Thermal Battery Research Articles

CuF2@C composites with inhibited side-reactions enables enhanced electrochemical performance in thermal batteries

Conversion-type compounds as cathodes for thermal batteries have recently attracted considerable attention due to their excellent specific capacities. CuF2 has been regarded as a promising candidate owing to its high theoretical discharge voltage (3.55 V, vs Li) and theoretical capacity (528 mAh·g−1). However, mass loss caused by side-reactions from CuF2 cathode and molten salt electrolyte leads to severe degradation of the discharge capacity of single-cells in thermal batteries. As a proof-of-concept, in this work, carbon coated CuF2 (CuF2@C) is employed as the cathode to fabricate thermal batteries, in which carbon serves as a protector to inhibit the mass loss of CuF2 in molten salt electrolyte. As a result, CuF2@C demonstrates obviously improved electrochemical performance with a discharge specific capacity of 462.45 mAh·g−1 at the current density of 10 mA·cm−2, which is 82.67 % higher than that of the counterpart (bare CuF2). This can be attributed to the reduced average polarization resistance of the single-cells in CuF2@C composites. This work provides a new route for developing high performance CuF2-based cathode material for thermal batteries and promoting its further practical application.

Modelling physical controls on mine water heat storage systems

The use of abandoned mines as a heat source and store has been receiving increased attention as a renewable heat source and storage solution in the transition away from traditional gas heating. The hydraulic, thermal and geomechanical processes governing heat storage and extraction are complex and understanding these processes is critical to safe heat extraction and injection into mine water systems. This paper outlines the development of a fully coupled thermo-hydraulic-mechanical (THM) 2D model to understand the mechanical stability of room and pillar workings during heat injection and extraction. It was found that the cyclical injection and extraction of heat does have an impact on both the modelled displacements and mechanical stability of the system. The impact risk reduces with temperature and the operational processes (e.g. injection temperature and water level) have more of an impact than the underlying geological conditions. These results are significant and could be included in a regulatory system to reduce the likelihood of stability impacts in mine water heating and cooling schemes. Thematic collection: This article is part of The Earth as a thermal battery: future directions in subsurface thermal energy storage systems collection available at: https://www.lyellcollection.org/topic/collections/thermal-energy

Thermal runaway and soot production of lithium-ion batteries: Implications for safety and environmental concerns

Global energy shortages are becoming increasingly severe, and lithium-ion batteries are becoming an important substitute for fossil fuels. However, thermal runaway of a battery is a significant factor impacting battery industry development. Here, we conducted tests on battery thermal runaway using a combustion test chamber, analysing the effects of natural aging and state of charge (SOC) on battery thermal runaway. Additionally, EDS and XPS were used to analyse the soot particles formed during thermal runaway. Four stages in thermal runaway, e.g., battery bulge, smoke release, jet fire, and fire extinction. LiFePO4 with a higher SOC is more likely to cause thermal runaway. In addition, natural aging has an obvious impact on the intensity of thermal runaway. The gas products generated during a battery fire are identified as C1–C4 hydrocarbons. The soot generated by battery combustion presents a typical “core-shell” structure. The soot surface exhibits C–C, C–O, and O–H bonds, while the soot from early manufactured batteries also contains O–CO and π bonds. Soot contains not only C and O but also trace amounts of Li, F, P and Fe. These results reveal the characteristics of soot emission during thermal runaway of batteries, providing valuable insights for evaluating their toxicity and environmental impact.

Current Status and Prospects of Research on Cathode Materials for Lithium-Based Thermal Batteries

Current Status and Prospects of Research on Cathode Materials for Lithium-Based Thermal Batteries

Preparation and performance of highly-conductive dual-doped Li7La3Zr2O12 solid electrolytes for thermal batteries

