Cellulose Nanofiber Electrode-Separator Composite for Flexible Batteries
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Solution Overview
Problem
Current lithium-ion secondary batteries face limitations in flexibility due to their standard structure, which leads to issues such as electrode desorption during bending, internal short circuits, and safety concerns like heat generation or explosion, primarily because of the use of binders and separate electrode current collectors.
Innovation Solution
An electrochemical element is developed using an electrode-separator composite with a nanofiber structure, where a cellulose nanofiber separator is combined with an active material and conductive material, eliminating the need for a separate binder and current collector, and formed through a filtration process for enhanced interfacial stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a standard structure with separate electrode current collector and binder is used, then adhesive strength between current collector and active material is improved, but physical flexibility and electronic conductivity deteriorate
Solution Approach 1:
The patent combines the electrode and separator into a single integrated structure where the separator serves as both the physical support and the electrode substrate. The active material is directly formed on the separator without requiring a separate current collector or binder, thus merging multiple components into one unified structure that eliminates the trade-off between adhesive strength and flexibility.
Solution Approach 2:
The invention extracts and removes the binder and separate current collector from the traditional battery structure. By eliminating these components, the patent achieves physical flexibility while maintaining structural integrity through the integrated electrode-separator design where the separator itself provides the necessary support.
2Strength
If a standard structure with binder is used, then adhesive strength is improved, but energy density and electronic conductivity deteriorate
Solution Approach 1:
The patent extracts and eliminates the binder from the electrode structure. By removing the binder, the active material content per unit volume increases, thereby improving energy density. The integrated electrode-separator design provides structural support without requiring additional binder materials that would occupy space and reduce active material quantity.
Solution Approach 2:
The invention merges the structural support function previously provided by the current collector and binder into the separator itself. This integration eliminates the need for separate binder layers, increasing the proportion of active material and improving overall energy density.
3Manufacturing precision
If a separate process is used to prepare positive electrode/separator/negative electrode, then manufacturing precision is improved, but productivity and ease of manufacture deteriorate
Solution Approach 1:
The patent merges the electrode and separator preparation into a single integrated process. The electrode-separator composite is formed in one step where the active material is deposited directly on the separator, eliminating the need for separate assembly processes and improving manufacturing efficiency while maintaining precise interfacial contact.
Solution Approach 2:
The separator serves multiple functions simultaneously: it acts as the physical support structure, the electrode substrate, and the ion-conducting medium. This multi-functionality simplifies the manufacturing process by reducing the number of separate components that need to be assembled, thereby improving productivity.
4Strength
If a metal current collector is used, then structural support is improved, but flexibility and resistance to electrode desorption during bending deteriorate
Solution Approach 1:
The patent extracts and removes the metal current collector from the structure. By eliminating the rigid metal component, the battery achieves flexibility while maintaining structural support through the integrated electrode-separator composite that is inherently resistant to electrode desorption during bending.
Solution Approach 2:
The invention combines the structural support function with the separator and electrode into a unified flexible composite structure. This integrated design provides necessary mechanical support without the rigidity of metal current collectors, enabling flexibility and resistance to electrode desorption during bending.
5Temperature
If a polyolefin separator is used, then heat resistance is improved, but interfacial stability under physical deformation deteriorates
Solution Approach 1:
The patent merges the separator and electrode into an integrated composite structure where the separator is directly coated with active material. This integration eliminates interfacial contact issues between separate components, providing stability under physical deformation while maintaining the heat resistance properties of the polyolefin separator.
Solution Approach 2:
The invention uses a composite electrode-separator structure where the separator material (polyolefin) provides heat resistance and the integrated electrode layer provides structural stability. The composite design ensures interfacial stability under physical deformation by eliminating separate interfaces that could fail during bending or stretching.
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
This approach results in improved mechanical properties, stable battery performance under deformation, reduced risk of ignition or explosion, and higher energy density with enhanced ionic and electronic conductivity.
Implementation Method 1
a cellulose nanofiber separator combined with the electrode
Implementation Method 2
forming a separator combined with an electrode by filtering the electrode mixture on a cellulose nanofiber separator
Data Source
AI summary
The present invention relates to an electrochemical element and a method for producing same, the electrochemical element comprising: electrodes comprising a composite of active material and conductive material having a nanofiber structure; and a cellulose nanofiber separator combined with the electrodes. The electrochemical element according to the present invention obviates the need for separate binder and electrode current collector, has a stable interfacial surface due to the physical union of the separator and electrode, can assure superb mechanical and physical properties, and can maintain stable battery performance even against deformations due to a variety of external impact.