Battery Separator Porosity for Thick-Electrode Li-Ion Cells
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Solution Overview
Problem
The increase in electrode thickness in lithium-ion batteries leads to higher internal resistance, reducing charging and discharging efficiency, which is a critical issue for achieving reasonable battery performance.
Innovation Solution
A secondary battery design with a positive electrode layer thickness of 10 to 200 mm, a negative electrode layer thickness of 5 to 150 mm, and an insulating layer with porosity ranging from 20% to 85% and thickness ratio conditions that optimize electrolyte ion diffusion, reducing internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If electrode thickness is increased to reduce auxiliary material usage and improve energy density, then energy density is improved, but internal resistance increases and charging-discharging efficiency deteriorates
Solution Approach 1:
The patent applies porous materials by designing the insulating layer with controlled porosity (20%-85%). The porous structure allows electrolyte ions to diffuse more efficiently through the insulating layer, reducing ion transport resistance despite increased electrode thickness. This resolves the contradiction by maintaining high energy density through thick electrodes while preserving charging-discharging efficiency through optimized porosity.
Solution Approach 2:
The patent changes physical parameters by optimizing the porosity of the insulating layer within the range of 20%-85% and controlling its thickness relative to electrode thickness. By adjusting these parameters, the patent achieves a balance where thick electrodes provide high energy density while the optimized insulating layer parameters maintain low internal resistance and high ion diffusion efficiency.
2Ease of manufacture
If electrode thickness is increased to reduce auxiliary material usage, then cost is reduced, but diffusion resistance of electrolyte ions increases
Solution Approach 1:
The patent uses porous insulating layer materials with controlled porosity (20%-85%) to reduce diffusion resistance. The porous structure provides channels for ion transport, allowing thick electrodes to be manufactured at lower cost without suffering from excessive ion diffusion resistance, thus resolving the contradiction between cost reduction and diffusion resistance.
Solution Approach 2:
The insulating layer acts as an intermediary between the positive and negative electrodes. By optimizing its porosity and thickness, it mediates the ion transport process, enabling thick electrode design for cost reduction while maintaining low diffusion resistance through its intermediate function of facilitating ion diffusion.
3Productivity
If insulating layer porosity is increased to improve ion diffusion, then charging-discharging efficiency is improved, but internal resistance may increase
Solution Approach 1:
The patent optimizes the porosity parameter within the specific range of 20%-85% to achieve the best balance. Within this range, ion diffusion efficiency is maximized for high charging-discharging efficiency, while the porosity remains controlled to prevent excessive internal resistance, thus resolving the contradiction between productivity and reliability.
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 optimized design significantly reduces impedance and improves battery capacity retention and charging-discharging efficiency, enhancing the energy density and safety of the secondary battery.
Implementation Method 1
the increase in electrode thickness can affect the diffusion efficiency of internal electrolyte ions between the positive and negative electrodes, increasing the diffusion resistance of the electrolyte ions
Data Source
AI summary
Secondary batteries are described, the batteries comprising a positive electrode layer, a negative electrode layer and an insulating layer. The insulating layer is located between the positive electrode layer and the negative electrode layer; the thickness of the positive electrode layer is about 10-200 mm; the thickness of the negative electrode layer is 5-150 mm; and the secondary battery meets the following condition: 20%≤a−(b/20)×5%≤35%; where the porosity of the insulating layer is a; and the thickness of the positive electrode layer is b mm. According to the secondary battery, the impedance of the secondary battery can be obviously reduced, and the capacity retention rate of the battery is increased in the long-term cycle process.