The ligand field theory, which combines the electrostatic interaction of crystal fields and the covalent interaction of molecular orbitals, was first proposed in 1952. It has become the basis for studying many physical/chemical problems in thermodynamic, geological, mineralogical and electrochemical systems, such as structural distortion, thermodynamic properties and magnetism. Among them, for the rapidly developing mono-/poly-valent metal-ion batteries field, the electrode materials used are primarily transition metal (TM) compounds containing d electrons. However, the understanding of the regulation of microstructural/electronic performances with different coordination fields, such as ion-?(de)intercalating voltage, specific capacity and phase structure stability is still incompletely understood. In this paper, by combining the ligand field theory method and first-principles calculations (FP/DFT) that can directly obtain the system electronic distribution/occupancy, the Fermi level calculation model that determines the ions-intercalation voltage, the crystal field stabilization energy formula that measures the phase stability, and the theoretical model for regulating anionic redox activity are rigorously deduced. On this basis, we propose a series of electrodes energy-density/phase-stability improvement strategies, viz., voltage regulation of rigid band system and phase stabilization prediction of TM-containing electrodes with different TM period. Finally, two new cathodes, the TM-free Li(Na)BCF₂/Li(Na)B₂C₂F₂ and the lithium-free intercalation-type MX₂ are successfully designed. This work expands the application of ligand field theory in ions-intercalation electrochemistry and opens up a new avenue for designing high-energy-density ions-intercalation electrode materials through electronic band structure regulation engineering.

Zinc-air batteries have attracted widespread attention for their excellent safety, high capacity, low cost, and low self-discharge performance. A critical problem in commercializing rechargeable zinc-air batteries is finding a suitable bifunctional catalyst, in which the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) can work consistently over a long period. Therefore, a zinc-air battery with a tri-electrode configuration is a solution. Nevertheless, antileakage performance is critical for commercial batteries. We report a high-capacity prismatic zinc-air battery using a novel tri-electrode configuration. We introduce a design assuring a better connection between the cathode current collector and tab and a better sealing configuration for antileakage. Four highlights of this work are as follows: (1) excellent discharge performance, (2) antileakage, (3) high capacity, and (4) novel structure. When the cell was loaded with small amounts of zinc gel, it showed a low voltage of 1.10 V when discharging because the small amount of zinc gel might not cover the current collector and separator completely. However, leakage after discharge was observed when the cell was loaded with excess zinc gel. The amount of zinc gel, while being antileakage, was optimized by filling the anode case cavity with a proper amount of zinc gel, i.e., 87%. When the cell was discharged under a high current, it incurred a low voltage problem. However, discharging under a low current took long, and the surrounding carbon dioxide can seriously deteriorate the cathode catalyst's performance. Consequently, an optimal zinc loading as high as 97% in the zinc gel was used in an effective current discharge process. Moreover, the cell showed low voltage in a highly humid environment because of the high humidity affecting the active sites for the three-phase reaction. Notably, no leakage was detected even after the extreme conditioning test, i.e., the high-low temperature cycle test (70 ℃ to -20 ℃?) and high-temperature storage (45 ℃) for one month test. The tests demonstrated excellent antileakage performance of our cells compared to other commercial zinc-air batteries. An impressively high capacity of 356 A·h/kg was obtained for a single Cell-14 under a 600 mA discharge current, whereas batteries packed with the Cell-14 connected in series and parallel possessed a high energy density of 405 W·h/kg. Also, our optimized design strategies (the larger size anode cavity design, optimized zinc gel recipe, and improved catalyst performance) could theoretically be used to design a cell to obtain an energy density as high as 650 W·h/kg. The novel structure of a double-layered air cathode with tri-electrode configuration increases the effective air catalytic area, doubling the power density. Ultimately, our novel zinc-air battery with a unique tri-electrode structure, combined with gel polymer electrolytes, can be used to develop and commercialize a rechargeable zinc-air battery in the future.

Plant power generation technology is a green energy technology that uses plants as the primary body for power generation and converts natural light, mechanical, and biomass energy into electric energy using electrochemical means and some physiological processes in the plant. Plant power-generation technology features several advantages such as energy conservation, environmental protection, low cost, and sustainability, which are significant in both basic scientific research and practical application. Based on recent publications, this study first summarizes the advances and progress of five types of plant power generation technologies, including the sacrificial electrode plant primary-battery power generation technology, plant ion-concentration difference power-generation technology, photosynthesis-like power generation technology, plant microbial fuel-cell power generation technology, and plant regional ion-concentration disturbance power-generation technology. The advantages, principles, methods to improve the power generation capacity, and application examples of various plant power generation technologies are emphatically introduced and discussed in this review. The energy conversion principle and application of concentration cells designed based on ion-selective nanofluidic channels are extended to plants, which is considered a promising technology for the future development of plant-based power generation. Finally, this study summarizes the existing challenges and significant technical difficulties of plant power generation technology, and the future application opportunities associated with plant power generation and supply technology. This review of the progress and advancements in plant power generation is expected to provide new insight into the harvesting of novel clean electric energy and enhance the real-world application process of plant power generation technology.

