Lithium Battery Cathode Gradient and Nitrile Electrolyte
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Solution Overview
Problem
Lithium secondary batteries face challenges with thermal instability and reduced lifespan due to metal component desorption from the cathode during high-temperature storage, especially when fully charged, and existing core-shell structured cathode active materials do not adequately address these issues.
Innovation Solution
A lithium secondary battery design featuring a cathode active material with a concentration gradient of metals between the core and surface parts, combined with a non-aqueous electrolyte containing a lithium salt and a polyfunctional nitrile compound, which enhances high-temperature storage and lifespan properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium transition metal oxide or composite oxide is used as cathode active material, then battery capacity is improved, but metal component desorption occurs during high-temperature storage causing thermal instability
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of metal elements within the cathode active material particles. The core region has a different metal composition than the surface region, with the surface having reduced metal content to prevent desorption while the core maintains high capacity. This spatial variation in composition resolves the contradiction between capacity and thermal stability.
Solution Approach 2:
The patent uses composite materials by combining multiple metal elements (Ni, Co, Mn) in a specific concentration gradient distribution within the cathode active material. This composite structure with varying local compositions allows the material to simultaneously achieve high capacity from Ni-rich core and thermal stability from Mn-rich surface, resolving the contradiction between capacity and reliability.
2Use of energy by moving object
If high nickel content is used in cathode active material, then battery capacity is improved, but lifespan is reduced
Solution Approach 1:
The patent applies local quality by concentrating high nickel content in the core region of cathode particles while reducing nickel content at the surface. This spatial distribution allows the bulk material to provide high capacity from Ni while the Ni-poor surface protects against degradation during cycling, thus extending lifespan. The local composition optimization resolves the contradiction between capacity and durability.
3Reliability
If core-shell structured cathode active material is used, then thermal stability is improved, but lifespan property shows lack of improvement
Solution Approach 1:
The patent improves upon conventional core-shell structures by implementing a continuous concentration gradient rather than a sharp interface. The metal composition transitions gradually from core to surface, which reduces internal stress and prevents cracking during cycling, thereby improving lifespan while maintaining thermal stability. This gradient structure resolves the limitation of traditional core-shell designs.
Solution Approach 2:
The patent applies parameter changes by varying the metal composition parameters continuously from core to surface. The concentration of metal elements changes gradually rather than abruptly, which modifies the structural and chemical properties throughout the particle. This continuous parameter variation enhances both thermal stability and lifespan by reducing mechanical stress and improving electrochemical stability.
Data Source
AI summary
Disclosed is a lithium secondary battery, including a cathode, an anode and a non-aqueous electrolyte, wherein the cathode includes a cathode active material containing lithium-metal oxide of which at least one of metals has a concentration gradient region between a core part and a surface part thereof, and the non-aqueous electrolyte includes a lithium salt, a polyfunctional nitrile compound and an organic solvent, such that the high-temperature storage and lifespan properties may be improved.