Polyimide-Coated Positive Electrode Particles for High-Voltage Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face rapid battery life shortening due to side reactions between the positive electrode and electrolyte, especially under high-voltage and high-temperature conditions, and existing surface coatings like oxides limit ion and electron conductivity.
Innovation Solution
Surface-coated positive electrode active material particles with a polyimide coating layer containing structures like pyrrole, aniline, and carbazole, which enhances lithium ion and electron mobility while preventing direct contact with the electrolyte, thereby improving battery life and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oxide coating layer (Al2O3, ZrO2, AlPO4) is applied on the surface of positive electrode active material, then the stability of the positive electrode active material is improved, but the ion conductivity deteriorates due to the ion-insulating nature of the oxide coating layer
Solution Approach 1:
The patent applies a composite coating layer comprising both oxide particles (Al2O3, ZrO2, or AlPO4) and polyimide. The oxide provides stability and protects the active material, while the polyimide matrix ensures ion conductivity by allowing lithium ion migration. This composite structure resolves the contradiction by combining the protective function of oxides with the conductive function of polyimide.
Solution Approach 2:
The polyimide acts as an intermediary material that facilitates lithium ion transport between the oxide coating particles and the electrolyte. It mediates between the ion-insulating oxide layer and the ion-conducting electrolyte, enabling ion conductivity while maintaining the protective function of the oxide layer.
2Reliability
If only polyimide is used as coating layer to provide uniform coverage and prevent direct contact with electrolyte, then side reaction between positive electrode and electrolyte is reduced, but electron conductivity cannot be achieved
Solution Approach 1:
The coating layer is designed as a composite of oxide particles and polyimide. The polyimide provides uniform coverage and prevents side reactions, while the oxide particles contribute to electron conductivity through their inherent electronic properties, thus achieving both protective and conductive functions.
3Loss of energy
If carbon black is added to polyimide coating layer to supplement electrical conductivity, then electron conductivity is improved, but uniform dispersion becomes difficult due to aggregation of carbon black particles
Solution Approach 1:
Instead of using carbon black which requires careful dispersion control, the patent employs oxide particles (Al2O3, ZrO2, AlPO4) that naturally provide sufficient electron conductivity without aggregation issues. These oxide particles are easier to disperse uniformly in the polyimide matrix while maintaining electrical conductivity.
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 polyimide coating layer ensures uniform conductivity and inhibits side reactions, leading to improved battery life and performance under both normal and high-voltage, high-temperature conditions by capturing lithium ions and facilitating electron migration.
Implementation Method 1
capturing lithium ions migrating in a secondary battery
Implementation Method 2
the unshared electrons generated from an NH group in the above structures dissociating to release the H as H+, thereby capturing lithium ions
Implementation Method 3
providing uniform coverage of the surface of the positive electrode material, and thus reducing a side reaction between the positive electrode and the electrolyte
Implementation Method 4
exhibit excellent lithium ion mobility and excellent electron mobility
Data Source
AI summary
The present invention relates to surface-coated positive electrode active material particles and a secondary battery including the same, and specifically, it provides surface-coated positive electrode active material particles including positive electrode active material particles and a coating layer applied on a surface of the positive electrode active material particles, wherein the coating layer includes a polyimide comprising one or more structures selected from the group consisting of pyrrole, aniline, and carbazole. The surface-coated positive electrode active material particles according to the present invention includes a coating layer including a polyimide and metal ions; and since a direct contact between the positive electrode active material particles and an electrolyte can be prevented, a side reaction therebetween can be inhibited, and both excellent lithium ion mobility and excellent electron conductivity can be exhibited. Accordingly, a secondary battery with improved battery life and cycle characteristics at high-voltage and high-temperature conditions can be obtained.