Composite Cathode Active Materials for Energy Density Retention
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Solution Overview
Problem
Existing cathode active materials for lithium-ion batteries suffer from limited energy density and energy density retention rate, particularly in Mn-rich materials, leading to reduced cycle life and voltage fade.
Innovation Solution
A process involving the combination of two cathode active materials, (α) and (β), each with specific compositions and densities, is used to enhance energy density and retention. This involves preparing precursors from transition metals as hydroxides or carbonates, mixing with lithium sources, and calcining at high temperatures, followed by post-treatments like washing and coating with Al2O3 or Li-Al oxide compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Mn-rich cathode active materials are used to increase energy density, then energy density is improved, but cycle life and voltage stability deteriorate due to limited energy density retention rate
Solution Approach 1:
The patent applies composite materials by combining two cathode active materials with different pressed densities into a mixture. Material (α) with higher pressed density (2.85-3.1 g/cm³) provides high energy density, while material (β) with lower pressed density (2.50-2.80 g/cm³) maintains structural stability. This composite approach allows the battery cathode to achieve both high energy density and good cycle life, resolving the contradiction between energy density and reliability.
2Quantity of substance
If high pressed density cathode materials are used to increase energy density, then energy density is improved, but manufacturing precision and material uniformity deteriorate
Solution Approach 1:
The patent applies local quality by creating a heterogeneous mixture where different regions contain materials with different pressed densities. Material (α) with higher density is distributed alongside material (β) with lower density in a mass ratio from 1:5 to 5:1. This local variation in density properties allows the overall cathode to achieve high energy density while maintaining manufacturability and uniformity through the combination of multiple materials with complementary characteristics.
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 process results in cathode active materials with improved energy density and retention rate, exhibiting excellent electrochemical properties such as high energy density and low capacity fade.
Implementation Method 1
The calcination—or firing—generally also referred to as thermal treatment or heat treatment of the precursor—is usually carried out at temperatures in the range of from 600 to 1000° C.
Implementation Method 2
In cases hydroxides or carbonates are used as precursors the lithiation reaction follows a removal of water or carbon dioxide.
Data Source
AI summary
Disclosed herein is a process for making an electrode active material for lithium-ion batteries. The process includes the steps of(a) providing a cathode active material (α) that has the general formula Li1+x1TM1−x1O2,(b) providing another cathode active material (β) that has the general formula Li1+x2TM1−x2O2, and(c) combining cathode active material (α) and cathode active material (β) in a mass ratio in the range of from 1:5 to 5:1.