Lithium-ion batteries (LIBs), as secondary batteries, have rapidly developed into mainstream energy storage devices in the field of new energy. Lithium iron phosphate (LiFePO₄) is considered the most promising cathode material for LIBs, with broad applications due to its high specific capacity, low cost, stable charge/discharge plateaus, environmental friendliness, and high safety. However, improving the output power, energy density, and cycle life at low temperatures is the main challenge for LiFePO₄. By exploring the recent relevant literature, this review summarizes recent studies on improving the electrochemical performance of LiFePO₄, which mainly includes elemental doping, surface coating modification, and lithium supplement additive adding strategies. The intrinsic mechanisms of improving the material's electrochemical performance using doping elements are analyzed in detail. The advantages and protection mechanisms of different types of coating agents for surface modification are summarized. The electronic conductivity and ion diffusion rate of LiFePO₄ can be effectively improved by doping and surface coating, which can achieve batteries with higher energy density, longer cycle life, and higher rate performance. The characteristics of common lithium phosphate supplement additives and their improved behavior on the cathode first turn Coulomb efficiency and discharge-specific capacity are also reviewed. Comprehensive analysis indicates that multiple-element co-doping, advanced carbon material coating, and the addition of high-capacity Li-rich materials are expected to become essential strategies for improving the electrochemical performance of LiFePO₄. Finally, prospects for the future development of LiFePO₄ cathode material are discussed. The direction and challenges associated with additional advancements in commercial production and the development of flexible electrodes are discussed.

Strict use requirements such as high endurance, long cycle, fast charging, and high safety of power batteries are driving the innovation of lithium-ion battery technology. However, this also makes the uniformity problem of batteries from the granular material to the cell level become prominent, and it has become a key factor in determining the overall performance of batteries. Studying the causes of multiscale nonuniformity of lithium-ion batteries and improvement strategies are important issues that need to be resolved in the current battery manufacturing and battery management. This overview systematically summarizes the influence of lithium-ion battery material particles, electrode microstructure, electrode plane, and cell monomer's nonuniform characteristics on the electrochemical uniformity of batteries and the evolution law during a battery cycle and focuses on the mechanism of nonuniformity damage to battery performance through the inherent parallel electrical structure. Finally, specific improvement measures are put forward for the nonuniformity of various scales.

The huge demand for long-life power batteries and large-scale energy storage equipment has generated considerable interest in nonaqueous lithium-oxygen batteries (LOB), a promising next-generation rechargeable battery, due to their super-high energy density, low cost, and environmental friendliness. Although extensive research has been conducted in recent decades, issues such as low specific capacity, high discharge/charge overpotential, and poor cycle life remain the challenges for their real commercialization. These critical issues point to the cathode, the location of the electrochemical reaction. During discharge, insoluble insulating discharge products (Li₂O₂) are deposited on the surface of the cathode, obstructing the diffusion channels of oxygen and electrolyte and covering the catalytic active sites, resulting in the battery's discharge being prematurely terminated. In the charging process, the high charging potential causes the decomposition of carbon materials, electrolytes, and binders, further resulting in the formation of by-products and the rapid decline of battery cycle life. Therefore, the design and investigation of the cathode catalysts with dense pore structure, high conductivity, and high catalytic activity for oxygen reduction reaction and oxygen evolution reactions (ORR/OER), as well as acceptable chemical/electrochemical stability, remain challenging. Metal-organic frameworks (MOFs) and their derivatives are a class of candidate catalysts in Li-O₂ batteries due to their flexible chemical composition, high specific surface area, and tailorable pore structure. The strategies discussed in this review include the use of MOF-derived carbon-based materials, MOF-derived single-atom catalysts, and pristine MOFs, which were successfully applied as high-performance cathode catalysts for Li-O₂ batteries. Additionally, suggestions are offered for improving the ORR/OER catalytic activity by optimizing the properties of MOFs and their derivatives. Finally, the future research direction of MOFs as cathode catalysts for nonaqueous Li-O₂ batteries is discussed.

