Thermal Index Research Articles

Thermodynamic properties of TPAC-EG deep eutectic solvents: A study based on the IGC method with molecular simulations

The study of thermodynamic properties and intermolecular interactions in deep eutectic solvents (DES) is an important innovative step in the development of DES. This research focuses on the synthesis of DES using a 1:2 M ratio of tetrapropylammonium chloride and ethylene glycol. Inverse gas chromatography (IGC) techniques are used to investigate DES of thermodynamics in the temperature range of 303.15–333.15 K. Additionally, molecular dynamics (MD) simulations and density functional theory (DFT) are used to explore intermolecular interactions in DES at both molecular and atomic levels. The research findings yield crucial insights, including the successful determination of infinite dilution activity coefficients, Flory-Huggin’s interaction parameters, solubility parameters, and Abraham solvation parameters of DES through IGC techniques. A careful study of the temperature-dependent trends in these parameters is provided. Analyses of structural properties, including radial distribution functions, hydrogen bond counts, and thermal fluctuation indices, reveal that, at experiments temperatures, the amount and nature of intermolecular hydrogen bonds in binary mixtures are the main factors influencing the thermodynamic properties of DES. Finally, based on DFT calculations, a quantitative assessment of the molecular interaction mechanisms of DES at the atomic level confirms the predominant role of hydrogen bonding in DES formation, with multicenter hydrogen bonds characterized by stronger hydrogen bond strengths emerging as the primary type.

Modelling of the heat and the cold risks in Sofia and Varna – preliminary results

According to future climate projections, the expected thermal stress environmental conditions will get worse if the authorities do not apply appropriate measures for mitigation and adaptation to these changes. The health issues concerning air pollution and extreme temperatures have assumed great importance in recent years. The objective of this study is to estimate the thermal comfort in two of the biggest cities in Bulgaria - Sofia and Varna and their surroundings for the year 2017 by biometeorological indexes. We use computer simulations of the atmospheric parameters that define the thermal comfort indexes, by Advanced Research Weather Forecast Model WRF ARW version 3.9. We performed the simulations on four domains for 2017 with an output frequency of 1 hour. The outermost domain has a horizontal resolution of 9 km and encompasses the Balkan Peninsula. It uses initial and boundary conditions from the 0.25-degree NCEP Final Operational Model Global Tropospheric Analyses datasets with a time-frequency of 6 hours. The estimation of the thermal comfort conditions is performed with characteristics called indexes. The differences in the number of cases between the indexes are due to the specific definitions and the meteorological factors that each of them takes into account. Some of these characteristics have applications depending on the specific thermal conditions.

Evolution and performance analysis of thermal comfort indices for tropical and subtropical region: a comprehensive literature review

Evolution and performance analysis of thermal comfort indices for tropical and subtropical region: a comprehensive literature review

A review of investigation of the metabolic rate effects on human thermal comfort

The precise analysis of the usage of thermal indices to evaluate and create an acceptable space is a research hotspot as thermal comfort increasingly comes to be the center of attention. The accurate measurement and calculation of the metabolic rate should be a top priority in research because it is the most important component of thermal indexmodels. This study includes a literature survey of the relevant fields to properly comprehend the present developments and flaws in calculating the metabolic rate. The ultimate objective is to apply the growth of human metabolic science to logical urban development. First, the interaction between the thermal environment and thermal comfort was analyzed, and then, the influence of the human metabolic rate on thermal comfort was discussed. The results show that the dynamic change of metabolic rate is the key human factor that directly affects the thermal regulation, and indirectly affects the evaluation accuracy of the thermal evaluation index standard. Through an inductive analysis of metabolic rate measurement methods that are widely used in various environments, this study identifies several issues with the current utilization of portable metabolic monitoring instruments in dynamic thermal comfort research, highlighting their limitations in addressing accuracy, portability, economy, and other relevant aspects. An essential future effort in this study path will be the continued research and development of a more portable, more affordable, more direct, and more efficient customized metabolic rate monitoring equipment. In addition, the fact that metabolic rate is represented as a constant or its impact on thermal comfort as a single factor in existing thermal index models also frequently results in incorrect findings in outdoor research. The fundamental condition for enhancing thermal comfort index forecast accuracy is accurate and continuous tracking of metabolic rate.

