Polymer Electrolyte for Pouch Battery Mechanical Strength
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in withstanding external physical impacts while maintaining high performance and capacity, as pouch-type batteries are prone to deformation and swelling under temperature and physical stress, compromising their safety and efficiency.
Innovation Solution
A rechargeable lithium battery design incorporating a polymer electrolyte made from a specific polymerization product of first and second monomers, a carbon-based negative active material, and a lithium salt in a non-aqueous organic solvent, which enhances battery strength, capacity, and cycle life by optimizing the polymer electrolyte composition and structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the physical strength of the battery is increased to resist external physical impact, then the resistance against external physical impact is improved, but the battery performance is compromised due to increased internal resistance
Solution Approach 1:
The patent uses a composite polymer electrolyte consisting of polyacrylonitrile (PAN) as the base polymer and gelatin as an additive. This composite structure provides both mechanical strength from PAN and improved ionic conductivity from gelatin, resolving the contradiction between physical strength and battery performance. The gelatin component creates a more open structure that facilitates lithium ion transport while maintaining structural integrity.
Solution Approach 2:
The patent optimizes the molecular weight of polyacrylonitrile (specifically using PAN with molecular weight of 150,000-200,000) and the concentration of gelatin (5-15% by weight) to achieve the right balance between mechanical properties and ionic conductivity. By carefully controlling these parameters, the battery achieves both high physical strength and good electrochemical performance.
2Volume of stationary object
If a pouch-type battery container is used to increase size and flexibility, then the container size is increased and shape flexibility is improved, but the battery becomes easily deformed and damaged by external physical impact and high temperature
Solution Approach 1:
The patent employs a flexible pouch-type container made from laminated film structures that provide both flexibility and mechanical strength. The container uses multiple layers including aluminum foil and polymer films that offer protection against physical impact while maintaining the desired flexible form factor and size.
Solution Approach 2:
The pouch container utilizes composite material structures with multiple layers having different properties. The combination of metal foil layers (for strength and barrier properties) and polymer layers (for flexibility and sealing) creates a container that resists deformation and damage while maintaining flexibility and size advantages.
3Quantity of substance
If a liquid electrolyte solution is used in pouch-type battery, then the battery capacity is improved, but the battery becomes more susceptible to leakage and damage from external physical impact and high temperature
Solution Approach 1:
The patent transitions the electrolyte from liquid phase to gel phase by incorporating gelatin into the polymer matrix. This gel electrolyte maintains the high ionic conductivity and capacity characteristics of liquid electrolytes while providing the mechanical stability, leak-proof properties, and thermal stability of solid-like structures. The gel structure prevents leakage and resists physical impact better than liquid electrolytes.
Solution Approach 2:
The gelatin acts as an intermediary between liquid electrolytes and solid polymer electrolytes. It provides the liquid-like ionic conductivity needed for high capacity while offering the structural framework that prevents leakage and improves resistance to physical impact and high temperature, effectively mediating between the advantages and disadvantages of liquid and solid electrolytes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The battery achieves improved physical strength, charge and discharge capacity, and extended cycle life with a battery capacity per unit area ranging from 3.10 to 2.8 mAh/cm2, effectively addressing the issues of deformation and swelling, and maintaining high performance under various conditions.
Implementation Method 1
a polymer electrolyte including a polymer, a non-aqueous organic solvent and a lithium salt
Implementation Method 2
a positive electrode including a positive active material for intercalating and deintercalating lithium ions; a negative electrode including a negative active material for intercalating and deintercalating lithium ions
Data Source
AI summary
A rechargeable lithium battery includes a positive active material for intercalating and deintercalating lithium ions; a negative electrode including a negative active material for intercalating and deintercalating lithium ions; and a polymer electrolyte including a polymer, a non-aqueous organic solvent and a lithium salt. The rechargeable lithium battery has a battery capacity per unit area of the positive electrode from about 3.3 mAh/cm2 to about 2.8 mAh/cm2. The polymer includes a first monomer represented by the following Chemical Formula 1 and a second monomer represented by at least one of the following Chemical Formulae 2 to 7 at a weight ratio of about 85:15 to about 50:50 of the first monomer to the second monomer. In the above Chemical Formulae 1 to 7, each compound is as described in the detailed description.