Positive Electrode Material with Dielectric Hetero-Interface for Short-Circuit Safety
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining low internal short-circuit resistance and high output characteristics, particularly when a conductive foreign object causes internal short-circuiting, leading to excessive temperature increases.
Innovation Solution
A positive electrode material is developed comprising a composite oxide dielectric (AmBnOδ) with a dielectric constant of 10 to 500, where m/n ratio is between 1.01 and 1.6, integrated with a lithium, nickel, cobalt, and manganese-containing composite oxide, forming a hetero-interface that reduces electrical resistance at normal temperatures but increases it at higher temperatures, thereby blocking current flow and minimizing temperature rise during internal short-circuiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a dielectric material is added to the positive electrode to improve output characteristics, then the electrical resistance decreases and output characteristics improve, but the internal short-circuit resistance also decreases making the battery more susceptible to overheating during internal short-circuiting
Solution Approach 1:
The patent applies local quality by creating a hetero-interface between the dielectric material and positive electrode active material, where the interface region has distinct electrical properties. The dielectric constant gradient and interfacial polarization effects create localized regions with different resistance characteristics, allowing low resistance for normal operation at the interface while maintaining higher resistance during abnormal conditions.
Solution Approach 2:
The patent utilizes parameter changes by exploiting the temperature-dependent dielectric constant of the material. The dielectric constant changes with temperature, causing the electrical resistance to decrease at normal operating temperatures (improving output characteristics) while increasing at elevated temperatures (blocking current during internal short-circuiting). This dynamic parameter change resolves the contradiction between low resistance for power and high resistance for safety.
2Power
If the dielectric constant is increased to reduce positive electrode resistance, then output characteristics improve, but the battery temperature increases more during internal short-circuiting
Solution Approach 1:
The patent exploits parameter changes by selecting a dielectric material whose dielectric constant is highly dependent on temperature. At normal operating temperatures, the high dielectric constant reduces positive electrode resistance and improves output characteristics. When temperature rises during internal short-circuiting, the dielectric constant decreases, which increases resistance and limits current flow, thereby controlling temperature increase. This dynamic parameter response resolves the contradiction between power performance and thermal safety.
Solution Approach 2:
The patent converts the harmful effect of high temperature into a beneficial protective mechanism. During internal short-circuiting, the temperature rise that would normally be harmful is instead utilized to trigger the dielectric constant reduction, which automatically increases resistance and limits further temperature increase. The temperature rise becomes self-regulating, transforming a dangerous condition into a protective response.
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 solution effectively enhances the battery's internal short-circuit resistance and output characteristics by quickly blocking current flow and reducing temperature increases during internal short-circuit events, while maintaining high discharging capacity and thermal stability.
Implementation Method 1
in a part with which the positive electrode active material and the dielectric are in contact, a specific hetero-interface is formed, and lattice distortion occurs in the crystal structure
Implementation Method 2
the electrical resistance at the hetero-interface has temperature dependence. That is, at the hetero-interface, the electrical resistance is reduced to a low level when the battery is in a general usage temperature range, but the battery resistance rapidly increases if the temperature exceeds the general usage temperature range
Implementation Method 3
when a dielectric (AmBnOδ) having a molar ratio between the element at the A site and the element at the B site, that is, m/n, in the above range, and having a dielectric constant in the above range is used, it is possible to reduce the resistance of the positive electrode and improve output characteristics
Data Source
AI summary
The present disclosure relates to a positive electrode material for a lithium secondary battery which includes a positive electrode active material and a dielectric. The dielectric is a composite oxide represented by a general formula AmBnOδ and has a dielectric constant of 10 to 500. Here, m and n are real numbers that satisfy 1.01≤m/n≤1.6, δ is a value that is determined so that charge neutral conditions are satisfied, A is one or more elements among alkali metal elements, alkaline earth metal elements, rare earth elements, Cu, Pb and Bi, and B is one or more elements among transition metal elements and Sn.