Analysis of the indoor thermal environment of traditional residents in the South Sichuan China region in summer and plum rainy seasons—taking Baiyang village in Yibin city as an example

ABSTRACT In hot summer and cold winter areas, the humid and sultry summer and rainy season problems have long affected the health of residents. Through a questionnaire survey and site measurements, the indoor thermal environment of typical southern Sichuan village houses was investigated. The average indoor humidity of the old traditional dwelling (85–95%) in the rainy season was much greater than that of the new rural house (70–80%), both of which are outside the standard thermal comfort range of the human body. In summer, the situation is slightly better but still uncomfortable. The APMV evaluation results reveal that in the rainy season, the new residential house is more comfortable than the traditional residential house, while in summer, the opposite situation occurs. The measurements show that the thermal inertia index of the old stone masonry house is large, which indicates that the house has a strong ability to resist temperature fluctuations. Therefore, we discussed different performance improvement strategies for these two types of rural residences. This study is conducive to improving the thermal environment of local residential buildings and provides a reference for the future design of rural ecological residential buildings.

Climatic Variations and Indoor Environmental Quality Performance of Houses in Selected Cities in Oyo State, Nigeria

Understanding how climatic variations influence Indoor Environmental Quality (IEQ) becomes crucial for designing sustainable and comfortable living spaces in this specific region. This study therefore investigates the effect of climatic variations on IEQ performance of houses in selected cities within Oyo State, Nigeria. The types of data collected for the study were numeric and ordinal. The numeric data of air temperature, relative humidity, air velocity and noise level, were gotten through objective measurements and IEQ through IEQ Calculator. The ordinal data were gotten through observation and questionnaire. Control Potential Zone technique on psychometric chat was used to analyze climate of Ibadan, Ogbomoso and Kisi. The physical measurements were conducted in the living, bedroom and kitchen spaces of the sampled houses in the low, medium and high residential density zones of the selected cities. A sample size of 581 houses from 3,490 were selected across each of the three residential density zones in the selected cities. The indoor temperature and relative humidity in the three cities were higher during the afternoon period with average thermal stress index of 39.40C, 36.90C and 38.40C respectively for Ibadan, Ogbomoso and Kisi respectively. None of the spaces satisfied the effective indoor ventilation comfort criteria of between 0.5m/s -1.5 m/s. All the spaces except the bedroom space in the compound impluvium house type satisfied the illumination range of between 50 – 60 lux. The maximum indoor noise level during the morning, afternoon and evening periods in study area were 58db, 59db and 58db respectively. Result from the IEQ calculator indicated that majority of the houses (83.6%) were star 2 in the IEQ performance. The implication was that these houses were below average in terms of IEQ performance.

Study on the optimal layout of roof vents and rooftop photovoltaic of the industrial workshop

Roof vents are crucial for facilitating natural ventilation within industrial workshops. However, their substantial size and height can limit available roof space and create extensive shadow areas, thereby impeding the installation of photovoltaic (PV) systems on industrial roofs. This study quantitatively assesses the influence of roof vent positioning, morphology, and roof architecture on the natural ventilation efficiency of workshops with varying indoor heat sources. Subsequently, the study evaluates how different vent configurations affect the installable area for rooftop solar panels. Findings suggest that shifting from traditional roof ridge vents directly above a heat source to north-side vents inclined towards the roof can marginally decrease the ventilation flow rate by approximately 5 %, translating to a minor temperature rise of around 0.46 °C within the occupied zone. Nonetheless, the Predicted Mean Vote (PMV) thermal comfort indices remain consistent across scenarios. Notably, adopting north-side vents, either flush with the roof or inclined, can enhance the annual energy yield of the rooftop PV system by 15.49 % and 22.67 %, respectively, under equivalent solar irradiation. Thus, strategic adjustments to vent positioning, form, and roof design can substantially boost the photovoltaic system's power output without compromising the workshop's natural ventilation performance.

A Bibliometric Analysis of the Outdoor Thermal Environment Based on CiteSpace

The outdoor thermal environment (OTE) is closely related to sustainable urban development and human living, and related research has attracted widespread attention. The research hotspots and research frontiers were obtained using CiteSpace to analyze 4473 relevant studies published in English from the Web of Science (WOS) core database from 1998 to 2023. The results show that (1) Hong Kong Polytechnic University, National University of Singapore, Chinese Academy of Sciences, Tsinghua University, and Harbin Institute of Technology are important in OTE research. China has the largest number of publications in the field of OTE, but the United States has the greatest centrality and significant influence. (2) The focus of OTE keyword clustering research is divided into four main categories: thermal environment perception, the thermal environment index, thermal environment quality, and thermal environment optimization. (3) The frontiers of OTE research have changed from focusing on environmental quality, thermal perception, numerical simulation, urban space, and thermal adaptation to thermal mitigation, energy conservation, energy consumption, and optimization strategies. Visualization research in the field of OTE helps to provide references for the direction of future research on improving climate change, human thermal comfort, urban planning, and pre-planning.

