Composite Cathode Coating for Active Lithium Compensation
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Solution Overview
Problem
The formation of a solid electrolyte interface (SEI) film during the first charging and discharging of secondary batteries leads to irreversible loss of active ions, limiting the energy density and cycle life of the battery.
Innovation Solution
A composite positive-electrode material is developed, comprising a core of lithium-rich metal oxide pre-lithiation material coated with a positive-electrode active material that serves as a good lithium ion conductor, isolating the core from the environment and enhancing pre-lithiation efficiency while maintaining purity and stability.
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 preliminary action by pre-lithiating the positive electrode material before battery assembly. The positive electrode is prepared with excess lithium content (lithium-rich metal oxide or lithium-containing compounds) that will be released during initial charging to compensate for the lithium consumed by SEI film formation on the negative electrode, thereby preventing irreversible capacity loss.
Solution Approach 2:
The patent changes the lithium content parameter of the positive electrode material by using lithium-rich metal oxides (such as Li2MnO3, Li2NiO3, Li2CuO2) or lithium-containing compounds with controlled lithium excess (0.01-0.5 mol/L). This parameter change enables the positive electrode to provide additional lithium during initial cycling to offset SEI formation losses.
2Loss of substance
If the positive electrode material is pre-lithiation material, then active lithium can be compensated, but the material stability and purity may be compromised
Solution Approach 1:
The patent employs composite materials by combining pre-lithiation materials (lithium-rich metal oxides or lithium-containing compounds) with conventional positive electrode active materials (such as layered lithium transition metal oxides, spinel structures, or olivine structures). This composite structure provides both lithium compensation capability and maintains electrochemical stability and purity.
Solution Approach 2:
The patent applies local quality by distributing the pre-lithiation material in specific forms within the positive electrode: either as surface-coated particles, internally doped regions, or mixed composites. This localized approach ensures that the pre-lithiation function is activated where needed while maintaining overall material stability and preventing unwanted side reactions.
3Loss of substance
If the mass ratio of pre-lithiation material to active material is increased, then more active lithium is available, but the energy density may be reduced due to inactive substances
Solution Approach 1:
The patent optimizes the mass ratio parameter of pre-lithiation material to active material within specific ranges (0.1-0.5, preferably 0.2-0.3) to achieve the right balance between lithium compensation and energy density. This controlled parameter change ensures sufficient lithium is available to compensate for SEI formation while minimizing the proportion of inactive material that would reduce overall energy density.
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 material effectively compensates for lost active lithium, improving first-time charging-discharging capacity and energy density, and significantly prolongs the cycle life of the battery by ensuring efficient lithium ion deintercalation and reducing side reactions.
Implementation Method 1
the coating layer with the positive-electrode active material is a good lithium ion conductor, and can greatly improve efficiency of pre-lithiation
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, and a battery module, a battery pack, and an apparatus containing such secondary battery. 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.