Composite Structural Battery: A Review

With the considerable technological advancements in electrochemical energy storage systems, lithium-ion batteries have been widely used in vehicles, aircraft, and sports equipment because of their energy advantages [1,2]. Since their inception, lithium-ion batteries (LIBs) have experienced remarkable progress, and their standards continue to increase in terms of safety, charge and discharge time, energy storage, and long service life. Moreover, the development of multifunctional material batteries integrating flexibility, structure, and wearable devices has continuously progressed [3–7]. However, batteries are frequently exposed to mechanical extrusion and deformation [8]. Endeavors have been made to avoid these issues, for instance, multilayer mechanical shells and protection systems for functional components [9–13]. These protective measures increase the battery volume and significantly reduce the battery energy density, which hinders the development of lightweight devices. An increase in the battery volume leads to a decrease in the payload volume for spacecraft, especially for CubeSats. Thus, there is an urgent need to develop a highly integrated structural composite battery with both a high-energy density and excellent mechanical properties.

Among the various composites, CFRP is commonly used to manufacture lightweight structural components because of its high specific stiffness and strength. Further weight loss can be achieved by integrating lithium-ion batteries (electrical energy) into composite materials (mechanical properties); these composite structural batteries (CSBs) have potential applications in aircraft, spacecraft, etc. [13–17]. Currently, the development of CSB can be divided into two categories, as identified by Hopkins and coworkers [18]:

1. Decoupled structural batteries, which employ a two-material system where one material bears loads while the other electrochemically stores energy. Commercially packaged battery systems are typically integrated with composite structures [19–21]. The most common structures for embedded batteries are laminated structures [22], sandwich structures [14,23,24], and modular stiffener structures [25]. The first comprises several batteries in the inner layer of the composite laminate. The sandwich structure houses a battery in the cavity of the core material, and its mechanical properties are inferior to those of the shell material. A battery with a modular stiffener structure can be positioned in the inner area of a stiffener [26].

2. The coupled structural batteries were designed to be multifunctional [27–29]. CSBs store electrical energy directly in the structure of the system [21,30]. Carbon fibers (CFs) act as high-performance structural reinforcements and collectors (sometimes as active materials). The electrolyte and separator were placed between the two CF layers. Compared to embedded CSBs, their internal structure is more uniform and continuous, which can ensure the continuity of force transmission and improve the bearing capacity. CSBs have been gradually been accepted by various industries because they provide lightweight energy storage for electrically powered structural systems. This has led to innovative changes to traditional batteries.

Several reviews have been published on CSBs, and the most recent ones have focused on the choice of materials [31–36]. This study focuses on the preparation of CF-coupled structural batteries and compares their electrical and mechanical properties. The structure is as follows: First, the assembly methods of the different battery forms depending on the type of electrolyte were investigated. Then, the electrical, mechanical, and multifunctional properties of these CSBs are compared and summarized. Finally, the potential applications and future research opportunities for CSB are discussed from multiple perspectives. Specific implementation schemes are provided to realize the full potential of multifunctional composites in engineering applications.

The manufacture of CSBs relies heavily on the form of the electrolyte. According to the state of the electrolyte, the CSBs manufacturing containing liquid electrolytes and solid electrolytes were introduced, respectively. For example, some structural batteries with liquid electrolytes are assembled using an anode and cathode, separator and collector at first, leaving a closed space and channel for the liquid electrolyte. The channel was sealed and formed. For instance, Chol et al. [37] stacked a carbon fabric prepreg electrode (coating and collector, the same below) and a separator. A channel was then created on one side of the stacked electrodes to enable the injection of the liquid electrolyte into the sealed reaction zone of the battery (Fig. 1(a)). Finally, high-pressure autoclave processes were used to mold the cured resins. Another process of preparation is the hand lay-up process. The hand lay-up process involves bonding materials with an epoxy resin mixture and other adhesives and squeezing the materials with a brush, roller, or spatula to evenly dip the glue and eliminate bubbles, as shown in Fig. 1(b). Then, the materials were then heated and cured under specific pressures. Finally, the composite specimens were demolded. This method was used by Chen et al. [43], Moyer et al. [38,44] and Han et al. [45]. The stacking order of the battery materials was as follows: epoxy-impregnated CF squares, an electrode, a separator infused with liquid electrolyte, an electrode, and epoxy-impregnated CF squares. Finally, the materials were vacuum infused and cured.

