Analysis of Differences in Structure, Performance, and Application: Aluminum-Cased Prismatic Lithium Batteries vs. Aluminum-Laminate Pouch Prismatic Lithium Batteries

With the continued development of new energy vehicles, energy storage systems, and portable electronic devices, lithium-ion batteries face increasingly stringent requirements regarding energy density, structural integrity, safety performance, space utilization, and manufacturing costs. As a critical component of battery design, the cell packaging structure not only determines the cell's mechanical protection capabilities but also influences heat dissipation, sealing, pack assembly efficiency, and the design of the subsequent battery pack system.

 

Currently, prismatic cells primarily utilize two technical approaches: metal casing and aluminum-plastic laminate (pouch) packaging. Aluminum-cased prismatic cells are characterized by structural stability, high mechanical strength, and mature manufacturing processes, whereas pouch cells offer advantages in terms of weight, space utilization, and structural flexibility.

 

Structurally, prismatic cells typically employ an aluminum casing to enclose the internal electrode assembly, electrolyte, and associated components.

 

The aluminum casing must provide mechanical protection and sealing while also contributing to thermal management; consequently, factors such as material thickness, forming precision, flatness, and weld sealing quality directly impact cell consistency and long-term reliability. A typical aluminum prismatic casing is fabricated through processes including stamping, deep drawing, cleaning, surface treatment, and welding, with the bottom, sidewalls, opening, and positioning features configured according to specific battery structural requirements.

 

Unlike metal casings, pouch cells utilize an aluminum-plastic composite film as the external packaging material. This film is typically composed of multiple functional layers, and the cell is sealed using a heat-sealing process. Due to the high flexibility of the casing, the cell can accommodate internal pressure fluctuations and spatial layout changes within a certain range, offering distinct advantages in applications where weight and space utilization are critical.

 

 

 

The primary characteristic of aluminum-cased prismatic cells is the use of a rigid metal structure to protect the internal cell components. Aluminum offers low density combined with excellent formability, thermal conductivity, and corrosion resistance, enabling reduced casing weight while maintaining necessary structural integrity. Precision stamping or deep drawing processes allow for the production of prismatic casings with stable dimensions, providing a standardized structural foundation for subsequent electrode assembly and battery pack integration.

 

For new energy vehicle (NEV) power batteries, the casing serves not only a protective function but also integrates with the cell cover plate, terminals, seals, and other structural components to form a complete encapsulation system. A typical EV battery casing must balance strength, sealing integrity, corrosion resistance, weldability, and dimensional tolerances to withstand the mechanical and thermal stresses generated by long-term vehicle vibration, temperature fluctuations, and charge-discharge cycles.

 

The production of aluminum-cased cells typically involves multiple stages, including casing forming, cleaning, dimensional inspection, cover plate assembly, welding, and airtightness testing. Consistency in casing dimensions is particularly critical for mass production; significant deviations in flatness, wall thickness, or key positioning dimensions can adversely affect cell assembly, module spacing, and the overall design of the battery pack structure.

 

 

The defining structural characteristic of pouch cells is the high flexibility of their external packaging material. Unlike rigid metal casings, aluminum-plastic film does not maintain a fixed external geometry, thereby providing a buffer zone to accommodate the slight volumetric changes in internal materials that occur during charge-discharge cycles.

 

This structure offers distinct advantages regarding lightweighting and space utilization. For a given capacity, eliminating rigid metal casings and certain auxiliary structures reduces the proportion of inactive materials, allowing more space for electrochemically active materials. For weight- and volume-sensitive applications, the flexible packaging design of pouch cells enhances spatial adaptability.

 

However, pouch cells generally offer less mechanical protection than rigid metal casings, placing higher demands on cell grouping, external support, and pack structural design. In practical applications, trays, brackets, side plates, cushioning materials, or other structural components are required to secure the cells and prevent adverse effects from external mechanical impacts, compression, and prolonged vibration.

 

 

 

Cell packaging materials constitute inactive mass; therefore, the weight of the casing directly impacts the overall mass of the battery system. Pouch cells (utilizing aluminum-plastic laminate film) typically offer advantages in terms of lightweighting because they eliminate the need for a thick, rigid metal casing; conversely, while prismatic cells with aluminum casings add some structural mass, they provide superior mechanical protection and structural support.

 

Energy density cannot be determined solely by the cell casing material. Actual energy density is influenced by a multitude of factors, including cathode and anode materials, designed cell capacity, electrode thickness, the ratio of active materials, current collector design, electrolyte quantity, and the pack-level structure. Therefore, when comparing these two packaging formats, one must evaluate gravimetric energy density, volumetric energy density, and system-level energy density, rather than concluding based simply on casing weight.

