I. Technical Definition and Core Characteristics

Lithium Polymer Batteries (Li-Po), developed from liquid lithium-ion battery technology, share the same cathode and anode materials as liquid batteries but utilize gel electrolyte and aluminum-plastic film packaging. This design delivers core advantages of lightweight, high energy density, and high safety, gaining widespread recognition among global clients for Technical Analysis of Lithium Polymer Batteries.
 
Technical Analysis of Lithium Polymer Batteries

II. Lithium Polymer Cell Specifications

Model Dimensions (Thickness × Width × Height, mm) Nominal Capacity (mAh) Internal Resistance (mΩ, <) Nominal Voltage (V)
3578131 3.5×78×131 4000 40 3.7
3463110 3.4×63×110 2700 40 3.7
3845120 3.8×45×120 2200 40 3.7
366090 3.6×60×90 2000 40 3.7
3435165 3.4×35×165 1800 40 3.7
2453135 2.4×53×135 1400 40 3.7
385085 3.8×50×85 1300 60 3.7
344461 3.4×44×61 1200 60 3.7
255480 2.5×52×80 1150 50 3.7
393278 3.9×32×78 1100 65 3.7
305060 3×50×60 900 40 3.7
383450 3.8×34×50 600 70 3.7
383450 3.8×34×50 450 80 3.7
233759 2.4×37×59 380 80 3.7
392339 3.9×23×39 330 80 3.7
302441 2.8×24×40.5 250 100 3.7
251776 2.5×17×76 230 120 3.7
302145 3×21×45 210 150 3.7
222530 2.5×25×30 120 180 3.7
321239 3.1×12×39 100 200 3.7

III. Classification System

(1) By Structure

  1. Wound Type: Uses the same winding process as liquid lithium-ion batteries, winding cathode, anode, and electrolyte films, then packaging with aluminum foil. Suitable for large-scale production.
  2. Laminated Type: Uses hot-pressing technology to laminate cut cathode, anode, and electrolyte films, sealed with aluminum foil for higher structural flexibility.

(2) By Electrolyte Type

  1. Gel Polymer Electrolyte Battery (GPE-LiPo): Adds conductive additives to solid polymer electrolytes, achieving room-temperature ionic conductivity of 10⁻³ S/cm for ambient operation.
  2. Solid Polymer Electrolyte Battery (SPE-LiPo): Electrolyte is a polymer-salt composite with low room-temperature conductivity (10⁻⁶ S/cm), suitable for high-temperature environments (>60°C).
  3. Composite Gel Polymer Cathode Battery (CPE-LiPo): Employs conductive polymers as cathode materials, offering 3× the specific energy of conventional lithium-ion batteries—next-generation technology.

IV. Core Advantages

Technical Index Performance
Safety No liquid electrolyte; aluminum-plastic film housing resists explosion. Thermal runaway temperature >200°C, reducing fire/explosion risk by 90%.
Thinness 6V/400mAh battery thickness down to 0.5mm, compatible with ultra-thin electronics.
Lightweight 40% lighter than steel-cased Li-ion batteries, 20% lighter than aluminum-cased ones. Energy density increased by 15-20Wh/kg.
Sealing Solid gel electrolyte eliminates leakage risk, operating in -40°C~60°C wide temperature range.
Capacity Density 10-15% higher capacity than steel-cased batteries, 5-10% higher than aluminum-cased ones. Typical value: 200-250mAh/cm³.
Internal Resistance Typical <35mΩ, supports >20C high-current discharge, power density 1500W/kg.
Structural Adaptability Customizable shapes (curved/ultra-thin/irregular) meet demands of wearables, drones, and other niche applications.

V. Key Technical Parameters

(1) Electrical Parameters

  • Voltage System
    • Nominal Voltage: 3.7V (single cell)
    • Charging Voltage: 4.1-5.0V (constant current/constant voltage charging)
    • Discharge Cut-off Voltage: 2.8V, Storage Voltage: 3.7-3.8V
  • Capacity Calculation
    Empirical formula: Capacity (mAh) = Thickness (mm) × Width (mm) × Length (mm) × K (K=0.15-0.25mAh/mm³, adjusted by material system)
  • Rate Characteristics
    • Charge Rate: 0.5C-5C (1C = rated capacity current, e.g., 2A for 2000mAh battery)
    • Discharge Rate: 1C-20C (continuous)/30C (peak), affected by internal resistance

(2) Environmental Parameters

  • Operating Temperature: Charging 0-45°C, Discharging -20-60°C
  • Storage Conditions: -20-35°C, humidity 45%-75%. Long-term storage requires 30-50% state of charge.

