Lithium Battery Separator Layers for Heat Stability and Electrode Bonding
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Solution Overview
Problem
Existing separators for rechargeable lithium batteries lack sufficient heat resistance and adhesive force, particularly at high temperatures, leading to potential ignition and thermal runaway issues.
Innovation Solution
A separator comprising a porous substrate with a heat-resistant layer made from a binder and inorganic particles, and an adhesive layer with a specific copolymer composition, enhancing both heat resistance and adhesive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional separator is used, then the battery can operate, but the separator lacks sufficient heat resistance and may shrink or lose shape at high temperatures, leading to safety issues
Solution Approach 1:
The separator is constructed as a composite material consisting of a polyolefin base layer combined with a heat-resistant coating layer containing inorganic particles (such as alumina, silica, or boehmite) and binder resin. This composite structure provides both the functional properties of the base separator and the thermal stability of the inorganic-containing coating, preventing shrinkage and maintaining shape at high temperatures up to 150°C or higher.
2Temperature
If the separator focuses on heat resistance, then thermal stability improves, but the adhesive force between the separator and electrode plate decreases
Solution Approach 1:
The separator employs local quality differentiation through its multi-layer structure: the base layer provides heat resistance, while the coating layer contains functional inorganic particles and binders that provide both thermal stability and adhesive properties. The coating layer is applied only where needed on the separator surface, creating different functional zones that simultaneously achieve heat resistance and strong adhesion to electrode plates without requiring high-temperature/pressure processes.
3Quantity of substance
If high nickel-based positive electrode active materials are used to increase capacity, then battery capacity and output improve, but gas generation increases at high temperatures, leading to lithium salt precipitation and pore blocking
Solution Approach 1:
The invention converts the harmful effect of gas generation during high-temperature operation into a beneficial outcome by using the heat-resistant separator to contain and manage the gas. The separator's enhanced thermal stability prevents pore collapse and maintains structural integrity even when gas is generated from high nickel-based electrodes, thereby preventing lithium salt precipitation and pore blocking that would otherwise occur. The separator effectively transforms the thermal stress environment into a controlled condition that maintains battery safety.
4Strength
If high temperature/high pressure processes are used to improve adhesive force, then bonding strength increases, but battery types that cannot withstand such processes cannot be manufactured
Solution Approach 1:
The invention changes the process parameters by using a coating formulation that cures or bonds at low temperature and low pressure. The coating layer contains binder resin and inorganic particles that form strong adhesive bonds without requiring extreme conditions. This parameter change enables the separator to achieve excellent adhesive force suitable for various battery types including those that cannot withstand high temperature/pressure manufacturing processes, thereby improving versatility and adaptability across different battery applications.
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 proposed separator achieves ultra-high heat resistance and improved adhesive force, maintaining its shape and suppressing lithium salt precipitation at high temperatures, thereby enhancing battery safety and reliability.
Implementation Method 1
the separator is required to have ultra-high heat resistance and high adhesive force to the electrode plate
Implementation Method 2
an adhesive layer on the heat resistant layer, wherein the heat resistant layer includes a first binder and inorganic particles
Data Source
AI summary
Disclosed are a separator for a rechargeable lithium battery, and a rechargeable lithium battery including the same, the separator for a rechargeable lithium battery including a porous substrate; a heat resistant layer on at least one surface of the porous substrate; and an adhesive layer on the heat resistant layer, wherein the heat resistant layer includes a first binder and inorganic particles, the first binder includes at least one selected from polyacrylate, polyacrylic acid, polyacrylonitrile, polyvinyl alcohol, polysulfonic acid, polyacrylamide, polyamide, polyurea, polyurethane, and a copolymer thereof, the adhesive layer includes a second binder, the second binder includes a copolymer including a first unit derived from a vinyl aromatic monomer, a second unit derived from an alkyl acrylate, and a third unit derived from a phosphonate-based monomer.