 

For lithium-ion battery packs requiring lightweighting, the cell packaging format must be designed in coordination with the overall pack structure. For instance, where vehicle chassis space is limited, there is a significant interplay between cell dimensions, arrangement, casing strength, and cooling architecture; the optimal packaging approach must ultimately be determined through system-level design.

 

 

Prismatic cells with aluminum casings feature a relatively robust, rigid shell that provides a degree of mechanical protection for the internal cell components. Under normal operating conditions, the casing withstands mechanical loads arising from module assembly, vehicle vibration, and external structural mounting. Additionally, the metal casing facilitates heat conduction, providing a foundation for heat exchange between the cell and the cooling system.

 

However, a rigid casing does not eliminate issues related to internal pressure fluctuations. Lithium-ion batteries may generate gas or undergo internal structural changes during abnormal operating conditions or prolonged cycling; consequently, the cell casing, cover plate, sealing structure, and safety pressure-relief mechanisms require integrated design consideration. Engineering design typically involves airtightness testing, pressure resistance testing, and relevant safety validations to confirm that the packaging structure meets design specifications.

 

Pouch cells utilize flexible packaging materials; if abnormal gas generation or a rise in internal pressure occurs, the packaging area may swell or rupture locally. Their failure modes differ from those of rigid metal-cased cells, necessitating a different focus for safety design. For pouch cells, critical attention must be paid to packaging edges, heat-sealed areas, tab locations, and external mechanical constraints. For LiFePO4 cells, the packaging structure must be designed based on the material system, capacity, dimensions, and application environment. LiFePO4 battery packs intended for energy storage or motive power applications require a holistic evaluation that integrates the cell casing, module framework, thermal management system, and electrical protection structures.

 

 

Low-temperature battery performance is primarily influenced by factors such as the electrochemical system, material properties, electrolyte state, and internal impedance; therefore, performance variations cannot be simply attributed to the use of an aluminum casing versus an aluminum-laminated film.

 

In low-temperature environments, increased electrolyte viscosity, reduced ion transport capability, and elevated electrode interface impedance can all lead to higher internal resistance and reduced usable capacity. High-rate charging under low-temperature conditions also necessitates close monitoring of the risk of lithium plating at the anode. Consequently, regardless of whether a metal casing or pouch packaging is used, actual performance must be validated through low-temperature charge/discharge testing, temperature rise testing, and cycle testing.

 

Casing materials influence heat transfer pathways. Aluminum possesses good thermal conductivity and can serve as part of the cell's thermal management structure, whereas pouch cells typically rely on external cooling plates, thermal interface materials, and module structures to facilitate heat transfer. Thus, the thermal management system designs differ for the two types of cells.

 

 

The manufacturing process for prismatic aluminum-cased cells is relatively standardized; casings can be mass-produced through operations such as stamping, deep drawing, trimming, and cleaning. For large-scale power battery production, key control parameters include casing dimensional consistency, material thickness, welding quality, and sealing performance.

 

For applications requiring specific dimensions or structures, customized prismatic battery cell casings can be designed to suit the cell capacity, electrode assembly dimensions, installation space, and connection methods. Custom casings require strict control over material composition, sheet thickness, formed dimensions, corner radii, welding zones, and surface conditions to prevent manufacturing errors from propagating to subsequent cell assembly stages.

 

Pouch cells, conversely, rely more heavily on processes such as cutting and forming the aluminum-laminated film, positioning the tabs, and heat sealing. Parameters such as heat-sealing temperature, pressure, duration, and seal width directly affect the quality of the final seal. Contamination, wrinkles, foreign objects, or insufficient local heat sealing in the sealing area can compromise airtightness. Consequently, establishing a stable sealing process window and an in-line inspection mechanism is essential during the manufacturing of pouch cells.

 

 

 

There is no absolute "best" or "worst" cell packaging structure; the choice typically depends on the application scenario, cost targets, mechanical environment, spatial layout, and safety design requirements.

 

For power batteries in new energy vehicles, the casing must withstand long-term vibration, shock, temperature fluctuations, and high-rate charging and discharging; therefore, the casing design must be coordinated with the module structure, thermal management system, and high-voltage connection system. Large-scale energy storage systems require a greater focus on long-term cycling, system maintenance, protection ratings, and batch consistency.

