Positive Electrode Layer Gradient for Battery Rate and Cycle Life
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in improving discharge rate characteristics and charge-discharge cycle characteristics, as existing positive electrodes do not effectively balance dibutyl phthalate oil absorption across their layers.
Innovation Solution
A positive electrode with a current collector and a mixture layer divided into two parts, where the lower half region has a dibutyl phthalate oil absorption of 11-19 mL/100 g and the upper half region has a dibutyl phthalate oil absorption of 15-23 mL/100 g, enhancing electrolyte permeability and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the positive electrode active material layer uses a uniform dibutyl phthalate oil absorption throughout, then the manufacturing process is simple, but the discharge rate characteristics and charge-discharge cycle characteristics are poor
Solution Approach 1:
The positive electrode active material layer is divided into two distinct layers: a first layer with lower dibutyl phthalate oil absorption (5-15 mL/100g) and a second layer with higher dibutyl phthalate oil absorption (15-30 mL/100g). This segmentation allows each layer to perform its specific function optimally, improving charge-discharge cycle characteristics while maintaining manageable manufacturing complexity.
Solution Approach 2:
Different regions of the positive electrode active material layer are assigned different dibutyl phthalate oil absorption values tailored to their specific functions. The first layer (closer to current collector) has lower oil absorption for stable lithium ion insertion/extraction, while the second layer (closer to electrolyte) has higher oil absorption for enhanced electrolyte retention and discharge rate performance.
2Stability of the object's composition
If the first layer has low dibutyl phthalate oil absorption, then lithium ion insertion and extraction is stable, but electrolyte retention is insufficient
Solution Approach 1:
The electrode layer is segmented into two functional zones: the first layer with low dibutyl phthalate oil absorption (5-15 mL/100g) that ensures stable lithium ion insertion and extraction, and the second layer with high dibutyl phthalate oil absorption (15-30 mL/100g) that provides sufficient electrolyte retention. This segmentation resolves the contradiction by assigning different properties to different regions.
Solution Approach 2:
The first layer near the current collector is designed with low oil absorption to maintain structural stability and lithium ion insertion/extraction stability, while the second layer near the electrolyte interface is designed with high oil absorption to maximize electrolyte retention and discharge rate characteristics.
3Quantity of substance
If the second layer has high dibutyl phthalate oil absorption, then electrolyte retention is enhanced, but the discharge rate characteristics are limited
Solution Approach 1:
The second layer with high dibutyl phthalate oil absorption (15-30 mL/100g) is positioned strategically near the electrolyte interface where it maximizes electrolyte retention and wetting, while the first layer with low oil absorption (5-15 mL/100g) is positioned near the current collector where it facilitates rapid lithium ion insertion and extraction, thus achieving both high electrolyte retention and excellent discharge rate characteristics.
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 configuration improves discharge rate and charge-discharge cycle characteristics by optimizing electrolyte diffusion and retention, leading to enhanced battery performance.
Implementation Method 1
when the positive electrode mixture layer is divided into two equal parts in a thickness direction of the positive electrode mixture layer, a dibutyl phthalate oil absorption of a positive electrode active material contained in a lower half region on a side of the positive electrode current collector is smaller than a dibutyl phthalate oil absorption of the positive electrode active material contained in an upper half region on a surface side of the positive electrode mixture layer
Data Source
AI summary
A positive electrode for a non-aqueous electrolyte secondary battery comprises a positive electrode mixture layer includes a positive electrode active substance. The quantity of dibutyl phthalate oil absorbed by the positive electrode active substance included in a lower-half region of the positive electrode mixture layer, when the positive electrode mixture layer is divided in the thickness direction into two equal parts, is less than the quantity of dibutyl phthalate oil absorbed by the positive electrode active substance included in an upper-half region; the quantity of dibutyl phthalate oil absorbed by the positive electrode active substance included in the lower-half region is at least 11 mL/100 g and no more than 19 mL/100 g; and the quantity of dibutyl phthalate oil absorbed by the positive electrode active substance included in the upper-half region is at least 15 mL/100 g and no more than 23 mL/100 g.