PVDF Porous Insulating Layer for Battery Thermal Runaway
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Solution Overview
Problem
Lithium ion secondary batteries lack effective heat generation suppression during internal short-circuits, despite having porous insulating films to prevent active material fallout and internal short-circuits, as existing methods do not clearly disclose heat generation suppression effects in tests like nailing, crushing, or overcharging.
Innovation Solution
A lithium ion secondary battery with a porous insulating layer formed between the electrode and separator, using a binding material containing polyvinylidene fluoride (PVDF) and a melting point lowering agent, such as a copolymer of vinylidene fluoride and another fluorine-containing or oxygen-containing monomer, which lowers the melting point to inhibit lithium ion permeation and promote gas generation at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous protective film is formed on the electrode surface to prevent active material fallout, then manufacturing reliability is improved, but heat generation suppression capability during internal short-circuit is insufficient
Solution Approach 1:
The patent applies local quality by creating a porous insulating layer with specific local properties (porosity, melting point) at the interface between the electrode and separator. This layer has different characteristics from both the electrode and separator, providing localized heat generation suppression and active material fixation functions exactly where needed during internal short-circuit events.
Solution Approach 2:
The patent uses composite materials by combining the porous insulating layer (made from PVDF and inorganic filler) with the electrode and separator. This composite structure integrates multiple functions: the porous insulating layer provides both mechanical support for active material and thermal protection through its melting behavior, while the separator provides electrical isolation. The composite system achieves both manufacturing reliability and heat generation suppression.
2Reliability
If a porous insulating film is formed to prevent internal short-circuit, then safety is improved, but heat generation suppression effect is not clearly disclosed
Solution Approach 1:
The patent applies phase transitions by utilizing the melting behavior of the porous insulating layer at elevated temperatures. When the battery experiences internal short-circuit and temperature rises, the PVDF-based porous insulating layer melts (phase transition from solid to liquid), causing pore closure and blocking lithium ion transport. This phase change mechanism provides automatic thermal protection without requiring additional control systems.
Solution Approach 2:
The patent converts the harmful effect of heat generation during internal short-circuit into a beneficial protective mechanism. The heat that would normally accelerate thermal runaway instead triggers the melting of the porous insulating layer, which then blocks ion transport and suppresses further heat generation. The harmful thermal energy activates the protective function of the porous insulating layer.
3Object-affected harmful factors
If a porous insulating layer with melting point lowering agent is used, then heat generation suppression is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the porous insulating layer: active material fixation, ion transport barrier, and thermal protection through melting. By combining these functions into a single layer rather than using separate components, the patent achieves effective heat generation suppression without proportionally increasing device complexity. The porous insulating layer integrates structural and protective functions that would otherwise require multiple separate elements.
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 porous insulating layer effectively suppresses heat generation during internal short-circuits by melting and inhibiting lithium ion permeation, while promoting gas generation to activate a pressure detection type current interrupt device, enhancing safety and reliability.
Implementation Method 1
The melting point lowering agent lowers one or more of a melting start temperature or a melting peak temperature of the binding material, which is measured by differential scanning calorimetry
Implementation Method 2
The porous insulating layer is formed of a binding material containing polyvinylidene fluoride (PVDF) and a melting point lowering agent
Data Source
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Figure 2
AI summary
A porous insulating layer is formed between an electrode and a separator, such that the porous insulating layer is melted when the temperature of a battery rises and permeation of lithium ions is inhibited, which suppresses heat generation at the time of an internal short-circuit of the battery. According to the invention, there is provided a lithium ion secondary battery including: a current collector; an electrode including a cathode or an anode that is provided on at least one surface of the current collector; a separator that separates the cathode and the anode from each other; a porous insulating layer that is formed between the electrode and the separator; and a non-aqueous electrolyte, in which the porous insulating layer is formed of a binding material containing polyvinylidene fluoride (PVDF) and a melting point lowering agent, and in which the melting point lowering agent lowers one or more of a melting start temperature or a melting peak temperature of the binding material, which is measured by differential scanning calorimetry under coexistence with the non-aqueous electrolyte, as compared to a case of using only polyvinylidene fluoride.