For CSBs with a solid-state electrolyte (SSE), some have also used a hand lay-up process to replace the separator infiltration electrolyte with the SSE [46]. Vacuum-assisted resin transfer process (VARTM) is the most commonly used method for the solid transfer process. In particular, the structural battery electrolyte (SBE), with a porous polymer structure for mechanical load transfer, is filled with an ionic liquid for ionic conductivity. This method involves placing stacks of CF electrodes and separator layers onto a plate, followed by sequential placement of the isolation film and SBE flow medium. The mold was then sealed with butyl tape and placed inside a vacuum bag. SBE infusion was performed using a pump until the SBE was fully impregnated with the material and then cured at room temperature or in an oven at different temperatures. An adhesive absorbent felt, peel ply, and isolation separator were arranged between the reinforcement and infusion mesh to improve the diffusion and infiltration of the resin into the reinforcement, as shown in Fig. 1(c). Snyder et al. [47–49], Yu et al. [50], Javaid and Ali [39], and other researchers [40,51–56] all used this method with CFs as the electrode material. Asp et al. [40] proposed a simpler fabrication method for SBE, as shown in Fig. 1(d). The liquid transfer was performed using a drip polymer electrolyte manufactured under Ar gas in the separator of the layered CF-structured battery. Pressure was applied, and the battery was cured in an oven.

With advances in 3D printing technology, a unique type of 3D printing continuous CF multifunctional composite has shown considerable potential for energy storage applications [41,57]. Each CF acts as a micro battery cell, as shown in Fig. 1(e). The SSE was electrodeposited to coat a tow of continuous CFs, which was then immersed in an uncured doped photopolymer with a coextrusion head, and the photopolymer was the cathode. The UV laser facilitated curing. Qian et al. [42] proposed a layer-by-layer printing method to fabricate sandwich structural stretchable batteries. As indicated in Fig. 1(f), the lower layer of the nanofibrillated cellulose (NFC)/carbon nanotubes (CNTs)/graphite powder was first 3D-printed onto the substrate, followed by the NFC/Al₂O₃ layer in the middle and the NFC/CNT/lithium iron phosphate (LFP) layer on the top. The three-layer patterns need to completely overlap to prevent direct contact between the lower and upper electrode layers.

The lithium-ion batteries’ energy density has experienced a remarkable enhancement, increasing from 80 Wh · kg⁻¹ to 250 Wh · kg⁻¹ [1,58]. Energy density is a crucial criterion for assessing the battery’s electrochemical properties, and it is an indispensable part of assessing CSB. It relies heavily on the properties of the electrolyte. During the processes of lithiation, delithiation, and circulation, the electrode interacts with the electrolyte, which significantly influences the interfacial conditions and internal structural alterations of the electrode material. Therefore, based on the electrolyte classification, CF structural batteries, which explicitly provide energy density, can be calculated by summing up the total composite mass of the structural battery, as illustrated in Fig. 2. Electrolytes can be divided into liquid and solid electrolytes. Overall, the energy densities of the CSBs with liquid electrolytes were generally higher than those of the CSBs with SSE. The high-energy density of the liquid electrolyte can be attributed to its significantly higher ionic conductivity compared to those of the other electrolytes. Furthermore, the SSE lacks fluidity indicating poor interfacial contact and low active surface utilization of the electrode material, which may be another contributing factor.

It is notable that the lithium-ion batteries produced by Moyer et al. [38] exhibit a superior energy density when compared to other batteries of this type. This is due to their utilization of a polyacrylonitrile (PAN, the active battery material was sandwiched between the CF collector and the PAN coating), which drastically improves the stability and energy density in comparison to their similar battery without PAN-reinforced interfaces [44]. The second energy highest density is observed in the Zn–MnO₂ solid-state batteries fabricated by Chen et al. [43], which is a result of the implementation of high-capacity Zn–Mn materials.

Scholz et al. [59] suggested that a minimum energy density of 51.8 Wh · kg⁻¹ is required for a structural battery in a small electric aircraft; some initial designs of structural batteries have not yet attained this level. Therefore, improving the ionic conductivity of the electrolyte is the preferred and significant method for improving the energy density of structured batteries. In addition, the battery energy density is related to various factors such as interface stabilization, electrode material, separator property, and collector.

