Lithium-ion Separator Moisture Control via Heat Treatment
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Solution Overview
Problem
Conventional lithium ion secondary battery manufacturing processes face challenges in sufficiently removing adsorbed moisture, leading to high moisture content which can deteriorate battery characteristics and performance.
Innovation Solution
A lithium ion secondary battery design with a separator having a shrinking ratio of 2% or less by heat treatment at 90 °C for 6 hours, and a manufacturing method that includes a heat-drying step at 90 °C or higher to reduce both physically and chemically adsorbed water, ensuring a moisture content of 2% or less in the electrode element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional manufacturing processes are used, then production efficiency is maintained, but moisture content in the battery remains high leading to deteriorated storage and cycle characteristics
Solution Approach 1:
The separator is pre-treated to reduce its moisture adsorption capacity before battery assembly. This preliminary action prevents the separator from absorbing moisture during the manufacturing process, thereby reducing the overall moisture content in the battery without requiring extreme drying conditions that would damage other components.
Solution Approach 2:
The invention changes the physical-chemical parameters of the separator through heat treatment and chemical processing to reduce its affinity for moisture. By modifying the separator's surface properties and thermal stability, the battery can maintain low moisture content under normal manufacturing conditions, improving storage and cycle characteristics.
2Quantity of substance
If high temperature heat treatment (120°C or higher) is applied to remove adsorbed moisture, then moisture content is reduced, but the manufacturing process becomes more complex and difficult to implement
Solution Approach 1:
The separator undergoes preliminary moisture reduction treatment during its manufacturing process, before being assembled into the battery. This advance preparation eliminates the need for high-temperature post-assembly drying, as the separator already has low moisture content when installed, simplifying the overall manufacturing process.
Solution Approach 2:
The invention replaces the mechanical/thermal approach of high-temperature drying with a chemical/physical pre-treatment of the separator. Instead of applying extreme heat to the assembled battery, the separator is chemically modified during manufacturing to inherently resist moisture absorption, substituting a complex thermal process with a simpler material science solution.
3Ease of manufacture
If adsorbed moisture is not sufficiently removed, then manufacturing process remains simple, but moisture reacts with supporting salt to generate HF deteriorating electrolyte solution and active material
Solution Approach 1:
The invention addresses the harmful effect of moisture by transforming the separator's properties through heat treatment and chemical processing. The separator is converted from a moisture-absorbing component to a moisture-resistant barrier, turning a potential source of HF generation into a protective element that prevents moisture from reaching the electrolyte and active materials.
Solution Approach 2:
The treated separator acts as an intermediary barrier between the external environment (source of moisture) and the sensitive battery components (electrolyte solution and active material). By modifying the separator's properties, it mediates the interaction between moisture and battery chemicals, preventing harmful reactions without requiring complex manufacturing controls.
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 approach effectively suppresses moisture-related deterioration, enhancing storage and cycle characteristics of the battery by maintaining low moisture levels within the battery.
Implementation Method 1
a separator having a shrinking ratio of 2% or less by heat treatment at 90 °C for 6 hours
Implementation Method 2
a manufacturing method that includes a heat-drying step at 90 °C or higher to reduce both physically and chemically adsorbed water
Implementation Method 3
shrinking ratio of 2% or less by heat treatment at 90 °C for 6 hours
Data Source
Figure 1~2
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Figure 5
AI summary
The present invention relates to a lithium ion secondary battery comprising an electrode element comprising a positive electrode, a negative electrode and a separator, and an electrolyte solution, wherein the separator has a shrinking ratio of 2% or less by heat treatment at 90 °C for 6 hours, and a content of physically adsorbed water of the electrode element is 2% by mass or less, or a content of chemically adsorbed water in a positive electrode active material layer of the positive electrode is 1% by mass or less.