Solvent-Free Lithium-Ion Cathode Using Electron Beam Curing
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Solution Overview
Problem
The existing Moisture Powder Sheeting method for producing cathodes for lithium-ion secondary batteries uses toxic solvents like N-Methyl-2-Pyrolidone, which can react with active materials, forming resistive layers and decreasing battery performance, and requires high energy consumption for solvent removal.
Innovation Solution
A method involving mixing active and conductive materials with an electron beam curable pre-polymer to create a solvent-free mixture, applying it using a 3-roll mill, polymerizing it with an electron beam, and pressing it onto a metallic foil at room temperature to produce a dense cathode layer without solvent removal, thereby eliminating the need for toxic solvents and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If NMP solvent is used in the MPS method, then the cathode can be formed with low solvent content (15-20% wt), but the toxic solvent reacts with active material forming resistive layers that decrease battery performance
Solution Approach 1:
The invention extracts and removes the harmful NMP solvent from the cathode formation process entirely, replacing it with a solvent-free slurry composition. This eliminates the toxic reaction between NMP and active material while maintaining the cathode formation capability through alternative binding mechanisms in the solvent-free system.
Solution Approach 2:
The invention changes the fundamental parameter of solvent content from 15-20% wt (NMP-based) to 0% solvent (solvent-free). This parameter change transforms the system from a solvent-dependent slurry to a solvent-free composite material system, eliminating harmful chemical reactions while maintaining processability through mechanical mixing and rolling.
2Object-affected harmful factors
If solvent removal is performed to eliminate toxic NMP, then battery performance improves, but energy consumption increases due to high temperature processing requirements
Solution Approach 1:
The invention extracts the solvent removal step entirely from the process by never introducing solvent in the first place. The solvent-free slurry composition is directly formed and processed without requiring energy-intensive drying or evaporation steps, thus eliminating both the harmful solvent and the energy consumption associated with its removal.
Solution Approach 2:
The invention performs preliminary action by preparing the solvent-free slurry composition before the cathode formation process, ensuring that no solvent is present to require removal. This preliminary formulation approach prevents the need for subsequent energy-consuming solvent elimination steps.
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 method produces cathodes with reduced IV resistance and eliminates the use of toxic solvents, achieving lower energy consumption and improved performance by increasing the density of the polymer active layer.
Implementation Method 1
polymerizing the pre-polymer with an electron beam so as to obtain a polymerized active layer on the metallic foil
Implementation Method 2
pressing the polymerized active layer on the metallic foil at room temperature so as to increase the density of the polymer active layer
Data Source
AI summary
Method (100) for making a cathode for secondary battery, including mixing (102) an active material and a conductive material with an electron beam curable pre-polymer so as to obtain a solvent-free mixture made of the active material, the conductive material and the pre-polymer, passing the solvent-free mixture in a Moisture Powder Sheeting device, polymerizing (108) the pre-polymer with an electron beam so as to obtain a polymerized active layer on the metallic foil, pressing (110) the polymerized active layer on the metallic foil at room temperature so as to increase the density of the polymer active layer.A composition for making a cathode for secondary battery, the composition including an active material, a conductive material and an electron beam curable pre-polymer, the composition being solvent-free. A cathode made from the composition and a secondary battery including the cathode.