Paraffin wax is an organic phase-change material with high heat storage density, but its low thermal conductivity and easy leakage limit its further development. To improve the thermal conductivity and anti-leakage properties of a paraffin phase-change material (PCM), Al₂O₃ fibers as the thermal conductive fillers were synthesized via a template method using natural fibers. The composite PCM was synthesized using a simple vacuum impregnation method. The microstructure, thermal conductivity, phase-change cycle stability, anti-leakage performance, and thermal response performance of Al₂O₃ fibers/paraffin PCMs were evaluated. The results show that the thermal conductivity increased linearly with the Al₂O₃ fiber content. Particularly, the α-Al₂O₃ produced via sintering at a high temperature of 1200 ?℃ exhibited higher thermal conductivity than the γ-Al₂O₃. When the mass ratio of α-Al₂O₃ reached 45% (mass), the thermal conductivity increased to 0.69 W/(m·K), which was 290% compared to pure paraffin. After 100 thermal cyclic tests, the phase-change enthalpy of the Al₂O₃ fibers/paraffin PCMs remained almost unchanged, indicating that the composite had good cycle stability. As the result of the leakage and thermal response tests, the composites filled to 30% and 45% also showed, good shape stability and heat transfer property. This will promote their practical application in thermal energy storage.

Phase-change heat storage technology can solve the volatility and instability of renewable energy during usage. However, available phase-change materials are challenged by their low thermal conductivity, which results in very slow heat storage/release rates, limiting industrial applications. Based on the fractal structure of snowflake crystals, herein, we propose a new type of fin structure to increase the storage/discharge rates of latent-heat storage units filled with phase-change materials. We performed a full three-dimensional multifield coupled numerical simulation on the heat storage/release process of the units. The results show that compared with longitudinal fins with the same volume, both the heat transfer rate and temperature uniformity are significantly enhanced by snowflake-shaped fins when the heat transfer fluids are under the same flow conditions. Further, for the longitudinal and snowflake-shaped fins, the complete melting/solidification time was reduced by 26.87% and 32.01%, respectively. Although the heat storage/release rate of the heat storage unit is greatly improved, the integral average value of the maximum velocity of the liquid phase change material is decreased by 26.83% during the charging process and increased by 18.00% during the discharging process.

To solve the key problems of unstable, discontinuous, and uneven radiation intensity in the process of solar heat utilization, phase change heat storage technology and solar heat utilization system are commonly synergized and coupled to achieve a stable and continuous heat output. To enhance the solid-liquid thermal storage/release process and improve the efficiency of thermal storage, the solid-liquid thermal storage/release characteristics of phase change materials (PCMs) (paraffin) in metal foam were experimentally studied at different temperatures of a heat transfer fluid. An experimental system for phase interface visualization was designed and built. During the experiment, a high-definition camera was set to record the phase interface changes during the melting and solidification phase change. By arranging multiple thermocouple measuring points inside the heat storage unit, the law of temperature change during the heat storage/release process was explored. The experimental results demonstrated that, under the influence of natural convection, the phase interface changed from top to bottom during the melting process. In the solidification process, the lower part of the heat storage unit had a lower temperature. Natural convection occurred merely at the beginning, and heat conduction dominated the whole solidification phase change. The phase interface moved from bottom to top with time elapsed. The higher the melting temperature was, the shorter the time required for melting was. Compared with the cases with a heat transfer fluid temperature of 65 ℃, the complete melting time at the heat transfer fluid temperatures of 85 ℃, 80 ℃, 75 ℃, and 70 ℃ was reduced by 56.0%, 46.7%, 15.4%, and 26.7%, respectively. The internal temperature of the PCM exhibited a distinct temperature rise when different heat storage temperatures were set. However, at the same cooling temperature for heat release, the law of temperature variation for the PCM tended to be the same.

The constant-volume water tank thermal heat storage system has the problem of insufficient flexibility and mismatch between the solar energy supply and heat load demand in the solar heating system. To make use of solar energy, a MATLAB numerical model, the two-stage variable-volume stratified-temperature water tanks thermal heat storage solar heating system, was established and verified by Trnsys, which was included four cycles, the heat collecting cycle, the heat charging cycle, the heat discharging cycle, the heating cycle, and the corresponding control strategies. The concept of effective volume of thermal heat storage is proposed, which is the volume of the water tank actually involved in heat charge, heat discharge or both in a period of time. To analyze the system, heat collected ratio, average temperature of the effective volume of thermal heat storage, heat discharge to charge ratio of the water tank, and heat loss ratio are also put forward. The results show that, compared with the traditional constant-volume water tank thermal heat storage solar heating system, the heat loss of the two-stage variable-volume water tanks thermal heat storage solar heating system is reduced by 17.2%, heat discharge to charge ratio is increased by 6.3%, the exergy efficiency is increased by 6.6%, and the auxiliary heat is reduced by 9.5% in the whole heating season in Beijing. In the initial stage of heating, the temperature response time of the two-stage variable-volume water tanks thermal heat storage system is reduced by 54.9%, which can be used for heating more quickly. The two-stage variable-volume water tanks thermal heat storage system is beneficial to adjust the matching of supply and demand for heating in different periods, and has a good energy-saving effect, to further guide the design and operation of solar heating systems.

