Gradient Cathode Particles for Lithium Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high capacity, power, and stability, particularly under harsh temperature conditions, and require improved resistance to penetration-induced failures like short-circuits and explosions.
Innovation Solution
A lithium secondary battery design incorporating a cathode active material with a first particle having a continuous concentration gradient and a second particle with a fixed concentration profile, utilizing lithium metal oxides with specific metal compositions and blending ratios to enhance electrical and mechanical reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a cathode active material with high nickel content is used to improve capacity and power, then the battery achieves higher energy density, but the stability and resistance to penetration-induced failures deteriorate
Solution Approach 1:
The cathode active material is designed with a concentration gradient structure where nickel content varies spatially: high nickel concentration at the core provides high capacity, while lower nickel concentration at the surface layer provides enhanced stability and penetration resistance. This local differentiation of material properties resolves the contradiction between capacity and stability.
Solution Approach 2:
The cathode active material comprises a composite structure with multiple metal elements (nickel, cobalt, manganese) distributed in a concentration gradient pattern. This composite material design allows the battery to simultaneously achieve high capacity from nickel-rich core regions and high stability from metal-diverse surface regions, overcoming the limitations of uniform composition materials.
2Power
If a cathode active material with high nickel content is used to improve power, then the battery achieves higher discharge rate, but the resistance to penetration-induced failures deteriorates
Solution Approach 1:
The concentration gradient structure creates high nickel content regions for power delivery and low nickel content regions for penetration resistance. The surface layer with reduced nickel content and increased cobalt/manganese content forms a protective barrier that resists penetration-induced failures while the nickel-rich core maintains high power output capability.
Solution Approach 2:
A surface layer with lower nickel content and higher cobalt/manganese content is formed beforehand to act as a protective barrier against penetration-induced failures. This pre-formed protective layer cushioning allows the battery to maintain high power from the nickel-rich core while being protected from external penetration damage.
3Ease of manufacture
If a cathode active material with uniform metal composition is used to simplify manufacturing, then the manufacturing process becomes easier, but the electrical and mechanical reliability deteriorates
Solution Approach 1:
The manufacturing process controls the concentration gradient formation by adjusting parameters such as metal precursor ratios, sintering temperature profiles, and atmosphere conditions. These parameter changes enable the formation of a concentration gradient structure during standard manufacturing processes, achieving both manufacturing feasibility and enhanced reliability without requiring complex additional processing steps.
Data Source
AI summary
A lithium secondary battery includes a cathode formed from a cathode active material including a first cathode active material particle and a second cathode active material particle, an anode and a separator interposed between the cathode and the anode. The first cathode active material particle includes a lithium metal oxide including a continuous concentration gradient in at least one region between a central portion and a surface portion. The second cathode active material particle includes a lithium metal oxide including at least two metals except for lithium which have constant concentrations from a central portion to a surface, and the second cathode active material particle includes an excess amount of nickel among the metals except for lithium.