Amid the Solid-State Battery Wave, Aluminum-Plastic Film: The Irreplaceable Key Incremental Material

As solid-state batteries (SSBs) gradually overcome technical bottlenecks such as electrolyte interface impedance and lithium dendrite suppression, moving from semi-solid to all-solid-state mass production, the upgrading of packaging materials has become a key link determining the speed of their commercialization. Compared with traditional liquid lithium-ion batteries, SSBs have exponentially higher requirements for packaging in terms of barrier properties, corrosion resistance, and flexibility. With its unique composite structure of "metal barrier + polymer flexibility", aluminum-plastic film (APF) has become the only packaging material that can meet these needs at the current stage, and it also demonstrates irreplaceable value in industrial increments.

1. "Packaging Necessity" of SSBs: Why Choose Aluminum-Plastic Film?

The core characteristics of SSBs directly drive the rigid demand for APF. First, the application of lithium metal anodes requires extreme barrier properties of packaging materials—lithium metal easily reacts with oxygen and moisture in the air to form by-products, leading to battery capacity decay. The core layer of APF (soft aluminum foil with 99.9% purity) can control the water vapor transmission rate below 0.01g/(m²·24h), far superior to traditional steel cases (0.1g/(m²·24h)) and aluminum cases (0.05g/(m²·24h)). Second, the interface stability of solid electrolytes depends on the corrosion resistance of packaging—some sulfide solid electrolytes easily react with metals. The outer layer (nylon) and inner layer (polypropylene) of APF are compounded with aluminum foil through special adhesives, which can withstand electrolyte erosion in the wide voltage range of 3.0-4.8V and avoid interface failure. Third, the lamination process and flexible design require material flexibility—SSBs mostly adopt a lamination structure to improve energy density, and APF can achieve forming processing with a minimum bending radius of 5mm, adapting to scenarios such as curved batteries and flexible wearable devices, which rigid casings cannot meet.

2. Technical Barriers: How Does APF Support the "Incremental Threshold"?

Not all APFs can be adapted to SSBs; the technical barriers of high-end products are the core of its status as a "key incremental material". In terms of structure, APF adapted to SSBs needs to meet the precise compounding of a "three-layer five-structure" (nylon layer + adhesive layer + aluminum foil layer + adhesive layer + polypropylene layer). The thickness of the aluminum foil must be controlled at 15-20μm (too thick affects flexibility, too thin reduces barrier properties), and the adhesive must use an epoxy resin system resistant to electrolytes (to avoid swelling at high temperatures). In terms of process, high-precision coating and hot-press forming are key—slit coating needs to control the adhesive thickness tolerance within ±1μm to ensure bubble-free bonding between the aluminum foil and the polymer layer, and the hot-press temperature must accurately match the thermal stability of the solid electrolyte (usually in the range of 80-120℃) to avoid electrolyte failure during packaging. Currently, only a few enterprises worldwide can mass-produce such high-end products. In the domestic field, Hangzhou Hongcheng Technology Co., Ltd. has achieved mass production of 12μm ultra-thin APF, with interface peel strength close to the 8N/15mm standard. By optimizing the aluminum foil passivation process and adhesive formula, the company has improved the long-term weather resistance of the product by 20%, providing key support for the localization of domestic SSB packaging materials.

3. Market Increment Logic: From "Supporting Demand" to "Industrial Pillar"

With the increase in SSB penetration, APF is upgrading from a "supporting material" to an "industrial incremental pillar". According to GGII data, the global installed capacity of semi-solid-state batteries will reach 50GWh in 2025, driving APF demand to exceed 80,000 tons; if the penetration rate of all-solid-state batteries reaches 20% in 2030, the corresponding APF demand will increase to 350,000 tons, with a compound annual growth rate of over 30%, far higher than the 15% growth rate in the liquid lithium battery era. From the application scenario perspective, new energy vehicles are the core incremental market—the amount of packaging materials used per SSB-equipped vehicle is 40% higher than that of liquid battery vehicles (due to the more complex lamination structure). Based on the supporting standards of mainstream automakers' SSB models, the APF usage per vehicle can reach 8-10㎡. If such models enter the mass production peak in 2027, the annual APF demand driven by a single model can exceed 50,000 tons. The energy storage field promotes the upgrading of APF to "large capacity and high temperature resistance". APF adapted to SSBs above 100kWh needs to withstand a long-term operating temperature of 60℃. Hangzhou Hongcheng Technology has developed a dedicated APF product for this scenario; by adjusting the aluminum foil thickness and composite layer structure, the product's temperature resistance is increased to 70℃, and it is currently in the customer verification stage.

4. Future Challenges and Upgrade Directions: How Can APF Sustain "Increment"?

To maintain its key position in the SSB industry, APF needs to overcome three major challenges, and Hangzhou Hongcheng Technology is also actively deploying in this field. First, temperature resistance upgrading—all-solid-state batteries may have an operating temperature increased to above 150℃, and the existing polypropylene inner layer (temperature resistance upper limit of 130℃) needs to be replaced with polyimide (temperature resistance of 260℃). The company has launched the R&D of polyimide composite layers; although the initial cost is expected to increase by 30%, it plans to control the cost reduction within 15% through large-scale production. Second, cost control—the current unit price of high-end APF is about 80 yuan/㎡, 5 times that of traditional aluminum cases. Hangzhou Hongcheng Technology is promoting the localization of the entire industrial chain of adhesives and aluminum foil, aiming to reduce the cost of high-end products to below 50 yuan/㎡ by 2027. Third, environmental adaptation—the EU Battery Regulation requires the recycling rate of packaging materials to reach 85% by 2030. The company has launched the development of an "easy-to-peel" APF structure; by optimizing the interlayer bonding process, it realizes efficient separation of aluminum foil and polymer materials. Currently, the utilization rate of recycled aluminum has exceeded 45%, and it plans to reach the 60% standard by 2026.

From semi-solid to all-solid-state, every technological breakthrough of SSBs is accompanied by the performance iteration of APF. This positive cycle of "demand driving technology and technology promoting increment" not only makes APF the "key incremental material" in the SSB era, but also makes it a core link connecting lithium battery material innovation and end applications. The technological breakthroughs and industrial layouts of domestic enterprises such as Hangzhou Hongcheng Technology are accelerating the localization process of this key material, injecting Chinese strength into the development of the global SSB industry.