VI. Comparison with Traditional Lithium Batteries

Dimension Lithium Polymer Battery (Li-Po) Liquid Lithium-ion Battery (Li-ion)
Electrolyte Form Gel/solid, no flow risk Liquid organic electrolyte, requires rigid casing
Shape Adaptability Customizable (thickness <1mm) Cylindrical/rectangular, fixed shape
Energy Density 200-250Wh/kg 150-200Wh/kg
Safety Thermal runaway >200°C, no explosion risk Thermal runaway 150°C, requires protection circuit
Internal Resistance <50mΩ (typical) 80-120mΩ
Production Cost High (complex aluminum-plastic film process) Low (mature steel/aluminum casing)
Cycle Life 500-800 cycles (0.5C charge/discharge) 300-500 cycles

VII. System Integration and Applications

(1) PACK Assembly Technology

Integrates cells via series-parallel connection (e.g., 3S1P=3 cells in series, 1 parallel, nominal 11.1V), including:
  • Battery Management System (BMS): Overcharge/over-discharge/overcurrent protection, supports Bluetooth communication.
  • Connection System: Molex 2510/JST SHR connectors, supports 20-100A current.
  • Structural Components: Insulating Highland barley paper layers, aluminum alloy frames (vibration-resistant).

(2) Typical Application Scenarios

  1. Consumer Electronics: Wearables (<2mm thickness), foldable smartphones (irregular batteries).
  2. Power Systems: Drones (25C discharge rate), power tools (40V series systems).
  3. Energy Storage: Portable power stations (100-500Wh), RV backup power.

VIII. Failure Analysis and Maintenance

(1) Swelling Mechanisms

  1. Encapsulation Defects: Aluminum-plastic film damage allows moisture ingress, causing electrolyte decomposition (H₂/O₂/CO₂).
  2. Process Contamination: Moisture >20ppm hydrolyzes LiPF₆ electrolyte, generating HF to corrode electrodes.
  3. Overcharge/Over-discharge: Charging >4.3V triggers lithium plating; discharging <2.5V ruptures SEI film.
  4. Mechanical Damage: >0.5mm dents may cause internal short circuits; pinprick test leakage >100mA.

(2) Maintenance Guidelines

  • Charging Standards: Constant current 1C≤I≤5A, constant voltage 4.20±0.03V, automatic cutoff >45°C.
  • Discharge Management: Cutoff voltage ≥2.75V, continuous current ≤2C, pulsed discharge ≤10C (<10s).
  • Storage Requirements: Discharge to 3.7V at 0.5C before long-term storage; check self-discharge rate (<5%/month) every 3 months.

IX. Sustainability and Recycling

(1) Environmental Impact

  • Hazardous Substances: Cathode LiCoO₂ contains carcinogenic cobalt; LiPF₆ electrolyte hydrolyzes to fluoride.
  • Degradability: Aluminum-plastic film recycling rate >90%; electrolytes require glovebox handling to avoid HF gas release.

(2) Recycling System

  1. Physical Methods: Crushing and screening to separate aluminum/copper foil, recovery rate >95%.
  2. Chemical Methods: Acid-base dissolution to recover Li/Co/Ni, metal recovery >90%.
  3. Policy Regulations: EU Battery Regulation mandates lithium recovery ≥50% by 2024, rising to 90% by 2027.

X. Selection and Procurement Guidelines

  1. Brand Certification: Prioritize products with UL 2580 (for EVs) and IEC 62619 (for energy storage) certifications.
  2. Capacity Verification: Require 0.2C discharge capacity (≥95% of nominal) and 1C cycle life (>500 cycles) reports.
  3. Protection Circuit: Confirm BMS has active balancing (voltage precision ±5mV) and overtemperature cutoff (>60°C).
  4. Design Fit: Customize battery profiles per device space. Ultra-thin devices recommend <3mm thickness; power applications prioritize high discharge rates (>15C).

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