Cathode Active Material Gradient Doping for Longer Battery Cycling
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in improving capacity, cycle performance, charge and discharge characteristics, reliability, safety, and cost, with existing positive electrode active materials experiencing deterioration due to charge and discharge cycles.
Innovation Solution
A positive electrode active material is developed containing lithium, a transition metal, oxygen, and an additive element, with a concentration gradient of the additive element from the inner portion to the surface, and incorporating graphene or a graphene compound to enhance stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive electrode active materials are used to increase capacity and output, then the battery performance improves, but the materials undergo deterioration during charge and discharge cycles
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of the additive element within the positive electrode active material particles. The additive element concentration increases from the inner portion toward the surface, forming a gradient distribution. This localized variation in composition allows the surface regions to provide protective effects during charge/discharge cycles while the inner portions maintain the electroactive properties, thereby improving cycle performance without sacrificing material stability
Solution Approach 2:
The patent employs composite materials by combining the positive electrode active material with an additive element to form a composite structure. This composite positive electrode active material integrates multiple functional components: the base active material provides electrochemical activity while the additive element forms a gradient distribution that enhances structural stability and reduces deterioration during cycling, achieving both high capacity and improved reliability
2Stability of the object's composition
If the additive element concentration is increased uniformly throughout the material, then stability improves, but capacity and charge-discharge characteristics deteriorate
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through a concentration gradient rather than uniform distribution. The additive element concentration varies spatially, being lower in the inner portions (preserving charge-discharge characteristics) and higher in the surface regions (providing stability). This gradient distribution allows different regions to fulfill different functional requirements simultaneously, achieving both material stability and good charge-discharge characteristics
Solution Approach 2:
The patent applies parameter changes by controlling the concentration parameter of the additive element as a function of position within the particle. Rather than maintaining a constant concentration, the additive element concentration parameter varies continuously from the center to the surface, creating an optimized profile that balances stability and electrochemical performance
Data Source
AI summary
A positive electrode active material that hardly deteriorates is provided. Alternatively, a secondary battery that hardly deteriorates is provided. Alternatively, a highly safe secondary battery is provided. The secondary battery includes a positive electrode; the positive electrode includes a positive electrode active material; the positive electrode active material contains lithium, a transition metal, oxygen, and an additive element; the positive electrode active material includes a plurality of primary particles; at least some of the plurality of primary particles adhere to each other to form a secondary particle; the primary particles each include a surface portion and an inner portion; and a concentration of the additive element in the surface or the surface portion of the primary particle is higher than a concentration of the additive element in the inner portion.