Multilayer Lithium Cathode Structure for Crack-Resistant High Capacity
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Solution Overview
Problem
Lithium metal oxide particles in secondary batteries are prone to cracking during pressing and undergo degradation due to lithium ion intercalation and deintercalation, leading to gas generation, reduced lifespan, and performance issues, especially in high-temperature environments.
Innovation Solution
A cathode active material layer with a multilayer structure comprising first, second, and third lithium metal oxide layers, each with specific thickness ratios and compositions, including secondary and single particle forms, to enhance electrochemical stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal oxide particles with secondary particle structure are used, then capacity and energy density are improved, but cracks occur during pressing and lithium ion intercalation/deintercalation
Solution Approach 1:
The cathode active material layer is segmented into multiple layers (first, second, and third layers) with different particle compositions and structures. The first layer contains particles with average diameter of 5-15 μm, the second layer contains particles with average diameter of 3-10 μm, and the third layer contains particles with average diameter of 1-5 μm. This segmentation allows each layer to handle different mechanical and electrochemical stresses, preventing crack propagation through the entire structure while maintaining high capacity.
2Quantity of substance
If high nickel content is used to improve capacity, then electrochemical performance is enhanced, but particle cracking and gas generation increase
Solution Approach 1:
Different layers are assigned different nickel concentrations and particle size distributions to optimize local properties. The first layer has higher nickel content (0.5-0.8) for high capacity, the second layer has moderate nickel content (0.3-0.6) for structural stability, and the third layer has controlled nickel content (0.2-0.5) to minimize cracking. This local quality variation allows the cathode to achieve high overall capacity while preventing gas generation through strategic placement of high-nickel regions.
3Reliability
If single particle structure is used, then particle stability is improved, but electrochemical performance and capacity are reduced
Solution Approach 1:
The cathode active material layer is constructed as a composite structure combining particles with different morphologies and compositions across three layers. The first layer uses particles with average diameter of 5-15 μm for high capacity, the second layer uses particles with average diameter of 3-10 μm for structural stability, and the third layer uses particles with average diameter of 1-5 μm for surface stability. This composite approach integrates the advantages of both secondary particle structures (high capacity) and single particle structures (stability) into a unified system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The multilayer cathode structure improves output characteristics, lifespan, high-temperature storage, and resistance, resulting in enhanced lithium secondary battery performance.
Implementation Method 1
cracks may occur in the particles during pressing in a process of preparing the cathode
Implementation Method 2
cracks may occur in the particles due to intercalation and deintercalation of lithium ions during repeated charging and discharging of the lithium secondary battery
Implementation Method 3
problems such as gas generation due to a side reaction between the lithium metal oxide particles and an electrolyte
Data Source
Figure 1~3
AI summary
A cathode for a lithium secondary battery according to exemplary embodiments may include: a cathode current collector; and a cathode active material layer formed on the cathode current collector. The cathode active material layer may include: a first cathode active material layer formed on the cathode current collector, and including first lithium metal oxide particles having a form of secondary particles; a second cathode active material layer formed on the first cathode active material layer, and including second lithium metal oxide particles having a form of single particles; and a third cathode active material layer formed on the second cathode active material layer, and including third lithium metal oxide particles having a form of secondary particles.