Coated Lithium-Rich Cathode Material for First-Cycle Lithium Loss
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Solution Overview
Problem
Secondary batteries face challenges in improving energy density due to irreversible capacity loss from the formation of a solid electrolyte interface (SEI) film at the negative electrode during first-time charging and discharging, which is difficult to eliminate, limiting their energy density and cycle life.
Innovation Solution
A composite positive-electrode material is developed, comprising a lithium-rich metal oxide core coated with a positive-electrode active material, which acts as a lithium ion conductor, isolating the core from the environment and enhancing stability and pre-lithiation efficiency, thereby compensating for lost active lithium and improving energy density and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SEI film is formed at the negative electrode during first-time charging and discharging, then the battery structure is stabilized, but active lithium is consumed resulting in 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) that will be released during initial charging to compensate for the lithium consumed by SEI film formation at the negative electrode. This preliminary lithium addition ensures that the battery achieves its full capacity potential despite the inevitable first-time lithium loss.
Solution Approach 2:
The patent employs parameter changes by modifying the composition and stoichiometry of the positive electrode material. Specifically, it uses lithium-rich metal oxides with formulas such as Li2M1O2, Li2M2O3, Li3M3O4, Li5M4O4, or Li6M5O4, where the lithium content exceeds the stoichiometric amount needed for standard operation. This parameter adjustment allows the positive electrode to serve dual functions: as the active electrode material and as a lithium reservoir to compensate for initial lithium loss.
2Ease of manufacture
If the positive-electrode pre-lithiation material is exposed to the external environment, then material processing is simplified, but the material stability decreases and purity is compromised
Solution Approach 1:
The patent applies the inert atmosphere principle by coating the lithium-rich metal oxide particles with a protective layer of positive electrode active material. This coating creates a physical barrier that isolates the highly reactive pre-lithiation material from moisture and carbon dioxide in the external environment during handling, transport, and assembly. The coating allows the material to be processed with relative ease while maintaining its stability and purity.
Solution Approach 2:
The patent employs composite materials by creating a core-shell structure where the core consists of lithium-rich metal oxide particles and the shell consists of positive electrode active material coating. This composite structure combines the benefits of both materials: the core provides the necessary lithium for pre-lithiation while the shell provides environmental stability and protection. The composite design enables the material to be manufactured and handled more easily without compromising its reactive properties.
3Reliability
If the positive-electrode pre-lithiation material is coated with positive-electrode active material, then material stability and pre-lithiation performance are improved, but device complexity increases
Solution Approach 1:
The patent applies the merging principle by combining the functions of the positive electrode active material and the protective coating into a single integrated layer. Rather than adding a separate coating material, the patent uses the positive electrode active material itself as the coating, thereby eliminating the need for additional materials or separate coating steps. This merging approach improves pre-lithiation performance while minimizing the increase in device complexity.
Solution Approach 2:
The patent employs universality by making the positive electrode active material serve multiple functions simultaneously. The coated positive electrode active material on the surface of lithium-rich metal oxide particles provides both the electrochemical function of the positive electrode and the protective function of isolating the pre-lithiation material from the environment. This multi-functionality reduces the need for additional components and simplifies the overall material structure.
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 effectively increases the first-time charging-discharging capacity, energy density, and cycle life of secondary batteries by preventing direct contact with moisture and carbon dioxide, reducing side reactions, and ensuring efficient lithium ion deintercalation.
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
Data Source
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.