Lithium-Ion Battery Factory Production Line Construction Analysis

Abstract
To better understand lithium-ion battery production processes and guide production line planning, this paper summarizes common line construction models in the lithium battery industry and provides layout optimization suggestions based on an engineering project case.

Keywords: lithium-ion battery, production line construction

1. Introduction

Due to the lack of unified domestic and international technical standards, lithium-ion battery production processes are not yet fully mature, and there is no fixed model for production line construction. Common line construction methods can be divided into product-based lines and process-based lines.

2. Product-Based vs. Process-Based Line Construction

• 2.1 Product-Based Line
• A product-based line is designed according to a specific battery model, with a single factory completing all production steps. The design requires unified planning of the plant layout, equipment, and construction facilities according to the product specifications, production capacity, and technical requirements.
• 2.2 Process-Based Line
• A process-based line is planned according to standard production processes, without requiring a single plant to cover all functions. Different factories handle different production steps, connected by automated logistics to complete battery manufacturing.

3. Advantages and Disadvantages

    3.1 Product-Based Line

     Advantages:

• Shorter construction cycle, with tightly connected processes facilitating automation and management.
• Centralized management within a single plant, clear responsibilities, and easy implementation of production plans.

      Disadvantages:

• Low equipment utilization; multiple product switches can lead to waste.
• Complex environmental control, high energy consumption.
• Multiple hazards within one plant, leading to higher safety risks.
• Low flexibility; process changes are difficult to implement.

     3.2 Process-Based Line

       Advantages:

• Centralized equipment layout, higher utilization, suitable for flexible production.
• Smaller plant areas, uniform environmental control, easier HVAC and fire safety management.
• Flexible process adjustment, facilitating upgrades.
• Better personnel management, reducing cross-process movement.

     Disadvantages:

• Longer construction cycle; all functional plants must be ready before production begins.
• Longer logistics between plants, making full automation challenging.
• Additional equipment required to control the environment during inter-plant transport.

     Recommendation:

• Multiple product types with low production volume → Product-based line
• Few product types with high per-product volume → Process-based line

4. Production Capacity and Line Choice

• The production capacity limit of a single factory is approximately 2.16 billion Wh (300,000 Wh/m² × 72,000 m², three-story plant).
• Recommendations:
  • ≤ 2.16 billion Wh → Product-based line (can combine process-based line)

  • 2.16 billion Wh → Process-based line

5. Lithium Battery Manufacturing Process

5.1 Battery Structure

• Main components: cathode, anode, non-aqueous electrolyte, separator
• Main types: Lithium Iron Phosphate (LFP) and Nickel Cobalt Manganese (NCM)
• Processes are similar; material and parameter differences make line conversion costly

 5.2 Production Process

1. Front-end (35–40% of cost): mixing, coating, calendaring, slitting
   • Core equipment: mixer, coating machine, calendering machine, slitting machine
2. Mid-end (30–35% of cost): electrode processing, winding, cutting, stacking, cell forming
   • Process: cylindrical/rectangular → winding; pouch → stacking
   • Core equipment: winding machine, stacking machine, cutting machine, electrolyte filling machine
3. Back-end (30–35% of cost): formation, grading, testing, packaging
   • Core equipment: formation machine, grading machine, automated storage and logistics
4. Pack assembly: connecting cells into battery packs, core equipment includes laser welding machines and testing equipment

5.3 Material Selection

• LFP (Lithium Iron Phosphate): high safety, long cycle life (>2000 cycles), low cost, lower energy density (~150–160 Wh/kg)
• NCM (Nickel Cobalt Manganese): high energy density (200–220 Wh/kg), higher cost, slightly lower safety

6. Project Case: Small-Scale Lithium-Ion Power Battery

6.1 Technical Solution

• Cathode: LFP, cycle life >2000 cycles, fast charging (~1 hour)
• Production process is domestically patented and technologically advanced

6.2 Main Process Flow

1. Electrode sheets: mixing → stirring → coating → drying → calendaring → slitting → welding tabs
2. Battery cells: electrode pairing → winding → casing → lid welding → vacuum baking → electrolyte filling → formation → aging → testing → packaging

6.3 Equipment Plan

• Annual production of 20 million cells requires 583 new pieces of equipment
• Core equipment: coating machine, calendering machine, formation cabinets, testing cabinets, drying ovens
• Mostly domestic general-purpose equipment, supporting rectangular, cylindrical, polymer, and power batteries

6.4 Plant Layout

• Total land area: 48,551 m² (~73 acres), total building area: 47,361 m²
• Plant and auxiliary facilities: 10 production workshops, 2 warehouses, boiler room, high-voltage substation
• Administrative and living facilities: 2 shift dormitories, staff dormitory, canteen, office building
• Layout design: production and office areas separated, logistics and personnel separated, simple utilities, efficient land use

Table 1: Equipment List Overview