Table 1 summarizes the rate performances of the CSBs. Owing to the lack of specific numerical values in this study, the data were within the approximate range obtained from the graph. Comparing the 0.1C, 0.5C, 1C charge–discharge rate performance, Dong et al. [60] proposed the FeOx NiOx battery, which has the best rate performance with a minimum capacity loss rate, followed by the Zn–Mn battery proposed by Chen et al. [43]. Many factors affect the rate performance of batteries, including the selection of the electrode materials, electrode size, electrode surface resistance, and electrolyte type. Therefore, it is important to identify and quantify the factors affecting the rate performance of structural batteries. To this end, physics-based or semi-empirical models can be developed to explain the rate performance. Conventional batteries are a useful example. For a physics-based model, Doyle and Newman [61] first derived analytical formulations of the specific capacity against discharge rate, considering diffusion limitations and concentration gradients. The result can be employed for design optimization. Hiroki et al. [62] utilized the Newman model, which accounts for some factors, such as the weight ratio of conductive carbon, porosity, and positive electrode thickness, to derive a design guideline for battery rate property. For semi-empirical models, Tian et al. [63] provided three parameters to comprehensively describe the rate performance, which can accurately fit the capacity data. Furthermore, this model has the capability to predict the upper-speed limit for both sodium and lithium batteries.

After cycling, the battery performance and capacity deteriorate owing to internal oxidation, damage to the electrode materials, loss of active substances, and increased internal resistance [64]. Consequently, to improve the performance of LIBs, it is necessary to analyze the causes of performance and capacity degradation after cycling. The cycle life of a battery refers to the number of cycles in a certain charge/discharge regime before the capacity decreases to a specified value. It is generally measured using indicators such as the cycle number, initial discharge capacity, and retained capacity.

Table 2 presents the cycling performance of several CSBs. A stable electrochemical reaction was achieved in all CSBs based on the long cycle life. Notably, the best performers are the experiments conducted by Chen et al. [43], who produced a battery with a high-capacity retention of 88.3% after 100 cycles and 50.2% after 500 cycles. Dong et al. [60] reported a battery with a capacity retention of 68% after 270 cycles.

Cycle life is influenced by various factors, which can be mainly divided into the battery design (such as material selection [65–67] and electrode structure design [68,69]), battery operating conditions [63] (such as temperature [70], charge/discharge current and cutoff voltage [63]), and battery production (such as manufacturing assembly [71,72] and formation method [73]). The exceptional cycle performance of the two aforementioned structural batteries can be attributed to various factors. In the case of Dong et al. [60], the use of an FeOx anode and NiOx cathode and PVA-KOH gel electrolyte helped to maintain the original shape and support continuous structures, resulting in stable electrochemical reactions. In the case of Chen et al. [43], the electrochemical deposition of Zn–Mn materials on CF led to an optimized interface contact, which ultimately enhanced the battery's performance.

CSBs have been shown to possess superior mechanical properties compared to traditional batteries. Therefore, diverse mechanical properties of CSBs have been summarized and compared with those of conventional lithium-ion cells that contain pouch batteries and cylindrical cells [74,75]. Different CSBs have distinct sizes that cannot be compared fairly; thus, we chose the elastic modulus rather than the strength. Despite the increasing number of articles published in this area, only a few publications report on CSB testing and provide exact values for the elastic modulus. (The papers only provided the value of the tensile modulus. The data from the three-point bending test load-displacement curve was extracted from the paper, and the battery's flexural modulus was roughly calculated according to ASTM D 7264/D 7264M-07 Standard Test Method [76].) As shown in Fig. 3, the mechanical characteristics of most CSBs exceed those of traditional lithium-ion cells, implying that the use of novel materials such as CFs as electrodes reduces the battery quality but improves the mechanical properties. In particular, great performers such as Pappas et al. [57] and Zhao et al. [55] have proposed batteries that take advantage of the favorable tensile and flexural properties of carbon fibers. Asp et al. [40] have improved the CF CSB proposed by their team [77] for application in spacecraft structures, and they reported an energy density of 24 Wh · kg⁻¹ and a high modulus of elasticity (25 GPa). The Zn–MnO₂ battery created by Chen et al. [43] achieved an optimal balance of energy density and mechanical properties, with the cell showing 55 Wh · kg⁻¹energy density, flexural modulus of 4.4 GPa, and tensile modulus of 12.8 GPa.

