Layered Positive Electrode Composition for High-Ni Battery Stability
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Solution Overview
Problem
Lithium-containing composite oxides with high Ni content generate excessive heat and suffer from reduced battery capacity due to repeated charging and discharging, especially in high-temperature environments, with existing solutions failing to address thermal stability and cycle characteristics effectively.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a positive electrode with a laminate structure, where the first layer contains a lithium transition metal composite oxide with a higher Ni content and the second layer has a lower Ni content, optimized by specific ratios of metal elements, enhancing thermal stability and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium-containing composite oxide with high Ni content is used as positive electrode active material, then battery capacity increases, but battery temperature increases at times of abnormality
Solution Approach 1:
The positive electrode active material is divided into two distinct layers: a first layer with high Ni content (0.90≤b≤0.95) for high capacity, and a second layer with lower Ni content (0.80≤g≤0.90) for thermal stability. This segmentation allows each layer to perform its specialized function, resolving the contradiction between capacity and temperature control.
Solution Approach 2:
Different regions of the positive electrode are assigned different Ni contents based on their functional requirements. The first layer (higher Ni content) provides high capacity where needed, while the second layer (lower Ni content) provides thermal stability at the electrode surface, creating local quality variations that resolve the global contradiction.
2Quantity of substance
If a lithium-containing composite oxide with high Ni content is used, then battery capacity increases, but the layered crystal structure is easily broken during charging
Solution Approach 1:
The positive electrode is segmented into two layers with different compositions. The first layer (high Ni content) provides capacity, while the second layer (lower Ni content with higher M1 and M3 content) protects the crystal structure during charging/discharging cycles, resolving the contradiction between capacity and cycle reliability.
Solution Approach 2:
The positive electrode uses a composite structure of two different lithium-containing composite oxides with complementary properties. The combination of high-Ni material (for capacity) and lower-Ni material with higher stabilizing elements (for structure integrity) creates a composite that achieves both high capacity and good cycle characteristics.
3Quantity of substance
If a lithium-containing composite oxide with high Ni content is used in high-temperature environment, then battery capacity increases initially, but capacity decreases due to repeated charging and discharging
Solution Approach 1:
The positive electrode is divided into two layers: the first layer (high Ni content) provides initial high capacity, while the second layer (lower Ni content with higher M1/M3 content) maintains structural stability during repeated charging/discharging in high-temperature environments, ensuring long-term durability.
Solution Approach 2:
The invention changes the compositional parameters of the positive electrode by creating a gradient in Ni content and stabilizing element content across two layers. This parameter variation allows the electrode to maintain both high initial capacity and long-term stability in high-temperature conditions.
Data Source
AI summary
A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure is provided with a positive electrode, a negative electrode, a separator that separates the positive electrode and the negative electrode from each other, and a nonaqueous electrolyte. With respect to this nonaqueous electrolyte secondary battery, the positive electrode comprises a positive electrode collector, a first positive electrode mixture layer that is formed on the surface of the positive electrode collector, and a second positive electrode mixture layer that is formed on the surface of the first positive electrode mixture layer; the first positive electrode mixture layer contains a first positive electrode active material; the second positive electrode mixture layer contains a second positive electrode active material; and the Ni content ratio in the second positive electrode active material is lower than the Ni content ratio in the first positive electrode active material.