Resisting the heat wave: Revealing inequalities in matching between heat exposure risk and healthcare services in a megacity

Climate warming and the growing urban heat island effect are exacerbating the unequal public health crisis in megacities, and thus it is important to assess the equity of matching relationship between the healthcare services and the heat exposure risk. We selected 255 census units in Tianjin city for the study, and calculated a heat exposure index based on the universal thermal climate index (UTCI) and constructed a comprehensive urban healthcare services evaluation system to measure the degree of mismatch between the two. The results showed the following. (1) The heat exposure risk and healthcare services followed an increasing pattern from the Outer suburb area (OSA) to the Metropolitan development area (MDA) and then to the Main urban area (MUA). (2) The overall imbalance in matching was low in the OSA, whereas the healthcare services were relatively insufficient in the MDA, and the heat exposure risk and healthcare services were relatively balanced in the MUA. (3) The degree of matching between the core and peripheral parts of the MUA was severely polarized, with an overall pattern of excess healthcare in the core area and a high risk of heat exposure in the peripheral areas. The results can provide effective guidance for rationalizing the allocation of healthcare resources from a heat exposure perspective, and provide a policy basis for risk management and fund investment.

Delimitation and Prioritization of Climate-Affected Areas Using the Example of a Post-Industrial City

This study adapted and tested an approach to identifying areas that are particularly vulnerable to climate-related hazards using the example of the post-industrial city of Knurów in Poland. This study applied a multi-criteria method using the analytical hierarchy process based on GIS map data. The analysis was divided into statistical regions defined for the city. Fifteen attributes were defined for each statistical region. The applied methods provided verified spatial information related to specific climate change hazards. The results showed that the most vulnerable areas were the areas with intensive development in the city center and in the southwestern part of the city. Among the 15 attributes, the most significant were T1 (number of inhabitants in zones with a higher potential thermal risk index by statistical district) with a value of 0.163, G2 (percentage of the sum of tree-shaded areas in built-up areas within the territory of a given statistical district) with 0.143 and H3 (number of buildings in areas of drainless basins and 100-year water). This method effectively identified the most vulnerable areas. The use of such a method can help in the preparation of planning documents and urban adaptation plans by determining the thermally and hydrologically vulnerable areas with the least developed green infrastructure as an exposure-mitigating factor.

Design and thermal performance evaluation of the thermal storage layer of a solar air collector with comprehensive consideration of six factors of phase-change materials

The heat storage layer of fully filled phase-change materials (PCM) does not melt completely, and this significantly reduces the heat storage capacity, heat-release time, output temperature difference, collection efficiency, heat peak migration ability, and PCM cost of PCM-based solar air collectors (SACs), thereby affecting the comprehensive heating requirements of building households. To solve these problems and obtain the optimal filling rate for PCM, four PCM filling schemes were designed with comprehensive consideration of the six factors of PCM. (Type I is a SAC filled with 0 % PCM, Type II is the upper portion filled with 25 % PCM, Type III is the upper portion filled with 50 % PCM, and Type IV is filled with 100 % PCM). Four models were constructed for comparative experiments. A comparative analysis of the thermal performance evaluation indices indicated that the phase-change heat storage process of the Type III thermal storage layer only uses 1.25 h to store 1.505 × 106 J of heat energy, thus indicating that Type III possesses a better heat storage capacity. The max-output temperature difference of the Type III collector decreased by 20.1 °C compared to that of Type I. This indicates that Type III collectors can balance the range of output temperatures and increase indoor thermal comfort. After the solar energy ceases, the continuous heat-release time of the Type III collector is 13.75 h, and the ratio of its heat-release time to non-solar time is 94.83 %. This indicates that Type III possesses a better heat release time. The daily average heat collection efficiency of Type III filled was 37.77 %, and this was only 6.72 % higher than that of Type IV, thus indicating that Type III exhibited better heat peak migration ability, PCM utilisation efficiency, and lower PCM cost.