Garnet Li7La3Zr2O12 (LLZO) electrolytes have been recognized as a promising candidate to replace liquid/molten-state electrolytes in battery applications due to their exceptional performance, particularly Ga-doped LLZO (LLZGO), which exhibits high ionic conductivity. However, the limited size of the Li+ transport bottleneck restricts its high-current discharging performance. The present study focuses on the synthesis of Ga3+ and Ba2+ co-doped LLZO (LLZGBO) and investigates the influence of doping contents on the morphology, crystal structure, Li+ transport bottleneck size, and ionic conductivity. In particular, Ga0.32Ba0.15 exhibits the highest ionic conductivity (6.11E-2 S cm−1 at 550 °C) in comparison with other compositions, which can be attributed to its higher-energy morphology, larger bottleneck and unique Li+ transport channel. In addition to Ba2+, Sr2+ and Ca2+ have been co-doped with Ga3+ into LLZO, respectively, to study the effect of doping ion radius on crystal structures and the properties of electrolytes. The characterization results demonstrate that the easier Li+ transport and higher ionic conductivity can be obtained when the electrolyte is doped with larger-radius ions. As a result, the assembled thermal battery with Ga0.32Ba0.15-LLZO electrolyte exhibits a remarkable voltage platform of 1.81 V and a high specific capacity of 455.65 mA h g−1 at an elevated temperature of 525 °C. The discharge specific capacity of the thermal cell at 500 mA amounts to 63% of that at 100 mA, showcasing exceptional high-current discharging performance. When assembled as prototypes with fourteen single cells connected in series, the thermal batteries deliver an activation time of 38 ms and a discharge time of 32 s with the current density of 100 mA cm−2. These findings suggest that Ga, Ba co-doped LLZO solid-state electrolytes with high ionic conductivities holds great potential for high-capacity, quick-initiating and high-current discharging thermal batteries.

Optimal discharging of solar driven sorption thermal battery for building cooling applications

In this study, optimal discharge conditions of sorption thermal battery (STB) are determined for stable supply of the building cooling load based on different load patterns. Parametric analysis is conducted to ascertain the influence of heat source temperature and the mass flow rate ratio between the solution and the heat transfer fluid on the performance of the STB. The maximum values of energy storage density (ESD) and coefficient of performance (COP) are estimated as 207.73 kWh/m3 and 0.74, respectively. The daily transient behaviors of STB are examined in detail, and the optimal solution charge and the solution flow rate are quantified based on the building types (residential, hospital, hotel, and office). For a building with an air conditioning floor area of 181.63 m2, the most suitable cooling load response is observed in the hotel scenario. The minimum deviated cooling output from the building load is 8.69%. Concurrently, COP and ESD are estimated of 0.69 and 101.99 kWh/m3. This paper demonstrates the cooling load responsiveness and optimal operating point of STB based on building load pattern. Additionally, a dimensionless number is defined to generate the discharge trend and enable to predict COP and ESD.

Conceptual design and numerical analysis of a miscibility gap alloy-based solid-state thermal battery for electric vehicles

Heating the passenger cabin of electric vehicles at low temperatures consumes a large amount of battery power, resulting in a significant reduction in cruising range. On-board thermal energy storage is an effective way to improve the cruising range of electric vehicles in winter. Miscibility gap alloy is a new type of shape-stabilized composite phase change material, which has the advantages of high energy storage density, high thermal conductivity, low cost, and good safety. Therefore, using it to heat electric vehicles can increase their cruising range, prolong battery life, and reduce cost. In this paper, the concept of a compact on-board solid-state thermal battery based on miscibility gap alloy is proposed for the first time, and the heat charging, thermal insulation and heat discharging performance of the design are analysed based on numerical simulations. The results show that the thermal battery can reach a heat storage density of 553.8 Wh/L, and the average heat discharging power can reach 1.326 kW. The results of this paper can provide guidance for the engineering development of miscibility gap alloy-based solid-state thermal batteries.