In the battery thermal management of electric vehicles, the maximum temperature (MTBM) and maximum temperature difference (MTDBM) of a battery module are the most important indicators to measure the heat dissipation system. Liquid cooling is an efficient way of dissipating heat, but it also has the defect of excessive temperature difference. Therefore, the influence of inlet coolant flow (ICF), inlet coolant temperature (ICT), liquid-cooled pipe flow channel height (LFCH), and contact angle between the liquid cooling pipe and battery (CALB) on the MTBM and MTDBM is studied through simulation, and the structure of the liquid cooling pipeline of the battery module is optimized by using the variable contact angle between the liquid cooling pipe and battery. The results show that the MTBM of the optimized battery module is reduced from 40.50 ℃ to 38.47 ℃, a decrease of 5.01%, and the MTDBM is reduced from 6.07 ℃ to 3.60 ℃, a decrease of 24.05%. Increasing the ICF can reduce the MTBM and MTDBM, but the decrease of MTBM and MTDBM is gradual and will increase the pressure difference. Increasing the LFCH and CALB and reducing the ICT can all reduce the MTBM to a certain extent; however, the improvement of the cooling effect continues to decrease, and it will cause the problem of excessive temperature difference in the module. Therefore, this research provides an effective solution to the problem of excessive temperature difference in the liquid cooling system in the battery module, which is conducive to the further development of liquid cooling in the direction of battery thermal management.

In this paper, a new type of air cooling battery thermal management system based on a heat spreader plate with a casing tube is proposed to extend the air cooling limit. The cylindrical lithium-ion batteries in the module are arranged in an orthogonal array. The bottom of the battery is connected to an aluminum base plate by a positioning insulation layer, whereas the heat spreader plate is allocated in the middle of the battery through a casing tube, thus enhancing the heat transfer from the battery to the air flow. First, the corresponding air cooling experimental system was constructed, and the feasibility of the numerical model was verified by comparing with the experimental results. Subsequently, the inlet velocity and structure parameters of the battery module were investigated by simulation; then, 25 cases were obtained on the basis of Central Composite Design to provide sample data for the buildup of surrogate models of optimization objectives. Desirability functions and surrogate models were introduced to conduct multiobjective optimization, including maximum temperature, maximum temperature difference, pressure drop, and grouping efficiency. Finally, an optimal configuration of the structural parameters of the heat spreader plate and the air velocity of the module were obtained. Compared to the design without a heat spreader plate, the maximum temperature and maximum temperature difference of the optimal design were decreased by 16.12% (6.36 ℃?) and 48.48% (2.72 ℃?), respectively, whereas the corresponding grouping efficiency was 87.1%, which is close to 89.73% of the conventional design. The temperature uniformity of the battery module was obviously improved while ensuring a high-level weight grouping efficiency for the air cooling battery modules.

The compressed air energy storage (CAES) system has broad application prospects with the characteristics of large capacity, extended cycle life, fast response, and flexible adjustment. The expansion process of a compressed air storage system is the intermediary process from pressure energy to mechanical energy and electricity. The shaft modeling and oscillation analysis are different from traditional synchronous generating units, wind turbines, and micro gas turbines. To study the shaft oscillation characteristics of CAES for analyzing the power system stability, this study focuses on a typical four-stage expansion CAES power generation system structure, establishes a segmented concentrated mass spring model of its shaft, and derives a system shafting standard model. For a certain example system with a capacity of 10 MW, the inherent characteristics of the shafting system were evaluated, and the natural oscillation frequency and oscillation mode were obtained. The stability analysis of the shafting system was performed from the grid side and the expander side, respectively. Based on the oscillation characteristics of the shafting system, the potential oscillation forms of the system are categorized into three types: shock oscillation, sub-synchronous oscillation, and super-synchronous oscillation. Principle analysis and simulation verification of each oscillation type are performed, and the corresponding suppression method is proposed according to the characteristics of each oscillation type.

