Heat-Resistant Porous Separator for High-Temperature Battery Stability
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Solution Overview
Problem
Large rechargeable batteries face challenges with heat dissipation, leading to internal temperatures exceeding 200°C, causing separator meltdown and short circuits, which can result in thermal explosions, as existing heat-meltable resin separators fail to maintain integrity and adhesion at high temperatures.
Innovation Solution
A separator with a heat-resistant porous layer composed of a crosslinkable and non-crosslinkable binder, including polyvinylidene fluoride-based polymers, applied to a porous substrate, providing enhanced tensile strength and adhesion, preventing fracture even at temperatures above 200°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heat-meltable resin separator is used to provide shutdown properties, then the separator melts at predetermined temperature to block pores and stop reactions, but the separator suffers meltdown at high temperatures (200°C or more) causing electrode contact and short circuit
Solution Approach 1:
The patent uses a composite structure consisting of a heat-meltable resin layer (for shutdown function) and a heat-resistant porous layer (for high-temperature structural support). The heat-resistant layer contains inorganic particles (such as alumina, silica) dispersed in a polymer matrix, creating a composite material that combines the shutdown capability of the heat-meltable resin with the high-temperature stability of the inorganic-reinforced porous structure, preventing both meltdown and maintaining fracture resistance above 200°C
Solution Approach 2:
The heat-resistant porous layer maintains a controlled porous structure that allows ion transport while providing mechanical strength at high temperatures. The porosity is optimized to ensure ionic conductivity during normal operation, while the pore walls are reinforced with inorganic particles to prevent collapse and meltdown when exposed to temperatures of 200°C or higher, thus maintaining fracture resistance
2Temperature
If the internal temperature of the battery is increased to 200°C or more in a few seconds, then the heat-meltable resin separator melts and pores are blocked, but the separator loses adhesion and fractures causing short circuit
Solution Approach 1:
The heat-resistant porous layer is constructed as a composite material incorporating inorganic particles (alumina, silica, or their combinations) within a polymer matrix. This composite structure provides both high-temperature resistance (maintaining integrity at 200°C+) and strong adhesion to electrodes, preventing the separator from fracturing or losing bonding under thermal stress while the heat-meltable layer performs its shutdown function
Solution Approach 2:
The heat-resistant porous layer acts as an intermediary protective layer between the heat-meltable resin separator and the electrodes. When the battery experiences thermal runaway, this intermediate layer maintains its structural integrity and adhesion at high temperatures, preventing direct contact between electrodes while allowing the heat-meltable layer to perform its shutdown function without compromising overall separator 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 separator maintains its form and prevents fracture at high temperatures, ensuring stable battery performance, efficient charge/discharge properties, and improved reliability by enhancing fracture resistance and adhesion, thus avoiding thermal explosions.
Implementation Method 1
the heat resistant porous layer includes a crosslinkable binder and a non-crosslinkable binder
Implementation Method 2
the separator provides shutdown properties, i.e. melts, at a predetermined temperature or more to allow pores to be blocked
Data Source
Figure 1
AI summary
Disclosed herein is a composition for a heat resistant porous layer, a separator including the heat resistant porous layer formed from said composition, and an electrochemical battery including the separator. The composition for the heat resistant porous layer includes: at least one selected from the group consisting of a monomer, oligomer, and polymer represented by Formula 1, and a mixture thereof; at least one selected from the group consisting of a polyvinylidene fluoride (PVdF)-based homopolymer, a polyvinylidene fluoride-hexafluoropropylene-based copolymer, and a mixture thereof; an initiator; and a solvent, wherein a unit originating from hexafluoropropylene is present in an amount of >0 wt% to ≤ 15 wt% based on the total weight of the polyvinylidene fluoride-hexafluoropropylene-based copolymer, and the polyvinylidene fluoride-hexafluoropropylene-based copolymer has a weight average molecular weight of ≥ 600,000 g/mol. Furthermore disclosed herein is a separator comprising a porous substrate and a heat resistant porous layer wherein the heat resistant porous layer comprises polymers of PVdF and/or PVdF-HFP and a crosslinkable binder and the separator has a tensile strength of 50 kgf/cm2 to 350 kgf/cm2, as measured after being left at 200°C for 10 minutes. Furthermore disclosed is an electrochemical battery, comprising: an anode; a cathode; said separator; and an electrolyte.