Experimental study on a two-stage absorption thermal battery with absorption-enhanced generation for high storage density and extremely low charging temperature (∼50 °C)

Absorption thermal battery (ATB) is a promising solution to balance the timing or intensity mismatch between low-grade renewable energy sources and end users, which can significantly alleviate the growing energy and environmental issues. However, the performance of the basic ATB needs to be improved, and there is still a lack of experimental research on advanced ATBs. This study proposes a two-stage ATB with absorption-enhanced generation to achieve high energy storage density (ESD) and extremely low charging temperature. A prototype is designed and manufactured, including the single-stage and two-stage modes. The experimental results indicate that the single-stage ATB is fully charged under a charging temperature of 90 °C with an energy storage efficiency (ESE) of 0.62 and an ESD of 137.3 kWh/m3 (357.2 kJ/kg). Under a charging temperature of 70 °C, the ESD of the single-stage ATB is only 62.7 kWh/m3 (163.1 kJ/kg), which can be greatly enhanced to 100.0 kWh/m3 (260.1 kJ/kg) by the two-stage ATB. The lowest charging temperature of the single-stage ATB is 60 °C, with an ESE of 0.31 and an ESD of 22.1 kWh/m3, while the two-stage ATB improves the ESE and ESD by 9.7% and 190.5%, respectively. Even under 50 °C, the ESE (0.33) and ESD (29.4 kWh/m3) of the two-stage ATB are higher than those of the single-stage ATB under 60 °C. The experiment results prove that the two-stage ATB has the advantages of higher ESD and lower charging temperature than the conventional ATB, which provides a promising option for low-grade renewable energy utilization.

Low-energy consumption LiCl–LiBr–KBr–CsBr electrolyte for high-energy thermal battery application

The activation of thermal batteries requires plentiful heat to melt the ambient solid electrolyte into an ionic conductor with high ionic conductivity for large current discharge. The process necessitates massive heating powder to provide heat, severely reducing the effective specific energy of the thermal battery. To decrease energy consumption, we developed the LiCl–LiBr–KBr–CsBr molten salt with low melting point of 239 °C, fusion enthalpy at 59.08 J/g, specific heat capacity of 0.38 J/K·g and 0.88 J/K·g in the solid and liquid states, correspondingly, which takes 44% less heat to reach the operating temperature (generally 500 °C) compared to the commonly used LiF–LiCl–LiBr electrolyte. These reductions not only enable the battery to discharge across a broad temperature range, but also lessens the quantity of pyrotechnic heating pellets and enhances the thermal battery's overall specific energy and safety.

Comparative thermal performance: An experimental study of self-stored U-pipe vacuum tube collectors operated in closed mode

ABSTRACT Hot water production using solar collectors is the utmost comprehensive application of solar energy. Solar water heaters are still incapable of operating in night/off-weather conditions and lacking in thermal performance. Researchers can see heat storage (thermal battery backup) as a potential solution. The novelty of this study is the fabrication and testing of newly designed U-pipe-based vacuum tube collectors (VTCs) integrated with thermal energy storage. Furthermore, Stearic acid and PEG6000 were selected as phase change materials in this study, and collectors were operated in closed mode for specially designed cases. Also, a cost analysis was evaluated for these collectors to show their economic viability. The thermal performance and economic outcomes of storage-based collectors were compared with conventional collector. Measured experimental data encompassed instantaneous inlet and outlet water temperatures, solar radiation and ambient temperature. The empirical findings showed that the maximum daily thermal performances were 69.81, 68.34%, and 61.33% obtained by stearic acid-filled collector-2, followed by PEG-filled collector-3 and conventional collector-1 at .334 LPM for case-III, respectively. Moreover, the maximum energy enhancement ratio was 6.28% for collector-2 and 6.21% for collector-3 at .5 LPM for case-II, respectively. From the economic analysis results, it was observed that the modified solar water heaters (collector-2 and collector-3) have an average levelized water heating cost of .06885 $/kWh and .06818 $/kWh, respectively, with a payback time of 5.37 and 5.15 years, which makes the modified collectors economically viable. Finally, the results indicate that the storage-based collectors can be used for applications with specific temperatures of hot water.

Experimental investigation of batteries thermal management system using water cooling and thermoelectric cooling techniques

The booming electric vehicle industry seeks fast charging solutions to address the safety risks posed by high-power charging, including thermal runaway and other safety issues. This study investigates the impact of combining liquid with thermoelectric cooling on battery thermal management. A series of experiments were conducted using various thermal batteries, liquid flow rates and batteries temperature thermoelectric. The experimental results compared air cooling (AC), water cooling (WC), and thermoelectric cooling (TEC) with different water flow (WF) rate in system and revealed that TEC with WF at 4.0 l/min was the best cooling system. This system can decrease the temperature by about 41-52% from the maximum temperature at discharge rates of 1.0, 1.5, 2.0, 2.5, and 3.0 °C. However, TEC with WF 1.0 and 2.0 l/min can effectively lower the temperature and reduce energy consumption compared to other cooling systems, while still maintaining the battery temperature within appropriate ranges.