Structural batteries with superior mechanical properties are mostly impregnated and wrapped with a polymer electrolyte whose manufacturing assembly is the same as that of composite materials. Batteries inherit the excellent structural properties of CFRP, both in tension and flexion, and they exhibit good load-bearing properties and resistance to deformation. In contrast, other lithium-ion batteries packaged in sandwich structures are prone to interface debonding, delamination damage, and other problems because there is no resin between the electrode materials [78,79], which results in a lower modulus. However, the energy storage capacity and electrical properties are reduced under a load [33,80], and the reduction in electrical properties is irreversible because of the polarization caused by the delamination damage of the cell. Many factors affect the mechanical properties of batteries and may be multifaceted. The plastic deformation of the metal collector and the adhesion of the collector to the CF also affect the electrochemical capacities of multifunctional cells subjected to tensile and mechanical loads.

Therefore, the electrochemical and mechanical performance of the structural batteries will be compared based on this method, as shown in the Fig. 4. It is obvious that all the structural batteries meet the requirement of multifunctional efficiency. Furthermore, the significant improvement in the mechanical properties, often by more than one order of magnitude, greatly surpasses the loss of electrochemical properties. Thus, multifunctional factors such as those designed by Pappas et al. [57] can attain up to 236.27. In addition, the structural batteries proposed by Asp et al. [40] exhibit excellent performance in terms of multifunctional efficiency.

The design schemes of energy storage batteries at present are far from industrial production and commercial applications, particularly in terms of battery capacity, although the development of CSBs in aircraft, marine, vehicle, and other fields has exhibited excellent application prospects. These design schemes cannot satisfy the severe requirements of the mass of the structure, multifunctional space, battery energy storage performance, and other aspects. A breakthrough can be achieved using the approaches suggested in the following subsections to strengthen the electrochemical and mechanical properties of CSBs.

Currently, CSBs cannot balance the electrochemical and mechanical performance; the improvement of the mechanical properties will inevitably result in a trade-off with the electrochemical properties. The directional movement of lithium-ion intercalation and stripping between the positive and negative electrodes realize the mutual conversion between chemical and electric energies. The stability of the battery and conductivity are influenced by the porosity and interfacial contact of each electrode material [83,84]. One effective way to enhance battery capacity is to increase the number of electrodes in the structure. For example, Xu et al. [85] linked several composite structural cells between CF/(Glass fibre) GF composite face sheets to form a multicell structural battery laminate, while Pandey [86] Javaid and Ali [39] utilized parallel cathode and anode stacks, respectively. Additionally, incorporating conductive materials into the active material can lift the electrode stack, not only increasing the volume capacity and porosity of the electrode but also facilitating the diffusion of lithium ions [87–89]. However, an increase in the number of layers leads to interfacial debonding during cycling. Similarly, an increase in the electrode thickness diminishes the charge–discharge ratio, which is a notable challenge that requires resolution for structural batteries.

There are various methods to enhance the interfacial compatibility of electrode materials, particularly to improve their ionic conductivity and charge transfer rate. Common techniques include coating the electrode surface and enhancing the conductive properties of active materials. Additionally, introducing a buffer layer and conductive coating can significantly reduce the electrode polarization and improve the electrode discharge capacity at a high rate, as demonstrated in previous studies [3,90,91]. For example, the inhomogeneous distribution of different conductive additive contents throughout the CF collector thickness direction (vertical direction) can promote electrochemical behavior. The efficiency of the electron transfer and diffusion of lithium ions is significantly improved through an increase in conductive additive content in the lower layer (contacting with the current collector) while maintaining the total mass of the conductive additive constant. Furthermore, the rate performance, specific capacity, and cycling life are enhanced, particularly at high current densities [92].

Although the coating significantly improves the electrochemical performance, its basic interface mechanism needs to be fully clarified. A potential research approach for the interfacial compatibility of CSBs is shown in Fig. 5. Solid electrolyte interphas (SEI) multiphysics models can answer these questions by combining common characterization methods for interfacial instability such as X-ray micro-computed tomography (XCT) and digital volume correlation (DVC) to obtain the evolution of the SSE interfacial strain field during electrochemical cycling. Scanning electron microscopy (SEM) imaging can be used to obtain the interfacial structural morphology, and X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) can be used to obtain the interfacial potential and electrochemical impedance. These data can be used to create SSE multiphysics field simulations and molecular dynamics (MD) simulation models and to understand interfacial failure, mechanical property degradation, and electrochemical degradation. Furthermore, battery interface compatibility and instability factors can be evaluated, and this crossover of experimental and numerical research allows for a more comprehensive study of the performance of CSBs under the effects of charge/discharge and thermal cycling. Thermodynamic analysis can be used to assess interfacial compatibility by forming stable interfacial passivation layers. A thorough comprehension of the mechanical properties and electrochemical degradation processes is obtained.

