Secondary Battery Cathode-Electrolyte Chelation for Low Self-Discharge
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Solution Overview
Problem
Existing secondary battery technologies face issues with high self-discharge rates and impedance growth due to interface reactions between the positive electrode and electrolyte, leading to reduced battery life and performance, despite attempts to stabilize the interface through coatings or doping which often fail to provide sufficient protection.
Innovation Solution
The introduction of a specific metallic element, Co, with a reduced molar ratio and the inclusion of Al in the positive active material, combined with a compound in the electrolytic solution that forms a chelate structure with Al, stabilizes the positive electrode surface and separates the electrolyte, reducing self-discharge and impedance growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doping or coating is performed on positive electrode material to separate electrolyte and positive interface, then interface stability is improved, but coating layer easily breaks causing continuous interface reactions and self-discharge
Solution Approach 1:
The patent introduces a specific compound (1,3-propanesultone) as an intermediary substance in the electrolyte that reacts with the positive electrode material to form a stable interface protective film. This mediator creates a robust interface layer that doesn't easily break, preventing continuous interface reactions and self-discharge while maintaining electrolyte separation.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by adding 1,3-propanesultone compound and adjusts its concentration (0.01-15% by mass). This parameter change transforms the interface properties, creating a stable protective film that resolves the contradiction between interface stability and self-discharge prevention.
2Ease of manufacture
If doping or coating substances are added in small amounts to protect positive interface, then cost is reduced, but protection is insufficient leading to limited battery performance improvement
Solution Approach 1:
The patent optimizes the concentration parameter of the 1,3-propanesultone compound in the electrolyte (0.01-15% by mass). This parameter adjustment ensures sufficient interface protection effectiveness while maintaining cost efficiency, avoiding the need for expensive large amounts of coating materials.
Solution Approach 2:
The 1,3-propanesultone compound in the electrolyte automatically reacts with the positive electrode interface to form a protective film during battery operation. This self-service mechanism eliminates the need for separate coating processes and reduces manufacturing costs while providing effective protection.
3Reliability
If sufficient amount of doping or coating substances is added to form stable interface protective film, then interface stability is improved, but interface impedance seriously deteriorates
Solution Approach 1:
The patent precisely controls the concentration parameter of the 1,3-propanesultone compound (0.01-15% by mass) to form a protective film with optimal properties. This parameter optimization ensures the film is stable enough to prevent interface reactions but thin and conductive enough to maintain low impedance.
Solution Approach 2:
The patent creates a composite interface structure consisting of the positive electrode material and the protective film formed by 1,3-propanesultone. This composite structure combines the stability of the protective film with the conductivity of the underlying electrode material, resolving the contradiction between stability and impedance.
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 approach effectively reduces the self-discharge rate, storage impedance growth, and improves rate discharge capacity efficiency while lowering the cost of the battery by stabilizing the positive electrode material and enhancing ion conductivity.
Implementation Method 1
the inclusion of Al in the positive active material, combined with a compound in the electrolytic solution that forms a chelate structure with Al
Implementation Method 2
stabilizes the positive electrode surface and separates the electrolyte, reducing self-discharge and impedance growth
Implementation Method 3
enhancing ion conductivity
Data Source
Figure 1~3
Figure 4~6
AI summary
The present application provides a secondary battery, which reduces costs of battery materials, effectively reduces a self-discharge rate of a battery cell, and improves storage impedance performance of the cell. The secondary battery includes a positive electrode sheet, a negative electrode sheet, and an electrolytic solution, where the positive electrode sheet includes a positive active material; in the positive active material, a contained rate of an element Co satisfies: Co≤0.09, and a content of an element Al satisfies: 500ppm≤Al≤10000ppm; and the electrolytic solution includes a compound represented by the following general formula (I).