In the background of peak carbon emissions and carbon neutrality, renewable energy generation will become the main generation form in future power systems. Simultaneously, randomness and volatility increase the reserve requirement in different time scales. Pumped-storage power station (PSPS), a mature type of energy storage, has the advantages of fast regulation speed and large capacity, and it has increasing importance in the aspect of ancillary services. Trading off the benefits of energy storage in the energy market and the multiple time-scale reserve market to maximize its benefits is an important issue for PSPS waiting to be addressed. In this regard, this paper establishes an optimal decision-making model for PSPS to participate in the energy market and the multiple time-scale reserve market. The impact of reserve compensation prices on the operation strategies is further analyzed. This work provides a solution for PSPS to participate in the electric energy market. Case studies show that the total revenue of PSPS is significantly increased through providing reserve service. The total revenue of PSPS when providing multiple time-scale reserves is higher than that when providing a single reserve service. In the test case, the total revenue of PSPS when providing multiple time-scale reserves is increased by 44.37% at least.

According to the energy storage demands of short term and high frequency in the wind solar new energy grid, this paper focuses on the demonstration application researches of the MW flywheel array in the wind solar energy storage field. In this paper, the system composition and topological structure of the flywheel array are firstly introduced as well as the working principle. On this basis, the system design of the flywheel energy storage array is provided. Finally, the real experimental tests by using the actual flywheel array system is developed in Tianjin and Qinghai wind solar energy storage field. After thousands of the charging-discharging cycle experiments, it can be shown that the designed flywheel system stays stable and reliable. Owing to the significant advantages, the total power, capacity and response characteristics can meet the requirements of the new energy frequency adjustment process.

The current power consumption of beam pumping units in service exceeds 50% of the total power consumption of oil field production, and their overall efficiency is often less than 30%. The low efficiency of the pumping unit system results in a significant waste of electricity. The operating principle and structural characteristics of the beam pumping unit allow for the incorporation of flywheel energy-storage devices to improve their efficiency. A flywheel energy-storage system suitable for beam pumping units was designed, a pumping unit dynamics simulation model was established, and a corresponding experimental test platform was built to validate the feasibility of the energy-storage systems using simulation analysis and experimental research, and the effect of adding energy-storage flywheel on the pumping unit's energy consumption was discussed. The results indicate that the energy-storage flywheel releases energy during the upper stroke and absorbs it during the lower stroke. With the addition of the flywheel, the peak value of the motor power curve decreases from 646 to 517 W, whereas the valley power of the motor changes from -361 to -296 W, implying that the peak value decreases and the valley value increases, resulting in a more smooth operation of the motor. Finally, the pumping unit's energy-saving effect was verified by comparing the experimental data. The result shows that under the condition of constant stroke times and similar load, the experimental result is close to the conclusion of the simulation analysis. Adding a flywheel energy-storage device saves 15.7% of energy and has an obvious energy-saving effect, and it serves as a reference for the use of flywheel energy-storage systems in beam pumping units to achieve energy saving and consumption reduction.

Wind energy output often shows randomness and fluctuation, making it difficult to adjust the frequency of the power grid. In this study, wind energy is smoothed by flywheel energy storage to reduce its power fluctuation and improve its grid-connection ability. First, a power coordinated control method is proposed to ensure that the power value allocated to each unit does not exceed its rated power and that the state of charge (SOC) of each unit converges to the same value. Simultaneously, the layered and grouped control method for the energy storage array is adopted to ensure the accuracy of power regulation and the energy storage system's response speed. Then, we develop a power-following control model for the flywheel energy storage unit and a power-following control model for the flywheel energy storage array. The feasibility and superiority of the proposed coordinated control technique are verified through charge and discharge simulations of a group of flywheel energy storage units. Finally, a flywheel energy storage array is used to compensate for the high frequency components of wind energy in real time, thereby smoothing out wind energy output power fluctuations. The 2 MW flywheel energy storage array is used to supplement 10 MW wind energy. The 2 MW flywheel energy storage array is composed of eight 250 kW/50 kW·h flywheel energy storage units, whereas the 10 MW wind energy system is composed of five 2 MW wind turbines. Finally, the flywheel energy storage is used to compensate for the high frequency components of wind energy in real time, thereby smoothing out the fluctuation in wind energy output power. The 2 MW flywheel energy storage array is used to supplement the wind farm's 10 MW capacity. The 2 MW flywheel energy storage array is composed of eight 250 kW/50 (kW·h) flywheel energy storage units, whereas the 10 MW wind energy system is composed of five 2 MW wind turbines. The flywheel energy storage array is modeled using simulation software, and the simulation data for 200 min of wind generation is used. The simulations verify the feasibility of the proposed control strategy and hierarchical grouping control method, as well as the fact that flywheel energy storage matched to wind energy can significantly reduce the fluctuation of wind power and satisfy the requirements of the national standards (GB/T 19963—2011).