Under an external load, the battery separators, electrode materials, and electrolytes produce deformations that reduce the ionic conductivity and inhibit the electrochemical reaction rate [93,94]. Moreover, the lithium ions force the precipitation and deposition of the damaged battery, which represents the growth of internal lithium dendrites that penetrate the insulation layer, leading to a short-circuit caused by positive and negative electrode contacts [95], increasing the risk of thermal runaway of the battery [95], and aggravating the electrode reactions and electrode/electrolyte phase interface side reactions [96–98]. These factors severely limit the application of batteries in high-energy and high-power fields [99]. Owing to the wide applications of structural batteries in aerospace, automotive, and marine applications, batteries are inevitably subjected to static and dynamic loads, particularly under high discharge rates, overheating, uneven temperature distribution, and long cycles. These long charging and discharging cycles are prone to severe performance degradation, reduced reliability, and early failure of electrochemical systems [100,101]. Therefore, research on the coupling effect between the mechanical and electrical properties of structural batteries is still not sufficient.

First, the investigation begins with each electrode material, focusing on its damage mechanism while maintaining its electrical properties. This targeted approach can improve the mechanical properties of the materials. For example, Zhang et al. [102] explained the differences in the battery short-circuit characteristics of separators under tensile, compressive, and biaxial punch loadings. Shirshova et al. [103,104] measured the ion conductivity and mechanical properties of SBE and obtained a resin-to-electrolyte ratio with the most balanced mechanical and electrical properties. Choi et al. [37] observed a crack propagation pattern on the surface of an LFP cathode after electrochemical charge/discharge under a mechanical load. Wang et al. [105] studied the relationship between the mechanical properties and state of charge of silicon electrodes using a nanoindentation system.

Based on the aforementioned experience, a specific analysis can be conducted at both the macro- and micro-levels by combining experiments and numerical simulations. Macroscopically, static load tests such as tensile and compressive tests can be conducted on different components of a battery, including separators, active materials, and CF collectors, to obtain key parameters such as the strength, modulus, and Poisson's ratio of different materials. A constitutive model can be established, and a finite-element analysis can be used to model and analyze each material. The numerical simulation results were used to determine the initiation and evolution laws of damage for each material after loading. The bonding strength between the active material particles and changes in the elastic modulus of the crystal structure during the charge and discharge processes can be measured microscopically using nanoindentation and atomic force microscopy (AFM). MD simulations can also be used to evaluate the structure–activity relationship between ion diffusion and conductivity in separators or electrolytes under different hydrostatic stresses and electrolyte concentrations during electrochemical processes. These results provide a theoretical basis and reference for the application of SSE in high-pressure environments through electrical simulations.

Second, this section discusses the analysis of the mechanical properties of the whole composite structure battery. The evaluation of the mechanical properties of the battery is mainly based on tensile and three-point loading tests in the current research. Moyer et al. [44] compared the electrochemical performance at different stress loadings (Fig. 6(a)). The structural material produced polarization when loaded, which resulted in a steep and ill-defined constant-current charge/discharge curve with a reduction in the first discharge capacity and energy density, respectively. The performance after releasing the load showed no significant recovery; therefore, evaluating the influence of the loading stress on the mechano-electrochemical performance of CSBs is critical for CSB design and performance assurance. This study can specifically focus on the remaining strength of the structure after impact, the remaining capacity of the battery, and the impact of thermal runaway on the design and performance of the CSB. Pattarakunnan et al. [106] examined the impact damage tolerance of CSBs for integrating lithium-ion batteries; low-impact energy (<4 J) had minimal impact on the energy storage capacity, whereas high-impact energy (>6 J) caused internal short circuits because of the excessive plastic deformation and extrusion (Fig. 6(b)).

