Trigonal Irreversible Additive for Stable Cathode Materials
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Solution Overview
Problem
The existing lithium secondary battery cathode materials face issues with impurity and gas generation due to structural changes during charge/discharge cycles, leading to reduced energy density and stability, particularly with commonly used irreversible additives like Li2NiO2 which undergo multiple crystal structure changes.
Innovation Solution
A cathode material incorporating an irreversible additive with a trigonal crystal structure, represented by Li2+aNi1−bTibO2, where −0.2≤a≤0.2, 0<b≤0.2, and 0≤c≤0.2, that maintains structural stability and reduces impurity and gas generation by substituting Ti for Ni, allowing for a higher oxygen formation energy and reversible crystal structure changes within the operating voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li2NiO2 with orthorhombic crystal structure is used as irreversible additive, then lithium ion supplementation is achieved, but impurity and gas generation occur due to crystal structure changes
Solution Approach 1:
The patent changes the crystal structure parameter from orthorhombic to trigonal system, and modifies the chemical composition parameters (Li2+aNi1-bTibO2+c) to achieve structural stability while maintaining lithium ion supplementation capability without undergoing harmful phase transitions during charge-discharge cycles
Solution Approach 2:
The patent creates a composite irreversible additive by substituting Ti for Ni in the Li2NiO2 structure, forming Li2+aNi1-bTibO2+c with trigonal crystal structure, which combines the benefits of lithium ion supplementation with enhanced structural stability and reduced impurity generation
2Use of energy by moving object
If irreversible additive undergoes crystal structure changes during charge/discharge, then lithium ion de-intercalation occurs, but structural stability is deteriorated
Solution Approach 1:
The patent modifies the crystal structure parameter from orthorhombic to trigonal system, which allows reversible lithium ion de-intercalation while maintaining structural integrity and preventing deterioration during charge-discharge cycles
3Stability of the object's composition
If orthorhombic crystal structure is maintained in 3.0 to 3.5V range, then structural stability is achieved, but three stages of structural changes occur after initial charge
Solution Approach 1:
The patent changes the crystal structure from orthorhombic to trigonal system, eliminating the need for three-stage structural transitions during charging, thereby maintaining structural stability throughout the entire operating voltage range and extending battery cycle life
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 proposed solution significantly reduces impurity and gas generation, enhances structural stability, and improves electrochemical properties and lifespan of lithium secondary batteries by maintaining a stable crystal structure during charge/discharge cycles.
Implementation Method 1
the irreversible additive has a trigonal system and is converted into a monoclinic system within a range in which the operating voltage range of the secondary battery is 4.0V or more
Implementation Method 2
the oxide has a trigonal crystal structure... and has a higher oxygen formation energy
Data Source
AI summary
An irreversible additive contained in a cathode material for a secondary battery according to one embodiment of the present disclosure, the irreversible additive being an oxide represented by the following chemical formula 1, wherein the oxide has a trigonal crystal structure,Li2+aNi1−bTibO2+c (1)in the above formula, −0.2≤a≤0.2, 0<b≤0.2, and 0≤c≤0.2.