The application scenario for redox flow battery (RFB) systems is large-scale energy storage, which aims at integrating renewable energy into national grids. RFBs are also used as a backup power source to provide energy on an hourly basis. The engineering advantages of this technical route are a flexible arrangement of system-rated power and storage capacity, as well as an effective method of improving electricity quality and transmission stability. Hook's Law was used to establish a force analysis model to determine the stack compression load. Since the application of this numerical simulation, a decrement logarithmic trendline of the model stiffness with an increased number of cells was discovered. During the battery assembly process, an increasing quadratic curve demonstrated self-weight-induced height decline. This mathematical approach was validated due to computational outputs of a full-scale stack consisting of 100 cells matched with recorded values in real assembly. Meanwhile, this battery stack passed tests evaluating its sealing properties.

Utilizing the peak-to-valley price difference on the user side, optimizing the configuration of energy storage systems and adequate dispatching can reduce the cost of electricity. Herein, we propose a two-level planning model for lead-acid battery-supercapacitor hybrid energy storage systems to calculate the annual return on energy storage investment. The outer objective function accounts for factors, such as energy storage peak shaving and valley filling income, demand defense income, and full life-cycle costs. Taking energy storage daily dispatch income as the inner objective function, the optimal energy storage period was studied. Energy storage performance constraints were considered during the development of the model to limit the daily charge and discharge times for different energy storage components according to the various properties of different energy storage components. According to the actual load of users in a certain place, the two-level programming model is solved by particle swarm algorithm and CPLEX solvers. We compare the rated power and capacity configurations of hybrid and single energy storage systems and verify the monthly comprehensive income of the hybrid energy storage model. The annual return on investment for the hybrid energy storage model is better than that of the single energy storage model. Furthermore, we compare the annual return on investment of different types of batteries and give suggestions for energy storage configuration planning.

The comprehensive energy system in the park has the characteristics of many energy supply subsystems. It is critical to coordinate and optimize multiple energy supply subsystems to improve the system's economic operation. Therefore, a coordinated and optimized scheduling method for the park's integrated energy system is proposed, based on an "end-edge cloud" architecture. In this method, considering the mutual economic complementarity of electricity, heat, and gas between adjacent energy supply subsystems in the park, an integrated energy system optimization model is established in the cloud, the synchronous ADMM algorithm is used to solve the scheduling scheme on the edge side, and the optimal scheduling scheme is controlled for each energy consuming equipment on the end side. The example results show that the proposed optimal scheduling method can improve the economy and reliability of system operation, as well as relieve the dispatching center's computational pressure.

2020 was the year of rapid hydrogen energy development. During the seventy-fifth United Nations General Assembly, Chinese President Xi Jinping proposed that China's carbon dioxide emission should peak by 2030 and aim for carbon neutrality by 2060. The decarbonization vision for addressing climate change has gradually become the primary driver of large-scale hydrogen energy deployment. However, the hydrogen industry's development goal and path under the carbon neutrality strategy in China remain unclear. This study analyzes and calculates the demand for hydrogen energy in China's transportation, industrial, construction, and power generating sectors using the scenario analysis method and long-range energy alternatives planning (LEAP) model. The results show that to achieve the carbon neutrality goal in 2060, the annual demand for hydrogen in China will increase from 33.42 million tons to 130 million tons, accounting for 20% of the terminal energy system. With the increasing demand for deep decarbonization and advancements in the low-carbon clean hydrogen economy; hydrogen energy has gradually penetrated the fields of industry, transportation, construction, and power generation. Hydrogen energy supply is gradually shifting away from non-low carbon-hydrogen dominated by fossil energy to clean hydrogen dominated by renewable energy, which will provide 80% of hydrogen energy demand. By 2060, the low-carbon clean hydrogen supply system will have reduced CO₂ emission by about 1.7 billion t/a, accounting for about 17% of China's total CO₂ emission today.

Lithium iron phosphate batteries (LFP) are widely used in large-scale battery energy storage systems. To improve the operating performance and ensure the safety of the battery system, people urgently need an on-site fault diagnosis for inconsistent cells that is engineered to be fast and accurate to support the rapid diagnosis and maintenance of the system. In this study, an algorithm based on battery charge and discharge characteristics is proposed to realize the classification of inconsistent cells by multiple-outlier detection. On this basis, the battery deviation capacity is computed and used as the optimization coefficient to prioritize the difficulties, which brings great ease to engineering operation and maintenance. Practical results show that the proposed method has the characteristics of high identification accuracy, simple parameter adjustment, and low computational complexity, which makes it suitable for on-site engineering and has important guiding significance for the maintenance of energy storage power stations.

