Composite Battery Separator for Transition Metal Ion Capture
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Solution Overview
Problem
Lithium-ion batteries face challenges with unstable cathode active material structures under high voltage, leading to transition metal ion release and potential lithium dendrite formation, which can pierce the separator, compromising safety and stability.
Innovation Solution
A composite separator is designed with a cation exchange layer grafted with alkali-metal-sulfonic or alkali-metal-phosphoric functional groups, combined with inorganic particles and polymer binders, to capture transition metal ions and reduce electrical conductivity, thereby enhancing electrochemical stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If higher voltage is applied to cathode active material to increase energy density, then battery capacity is improved, but cathode structure becomes unstable and releases transition metal ions
Solution Approach 1:
A cation exchange layer is introduced as an intermediary between the cathode and anode. This layer captures transition metal ions released from the cathode through ion exchange mechanisms, preventing them from reaching the anode and forming dendrites. The layer acts as a mediator that allows ion transport while filtering harmful metal ions, thus resolving the contradiction between high voltage operation and structural stability.
Solution Approach 2:
The harmful transition metal ions released from the cathode at high voltage are converted into a beneficial effect by using them to populate the cation exchange layer. These ions are captured and stored in the exchange layer, preventing their harmful accumulation on the anode while maintaining charge balance in the battery system.
2Ease of operation
If transition metal ions are not captured, then battery operation is simple, but lithium dendrites form on anode and pierce separator
Solution Approach 1:
The cation exchange layer serves as a protective intermediary between the electrolyte and anode, selectively capturing transition metal ions before they can reach the anode surface. This mediator prevents dendrite formation without complicating the overall battery operation, as the layer integrates seamlessly into the existing cell structure.
Solution Approach 2:
The cation exchange layer is designed with a porous structure that allows efficient ion transport while providing sufficient surface area for ion capture. The porous morphology enables the layer to maintain low resistance to ion flow while effectively trapping transition metal ions, thus protecting separator integrity without impeding battery operation.
3Device complexity
If conventional separator is used, then device structure is simple, but electrochemical stability is insufficient under high voltage
Solution Approach 1:
The separator is enhanced by combining a base separator material with a cation exchange layer, creating a composite structure. This composite design integrates the mechanical strength and porosity of the base separator with the ion-capturing functionality of the exchange layer, achieving superior electrochemical stability under high voltage conditions while maintaining reasonable structural simplicity.
Solution Approach 2:
The separator's functional properties are changed by introducing the cation exchange layer with specific ion exchange capacity and porosity parameters. This parameter modification enables the separator to maintain stability at higher voltages by dynamically adjusting ion transport and capture based on operational conditions.
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 composite separator effectively increases transition metal capture rates, reduces self-discharge rates, and improves cycling performance and safety of lithium-ion batteries by preventing dendrite formation and maintaining electrochemical stability.
Implementation Method 1
a cation exchange layer, wherein the cation exchange layer comprises a second porous substrate grafted with a functional group... to capture transition metal ions
Data Source
AI summary
The present application relates to a composite separator, and an electrochemical device and an electronic device comprising the same. Some embodiments of the present application provide a composite separator, comprising: a first porous substrate and a cation exchange layer, wherein the cation exchange layer comprises a second porous substrate grafted with a functional group, wherein the functional group is selected from the group consisting of an alkali-metal-sulfonic functional group, an alkali-metal-phosphoric functional group and a combination thereof. The composite separator of the present application can effectively capture the transition metal ions eluted from a cathode through the cation exchange layer, thereby reducing the deposition of the transition metal ions on an anode and the self-discharge rate of the electrochemical device. Therefore, the electrochemical stability and cycling performance of the electrochemical device are enhanced, and the safety of the electrochemical device is also significantly improved.