Lithium Battery Cathode Composition for Crack-Resistant High Energy Density
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving improved structural stability and high-temperature storage properties, particularly as the size of lithium metal oxide particles increases, leading to decreased capacity and power.
Innovation Solution
A cathode for lithium secondary batteries is developed, featuring a cathode active material layer with lithium metal oxide particles that have a specific chemical-mechanical property parameter (CM) of 70 or more, defined by Equation 1. This cathode includes a bi-modal distribution of large-diameter and small-diameter particles, with adjusted average particle diameter, modulus, and hardness values to enhance mechanical and chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the size of lithium metal oxide particles is increased to achieve higher energy density, then the energy density is improved, but the capacity and power are decreased
Solution Approach 1:
The cathode active material layer is designed with a bi-modal particle size distribution, containing both large-diameter particles (providing high energy density) and small-diameter particles (providing high capacity and power). This segmentation allows different particle sizes to fulfill different functional requirements simultaneously, resolving the contradiction between energy density and capacity/power.
2Quantity of substance
If the size of lithium metal oxide particles is increased to achieve higher energy density, then the energy density is improved, but the structural stability is decreased
Solution Approach 1:
Different regions of the cathode active material layer contain particles with different sizes and properties. Large-diameter particles provide high energy density while small-diameter particles provide structural stability. This local quality differentiation allows the system to achieve both high energy density and structural stability simultaneously.
3Ease of manufacture
If the cobalt content is reduced to achieve lower cost, then the cost is decreased, but the stability at high temperatures is decreased
Solution Approach 1:
The patent optimizes the chemical-mechanical property parameter (CM) by adjusting particle size, modulus, and hardness parameters. By controlling these parameters, particularly maintaining CM ≥ 70, the cathode achieves high-temperature stability without requiring high cobalt content, thus reducing cost while maintaining reliability.
Data Source
AI summary
A cathode for a lithium secondary battery includes lithium metal oxide particles having CM defined by D*(EIT/HIT)/[(Li/Me)2] of of 70 or more. D is an average particle diameter value calculated in micrometers after measuring diameters of particles with a diameter of 4 μm or more in the lithium metal oxide particles included in a scanning electron microscope (SEM) image showing a thickness*width cross-section of the cathode active material layer. EIT is a modulus value of the lithium metal oxide particles measured by a nano indentation method. HIT is a hardness value of the lithium metal oxide particles measured by a nano indentation method. Li/Me is a molar ratio of lithium to metals other than lithium in the lithium metal oxide particles.