Aquatic photosynthetic carbon pump driven by periodic temperature variations affects dissolved inorganic carbon and hydrochemical characteristics in a groundwater-fed reservoir

Under the influence of periodic temperature variations, biogeochemical cycling in water bodies is markedly affected by the periodic thermal stratification processes in subtropical reservoirs or lakes. In current studies, there is insufficient research on the influence and mechanism of dissolved inorganic carbon (DIC) distribution in karst carbon-rich groundwater-fed reservoirs under the coupled effects of thermal structure stratification and the biological carbon pump (BCP) effect. To address this issue, the Dalongdong (DLD) reservoir in the subtropical region of southern China was chosen as the site for long-term monitoring and research on relevant physicochemical parameters of water, DIC, and its stable carbon isotope (δ13CDIC), CO2 emission flux, as well as the reservoir's thermal stratification index. The results show that: (1) the DLD reservoir is a typical warm monomictic reservoir, which exhibits regular variations of mixing period-stratification period-mixing period on a yearly scale due to thermal structure changes; (2) DIC was consumed by aquatic photosynthetic organisms in the epilimnion during the stratification period, leading to a decrease in DIC concentration, partial pressure of CO2 (pCO2) and CO2 emission flux, and an increase in stable carbon isotope (δ13CDIC). During the mixing period, the trend was reversed; (3) During the thermal stratification, aquatic photosynthesis and water temperature were the primary factors controlling DIC variations in both the epilimnion and thermocline. Regarding the hypolimnion, calcite dissolution, organic matter decomposition, and water temperature were the dominant controlling factors. These results indicate that although carbon-rich karst groundwater provides a plentiful supply of DIC in the DLD reservoir, its availability is still influenced by variations in the reservoir's thermal structure and the metabolic processes of aquatic photosynthetic organisms. Therefore, to better estimate the regional carbon budget in a reservoir or lake, future studies should especially consider the combined effects of BCP and thermal structure variations on carbon variations.

Observed Climatology and Variability of Cattle Heat Stress in Australia

Abstract Exposure to weather extremes, such as heatwaves, can cause discomfort, harm, or death in grazing cattle in pastures. While the Australian Bureau of Meteorology issues sheep graziers alerts when there is an exposure risk to chill for livestock, there is no equivalent alert for heat stress for Australian cattle. Before any such alert system can be developed, a robust assessment and comparison of relevant cattle thermal stress indices is required. This study evaluates and compares the multiyear climatology of three cattle thermal heat stress indices across Australia in the warm season months (October–March). The same indices are then used to assess historical Australian heat events where cattle died from heat exposure. These events are based off official records and survey responses from northern Australian graziers. In the seven historical heat events studied, high relative humidity combined with low wind speeds, or high solar exposure combined with high surface temperatures, exacerbated the impact of heat stress on cattle. In the two historic events where multiple compounding weather factors combined (e.g., high humidity, low winds, and high solar exposure), the cattle mortality levels were significantly high. These events were characterized by rainy conditions followed by a rapid warming, meaning cattle were likely unable to acclimatize to such dramatic temperature changes. This study highlights the need for using more than one thermal stress index when verifying cattle heat stress events and, importantly, calls for further research on standardizing the risk classifications of these thermal indices for cattle in Australia’s variable climate. Significance Statement Cattle across Australia’s northern tropical and semiarid regions often experience extreme hot and humid conditions in the summer months, which increases the risk of heat stress. This is the first study of its kind to evaluate observations of cattle heat stress across Australia using indices that describe the combined effects of solar exposure, wind speed, relative humidity, and surface temperatures. These cattle heat stress indices can be used to evaluate historical cattle mortality events in feedlots and in grazed pastures. This study lays the groundwork for the development of Australian-wide cattle heat stress forecast products on the 7-day to multiweek time scales.

