Lithium Nickel-Based Oxide Surface Modification for Battery Stability
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Solution Overview
Problem
Rechargeable lithium batteries with lithium nickel-based oxides face challenges in maintaining high capacity and cycle-life characteristics due to the presence of excess lithium on the surface, which leads to reduced stability and increased gas generation during charge and discharge.
Innovation Solution
A positive active material is developed by incorporating a phosphorus-containing compound, such as lithium phosphate, on the surface of lithium nickel-based oxides, achieved through a washing process with a phosphorus-containing aqueous solution, reducing the residual lithium and enhancing electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If excess lithium is present on the surface of lithium nickel-based oxides, then high capacity is achieved, but stability is reduced and gas generation increases
Solution Approach 1:
The patent applies local quality by creating a phosphorus-containing compound layer specifically on the surface of the lithium nickel-based oxide particles. This surface modification maintains the bulk composition for high capacity while altering the surface properties to reduce gas generation and improve stability. The phosphorus content is controlled at 0.1-10 atom% on the surface, creating a localized functional layer that addresses the stability issue without compromising the overall lithium capacity.
Solution Approach 2:
The patent creates a composite material structure consisting of lithium nickel-based oxide core material combined with a phosphorus-containing compound surface layer. This composite approach allows the bulk material to provide high lithium capacity while the surface layer provides stability and reduces gas generation. The composite structure effectively combines the advantages of both materials to resolve the contradiction between capacity and stability.
2Quantity of substance
If excess lithium is present on the surface of lithium nickel-based oxides, then high capacity is achieved, but gas generation increases
Solution Approach 1:
The phosphorus-containing compound is applied locally on the surface of the lithium nickel-based oxide particles to create a functional surface layer. This localized modification suppresses gas generation at the particle surface while maintaining the bulk lithium content for high capacity. The surface layer acts as a protective interface that prevents harmful gas evolution during battery operation.
Solution Approach 2:
The patent converts the potentially harmful excess surface lithium into a beneficial configuration by reacting it with phosphorus-containing compounds to form a stable surface layer. This transformation turns the source of gas generation into a protective surface modification that actually prevents gas evolution while maintaining lithium availability for capacity.
3Duration of action of stationary object
If phosphorus content is increased to improve stability, then cycle-life characteristics improve, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating the phosphorus-containing compound during the synthesis process itself, rather than requiring separate post-synthesis coating steps. The phosphorus source is added to the precursor mixture before calcination, allowing the phosphorus-containing compound to form in-situ on the particle surface during the standard synthesis process. This approach improves cycle-life characteristics while avoiding additional manufacturing complexity.
Solution Approach 2:
The patent merges the synthesis of the lithium nickel-based oxide with the formation of the phosphorus-containing surface layer into a single integrated process. Both the core material formation and surface modification occur during the same calcination step, eliminating the need for separate coating or treatment steps. This combined approach achieves improved cycle-life characteristics without increasing manufacturing process complexity.
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 approach results in a rechargeable lithium battery with improved capacity, cycle-life characteristics, and stability, while minimizing gas generation, by adjusting the phosphorus content within specific ranges.
Implementation Method 1
washing a first active material with an aqueous solution of a phosphorus (P)-containing material to obtain a second active material
Data Source
AI summary
A positive active material for a rechargeable lithium battery including a lithium metal compound and a phosphorus (P)-containing compound on the surface of the lithium metal compound. A content of phosphorus (P) of the phosphorus-containing compound is about 0.1 atom % to about 10 atom % based on the total amount of elements on the surface of the positive active material. A method of preparing the same and rechargeable lithium battery including the same are also provided.