Composite Binder Positive Electrode for High-Voltage Cycle Life
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density, high capacity, and stable operation at high voltages while maintaining cost-effectiveness and long cycle-life characteristics.
Innovation Solution
A positive electrode comprising a mixture of lithium iron phosphate-based and lithium nickel-based composite oxides as active materials, combined with a specific ratio of fluorine-based binders with and without polar functional groups, enhances adhesion, flexibility, and dispersibility, thereby stabilizing the electrode structure and enabling high-voltage operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-voltage operation is implemented to increase energy density, then capacity and energy density are improved, but cycle-life stability and high-temperature storage characteristics deteriorate
Solution Approach 1:
The patent uses a composite binder system comprising both polar and non-polar fluorine-based binders. The polar fluorine-based binder (e.g., polyacrylic acid) provides strong adhesion to the positive electrode active material at high voltage conditions, while the non-polar fluorine-based binder (e.g., polyvinylidene fluoride) contributes to overall structural stability and flexibility. This composite approach allows the electrode to maintain integrity during high-voltage cycling, thereby improving cycle-life characteristics while preserving high capacity.
2Stability of the object's composition
If binder content is increased to improve adhesion and structural stability, then electrode structure is stabilized, but energy density and capacity are reduced
Solution Approach 1:
The patent optimizes the binder content to a specific range of 1 wt% to 4 wt% based on the total weight of the positive electrode active material layer. This parameter optimization ensures sufficient adhesion and structural stability without excessive binder content that would reduce the proportion of active material. Additionally, the patent adjusts the weight ratio between polar and non-polar fluorine-based binders to achieve the desired balance between adhesion strength and energy density.
3Ease of manufacture
If conventional single-type binders are used to simplify manufacturing, then ease of manufacture is improved, but adhesion strength and flexibility are insufficient
Solution Approach 1:
The patent employs a composite binder system combining polar and non-polar fluorine-based binders in specific weight ratios. The polar fluorine-based binder (e.g., polyacrylic acid) provides strong chemical adhesion to the positive electrode active material, particularly effective at high voltage conditions. The non-polar fluorine-based binder (e.g., polyvinylidene fluoride) contributes to mechanical flexibility and overall bond strength. This composite approach enhances adhesion strength and flexibility while maintaining manufacturing feasibility through established coating processes.
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 proposed positive electrode design increases capacity, ensures long cycle-life characteristics, and improves high-voltage stability, resulting in a rechargeable lithium battery with enhanced energy density and efficiency.
Implementation Method 1
The binder includes a first fluorine-based binder not including a polar functional group and a second fluorine-based binder including a polar functional group
Data Source
AI summary
A positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector and including a positive electrode active material and a binder. The positive electrode active material includes a first positive electrode active material including a lithium iron phosphate-based compound and a second positive electrode active material including a lithium nickel-based composite oxide. The binder includes a first fluorine-based binder not including a polar functional group, and a second fluorine-based binder including a polar functional group. A weight ratio of the first fluorine-based binder to the second fluorine-based binder is in a range of about 1:1 to about 4:1. The rechargeable lithium battery including the positive electrode may exhibit high initial charge/discharge capacity and efficiency even under high voltage driving conditions, and can exhibit long cycle-life characteristics.