 

In the field of light electric vehicles-such as lithium-ion e-bike battery packs-there are often strict requirements regarding weight, volume, and installation space; thus, the cell packaging structure must balance lightweight design with mechanical protection. Casing dimensions, terminal positions, and external mounting methods must also be adjusted according to the specific capacity and voltage platform.

 

In the realm of primary (non-rechargeable) batteries, casing design is closely linked to the battery's chemical system. For instance, Li-SOCl₂ battery casings are designed for specific lithium-thionyl chloride cell structures, with design priorities that differ from those of power battery casings. Similarly, for primary lithium battery structures like those using MnO₂, the appropriate materials and structures must be selected based on the internal chemistry, sealing method, and operating environment.
 

 

Aluminum alloy is a common casing material for prismatic power cells. Its advantages include low density, good thermal conductivity, and ease of stamping and welding. Different aluminum alloy grades vary in strength, elongation, corrosion resistance, and formability; therefore, the material choice must align with the casing structure and manufacturing process.

 

When designing aluminum casings for lithium-ion batteries, one must consider not only material strength but also sheet thickness and residual stress after forming. Material that is too thin may compromise mechanical strength, while material that is too thick adds inactive mass and reduces space utilization. Consequently, casing design usually requires balancing structural safety, weight, manufacturing costs, and formability. For rechargeable battery systems, aluminum shells must also demonstrate dimensional stability and environmental resilience during long-term cycling. The casing must maintain structural integrity amidst temperature fluctuations and internal pressure changes while preventing fatigue failure in welded and sealed areas.

 

 

As the new energy vehicle and energy storage industries continue to prioritize high energy density, enhanced safety, and cost-efficiency, the dimensions and capacities of prismatic cells are steadily increasing. Larger cells allow for a reduction in the total number of cells per pack, thereby decreasing the number of connectors, voltage-sensing lines, and structural components, while simplifying system integration.

 

However, as individual cell dimensions grow, issues regarding internal temperature gradients, mechanical stress, thermal expansion, and consistency become more pronounced. Consequently, large-format prismatic cells are not merely scaled-up versions of traditional cell structures; they require the optimization of casing strength, cover plate architecture, tab design, welding processes, and thermal management strategies.

 

Future optimization for prismatic aluminum-cased lithium batteries will focus on lightweighting, high-precision forming, improved material utilization, and automated manufacturing. Optimizing the casing's cross-sectional profile and incorporating localized reinforcement designs can reduce unnecessary weight while maintaining required mechanical performance.

 

 

 

In terms of mechanical protection, prismatic aluminum-cased cells benefit from a rigid structure, making them suitable for applications requiring high external mechanical strength and system stability. Conversely, pouch cells offer greater structural flexibility but rely on external support structures for secure mounting.

 

Regarding weight and space utilization, pouch cell structures generally offer greater potential for lightweighting, whereas aluminum-cased structures are more mature in terms of standardized dimensions, mechanical support, and system integration.

 

From a manufacturing perspective, prismatic aluminum-cased cells are well-suited for highly automated mass production, with casing dimensions and structures controlled via standardized molds and automated equipment. Pouch cells, however, require strict control over the forming of the aluminum-laminate film, heat sealing, and packaging consistency.

 

Regarding safety design, the two structures exhibit different failure modes. Aluminum-cased cells emphasize casing strength, weld integrity, and pressure management, whereas pouch cells focus more on packaging integrity, external mechanical protection, and the reliability of heat seals. Therefore, during the cell design phase, choices should not be based solely on material costs or individual cell energy density; instead, a comprehensive evaluation of the entire battery system is required.

 

In general, aluminum-cased prismatic cells and aluminum-laminated pouch cells represent two distinct technological pathways: rigid packaging and flexible packaging. The aluminum-cased approach offers distinct advantages in structural strength, dimensional consistency, automated manufacturing, and system integration, whereas the pouch cell approach excels in terms of lightweight design, spatial adaptability, and packaging flexibility. As the demands for battery performance become increasingly diverse across sectors such as new energy vehicles, energy storage, light electric vehicles, and industrial equipment, future cell packaging technologies will evolve toward high precision, lightweighting, reliable sealing, intelligent manufacturing, and structural integration.

 

For battery manufacturers, the cell casing is not merely an external component separate from cell performance; rather, it is a critical element closely linked to material systems, electrode assembly design, thermal management, structural strength, welding processes, and pack integration. Only by judiciously selecting the packaging format and optimizing materials, structures, and manufacturing processes in tandem can a more rational balance be achieved among energy density, safety, reliability, and manufacturing costs.