Dual-Nickel Cathode Layering for High-Temperature Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges with high-temperature characteristics due to side reactions and capacity deterioration, particularly with nickel-based positive electrode active materials, which exhibit low safety and chemical instability when nickel content is high, and poor cycle characteristics when manganese-based materials are used.
Innovation Solution
A multilayer positive electrode structure is implemented, where a first layer with high nickel content (42% or more) is combined with a second layer having lower nickel content (37% or less), with the second layer being 50% or less of the first layer, to minimize side reactions with the electrolyte and maintain energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high nickel content positive electrode active material is used, then energy density and discharge capacity are improved, but high-temperature stability and safety deteriorate due to side reactions with electrolyte
Solution Approach 1:
The patent applies local quality by creating a positive electrode with non-uniform nickel content distribution. The nickel content is higher in the lower layer (closer to current collector) and lower in the upper layer (closer to electrolyte), allowing different regions to serve different functions: high nickel regions provide energy density while low nickel regions provide high-temperature stability
Solution Approach 2:
The patent segments the positive electrode into multiple layers with different nickel content compositions. This segmentation allows the electrode to simultaneously contain high-nickel regions for energy density and low-nickel regions for thermal stability, resolving the contradiction between discharge capacity and high-temperature stability
2Use of energy by moving object
If nickel content is increased to improve energy density, then capacity increases, but chemical stability and safety decrease
Solution Approach 1:
Different regions of the positive electrode have different nickel content to balance energy density and chemical stability. The lower layer has higher nickel content for energy density while the upper layer has lower nickel content for chemical stability and safety
Solution Approach 2:
The positive electrode is constructed as a composite structure with multiple layers containing different nickel-based active materials with varying nickel contents, combining the advantages of high-energy-density materials with the stability of low-nickel materials
3Ease of manufacture
If uniform mixing of high and low nickel content materials is used, then manufacturing is simplified, but side reactions with electrolyte cannot be suppressed
Solution Approach 1:
Instead of uniform mixing, the patent segments the electrode into distinct layers with different nickel content compositions. This segmentation ensures that low-nickel material is positioned in the upper layer where it can effectively suppress side reactions with electrolyte, while maintaining manufacturing feasibility through a layered coating process
Data Source
AI summary
A secondary battery comprising a positive electrode current collector, a first positive electrode mixture layer disposed on the positive electrode current collector and including a first positive electrode active material and a binder, and a second positive electrode mixture layer disposed on the first positive electrode mixture layer and including a second positive electrode active material and a binder. A nickel content of the second positive electrode active material is 80% by weight or less of a nickel content of the first positive electrode active material. By providing a secondary battery including a positive electrode of a multi-layer structure that includes positive electrode active materials having different contents of nickel, a secondary battery capable of improving high-temperature characteristics while maintaining energy density may be provided.