Impact of spatial layout on vertical wind conditions and comfort levels in high-rise residential buildings in Shenzhen

Urban residential areas' rational spatial height distribution plays a crucial role in achieving a more balanced wind speed distribution, smoother air exchange, and improved space comfort. This study used Shenzhen as a representative city to analyse the effect of high-rise residential building layouts on vertical ventilation. Nine typical height-layout schemes were determined within an area of 220 × 200 m. Wind tunnel tests were conducted to validate the accuracy of the enhanced computational fluid dynamics simulations. Various parameters were comprehensively evaluated, including wind speed, wind pressure, mean age of air (MAA), and the universal thermal climate index (UTCI). The results show that different height layout schemes affect the distribution rates of wind speed, wind pressure, MAA, UTCI, and the rate of change with height. Compliance with the building row spacing specification enabled the nine schemes to obtain >83% of the windward wind speed and >48% of the leeward reasonable wind speed; the reasonable wind pressure distribution was >32% higher on the leeward side than that on the windward side. MAA statistics show that the air displacement efficiency per unit volume is generally between 120 and 300 s. >90% of the windward space in the UTCI was comfortable, and >60% of the leeward space felt slightly hot. This study shows the impact of high-rise residential layouts on comfort in hot summer and warm winter areas. It clarifies a reasonable height layout that helps realise the green liveability of residential areas.

The thermal perception of outdoor urban spaces in a hot arid climate: A structural equation modelling (SEM) approach

Human thermal comfort is linked to multi-sensory attributes and psychological cognition besides the influence of prominent meteorological parameters. To date, even the most advanced thermal comfort models like UTCI consider the interaction between human and external surroundings to be a heat transfer problem applying thermodynamic equations in the derivation behind thermal comfort indices. Machine learning (ML) models offer the advantage of improving the accuracy of predictor variable, but they fail to determine the relationship between the independent variables and data-driven prediction models. Structural Equation Modelling (SEM), an advanced modelling technique, can expose all hidden relationships among variables using latent variables while not being data-driven like ML. This study aimed to develop a structural framework which systematically explains these relationships and quantify the effects of 24 variables on outdoor thermal comfort using SEM due to its ability to represents the response of the dependent variable to a unit change in an explanatory variable. The method employed 635 structured interviews, observations, and wide-ranging micrometeorological measurements conducted concurrently in three Pedestrianized urban alleys in Cairo. The model statistically confirmed the hypothesis that overall thermal comfort in urban spaces is significantly influenced by multiple factors. Of these, background microclimatic conditions had the greatest relevance and certain urban features the least. 1 unit increase microclimate leads to a change in thermal comfort by 0.423 and 0.349 in summer and winter, respectively. In terms of thermal perception, the model shows that individuals are willing to tolerate a wider range if certain urban features are present such as shaded seating opportunities. These outcomes may aid to provide important guidance for urban designers to enhance thermal perception in urban streets.

Highly efficient and thermally conductive phosphor in glass based on two-component regulatory and h-BN addition

Achieving laser-driven solid-state lighting with higher brightness and laser power density engenders new requirements for higher-performance phosphor conversion materials. In this study, a highly efficient and thermally conductive tellurite phosphor-in-glass (PIG) added with hexagonal boron nitride (h-BN) was prepared for high-power laser driving. Reduction in the thermal expansion coefficient and refractive index matching with phosphor were realized by two-component regulation of the tellurite glass, which contributed to an enhanced laser irradiation threshold and luminous efficiency of the PIG. Furthermore, the micron h-BN powder, which served as a heat dissipation material and light scattering center, was uniformly dispersed within the PIG by stirring, which increased the thermal conductivity of the composite by 42 %. Microstructural characterization and XRD analysis indicated the ideal compound effect of h-BN and the integrity of the phosphor crystal phase. Notably, under irradiation with a high-power laser, the thermal stability of the composite material was significantly improved, and the luminous efficiency increased to 183.2 lm/W. Therefore, through component regulation and process optimization, the h-BN-added tellurite PIG acquired a high laser irradiation threshold and superior luminous efficiency, making it promising for applications in laser-driven white lighting.

Parametric study on thermal performance augmentation of TiO2/water nanofluids flowing a tube contained with dual counter twisted-tapes

The study of compound heat transfer enhancement technique using dual counter twisted tapes (DCTs) together with TiO2/water nanofluids was carried out. The dual twisted tapes in form of counter-swirl tape arrangement were utilized at three twist ratios (y/w = 1.5, 2.0 and 2.5). TiO2/water nanofluids having three different volume concentrations (φ = 0.05, 0.10 and 0.15 %) were employed as the testing fluids. The results indicated that heat transfer rate, friction factor and thermal enhancement index rose with decreasing tape twisted ratio and elevating nanofluid concentration. The TiO2/water nanofluids applied in the present work offered higher Nu than pure water (the base fluid) by 7.3–10.0 %. The application of DCT with the smallest y/w of 1.5 and TiO2/water nanofluids with the largest φ of 0.15 vol% led to the highest thermal enhancement index (TEI) of 1.53, under the same pumping power criteria. Additionally, the k-nearest neighbor (k-NN) and artificial neural network (ANN) were developed to predict the thermal enhancement index (TEI). It was found that the k-NN and ANN models provided maximum R2 values of 0.919 and 0.992 f, respectively.

