Dual-Layer Positive Electrode for High-Density Li-Ion Battery Life
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Solution Overview
Problem
Lithium ion secondary batteries with improved energy density require a long life span.
Innovation Solution
A positive electrode for lithium ion secondary batteries is designed with a dual-layer structure, where the first active material layer contains a lithium-containing composite oxide with a higher nickel molar fraction and the second active material layer contains a lithium-containing composite oxide with a lower nickel molar fraction, enhancing both energy density and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a positive electrode active material layer with high nickel content is used to improve energy density, then the energy density increases, but the battery life decreases due to formation of inert nickel oxide layers
Solution Approach 1:
The positive electrode active material layer is divided into two distinct layers: a first layer with high nickel content (0.6-0.95 molar fraction) for high energy density, and a second layer with low nickel content (0.01-0.3 molar fraction) for long life. This segmentation allows each layer to perform its specialized function without compromise.
Solution Approach 2:
Different regions of the positive electrode active material layer have different compositions tailored to their specific functions. The first layer near the current collector has high nickel content optimized for energy storage, while the second layer at the electrolyte interface has low nickel content optimized for stability and resistance to inert layer formation.
2Quantity of substance
If the nickel content is increased to achieve high capacity, then the energy density improves, but the cycle durability and storage durability deteriorate
Solution Approach 1:
The electrode is segmented into two layers with different nickel contents. The first layer provides high capacity through high nickel content, while the second layer ensures reliability by having low nickel content that resists degradation during cycling and storage.
Solution Approach 2:
The second layer with low nickel content acts as an intermediary protective layer between the high-nickel first layer and the electrolyte. This intermediary layer prevents direct exposure of the high-nickel material to the electrolyte, thereby improving cycle and storage durability while maintaining high capacity.
Data Source
AI summary
A positive electrode for the lithium ion secondary battery includes a positive electrode current collector, and a positive electrode active material layer laminated thereon. The positive electrode active material layer includes a positive electrode first active material layer laminated on the positive electrode current collector, and a positive electrode second active material layer laminated on the positive electrode first active material layer, the positive electrode first active material layer includes a positive electrode first active material containing a lithium-containing composite oxide containing Li and Ni, the positive electrode second active material layer includes a positive electrode second active material containing a lithium-containing composite oxide containing Li and Ni, and a molar fraction of Ni in the positive electrode second active material of the positive electrode second active material layer is smaller than that of Ni in the positive electrode first active material of the positive electrode first active material layer.