This work built a lithium-ion battery combustion-inhibition experimental platform, took a ternary aluminum shell power lithium-ion battery monomer with a rated capacity of 150 A·h as the research object, induced thermal runaway by electric heating, and studied the fire suppression and cooling effect of the perfluorohexanone and water mist extinguishing device on the thermal runaway lithium-ion battery. The fire extinguishing time, maximum temperature, quality loss, and fire extinguishing efficiency were measured under different working conditions. The experimental results show that the standard design of the perfluorophanketone fire extinguishing device can quickly extinguish the fire, with a maximum cooling rate of -15.4 ℃/s. However, as the concentration of the fire extinguishing agent in the test box decreases, the lithium-ion battery refires in 60 s after the fire extinguishing, and the water mist fire extinguishing device can effectively extinguish the fire. After the spray, the temperature of the lithium-ion battery drops to about 78.8 ℃?, and the maximum cooling rate is -26.9 ℃/s. However, it is difficult to carry out practical application because of its large water consumption. This experiment can provide experimental support for further research on fire suppression technology of ternary lithium-ion batteries.

An accurate lithium-ion battery model is very important to ensure the reliability of the battery. Accurate estimation of state of charge (SOC) ensures the safety and efficient operation of specific applications. To improve the estimation accuracy of SOC, an equivalent circuit model is established and the parameters are identified using bias compensation recursive least squares (BCRLS) of the forgetting factor. The SOC is then estimated using the adaptive unscented Kalman filter (AUKF) algorithm. The AUKF algorithm defined by weight vectors was proposed to improve the estimation accuracy of SOC because of the vulnerability of the unscented Kalman filter technique to nonlinear variables. However, the internal characteristics of the battery will change during the discharge process, and the ohmic internal resistance of the battery will have a direct effect on the SOC estimations. Based on this, we propose a dual AUKF to further improve the estimation accuracy of SOC. Compared with other algorithms, the experimental results show that the proposed algorithm's error in estimating SOC is less than 2%, demonstrating the effectiveness of the algorithm.

The capacity and other parameters of a single power battery are different, which causes imbalance on charging and discharging, poor performance, and reduced service life of series and parallel power batteries. To solve this problem, an active equalization battery management system based on state of charge (SOC) is designed. After estimating the SOC of a single power battery using the ampere-hour integral method, the battery management system will compare the SOC of the single power battery with the average SOC of the power battery. If the difference value is greater than or less than the set threshold, discharging and charging of the single power batteries will be carried out separately. The validity of the battery management system is verified by simulation through taking four single batteries in series. The simulation results show that the SOC difference values of the single power battery are less than 3% after 3608 s and 1% after 5600 s through active equalization, which greatly reduce the SOC inconsistency of the power batteries.

To improve the speed and accuracy of estimating the state-of-health (SOH) of decommissioned batteries, for retired prismatic lithium-iron-phosphate batteries of certain electric buses, eight batteries were selected to continue the cyclic aging experiment, and electrochemical impedance tests were conducted for different cycles. According to the impedance characteristics of lithium-ion batteries, the real part, imaginary part, and modulus at 300 Hz, 60 Hz, and 1 Hz were extracted as characteristic parameters, which reduced the test time from 10 min to a few seconds. Using characteristic parameters as input parameters, combined with BP neural network algorithm, we developed a fast estimation model of retired battery health based on electrochemical impedance and BP neural network and verified the model using 19 datasets that did not participate in model training. The average absolute percentage error of the verified sample's SOH estimate was 1.46%, and the root-mean-square error was 1.60%. The results show that the overall error is low. The method has high estimation accuracy and short test time, realizes rapid estimation of the health status of retired batteries, and is conducive for practical applications.

Currently, the aging performance degradation of vehicle power batteries is becoming increasingly prominent, and their performance after aging is concerning. In this study, a 18650-type ncm811 lithium-ion battery was used as the research object to study the discharge performance and charge-discharge heat generation characteristics after aging. The performance change of the battery after aging is explained by taking the corresponding performance parameters of the new battery of the same model as the reference. The battery's discharge performance was evaluated at varying ambient temperatures and discharge rates. The discharge voltage curve, discharge capacity, and temperature variation of the battery's outer surface during discharge were obtained. The battery's thermal power and heat production during charging and discharging were measured using an isothermal adiabatic calorimeter. The results show that at 25 ℃, the discharge capacity of the aged battery accounts for 72%, 69.5%, 66.2%, and 62.2% of that of the new battery at 0.2 C, 0.5 C, 1 C, and 2 C, and the aged battery's surface temperature increase is 147%, 208%, 331%, and 138%, respectively, of that of the new battery. At 0.5 C, -20 ℃, -10 ℃, 0 ℃, 20 ℃, and 40 ℃, the aging battery's capacity is 57.5%, 63.4%, 66.9%, 69.5%, and 69.3% of that of the new battery, and the aging battery's temperature increase is 91%, 120%, 106%, 208%, and 146%, respectively, of that of the new battery. During charging and discharging, the aging battery's heat production power and heat production are larger than that of the new battery. However, because the aging battery's charging and discharging times are sometimes short, its heat production power or heat production is smaller than that of the new battery.