Multi-Objective Optimization for Winter Heating Retrofit in Rural Houses of Cold Regions: A Case Study in the Wusu Area

In regions of China experiencing severe cold, the duration of the winter heating season significantly contributes to elevated heating energy consumption in rural dwellings. This study focuses on typical brick-and-concrete rural homes in the Wusu area. Utilizing the Rhino–Grasshopper parametric modeling platform, it aims to minimize heating-related carbon emissions and the overall costs associated with retrofitting. The approach involves improving the insulation properties of the building envelope to reduce energy requirements. Additionally, the study incorporates solar photovoltaic systems atop rural homes, building upon low-carbon, passive, energy-efficient design principles. By examining the influence of various factors on rural housing energy consumption, the research employs the entropy weight method to identify the most effective design solutions. The goal is to explore strategies for the energy-efficient retrofitting of rural dwellings in areas faced with harsh winter conditions, aligning with the objectives and preferences of Applied Sciences. The simulation results reveal the following: (1). In comparison with the baseline scenario, 42.2% of the optimized solutions within the Pareto frontier satisfy the current standards for 75% energy savings in energy-efficient residential design. (2). The lowest recorded thermal consumption index for the buildings can reach 12.427 W/m2, at which point the rate of energy savings is elevated to 79.5%. (3). Within the solutions identified by the Pareto frontier, 80% exhibit initial investments that are lower than the cost savings over the lifecycle due to reduced energy consumption (dCg < 0), demonstrating the economic feasibility of the proposed retrofitting strategies.

Investigating the potential of integrated urban greening strategies for reducing outdoor thermal stresses: a case of asymmetrical configuration in the tropical city of Bhopal.

In Indian cities where streets are the only affordable outdoor public space, pedestrians are always exposed to extreme heat related health risk. However, it's a challenge to reduce heat stress in existing streets characterized by asymmetrical urban configuration. Integrating vegetation without reconstituting the original orientation and geometry is one of the feasible ways to alleviate stress. Therefore, current study focuses to analyse the heat stress reduction potential of urban greenery strategy in asymmetrical urban configuration from spatiotemporal perspective. It initiates with the selection of commercial streets in extreme hot climate with an on-site measurement of its climatic and morphological attributes. Furthermore, it leads to the classification and prioritizing of street's sections linked to hot-spots determined by varied sky view factor and asymmetrical aspect ratio. Finally, an Envi-Met model with iterated scenarios at the building and street levels is developed, incorporating three strategies (trees, grass, green-walls). The impact of heat related health risk is quantified using a thermal index Universal Thermal Climate Index along with air temperature and mean radiant temperature. The results suggested that due to asymmetricity a fixed strategy would not be applicable across the street. The highest reduction was observed by trees in asymmetrical sections while lowest was recorded by green-wall. However, it would be worthwhile to adopt green-wall along with dense tree's (leaf area density, 0.3) in order to reduce the heat stress in deeper sections. The evidence-based integration of Urban greenery can assist planners and designers in mitigating extreme heat stress in similar complex urban environment.

A polyimide separator inlaid by methylsilyl-modified silica aerogels for high thermal safety and low polarization lithium-ion battery

The separator is a crucial component of lithium-ion batteries, playing a vital role in ion transfer and preventing polarization of the battery. To solve the problem of poor thermal safety of separators in lithium-ion batteries, in this work, three types of hydrophobic silica aerogels are compared. A suitable separator is fabricated by adding hydrophobic silica aerogels with monomethylsilyl as a modifier to pure polyimide. The aerogel composite separator displays a highly cross-linked three-dimensional nanoporous network, a low thermal shrinkage rate (<4 % at 200 °C), and high thermal stability (peak temperature of 670 °C) and oxygen index (>45 %). In addition, owing to the introduced hydrophobic functional groups of Si–CH3, the prepared separator decreases the polarization of the lithium-ion batteries and leads to improved power performance and cycle stability (its discharge voltage difference is 0.42 V higher than that of Celgard 2325 at 5 C). This work provides a new method of improving the safety and simultaneously reducing the polarization of lithium-ion batteries, which has promising application potential in power batteries.