Secondary Battery Electrode Capacity Balance for Gas Suppression
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Solution Overview
Problem
Secondary batteries face challenges in suppressing gas generation and deterioration of cycle characteristics, particularly when using high-potential negative electrode materials like lithium titanate, where the capacity balance between positive and negative electrodes is not adequately defined.
Innovation Solution
A secondary battery design incorporating a positive electrode with a lithium iron phosphate or lithium-manganese composite oxide active material and a negative electrode with titanium-containing inorganic oxide, where the electrode areas and charge capacities are balanced to ensure that the charge termination is defined by the positive electrode, preventing negative electrode potential drop and gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-potential negative electrode materials like lithium titanate are used to improve battery output and capacity, then battery power and capacity are improved, but gas generation increases and cycle characteristics deteriorate
Solution Approach 1:
The patent changes the electrode capacity ratio parameter from conventional designs to a specific range (0.95-1.05), which balances the charge termination between positive and negative electrodes. This parameter adjustment prevents negative electrode potential drop and subsequent gas generation while maintaining high power output from lithium titanate-based negative electrodes
Solution Approach 2:
The patent applies preliminary anti-action by pre-defining the charge termination criterion based on positive electrode potential change before gas generation can occur. By monitoring and controlling the charge process to terminate when the positive electrode reaches its potential limit, the patent prevents the negative electrode potential drop that would otherwise lead to electrolyte decomposition and gas generation
2Quantity of substance
If high-potential negative electrode materials are used to improve battery capacity, then battery capacity is improved, but cycle characteristics deteriorate
Solution Approach 1:
The patent adjusts the electrode capacity ratio parameter to a balanced range (0.95-1.05), ensuring that charge termination is properly defined by positive electrode potential changes. This parameter optimization maintains high battery capacity from lithium titanate while preventing the potential drop that causes capacity loss during cycling
Solution Approach 2:
The patent implements feedback control by using positive electrode potential change as the charge termination criterion. This feedback mechanism ensures that charging stops at the appropriate point, preventing overcharge conditions that would cause negative electrode potential drop and capacity degradation over cycles
3Ease of operation
If charge termination is not properly defined, then battery operation is simplified, but negative electrode potential drop occurs causing gas generation
Solution Approach 1:
The patent introduces positive electrode potential change as an intermediary criterion to define charge termination. This intermediary measurement provides a clear, objective signal for when to stop charging, preventing negative electrode potential drop and gas generation while maintaining ease of operation through a well-defined termination point
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
This design effectively suppresses gas generation and maintains long-term cycle stability by ensuring the positive electrode defines the charge termination, thereby preventing electrolyte decomposition and improving output.
Implementation Method 1
a positive electrode active material layer having a positive electrode active material... wherein the positive electrode active material contains at least either a lithium iron phosphate compound having an olivine structure and containing at least lithium, iron, and phosphorus, or lithium-manganese composite oxide having a spinel structure and containing at least lithium and manganese
Implementation Method 2
a negative electrode active material layer having a negative electrode active material... wherein the negative electrode active material contains titanium-containing inorganic oxide
Implementation Method 3
an electrolyte... wherein the secondary battery satisfies Formula (A), Formula (B), and Formula (C)
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3A~3B
AI summary
A secondary battery includes a positive electrode including a positive electrode active material layer having a positive electrode active material, a negative electrode including a negative electrode active material layer having a negative electrode active material, and an electrolyte. The positive electrode active material contains either a lithium iron phosphate compound having an olivine structure or lithium-manganese composite oxide having a spinel structure. The negative electrode active material contains titanium-containing inorganic oxide. In the secondary battery, electrode areas of the positive electrode and the negative electrode, and first charge capacities and irreversible capacities per unit area of the positive electrode and the negative electrode satisfy predetermined formulas.