Controlling reaction transfer between Al/Ni reactive multilayer elements on substrates

Reactive multilayers produce exothermic reaction with definite velocity and maximum temperature after ignition, which are the fundamental properties of the reactive multilayer systems. The generated heat with certain velocity makes it widely used in joining, bonding in the packaging, thermal batteries and many more applications. In this work, a distinct approach for achieving a reaction transfer between the reactive multilayers and different materials is demonstrated which can affect the generated temperature and velocity from the self-propagating properties of the reaction. For these intensions, we fabricated the Al/Ni reactive elements with certain separations between elements which allow to observe the reaction front transfer and emitted temperature in the reaction chain. The created separation between reactive elements are periodical and ordered systems with different thermal conductive properties. The temperature and definite velocity were measured by time-resolved pyrometer and high-speed camera measurements. SEM analysis showed the characteristics of the reaction transfer between reactive multilayer elements. It is predicted that: (I) The reaction front stops at a space with critical length; (II) Reducing heat loss through the substrate supports reaction front propagation through spaces; (III) Thermal property design of the spaces between the reactive elements enables property modification of the self-propagating reaction.Graphical abstract

Predictive thermal performance analysis of T-wall based adsorption thermal battery for solar building heating

Moisture-based adsorption thermal battery (ATB) holds great potential for addressing energy storage and utilization challenges. In this work, a proof-of-concept solar harvesting building envelope using the Trombe-wall (T-wall) based ATB design is proposed and investigated, featuring a developed composite sorbent as the porous wall for effective heat storage and utilization. To demonstrate the feasibility of employing the ATB-based building envelope for day-and-night space heating, a 3-dimensional simulation model of the ATB wall is meticulously designed and comprehensively studied. Parametric analyses of various working conditions, including examining the effects of solar radiation intensity, air temperature, air humidity, and airflow velocity on the heat charging and discharging performances of the ATB wall, are conducted using the numerical model. Simulation results indicate that, under a solar irradiance level of 700 W m−2 during the daytime, an average output air temperature of 42.4 °C and an average heating power density of 2.5 kW m−3 are achieved. Extending the heat charging time to 8 h and 12 h significantly improves the desorption efficiency, which is able to reach 47.2% and 75.0%, respectively. In terms of heat discharging performances, various working conditions investigated in the ATB wall model will lead to different thermal output performances.

Failure Mechanism and Residual Stress Analysis of Crystal Materials for the Thermal Battery

This paper investigates the thermal battery as a research topic. We conducted an in-depth analysis of various thermal battery aspects, such as the cathode material CoS2 and electrolyte material morphology, crystal type, and interface state changes before and after service. The aim was to explore the core reaction and main failure mechanisms of the thermal battery. Prior to the reaction, the thermal battery cathode and electrolyte material consisted of pure-phase CoS2 and a composition of MgO-LiF/LiBr/LiCl. After service, the cathode and electrolyte of the single thermal battery exhibited significant morphological alterations caused by the presence of a molten state. The cathode transformed from CoS2 to Co3S4 and Co9S8 together with the presence of a marginal quantity of Co monomers visible throughout the discharge process, which was confirmed by means of XRD and XPS analyses. After the reaction, the electrolyte material was primarily made up of LiF, LiBr, and LiCl while the crystal components remained largely unaltered, albeit with apparent morphological variations. As was deduced from the thermodynamic analysis, the cathode material’s decomposition temperature stood at 655 °C, exceeding the working temperature of the thermal battery (500 °C) by a considerable margin, which is indicative of outstanding thermal durability within the thermal battery’s operational temperature range. Furthermore, the discharge reaction of the positive electrode was incomplete, resulting in reduced CoS2 residue in the thermal battery monomer after service. The reaction yielded a combination of Co3S4, Co9S8, and small amounts of Co monomers, indicating possible inconsistencies in the phase composition of the pole piece during the reaction process. In this study, we examine the distribution of residual stress in the thermal battery under various operating conditions. The simulation results indicate that exposure to a 70 °C environment for 2 h causes the maximum residual stress of the battery, which had an initial temperature of 25 °C, to reach 0.26 GPa. The thermal battery subjected to an initial temperature of 25 °C exhibited a maximum residual stress of 0.42 GPa subsequent to a 2-hour exposure to a temperature of −50 °C.