Self-discharge is a vital function of lithium-ion capacitors. Based on electrochemical theory and practical application, we study the voltage-holding capacity (K value) of lithium-ion capacitors at 3.8 V and 3 V, the results show that the K value range of lithium ion capacitor is 0.0037～0.0102 V/day at 3.8 V and -0.0003～0.0007 V/day at 3 V. The K value at 3.8 V can be used to detect the self-discharge performance of the cells more efficiency. For the purpose of improve the self-discharge detecting efficiency, and propose a method for detecting the self-discharge performance of lithium-ion capacitors (leakage capacity method) for the first time, verified by experiments. when testing the self-discharge performance of lithium-ion capacitors, the voltage holding capacity method usually needs dozens of hours, while the leakage capacity method can complete the detection within 1 hour, and its self-discharge detection efficiency is higher. The leakage capacity method can quickly and accurately detect and judge the self-discharge performance of lithium-ion capacitors.

The latest research on lithium-ion battery modeling technology for large-scale energy storage in China is described briefly. Because energy storage technology can stabilize fluctuations and improve power quality, the energy storage demand in power grids has increased yearly. The large-scale energy storage system comprises a lithium battery pack, bidirectional inverter, and battery energy management system. Assuming the bidirectional inverter and battery energy management system have ready-made models, developing an accurate and reliable lithium-ion battery model has become the focus of applying large-scale energy storage engineering. This study describes current popular battery modeling methods. The electrochemical model is constructed by simulating the battery electrochemical reaction process. Although the accuracy is high, the model is complex; therefore, it should be properly simplified for use. It is typically used for battery principle analysis. Different equivalent circuit models are designed using different simulation degrees of the battery's external characteristics. Although we do not pay attention to simulating the principle, it is more suitable for application in engineering practice. The neural network model is constructed by studying the relationship between battery input and output, but its accuracy requires high quantity and quality data. Finally, to better realize the application in power systems, the reaction principle of lithium-ion batteries should be studied more deeply and described quantitatively to improve the application ability of the model in various scenarios.

The dual-carbon goal in developing the energy industry has changed the position of renewable energy. The grid's stable operation faces new challenges because of large-scale intermittent new energy grid connections, and energy storage is essential to ensure power quality stability. Therefore, the demand for coordinated control effects and performance parameters of the energy storage system is increasing in the growing energy storage market. In the energy storage market evolution, policies on energy storage show a positive trend. By systematically combing the operation status and typical cases of energy storage combined with other energies to participate in auxiliary services, the energy storage system has low revenue and narrow channels, which cannot ensure effective system cost reduction. Therefore, to discuss key issues in optimizing energy storage policies, accelerating energy storage equipment research, equipping energy storage with multiple energy sources, and developing the concept of energy storage plus, we analyzed the development trend of new energy, the power industry demand, and the role of energy storage under the dual-carbon goal. Finally, we propose constructive opinions on the key content of the future development of energy storage marketization to help achieve the long-term goal of carbon neutrality.

The tide of electric vehicle power battery decommissioning is approaching, and the disposal of numerous retired power batteries has currently become a major problem. An effective way to solve this problem is by applying them to energy storage systems on a large scale. Research on the economics of cascaded energy storage will promote scale. The application has significant practical importance. First, the cost types of the cascade energy storage system are analyzed, and its cost sensitivity parameters are analyzed using the levelized cost model. Second, it analyzes the current state of echelon usage of decommissioned batteries and discusses the development trend of key echelon usage technologies. Finally, it analyzes the boundary values of profitability and superiority over new batteries in the large-scale application of echelon energy storage to guide echelon usage.

With the announcement of the "Energy Storage Technology Professional Discipline Development Action Plan (2020—2024)," 26 universities across the country have set up an undergraduate major in "Energy Storage Science and Engineering." Energy storage science and engineering is a multidisciplinary and deeply intersecting major involving many fields, such as materials, electrochemistry, and engineering thermophysics. Therefore, the undergraduate professional knowledge system and curriculum design are crucial, especially the setting of the core courses. Considering the energy storage science and engineering curriculum of several representative universities, combining the core courses in related traditional majors, and considering national needs and the degree of professional knowledge coverage in the discipline, it is recommended to select energy storage materials, engineering thermodynamics, engineering mechanics, heat and mass transfer, electrical and electronic technology, and control theory as the core courses of the undergraduate major in energy storage science and engineering. The training objectives and curriculum contents are also being analyzed, hoping to provide a reference for constructing the core curriculum in the energy storage science and engineering major.