Cathode Active Material Coating to Block Interfacial Electron Transfer
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Solution Overview
Problem
Lithium secondary batteries face rapid degradation due to oxidation/reduction reactions at the interface between the positive electrode active material and the electrolyte solution, particularly in high-voltage batteries, leading to reduced energy density and lifespan.
Innovation Solution
A film-shaped coating layer with lithium ion conductivity is applied to the surface of lithium composite metal oxide particles, using compounds like LiBH4, LiBH4-LiI, or Li2NH, with a band gap of 5.5 eV to 10 eV, to prevent electron movement and optimize thickness to minimize resistance and prevent dielectric breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer is applied to block electron movement and prevent oxidation/reduction reactions, then battery life and energy density are improved, but electron conductivity may be reduced
Solution Approach 1:
The coating layer is applied selectively only on the particle surfaces of the positive electrode active material, leaving the bulk material properties unchanged. This localized coating approach blocks electron movement at the interface where oxidation/reduction reactions occur, while maintaining the overall electron conductivity of the electrode structure through conductive agents and matrix materials.
Solution Approach 2:
The coating layer acts as an intermediary substance between the active material particles and the electrolyte solution. It provides a barrier function that prevents direct electron transfer and oxidation/reduction reactions, while still allowing ionic transport. The coating material serves as a mediator that reconciles the conflicting requirements of electron blocking and energy retention.
2Reliability
If the coating layer thickness is increased to improve blocking effectiveness, then oxidation/reduction reaction prevention is enhanced, but resistance increases and dielectric breakdown may occur
Solution Approach 1:
The coating layer thickness is optimized to specific parameter ranges that balance blocking effectiveness with resistance control. By carefully controlling the thickness parameter, the coating provides sufficient electron blocking to prevent oxidation/reduction reactions while maintaining low enough resistance to avoid excessive energy loss and prevent dielectric breakdown under operating conditions.
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 coating layer effectively suppresses oxidation/reduction reactions, enhancing energy density and battery life by blocking electron movement while maintaining lithium ion conductivity, thus improving the performance and longevity of lithium secondary batteries.
Implementation Method 1
the coating layer includes at least one lithium ion conductive compound having a band gap of 5.5 eV to 10 eV
Implementation Method 2
a film-shaped coating layer which surrounds the surface of the particles in a film shape and has lithium ion conductivity
Data Source
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AI summary
In the present invention, since a film-shaped coating layer including at least one lithium ion conductive compound having a band gap of 5.5 eV to 10 eV is formed on the surface of a core including a lithium composite metal oxide to a thickness at which dielectric breakdown does not occur according to types of the lithium ion conductive compound and the lithium composite metal oxide under charge and discharge conditions, an oxidation/reduction reaction is suppressed by blocking the movement of electrons at an interface between an active material and an electrolyte solution by the coating layer which surrounds the surface of particles and has lithium ion conductivity, and, as a result, a positive electrode active material for a secondary battery, which may improve energy density of an electrode and life characteristics of a battery, and a secondary battery including the same are provided.