A new strategy of dual-material reactors for stable thermal output of sorption thermal battery

Sorption thermal battery driven by air humidity is a promising alternative technology to traditional methods of burning fossil fuels for space heating. Its dominant design of one-material reactor faces technical bottlenecks of unstable discharging thermal output and low energy efficiency. Herein, a new strategy of cascaded dual-material reactors was proposed as a solution, by utilizing their different sorption characterizations at material level and “reaction wave” properties at system level. A proof-of-concept prototype was established, whose main and regulatory reactor were packed with AA-15% LiCl composite and SrBr2·H2O, respectively. Experimental results demonstrated that the regulatory reactor has a strong stabilization function of the unstable output temperature of the main reactor, with the average output temperature fluctuations under 1.5 °C. The discharging/charging energy efficiency was increased by 0.4–1.7 times compared with one-material reactor. The output temperature level and heating power can be simply adjusted by changing the inlet air humidity and air velocity. Moreover, the influences of the lengths of two reactors on the thermal output and system operations were evaluated. Possible strategies to further enhance the multistage utilization of the charging energy were proposed. This new design strategy can contribute to the popularization and application of sorption thermal battery.

Review of Transition Metal Chalcogenides and Halides as Electrode Materials for Thermal Batteries and Secondary Energy Storage Systems.

Transition metal chalcogenides and halides (TMCs and TMHs) have been extensively used and reported as electrode materials in diverse primary and secondary batteries. This review summarizes the suitability of TMCs and TMHs as electrode materials focusing on thermal batteries (utilized for defense applications) and energy storage systems like mono- and multivalent rechargeable batteries. The report also identifies the specific physicochemical properties that need to be achieved for the same materials to be employed as cathode materials in thermal batteries and anode materials in monovalent rechargeable systems. For example, thermal stability of the materials plays a crucial role in delivering the performance of the thermal battery system, whereas the electrical conductivity and layered structure of similar materials play a vital role in enhancing the electrochemical performance of the mono- and multivalent rechargeable batteries. It can be summarized that nonlayered CoS2, FeS2, NiS2, and WS2 were found to be ideal as cathode materials for thermal batteries primarily due to their better thermal stability, whereas the layered structures of these materials with a coating of carbon allotrope (CNT, graphene, rGO) were found to be suitable as anode materials for monovalent alkali metal ion rechargeable batteries. On the other hand, vanadium, titanium, molybdenum, tin, and antimony based chalcogenides were found to be suitable as cathode materials for multivalent rechargeable batteries due to the high oxidation state of cathode materials which resists the stronger field produced during the interaction of di- and trivalent ions with the cathode material facilitating higher energy density with minimal structural and volume changes at a high rate of discharge.

1T-VS2@V2O3 Synergistic Nanoarchitecture-Based Lamellar Clusters as the High Conductivity Cathodes of Thermal Batteries.

Thermal batteries are solid-state, thermally activated batteries with long storage times and high reliability. FeS2 is used as a cathode material commonly, but the high internal resistance and low voltage platform limit the improvement of battery performance. Herein, the 1T-phase vanadium disulfide (VS2) is prepared via the scalable hydrothermal method and applied to thermal battery cathode materials for the first time. 1T-VS2 lamellar flower clusters have high electronic conductivity (1.583 S cm-1) at room temperature, which is 75 times higher than FeS2 (0.021 S cm-1). Mechanism analysis shows that 1T-VS2@V2O3 can be formed based on the part of 1T-VS2 being oxidized to V2O3 at the discharge temperature. Benefiting from the synergistic effect of vanadium sulfide and vanadium oxide as a cathode for thermal batteries enhanced specific capacity (292.4 mA h g-1) and mass energy density (572.5 W h kg-1) when cutoff voltage is 1 V. Additionally, the discharge results indicate that the cells utilizing 1T-VS2 cathodes provided a higher voltage platform of 2.11 V than 1.84 V for FeS2. This impressive work can offer a good strategy for boosting cathode materials for a high-performance thermal battery.

