Composite Cathode Coating for Pre-Lithiation and SEI Lithium Loss
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Solution Overview
Problem
The formation of a solid electrolyte interface (SEI) film during the first-time charging and discharging of secondary batteries leads to irreversible capacity loss, limiting the energy density improvement of secondary batteries.
Innovation Solution
A composite positive-electrode material is developed, comprising a core of lithium-rich metal oxide coated with a positive-electrode active material, which acts as a lithium ion conductor and environmental isolator, ensuring purity and stability, and compensates for lost active lithium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SEI film is formed during first-time charging and discharging, then the negative electrode is protected, but active lithium is consumed causing irreversible capacity loss
Solution Approach 1:
The patent applies pre-lithiation technology by introducing a lithium-rich positive electrode material before battery operation. This preliminary action compensates for the lithium that will be consumed during SEI film formation, ensuring that sufficient active lithium remains for subsequent cycling and maintaining battery capacity.
Solution Approach 2:
The patent changes the composition parameter of the positive electrode by incorporating a lithium-rich material with excess lithium content. This parameter change allows the positive electrode to release additional lithium during initial charging, compensating for the lithium trapped in the SEI film and improving overall battery efficiency.
2Reliability
If the positive electrode material is coated to improve stability, then material purity and pre-lithiation performance are ensured, but the coating layer must also maintain good lithium ion conductivity
Solution Approach 1:
The patent applies a coating layer selectively on the surface of the lithium-rich positive electrode material particles. This local modification provides protection and ensures purity where needed (at the particle surface exposed to electrolyte and other materials) while maintaining the bulk lithium-rich composition's ability to release lithium and provide pre-lithiation functionality.
Solution Approach 2:
The patent creates a composite structure combining the lithium-rich positive electrode material core with a protective coating layer. This composite material integrates the benefits of both components: the core provides excess lithium for pre-lithiation while the coating ensures stability, purity, and maintains lithium ion conductivity for efficient ion transport.
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 composite positive-electrode material enhances the first-time charging-discharging capacity and energy density of secondary batteries while prolonging their cycle life by effectively utilizing lithium and maintaining material stability.
Implementation Method 1
the coating layer with the positive-electrode active material is a good lithium ion conductor
Implementation Method 2
the surface of the positive-electrode pre-lithiation material is coated by the positive-electrode active material, so as to isolate external environment, improve stability of the material
Data Source
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AI summary
This application provides a composite positive-electrode material and a preparation method thereof, a positive-electrode plate, a secondary battery (5), and a battery module (4), a battery pack (1), and an apparatus containing such secondary battery (5). The composite positive-electrode material includes a core and a coating layer covering at least part of a surface of the core, where the core includes a positive-electrode pre-lithiation material, the positive-electrode pre-lithiation material includes a lithium-rich metal oxide, and the coating layer includes a positive-electrode active material.