Lithium Battery Cathode Segmentation for Crack Reduction
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Solution Overview
Problem
Lithium secondary batteries face issues with crack generation and gas formation due to the intercalation and deintercalation of lithium in lithium metal oxide particles, leading to reduced lifespan and performance, especially at high temperatures, and existing solutions do not adequately address these problems.
Innovation Solution
A cathode for lithium secondary batteries is designed with a combination of first lithium metal oxide particles in a secondary particle shape and second lithium metal oxide particles in a single particle shape, optimized by specific area ratios, nickel concentration, and particle diameters, which are mixed to satisfy specific equations to reduce crack formation and gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal oxide particles are used as cathode active material, then high operational voltage and energy density are achieved, but cracks occur within particles due to intercalation and deintercalation of lithium
Solution Approach 1:
The cathode active material layer is segmented into two distinct particle types: first lithium metal oxide particles with secondary particle shape (aggregated structure) and second lithium metal oxide particles with single particle shape. This segmentation allows each particle type to contribute different properties - the secondary particles provide buffer space for volume changes while single particles maintain structural integrity, thereby resolving the contradiction between energy density and particle integrity during lithium intercalation and deintercalation cycles.
Solution Approach 2:
The invention creates a composite cathode active material layer combining two different lithium metal oxide particle morphologies (secondary particles and single particles) with different nickel concentrations. This composite structure leverages the advantages of both particle types - the aggregated secondary particles accommodate mechanical stress from lithium insertion/extraction while the single particles provide stable electrochemical performance, thus maintaining both high energy density and particle integrity over repeated cycles.
2Duration of action of moving object
If lithium metal oxide particles are repeatedly charged and discharged, then battery capacity is maintained, but cracks occur and gas generation increases
Solution Approach 1:
By segmenting the cathode active material into two particle types with different structures, the invention distributes the mechanical stress of repeated charging and discharging across different particle morphologies. The secondary particles with aggregated structure can better accommodate volume expansion and contraction, reducing crack formation and subsequent gas generation, while maintaining battery capacity over extended charging cycles.
Solution Approach 2:
The invention changes the physical parameters of the lithium metal oxide particles by controlling their morphology (secondary vs. single particle shape) and nickel concentration (85 mol% or more in first particles, lower in second particles). These parameter changes result in different mechanical and electrochemical properties that collectively reduce gas generation during repeated charging and discharging while maintaining long-term capacity.
3Power
If high temperature environment is used, then battery power is improved, but life-span deteriorates due to side reactions
Solution Approach 1:
The invention changes the compositional parameters of the lithium metal oxide particles by controlling nickel concentration (85 mol% or more in first particles) and particle morphology. These parameter changes result in particles with enhanced stability at high temperatures, allowing the battery to deliver high power while maintaining life-span through reduced side reactions between the cathode material and electrolyte in elevated temperature conditions.
Solution Approach 2:
The composite structure combining two types of lithium metal oxide particles with different nickel concentrations and morphologies provides synergistic effects at high temperatures. The first particles with high nickel content and secondary structure provide stable framework that resists degradation, while the second particles contribute to electrochemical activity, enabling the battery to maintain both high power output and extended life-span in high temperature environments.
4Quantity of substance
If nickel concentration is increased in lithium metal oxide particles, then capacity is improved, but particle stability decreases leading to more cracks
Solution Approach 1:
The invention segments the cathode active material into two particle groups with different nickel concentrations and structures. The first lithium metal oxide particles contain 85 mol% or more nickel with secondary particle shape, providing high capacity. The second particles have lower nickel content with single particle shape, providing structural stability. This segmentation allows the system to achieve high overall capacity while the lower-nickel particles act as structural stabilizers that prevent crack formation.
Solution Approach 2:
The invention applies local quality by creating spatial variation in nickel concentration within the cathode active material layer. Regions with high nickel concentration (first particles) provide high lithium storage capacity, while regions with lower nickel concentration (second particles) provide structural stability and crack resistance. This local differentiation of composition allows the material to simultaneously achieve high capacity and maintain particle strength during cycling.
Data Source
Figure 1~2
Figure 3~4
AI summary
A cathode for a lithium secondary battery according to embodiments of the present invention includes a cathode current collector, and a cathode active material layer formed on the cathode current collector. The cathode active material layer includes first lithium metal oxide particles each having a secondary particle shape in which primary particles are aggregated and second lithium metal oxide particles each having a single particle shape. A cross-section of the cathode active material layer from an SEM satisfies Equations 1 and 2.