment with PEI, promoting the dual trapping for both electrons and holes. It highly suppresses leakage current and reduces conduction loss. Typically, introducing fillers can compromise the properties of interfacial layers, creating weak points that trigger breakdown. Conversely, fluorinated interfaces exhibit an increased Young’s modulus and a reduced dielectric constant. According to the electromechanical breakdown theory, the interfacial Eb is increased. The breakdown phase propagation along the interfaces is thereby impeded, ultimately resulting in a further increase in overall Eb, reaching up to 589 kV/mm at 150 °C. Fluorinated interface engineering addresses interfacial challenges posed by fillers, enabling high-temperature energy storage capability in PEI-based capacitors.

Optimizing high-temperature energy storage in tungsten bronze-structured ceramics via high-entropy strategy and bandgap engineering

As a vital material utilized in energy storage capacitors, dielectric ceramics have widespread applications in high-power pulse devices. However, the development of dielectric ceramics with both high energy density and efficiency at high temperatures poses a significant challenge. In this study, we employ high-entropy strategy and band gap engineering to enhance the energy storage performance in tetragonal tungsten bronze-structured dielectric ceramics. The high-entropy strategy fosters cation disorder and disrupts long-range ordering, consequently regulating relaxation behavior. Simultaneously, the reduction in grain size, elevation of conductivity activation energy, and increase in band gap collectively bolster the breakdown electric strength. This cascade effect results in outstanding energy storage performance, ultimately achieving a recoverable energy density of 8.9 J cm−3 and an efficiency of 93% in Ba0.4Sr0.3Ca0.3Nb1.7Ta0.3O6 ceramics, which also exhibit superior temperature stability across a broad temperature range up to 180 °C and excellent cycling reliability up to 105. This research presents an effective method for designing tetragonal tungsten bronze dielectric ceramics with ultra-high comprehensive energy storage performance.

High-temperature high-performance capacitive energy storage in polymer nanocomposites enabled by nanostructured MgO fillers

High-temperature high-performance polymer dielectric capacitors are essential for cutting-edge electronics and high-power systems operated in harsh environment conditions. Herein, dielectric composites comprising polyetherimide (PEI) polymers and easily prepared magnesium oxide (MgO) nanoparticles are fabricated by tape casting to promote capacitive performance at high temperatures. Benefiting from high-insulation behavior and wide bandgap of the MgO nanoparticles, the designed PEI nanocomposites deliver the significantly suppressed leakage current density and prominent enhancement of the breakdown strength, especially under high temperatures, the rationality of which is further revealed by finite element simulations on high-field distribution and electrical tree evolution. Accordingly, the nanocomposites containing ultra-low loading volume (0.5 vol%) MgO nanoparticles endow a large discharged energy density (~ 6.60 J cm−3) at 150 °C, which is ahead of most investigated 0–3 dielectric nanocomposites with inorganic fillers. Moreover, the excellent fatigue resistance at 150 °C is simultaneously achieved. This study demonstrates a practical route to develop scalable high-temperature polymer nanocomposite dielectrics blended with inorganic nanoparticles with superior capacitive performance, thus accelerating the development of dielectric polymer capacitors.

Cost-effective strategy for high-temperature energy storage performance of polyimide nanocomposite films

The performance of most polymer-based film capacitors deteriorates severely at high temperatures, while high Tg polymer capacitors, despite their good performance at high temperatures, but their performance still decays severely after prolonged operation at high temperature. This study involves the deposition of a wide bandgap SiO2 inorganic layer on both surfaces of polyimide (PI) films using electron beam thermal evaporation. The findings indicate a substantial enhancement in the breakdown field strength and energy storage density of the composite films at elevated temperature following the deposition of the SiO2 inorganic layer. Specifically, a 100-nm-thick inorganic layer resulted in a breakdown field strength of 459.65 MV m−1 and an energy storage density of 3.2 J cm−3 at 150 °C. Subsequently, the polyimide film coated with a 100 nm SiO2 inorganic layer was infused with small quantities of SrTiO3 nanoparticles, leading to a breakdown field strength of 504.08 MV m−1 and an energy storage density of 6.75 J cm−3 and maintained an efficiency of 90.9 %. These results surpass the performance of the majority of high-temperature polymer films reported to date, with the inorganic layer deposited via electron beam thermal evaporation matching that of the costly magnetron sputtering method. The study presents a cost-effective method suitable for large-scale industrial production, significantly enhancing the electrical performance of PI at elevated temperatures and offering an economical solution for the commercialization of poly composite-based high-temperature capacitors.

An assessment of the performance of heat transfer enhancement for optimizing high-temperature thermal energy storage

