II. Three Mainstream Packaging Types: Advantages and Disadvantages at a Glance<\/h3>\n\n\n\n
1. Soft-Pack Cell Packaging (Aluminum-Plastic Film Packaging)<\/p>\n\n\n\n
Using an aluminum-plastic composite film as the outer shell, this is the mainstream solution for mobile phones, tablets, Bluetooth headsets, and small energy storage batteries.<\/p>\n\n\n\n
Advantages: Lightweight and thin, high energy density, flexible design<\/p>\n\n\n\n
Disadvantages: Low shell strength, poor compression resistance, extremely high requirements for sealing precision, and difficult mass production process.<\/p>\n\n\n\n
2. Prismatic Hard-Shell Packaging (Aluminum\/Steel Shell)<\/p>\n\n\n\n
Using an aluminum alloy or steel hard shell, this is the core solution for new energy vehicle power batteries and large energy storage cells. It has a stable structure and is suitable for modular assembly.<\/p>\n\n\n\n
Advantages: Robust structure, impact resistance, good heat dissipation, suitable for series and parallel module integration, and strong lifespan stability.<\/p>\n\n\n\n
Disadvantages: Relatively heavy, slightly lower energy density<\/p>\n\n\n\n
3. Cylindrical Hard-Shell Packaging<\/p>\n\n\n\n
Classic 18650 and 21700 models use this process. It has a high degree of standardization and is mostly used in power banks and power tools.<\/p>\n\n\n\n
Advantages: Standardized mass production, high consistency, low cost<\/p>\n\n\n\n
Disadvantages: Limited unit capacity, low space utilization in module assembly<\/p>\n\n\n\n
III. Complete Battery Cell Packaging Process (Industry Standard Procedure)<\/h3>\n\n\n\n
Many people mistakenly believe that packaging only involves the “sealing” step. In reality, complete packaging is a continuous and precise chain of processes, from pre-processing to final inspection, each step interconnected. A defect in any step can lead to the scrapping of the battery cell.<\/p>\n\n\n\n
Step 1: Battery Cell Pre-processing and Sorting (Fundamental Pre-packaging Preparation)<\/p>\n\n\n\n
Bare battery cells, after being wound\/stacked, are not directly packaged; they require pre-processing for quality improvement: First, the tabs are shaped, cut, and dusted to ensure proper length and flatness, removing residual dust and burrs from the production process to prevent short circuits later. Then, high-precision equipment is used for capacity sorting, classifying cells according to internal resistance, voltage, and capacity parameters to ensure consistency within the same batch, laying the foundation for subsequent series and parallel assembly. Finally, high-temperature baking completely removes residual moisture from the battery cell, preventing later gas expansion and leakage problems.<\/p>\n\n\n\n Step 2: Housing\/Wrapping Positioning (Cell Shaping)<\/p>\n\n\n\n This is the “shaping stage” of packaging, and the operation differs depending on the process:<\/p>\n\n\n\n For soft-pack cells: The bare cell is precisely placed into the pre-formed aluminum-plastic film packaging bag, accurately aligned with the tabs, and a standard electrolyte injection port is provided. This ensures the cell is centered, without offset or wrinkles, preparing for subsequent sealing.<\/p>\n\n\n\n For hard-pack square\/cylindrical cells: The bare cell is precisely installed into the aluminum or steel casing, the insulating gaskets are placed, and the terminals are aligned. A grooving process is used to fix the cell’s position, preventing internal loosening and movement.<\/p>\n\n\n\n Step 3: Multi-directional Heat Sealing\/Welding Sealing (Core Sealing Process)<\/p>\n\n\n\n Sealing is paramount in packaging, directly determining the battery’s airtightness and lifespan. Soft-pack cells employ a three-stage heat sealing process:<\/p>\n\n\n\n 1. Top Sealing: Sealing the area around the tabs. This is the most precise and difficult process to control, requiring precise control of temperature, pressure, and time to prevent leaks or incomplete sealing.<\/p>\n\n\n\n 2. Side Sealing: Sealing both sides of the cell, closing most of the cavity, leaving only the electrolyte filling port.<\/p>\n\n\n\n 3. Corner Sealing: Strengthening the seal at corner bends, releasing stress, and preventing cracking and leakage after long-term use.<\/p>\n\n\n\n Rigid-shell cells use laser welding to seamlessly weld the top cover, outer shell, and electrolyte filling port, resulting in uniform, pore-free welds that ensure absolute cavity sealing.