Composite Negative Electrode Sheet With Ion-Conductive Insulation
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Solution Overview
Problem
Conventional lithium ion battery separators made of resin materials like polyethylene or polypropylene are prone to shrinkage or melting at high temperatures, leading to direct contact between the positive and negative electrode sheets, causing thermal runaway, battery combustion, and explosion.
Innovation Solution
A composite negative electrode sheet is developed with a current collector, an active coating, and an insulation coating comprising a polymer, inorganic filler, and fast ion conductor, where the solubility parameter difference between the polymer and binder is maintained above 0.5, enhancing interfacial isolation and ion transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional resin separator (polyethylene or polypropylene) is used, then the battery structure is simple and manufacturing is easy, but the separator shrinks or melts at high temperature causing short circuit and thermal runaway
Solution Approach 1:
The patent applies composite materials by combining polymer binder, inorganic filler, and fast ion conductor to create an insulation coating that maintains both manufacturability and high thermal stability. The composite structure allows each component to contribute its strengths: polymer provides binding, inorganic filler provides thermal stability, and fast ion conductor enables ion transport.
Solution Approach 2:
The patent changes the thermal and chemical parameters of the separator by introducing inorganic fillers and fast ion conductors into the polymer matrix. This transforms the separator from a simple resin material with low thermal stability to a composite material that maintains structural integrity at high temperatures while enabling ion conduction.
2Reliability
If an insulation coating is added to prevent short circuit, then thermal stability is improved, but the device structure becomes more complex
Solution Approach 1:
The insulation coating is designed to perform multiple functions simultaneously: it provides thermal stability through inorganic filler, enables ion transport through fast ion conductor, and maintains structural integrity through polymer binder. This multi-functionality reduces the need for additional separate components, thereby limiting complexity increase.
Solution Approach 2:
The patent applies local quality by creating an insulation coating specifically on the negative electrode sheet where it is most needed for preventing short circuits. The coating is not applied uniformly throughout the entire battery structure, but rather locally where thermal and electrical isolation is critical, thus minimizing overall structural complexity.
3Reliability
If the solubility parameter difference between polymer and binder is increased, then interfacial isolation is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes the chemical parameter of solubility parameter difference between polymer and binder to achieve optimal interfacial isolation. By selecting materials with appropriate solubility parameter differences (greater than 0.5), the patent ensures proper phase separation and interface formation without requiring excessive manufacturing precision.
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 composite negative electrode sheet provides stable structure, high ion transmission, and thermal stability, preventing short circuits and safety hazards by maintaining insulation and promoting lithium ion intercalation, thereby improving battery performance and cycle life.
Implementation Method 1
an insulation coating that comprises a polymer binder, an inorganic filler, and a fast ion conductor
Implementation Method 2
the insulation coating has the advantages of electronic insulation and high ion transport efficiency
Implementation Method 3
a polymer binder, an inorganic filler, and a fast ion conductor
Implementation Method 4
a solubility parameter difference between the polymer and the binder is expressed as |Δδ| that is greater than 0.5
Data Source
Figure 1
AI summary
A composite negative electrode sheet, a preparation method thereof, and a lithium ion battery using the same are provided. The composite negative electrode sheet includes a current collector, an active coating and an insulation coating that are disposed in sequence. The insulation coating includes a polymer, an inorganic filler, and a fast ion conductor, the active coating includes a binder and an active material, and a solubility parameter difference between the polymer and the binder is expressed as |Δδ| that is greater than 0.5 (J/cm3)1/2.