Chlorine-Modified Spinel Cathode for Cycle Life
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Solution Overview
Problem
Conventional lithium manganese-based AB2O4 spinel cathode materials in rechargeable lithium batteries suffer from limited cycle life, capacity fading due to mechanical strain, manganese dissolution, and phase transitions, leading to reduced reversibility and increased processing time.
Innovation Solution
A chlorine-modified lithium manganese-based AB2O4 spinel cathode material with evenly distributed chlorine, prepared using the glycine nitrate combustion method, which enhances overvoltage and under-voltage tolerance, maintaining reversibility and improving cycle life by reducing particle size and crystallite size, and shortening processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional lithium manganese-based AB2O4 spinel cathode materials are used, then the battery can operate with high energy density, but the cycle life is limited due to capacity fading from mechanical strain and phase transitions
Solution Approach 1:
The patent modifies the crystal structure parameters of the spinel cathode material by controlling the Li content (x in LixMn2O4) and applying chlorine modification. This changes the lattice parameters and stabilizes the cubic spinel structure against Jahn-Teller distortion, preventing phase transitions and maintaining structural integrity during cycling, thereby extending cycle life while preserving energy density
Solution Approach 2:
The patent creates a composite structure by incorporating chlorine into the spinel lattice (forming LixMn2O4-yClz composition). This composite approach combines the high energy density characteristics of lithium manganese spinel with the structural stability provided by chlorine modification, resolving the contradiction between energy density and cycle life
2Ease of operation
If the active material undergoes repeated phase transitions during cycling, then lithium insertion/extraction is enabled, but mechanical strain causes fracture and dissociation of active material from the electrode
Solution Approach 1:
The patent applies chlorine modification beforehand to cushion and compensate for the mechanical strain that occurs during lithium insertion/extraction. The chlorine atoms in the lattice help accommodate volume changes and reduce stress concentration, preventing fracture and maintaining the connection between active material and electrode throughout cycling
3Reliability
If manganese dissolution occurs in the electrolyte, then the cathode material degrades, but this limits the practical number of cycles
Solution Approach 1:
The patent converts the potential harm of manganese dissolution into a benefit by using chlorine modification. The chlorine atoms preferentially interact with the electrolyte, forming a protective interface layer that actually protects the manganese from dissolving. This transforms the harmful dissolution process into a beneficial protective mechanism, extending practical cycle life
4Reliability
If rigid stoichiometric control is applied to maintain reversibility, then capacity fading is reduced, but processing time increases
Solution Approach 1:
The patent changes the stoichiometric parameters to LixMn2O4-yClz, allowing flexibility in Li content (x) and chlorine content (z) while maintaining structural stability. This parameter flexibility enables optimization of both reversibility and processing efficiency, reducing the need for rigid stoichiometric control and thereby decreasing processing time
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 chlorine-modified spinel material exhibits extended cycle life, improved reversibility, and reduced processing time, maintaining performance at elevated charge potentials and low impedance, while avoiding capacity fading and phase transitions.
Implementation Method 1
heating the mixture to produce an ash
Implementation Method 2
glycine nitrate combustion method
Implementation Method 3
calcining the ground ash for a time period no greater than 5 hours at a temperature of at least 350° C. to produce the homogeneously dispersed chlorine-modified lithium manganese-based AB2O4 spinel cathode material
Data Source
AI summary
A method of preparing a homogeneously dispersed chlorine-modified lithium manganese-based AB2O4 spinel cathode material is provided. Furthermore, a homogeneously dispersed chlorine-modified lithium manganese-based AB2O4 spinel cathode material is provided. In addition, a lithium or lithium ion rechargeable electrochemical cell is provided incorporating a homogeneously dispersed chlorine-modified lithium manganese-based AB2O4 spinel cathode material in a positive electrode.