Ferroelectric Separator Film for Higher Li-Ion Conductivity
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Solution Overview
Problem
Insufficient ionic conductivity in lithium ion battery separators leads to increased internal resistance, affecting the electrochemical performance of the battery.
Innovation Solution
A separator comprising multiple layers of microporous films with an intermediate layer containing a ferroelectric, such as barium titanate, lead titanate, or bismuth titanate, to enhance ionic conductivity by utilizing the ferroelectric's built-in electric field to accelerate ion passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional microporous film separator is used, then the mechanical strength is sufficient, but the ionic conductivity is insufficient leading to increased internal resistance
Solution Approach 1:
The patent applies parameter changes by introducing a ferroelectric coating layer on the microporous film separator. The ferroelectric material undergoes phase transition at the Curie temperature, changing its dielectric constant and polarization state. This parameter change creates an internal electric field that enhances ion transport through the separator, thereby improving ionic conductivity while maintaining mechanical integrity. The controlled phase transition allows dynamic adjustment of ionic conductivity based on temperature conditions.
Solution Approach 2:
The patent employs composite materials by combining the microporous film separator with a ferroelectric coating layer. The composite structure integrates the mechanical strength of the microporous film with the electroactive properties of the ferroelectric material. This composite design enables the separator to simultaneously provide structural support and enhance ion transport through the ferroelectric-induced internal electric field, resolving the contradiction between mechanical strength and ionic conductivity.
2Strength
If the separator thickness is increased to improve mechanical strength, then the puncturing resistance improves, but the ionic conductivity decreases due to longer ion path
Solution Approach 1:
The patent uses parameter changes by introducing a ferroelectric coating layer that generates an internal electric field through phase transition. This internal electric field acts as a driving force for ion transport, effectively reducing the energy barrier for ions to traverse the separator thickness. As a result, even thicker separators can maintain high ionic conductivity because the ferroelectric effect compensates for the increased path length, allowing simultaneous improvement of puncturing resistance and maintenance of ionic conductivity.
Solution Approach 2:
The patent applies mechanics substitution by replacing the purely mechanical ion transport mechanism with an electroactive mechanism. Instead of relying solely on concentration gradients and thermal motion to drive ions through the separator, the ferroelectric coating layer introduces an internal electric field that actively propels ions across the separator. This substitution of the driving mechanism allows the separator to be thicker for improved puncturing resistance without sacrificing ionic conductivity, as the electroactive force compensates for the increased mechanical barrier.
3Reliability
If a ferroelectric coating layer is added to enhance ionic conductivity, then the electrochemical performance improves, but the device complexity increases
Solution Approach 1:
The patent applies porous materials by using a microporous film as the base separator structure. The porous structure provides inherent ion transport channels that maintain good ionic conductivity. When combined with the ferroelectric coating layer, the porous structure allows the internal electric field to effectively penetrate and act on ions throughout the separator thickness. This porous design enables enhanced electrochemical performance without requiring a completely new separator architecture, thus limiting the increase in device complexity.
Solution Approach 2:
The patent uses an intermediary approach by introducing a thin ferroelectric coating layer on the microporous film separator. This coating layer acts as an intermediary that mediates between the electrolyte and the separator bulk, generating an internal electric field that enhances ion transport. The coating layer is thin enough to minimize added complexity while providing sufficient ferroelectric effect to improve electrochemical performance. This intermediary design allows the separator to maintain its original microporous structure for mechanical support while adding electroactive functionality through the coating.
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 design improves mechanical strength, reduces puncturing risk, and significantly enhances ionic conductivity, thereby optimizing battery performance.
Implementation Method 1
the intermediate layer includes a ferroelectric... utilizing the ferroelectric's built-in electric field to accelerate ion passage
Implementation Method 2
the ferroelectric's built-in electric field
Implementation Method 3
the separator allows ions in the electrolytic solution to pass through
Data Source
AI summary
A separator film comprises a plurality of layers of microporous films, wherein an intermediate layer is provided between at least two layers of microporous films arranged to be adjacent to each other, and the intermediate layer includes a ferroelectric. In the solution of the present application, the separator film is configured to comprise a plurality of layers of microporous films, and an intermediate layer including a ferroelectric is provided between at least two layers of microporous films arranged to be adjacent to each other. Since the ferroelectric has a spontaneously polarized built-in electric field, which is equivalent to establishing an ion accelerator on an intermediate layer of the separator film, ions are accelerated under the action of the electric field when passing through the intermediate layer of the separator film.