By combining the above methods, Fig. 7 shows a potential method for the post-impact reliability research on CSBs as an example. First, the evolution of the deflection and strain fields during compression after impact or shear is obtained using optical measurements such as fringe projection profilometry (FPP) and 3D-digital image correlation (DIC). The shape, depth, and area impact damage parameters are then obtained using ultrasonic C-scan or ultrasonic phased-array technology. These are used to establish a finite-element model [107]. A battery testing system can be used to track changes in the current and voltage status during loading. Additionally, infrared technology can be used to monitor the temperature changes in the battery during loading. Finally, based on the Hashin failure criterion, electromechanical coupling analyses of the composite battery capacity loss, rate performance, interface failure, residual strength, and residual service life are performed. This research method combines experiment and numerical analysis, which can enable the evaluation of the ultimate strength and damage mechanism of CSBs bearing mechanical impact, and also provides basic data for the development of data-driven approaches to evaluate and predict the relationship between key parameters and performance degradation of batteries.

Owing to the complexity of the electrolyte and its interface behavior in CSB, it is still difficult to clarify the structure/component characteristics, chemical/electrochemical reaction, and thermodynamic/dynamic behavior of the SEI electrode interface. Further research and design development requires interdisciplinary cooperation between the chemistry, physics, materials science, and nanoscience fields. However, the experimental content is vast and complex, and theoretical modeling is difficult to implement. Methods based on data science can quickly bridge the gap between electrochemical experiments and battery performance prediction and can also reduce the experimental cost by optimizing the experimental design.

Benayad et al. [108] reviewed a high-throughput material screening method for exploiting new battery chemicals and believed that strengthening the integration with machine learning (ML) to develop reliable prediction models is the key to the large-scale manufacturing of renewable batteries. Peter et al. [109] developed an ML method to effectively optimize the battery voltage and capacity parameters; this method can complete rapid charging and maximize the battery cycle life. Jiang et al. [110,111] used three different EIS characteristics to evaluate the impact of battery aging. They then proposed the relevance vector machine multi-kernel model, which accurately predicts the failure cycle and capacity attention trajectory of different types of batteries.

Data prediction in composite material structures includes the following: Sun et al. [112,113] used the secondary-developed abaqus parametric modeling technology to calculate and generate an artificial neural network (ANN) to study the hat-stiffened plates compression/shear buckling behavior. Similarly, Zou [114] used python secondary development to establish a finite-element model that considered impact/material factors (impact energy, impact position, impact hammer size, composite laminate thickness, stacking sequence, etc.) as the input and predicted the impact damage (impact damage area, pit depth, and impact penetration degree) as the output. The degree of impact damage under different input variable configurations and constructions could be predicted using this ANN process.

Therefore, a potential data research method to predict the mechanical and electrical characteristics of CSBs is proposed, as shown in Fig. 8. The use of simulation in the bottom-up design of battery components enables precise control of related physical and chemical properties. This approach represents the future of data-driven developments. Electrochemical experiments are used to verify the electrochemical model and generate a model set with various material properties such as active material porosity, electrolyte conductivity, and diffusion coefficient as the inputs and the battery capacity as the output. Electrochemical models can either be obtained from MD or finite-element models (FEMs).

Utilize finite-element parameterized modeling for secondary development to perform mechanical testing on the obtained electrochemical model. A dataset is generated in batches for impact damage parameters as the input and residual strength, failure cycle and capacity, and temperature as the output. The data-driven method can be used to evaluate and predict the relationship between key parameters and mechanical and electrical performance degradation of CSBs.

This paper discusses a new multifunctional CSB, which comprises lightweight materials able to store electrical energy simultaneously and support high mechanical loads. The review focuses on the comparison of the battery performance with existing problems and solutions. Most structural batteries have a certain gap in energy density compared to commercial batteries; however, they have good cycling and rate performance, and their mechanical properties are far superior to those of commercial batteries. Currently, research on CSB is still in its preliminary stage, and there is a need to design and develop high-performance electrode materials and electrolytes. Moreover, the degradation of the electromechanical coupling of batteries under external loads has not yet been elucidated. The recommendations for CSB can provide references for optimizing integrated design and manufacturing, structural and functional reliability. However, the identification of potential risks in the design process of CSBs and the implementation of measures to prevent those risks from occurring, promoting storage capacity, damage tolerance and cycle performance are difficult and profound scientific tasks.

• The National Key Research and Development Program (No. 2019YFA0706803).

• The National Natural Science Foundation of China (No. 11972106).

There are no conflicts of interest.

The datasets generated and supporting the findings of this article are obtainable from the corresponding author upon reasonable request.