Polyurethane Binder for Lithium Battery Electrode Stability
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Solution Overview
Problem
Conventional binders used in electrochemical cells, such as lithium batteries, face challenges in maintaining high efficiency discharge characteristics due to weak binding forces, leading to electrode degradation and increased failure rates, especially when lithium metal anodes form needle-shaped dendrites causing internal short-circuits and instability.
Innovation Solution
The use of a poly(dialkylene ester) thermoplastic polyurethane composition as a binder in electrochemical cells, optionally combined with conducting agents and organic solvents, to enhance the binding force and stability of electrodes, thereby improving charge/discharge efficiency and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional rubber-based polymer material is used as a binder, then the binding force between the binder and core material is weak, but adding a large amount of binder to enhance binding force causes the surface of carbonaceous material to be coated, thereby hindering intercalation and deintercalation of lithium ions and deteriorating discharge characteristics
Solution Approach 1:
The patent changes the chemical and physical parameters of the binder by using poly(dialkylene ester) thermoplastic polyurethane instead of conventional rubber-based polymers. This new binder composition has different adhesive properties, molecular weight, and glass transition temperature that enable strong binding force at lower concentrations without coating the carbonaceous material surface, thus maintaining lithium ion intercalation and deintercalation efficiency.
Solution Approach 2:
The patent employs a composite binder system comprising poly(dialkylene ester) thermoplastic polyurethane in combination with conducting agents and organic solvents. This composite material approach creates a synergistic effect where the polyurethane provides strong adhesion while the conducting agents maintain electrical conductivity and the organic solvent facilitates proper dispersion, achieving both strong binding force and good discharge characteristics simultaneously.
2Reliability
If a small amount of binder is used to maintain discharge characteristics, then the sheet-type electrode cannot be easily manufactured because material separates from the core material, and the failure ratio increases
Solution Approach 1:
The patent modifies the binder parameters by selecting poly(dialkylene ester) thermoplastic polyurethane with specific molecular weight and glass transition temperature ranges. These parameter changes enable the binder to maintain effective adhesion at low concentrations, ensuring electrode material stays bound to the core material during manufacturing processes while preserving high discharge characteristics.
3Use of energy by moving object
If metal lithium is used as an anode active material, then lithium ions can be intercalated and deintercalated, but needle-shaped lithium dendrites grow on the surface causing internal short-circuits and instability
Solution Approach 1:
The patent introduces poly(dialkylene ester) thermoplastic polyurethane as an intermediary material between the lithium metal anode and the electrolyte. This binder forms a stable interface layer that mediates the interaction between lithium ions and the anode structure, preventing direct contact and dendrite formation while maintaining efficient lithium ion transport, thus resolving the contradiction between charge/discharge efficiency and stability.
Data Source
AI summary
The invention relates to an electrode binder composition, an electrode made using the described binder composition, and an electrochemical cell made using the described electrode, where the all of these materials are made using a composition of a poly(dialkylene ester) thermoplastic polyurethane composition. The electrode is made using the described thermoplastic polyurethane and an electrode active material. The electrochemical cells can be made using the described electrodes and also using (i) membranes and/or separators made using the described poly(dialkylene ester) thermoplastic polyurethane composition; (ii) an electrolyte system based on the described poly(dialkylene ester) thermoplastic polyurethane composition; or (iii) a combination thereof.