<\/p>\n\n\n\n Step 4: Vacuum Injection (Giving the Cell Energy Storage Capacity)<\/p>\n\n\n\n The sealed cells are then placed in a vacuum drying environment\/glove box for electrolyte injection. This is a crucial step in transforming the cell from a “semi-finished product” into an “energy storage body.”<\/p>\n\n\n\n A high-precision metering pump precisely injects a fixed amount of electrolyte into the battery cell. The vacuum environment completely removes air from the cavity, preventing electrolyte oxidation and bubble formation. After injection, the cell needs to stand for 12-24 hours to allow the electrolyte to fully wet the electrodes and separator, forming a stable SEI film, which directly affects the battery’s cycle life and charge-discharge stability.<\/p>\n\n\n\n Step 5: Secondary Sealing and Shaping (Final Sealing and Shaping)<\/p>\n\n\n\n After electrolyte impregnation, the final sealing process begins: For soft-pack cells, a vacuum double-sealing process removes excess gas, completely sealing the injection port and smoothing out membrane wrinkles and shaping the cell. For hard-shell cells, laser welding seals the injection hole, achieving a fully sealed environment and ensuring complete isolation of the cell cavity from the external environment.<\/p>\n\n\n\n Step 6: Formation, Capacity Testing, and Aging (Cell Activation + Screening)<\/p>\n\n\n\n Newly packaged cells are in a “dormant state” and require activation through a formation process: A small current charge-discharge cycle activates the electrode materials and repairs the internal interface structure.<\/p>\n\n\n\n Following this, capacity testing is conducted to accurately calibrate the actual capacity, internal resistance, and voltage parameters of the cells, eliminating defective products with bulging, leakage, substandard capacity, or abnormal internal resistance. Finally, a long-term room-temperature aging process stabilizes the cell performance, identifying products with potential for future failure.<\/p>\n\n\n\n Step Seven: Final Inspection and Insulation Protection (Final Quality Control Before Shipment)<\/p>\n\n\n\n Qualified cells undergo final visual inspection, airtightness testing, and insulation testing. Insulating adhesive and protective film are then applied, and the model number, parameters, and production date are printed on them, completing the entire encapsulation process and preparing them for subsequent module and PACK assembly.<\/p>\n\n\n\n In lithium battery packaging, even minor errors can lead to serious quality problems. The core quality control points are concentrated in three areas:<\/p>\n\n\n\n 1. Sealing Accuracy (Preventing Gas Inflation and Leakage)<\/p>\n\n\n\n The heat-sealing temperature, pressure, and time parameters must be precisely matched. Incomplete sealing, leaks, or excessively narrow sealing edges can cause water and air to enter the cell, resulting in gas inflation, leakage, and a significant drop in capacity. Excessively wide sealing edges waste space and reduce energy density.<\/p>\n\n\n\n 2. Electrolyte Volume and Wetting Dependence (Determining Lifespan)<\/p>\n\n\n\n Excessive electrolyte filling can cause bulging, while insufficient filling leads to inadequate electrode wetting, accelerated cycle decay, and reduced battery life. Vacuum filling combined with sufficient settling is crucial for ensuring long-term cell stability.<\/p>\n\n\n\n 3. Internal Cleanliness (Preventing Short Circuit Hazards)<\/p>\n\n\n\n The entire packaging process must be carried out in a low-dust, low-humidity environment. Dust and metal debris residue can directly puncture the separator, causing micro-short circuits, excessive self-discharge, and in severe cases, thermal runaway.<\/p>\n\n\n\n <\/p>","protected":false},"excerpt":{"rendered":" The electric vehicles and energy storage devices we use daily all rely on lithium-ion battery cells for power. The capacity, lifespan, safety, and waterproof\/explosion-proof capabilities of these cells depend 70% on the packaging process. If electrode coating and winding are like “building the skeleton and filling the flesh” of the battery, then cell packaging is […]<\/p>\n","protected":false},"author":1,"featured_media":2803,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-2802","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"yoast_head":"\n<\/figure>\n\n\n\n
IV. Core Quality Control Points in Packaging Process (Key to Yield)<\/h3>\n\n\n\n