Improved properties of the Co/Al-doped carbide slag pellet as a potential high-temperature thermal battery by tunable coating strategy

CaO-based materials have been considered as the viable high-temperature thermal battery for concentrated solar power (CSP) plants. However, natural CaO-based materials have poor mechanical strength, optical properties and anti-sintering ability, which limits their applications. With the aim of enhancing the energy storage performance of CaO-based materials, the Co/Al-doped carbide slag pellets were prepared by tunable coating strategy in this work. The effects of bamboo powder, Al doping amount and Co doping modes on the energy storage, mechanical and optical properties of the composites were investigated. The Ca/Al molar ratio and the impregnation time in Co solution of the optimal material are 100:10 and 20 min, respectively. After 50 cycles, the energy storage density of optimal material is 989 kJ/kg, which is 1.67 times higher than that of unmodified carbide slag. The solid-phase reaction between CaO and Al2O3 produces Ca12Al14O33. Ca12Al14O33 inhibits the growth of CaO grains and improves sintering resistance. Ca3Co2O6 is a stable phase formed by Co2O3 and CaO, which improves the optical absorption of CaO-based materials but exacerbates the sintering of CaO. Compared with the homogeneous strategy, Co/Al-doped carbide slag pellets by coating strategy has a structure with the Al-doped internal core and the Co-rich external shell, which combines the advantages of high cycle stability and high optical absorptivity. The average mechanical strength and optical absorption of optimal material are 4.2 and 4.17 times higher than those of unmodified carbide slag, respectively. Therefore, the novel material has a good application prospect in the CaO-based energy storage system.

Facile synthesis of Ni anchored on N-doped carbon nanotube as cathodic electronic conductive agent for thermal battery

Carbon series material is currently the most prevalent electronic conductive agent of thermal battery cathode. For practical applications, such materials suffer from issues such as light density and low conductivity, which can cause dust pollution and affect formability of electrode. Herein, nickel dispersed by bamboo-like nitrogen-doped carbon nanotube (Ni/NCNT) is conveniently synthesized by pyrolysis of nickel-dicyandiamide complex. Benefiting unique structure and the existence of metallic nickel, the single cell with Ni/NCNT cathodic electronic conductive agent yields a long discharge lifetime, accompanying with outstanding current carrying capacity. Concurrently, the Ni/NCNT presents a certain attenuating voltage spike capacity, and thus improving discharge stability. This study offers a potential alternative to conventional conductive agent and antipeak agent for thermal battery.

Large-Scale Synthesis of High Energy Thermal Battery Cathode Ni0.5Co0.5S2 by a Simple Sintering Technique.

With the synergies of multiple elements, bimetallic sulfides exhibit excellent performance as splendid electrode materials and effective catalysts. However, large-scale synthesis of high-performance single-phase multicomponent sulfides has always been a challenge. Based on thermodynamic calculations, the intermediate phases NiS2 and Co3S4 are devoted to the synthesis of single-phase Ni0.5Co0.5S2. Because the reaction from NiS2 and Co3S4 to Ni0.5Co0.5S2 goes through a lower energy, it thermodynamically contributes to achieving a single-phase structure. Thus, single-phase Ni0.5Co0.5S2 can be simply and quickly prepared by two-step sintering and successfully scalable for mass production. This technique can extend to the whole ingredients Ni1-xCoxS2. Ni0.5Co0.5S2 demonstrates excellent thermal stability and good conductivity. It delivers a specific capacity of 671 mAh·g-1 and a specific energy of 1173 Wh·kg-1 when applied to a thermal battery cathode, which are increased by 18.6% and 25.0%, respectively, compared to pristine NiS2 (566 mAh·g-1) and CoS2 (537 mAh·g-1). This work proposes an innovative sintering method, which is applicable for cost-efficient and large-scale synthesis of single-phase multicomponent sulfides.