Aramid Non-Woven Separator for Lithium Ion Pre-Doping
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Solution Overview
Problem
Lithium ion pre-doping in electric storage devices is not performed evenly due to variations in electrode surface state, separator structure, and cell structure, affecting the reliability and cycle characteristics of the devices.
Innovation Solution
An electric storage device with a lithium electrode separated from the positive and negative electrodes by a non-woven fabric separator made of aramid fibers, with an average fiber diameter of 0.1 µm to 10 µm and a thickness of 5 µm to 500 µm, which enhances the liquid retaining property and allows even lithium ion pre-doping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used for lithium ion pre-doping, then the device structure is simple, but the lithium ion pre-doping is not performed evenly and cycle characteristic deteriorates
Solution Approach 1:
The patent applies parameter changes by specifying precise fiber diameter (0.1-10 μm) and thickness (5-500 μm) parameters for the aramid non-woven fabric separator. These parameter optimizations enable even lithium ion pre-doping while maintaining structural simplicity, directly improving cycle characteristic without excessive complexity
Solution Approach 2:
The patent uses aramid fibers as the separator material, which is a composite material with superior liquid retaining properties. This material selection enables even lithium ion pre-doping distribution while maintaining a relatively simple single-layer separator structure, resolving the contradiction between reliability improvement and device complexity
2Reliability
If the separator has poor liquid retaining property, then the separator structure is simple, but lithium ion pre-doping is uneven and reliability deteriorates
Solution Approach 1:
The patent optimizes the separator's liquid retaining property by controlling fiber diameter (0.1-10 μm) and thickness (5-500 μm) parameters of the aramid non-woven fabric. These parameter changes enhance electrolyte retention capability, enabling uniform lithium ion pre-doping while maintaining a simple single-layer separator structure
Solution Approach 2:
The patent employs aramid non-woven fabric as the separator material, which possesses superior liquid retaining properties compared to conventional separators. This material choice improves pre-doping uniformity through enhanced electrolyte retention without requiring complex multi-layer or composite separator structures
3Use of energy by moving object
If lithium metal is used as ion supply source, then energy density is improved, but internal short-circuit and lithium metal loss occur
Solution Approach 1:
The patent introduces an aramid non-woven fabric separator as an intermediary between the lithium metal electrode and the other electrodes. This separator with superior liquid retaining properties ensures even lithium ion pre-doping and prevents direct contact between lithium metal and other electrodes, thereby preventing internal short-circuits while maintaining high energy density
Solution Approach 2:
The patent optimizes the separator thickness (5-500 μm) and fiber diameter (0.1-10 μm) parameters to achieve the right balance between preventing lithium metal loss through even pre-doping and maintaining electrical isolation to prevent short-circuits, while preserving the high energy density benefit of lithium metal
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 improved separator design leads to a significant enhancement in the cycle characteristic of the electric storage device, with a discharge capacity retention ratio improved by approximately 50% over 35 to 40 cycles, and prevents internal short-circuits and lithium metal loss.
Implementation Method 1
a non-woven fabric separator made of aramid fibers... which enhances the liquid retaining property
Data Source
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AI summary
In an electric storage device (10), lithium electrodes (17) are disposed on respective outermost portions of an electrode laminated unit (12) in which a positive electrode (13) and a negative electrode (14) are laminated alternately via positive/negative electrode separators (15). The lithium electrode (17) includes lithium metal (25) serving as a lithium ion supply source, and a lithium electrode separator (16) (a non-woven fabric separator) constituted by a non-woven fabric that satisfies the following conditions: (a) an average fiber diameter of 0.1 to 10 µm; and (b) a thickness of 5 to 500 µm is provided. By forming the lithium electrode separator (16) that contacts the lithium electrode (17) including the lithium ion supply source from a non-woven fabric in this manner, a dramatic improvement can be achieved in the cycle characteristic of the electric storage device (10).