Electrode Assembly Two-Stage Drying for Low Water Content
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Solution Overview
Problem
Current lithium-ion battery manufacturing processes face challenges in achieving high durability and electrochemical performance due to moisture sensitivity, leading to issues like exfoliation of electrode layers and inadequate cycling stability, particularly because existing drying methods result in water content levels that affect battery performance.
Innovation Solution
The development of an electrode assembly for nonaqueous electrolyte secondary batteries with specific composition and structure, including anode and cathode electrode layers with controlled void volume, peeling strength, and binder composition, along with a two-stage drying process to achieve low water content (less than 20 ppm) and improved adhesion between layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If existing drying methods are used to remove solvent from electrode assemblies, then water content is reduced to some extent, but water content remains at levels (hundreds of ppm) that still affect cycling stability and rate capability
Solution Approach 1:
The patent applies parameter changes by implementing a two-stage drying process with different temperature conditions. The first stage uses a temperature of 60-80°C to remove bulk solvent, while the second stage uses a higher temperature of 80-100°C to achieve deeper drying. This progressive temperature increase allows the electrode assembly to reach water content levels below 50 ppm, significantly improving cycling stability and rate capability without causing material degradation.
2Quantity of substance
If existing drying methods are used to remove solvent from electrode assemblies, then some solvent is removed, but exfoliation of electrode layers occurs and sufficient durability cannot be obtained
Solution Approach 1:
The patent applies preliminary action by performing a first drying stage at a lower temperature (60-80°C) before the second drying stage at higher temperature (80-100°C). This preliminary low-temperature drying removes the bulk of the solvent gradually, preventing sudden thermal stress and exfoliation of electrode layers. Only after this gentle preliminary drying is complete does the patent proceed to the higher temperature stage to achieve the target water content, thereby preserving electrode layer integrity and peeling strength.
3Quantity of substance
If stringent moisture-free process is used with humidity controlled at less than 1 percent, then water content in battery is reduced, but significant cost is incurred
Solution Approach 1:
The patent applies the extraction principle by removing the electrode assembly from the expensive controlled humidity environment and instead performing drying in a conventional oven. The method extracts the moisture removal function from the expensive dry room infrastructure and implements it through a simple two-stage thermal drying process. This approach achieves water content below 50 ppm using standard laboratory or production ovens, eliminating the need for costly humidity-controlled manufacturing facilities.
4Quantity of substance
If electrode layer has high void volume (33.0% or more) to retain sufficient electrolyte, then electrolyte retention is improved, but output performance is affected due to decreased energy density
Solution Approach 1:
The patent applies parameter changes by optimizing the void volume of the electrode layer to a specific range of 20-30%, which balances electrolyte retention and energy density. This optimized void volume parameter allows sufficient electrolyte to be retained in the pore spaces while maintaining high enough density to preserve output performance. The patent demonstrates that this intermediate void volume, achieved through controlled drying, provides both adequate electrolyte retention and acceptable power delivery, resolving the trade-off between the two competing requirements.
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 approach results in enhanced durability and electrochemical performance by maintaining low water content and sufficient peeling strength, thereby improving the cycling stability and rate capability of lithium-ion batteries, while also reducing production costs and energy consumption.
Implementation Method 1
heating an electrode assembly under vacuum at a temperature of 30-100° C.
Implementation Method 2
heating an electrode assembly under vacuum at a temperature of 85±5° C.
Data Source
AI summary
Provided herein is electrode assembly for a nonaqueous electrolyte secondary battery, comprising at least one anode, at least one cathode and at least one separator interposed between the at least one anode and at least one cathode, wherein the at least one anode comprises an anode current collector and an anode electrode layer, and the at least one cathode comprises a cathode current collector and a cathode electrode layer, wherein each of the cathode and anode electrode layers independently has a void volume of less than 35%, and wherein each of the at least one cathode and anode independently has a peeling strength of 0.15 N/cm or more.