Background: High-temperature phase change materials (PCMs) are increasingly recognized for their potential in applications such as solar energy utilization, industrial waste heat recovery, and power load regulation. These materials can store and release significant amounts of latent heat, making them highly efficient for thermal energy storage. Purpose: This study aims to propose and analyze a novel structure to enhance latent heat energy storage using a graphite sheet combined with a PCM (KNO3-NaNO3) with a melting point of 220 K. The focus is on improving heat transfer efficiency and understanding the parameters affecting the exothermic process. Research Design: A numerical simulation approach was employed, using Fluent 7.1 software to analyze the exothermic process. The simulation method was validated with two examples before being applied to study the energy storage system incorporating graphite sheets. Study Sample: The study analyzed the performance of a high-temperature thermtotal energy storage (HTTES) system using graphite sheets of varying thicknesses, tube spacing, tube temperatures, and PCM thermal conductivities. Data Collection and/or Analysis: The study utilized numerical simulations to examine how different parameters i.e. thickness of graphite sheets, spacing between tubes, tube temperatures, and the thermal conductivity of PCM—affect heat transfer efficiency and exothermic time. Results: The integration of graphite sheets with a thickness of 2 mm was found to significantly improve heat transfer efficiency. The results indicated that increasing the spacing between graphite sheets and tube diameter influenced the total exothermic time. A logarithmic relationship was observed between the thermal conductivity coefficient and exothermic time, suggesting diminishing returns beyond 3.5 W/(m·K). Additionally, increasing the quantity of graphite sheets enhanced heat transmission and overall system efficiency. Conclusions: The study provides valuable insights into the performance of HTTES systems, demonstrating that incorporating graphite sheets can significantly enhance heat transfer and system efficiency. These findings guide the design of more effective thermal energy storage systems, supporting the broader adoption of HTTES technologies and contributing to the transition toward sustainable energy solutions. Further research and development in this field are essential to drive advancements and promote the widespread implementation of high-temperature thermal energy storage systems. Practical applications The enhanced heat transfer techniques developed in this research offer practical applications across various sectors. These techniques, utilizing PCMs and innovative graphite structures, enhance the efficiency and reliability of high-temperature thermal energy storage systems. This advancement enables continuous power generation in concentrated solar power (CSP) plants, optimizes energy utilization in district heating and cooling systems, and improves industrial waste heat recovery. By implementing these techniques, energy costs can be reduced, system performance can be optimized, and greenhouse gas emissions can be lowered, contributing to a more sustainable energy future.

Scalable multilayered dielectric polymer film exhibiting significantly improved high-temperature energy density

Dielectric polymers, serving as crucial dielectric media in high-power-density energy storage devices, play a pivotal part in modern industries and electrical systems. However, the rapid degradation of breakdown strength and charge-discharge efficiency in elevated temperature environment imposes formidable limitations on the utilization of polymer dielectric under extreme conditions. Here, a series of polyetherimide/polysulfone alternating multilayer composite films are prepared using a non-equilibrium processing method, which effectively blocks the development of breakdown paths by the interface barriers in the multilayer structure. The deep trap sites within the interface capture the charge carriers excited at high temperatures, thus decreasing conduction loss and enhancing the efficiency and breakdown field strength of the dielectric polymer. Consequently, excellent capacitive performances including a high energy density of 5.4 J cm−3 with an efficiency exceeding 90% at 200 °C and cycle stability up to 106 cycles have been obtained. Furthermore, the multilayer polymer capacitors (MLPC) constructed from composite films also exhibit significant flexibility and thermal stability. This work provides valuable insights for the advancement of high-temperature energy storage polymers with commercial application value.

Polymer nanocomposites with concurrently enhanced dielectric constant and breakdown strength at high temperature enabled by rationally designed core-shell structured nanofillers

Polymer dielectrics are required to maintain high energy density at elevated temperatures for advanced power and electronic systems. Herein, we report a novel solution-processed core-shell structured polyimide (PI) nanocomposite with moderate dielectric constant HfO2 core and wide-bandgap Al2O3 shell, effectively addressing the typical trade-off between dielectric constant and breakdown strength in dielectric nanocomposites predominant at elevated temperatures. The formation of improved dielectrically matching interfaces by the rationally designed dielectric constant gradient from core-shell-matrix remarkably mitigates the distortion of the electric field around the interfaces, resulting in a high breakdown strength. Wide band gap Al2O3 shell also introduces deeper traps to impede the conduction loss. The validity of Al2O3 shell has been proved via experiments and simulations. Accordingly, HfO2@Al2O3/PI nanocomposite exhibits an excellent charge-discharge efficiency of 91.7 % at 300 MV/m and a maximum discharged energy density of 2.94 J/cm3 at 150 °C, demonstrating its potential for high-temperature energy storage.

Pendant Group Functionalization of Cyclic Olefin for High Temperature and High-Density Energy Storage.

High-temperature flexible polymer dielectrics are critical for high-power-density energy storage and conversion under harsh operating conditions. These types of dielectrics will need to simultaneously possess a high bandgap, dielectric constant and glass transition temperature - a substantial challenge when designing novel dielectric polymers. In this work, by varying halogen substituents of an aromatic pendant hanging off a bicyclic mainchain polymer, a class of high-temperature olefins with adjustable thermal stability are obtained, all with uncompromised large bandgaps. Halogens substitution of the pendant groups at para or ortho position of polyoxanorborneneimides (PONB) imparts it with tunable high glass transition temperature from ∼220 to 245°C, while with also moderate dielectric constant of ∼ 2.8-3.0 and high breakdown strength of ∼625-800MV/m. A high energy density of 7.1 J/cc at 200°C is achieved with p-POClNB, representing the highest reported energy density among all-organic homo-polymer dielectrics. Molecular dynamic simulations and ultrafast infrared spectroscopy were used to probe the free volume element distribution and chain relaxations of the polymers to provide insights to the dielectric thermal properties. An increase in free volume element is observed with the change in the pendant group from fluorine to bromine at the para position; however, a decrease in free volume element is observed as we change the pendant group from fluorine to chlorine at the ortho position because of the steric hindrance. Overall, the dielectric constant and band gap remain stable while the glass transition temperature changes more obviously. Consequently, by proper designing the pendant groups, the thermal stability of PONB can be improved for harsh condition electrification. This article is protected by copyright. All rights reserved.