Sulfur-Stabilized Cathode Material for High-Nickel Cycle Life
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high capacity, stability, and cycle-life characteristics, particularly with nickel-based composite oxides that are prone to structural instability and capacity deterioration due to lithium deintercalation.
Innovation Solution
A positive active material for lithium batteries is developed, comprising a core with a high nickel content and a functional layer having a different crystal structure, stabilized by a thin layer of sulfur, which enhances structural stability and suppresses side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel-based composite oxide is used as positive active material to increase capacity, then battery capacity is improved, but structural stability deteriorates due to lithium deintercalation
Solution Approach 1:
The patent uses a composite material structure consisting of a core positive active material (nickel-based composite oxide with high capacity) and a functional layer (different crystal structure) on the surface. This composite structure allows the core to provide high capacity while the functional layer maintains structural stability during lithium deintercalation, resolving the contradiction between capacity improvement and structural stability deterioration.
2Quantity of substance
If high nickel content is used to achieve high capacity, then battery capacity is improved, but cycle-life characteristics worsen due to capacity deterioration
Solution Approach 1:
The patent employs a composite material where the core contains high nickel content (0.5 ≤ x ≤ 0.93) to achieve high capacity, while the functional layer with different crystal structure protects against capacity deterioration during cycling. This composite approach maintains both high capacity and excellent cycle-life characteristics by preventing the harmful effects of high nickel content.
3Stability of the object's composition
If functional layer with different crystal structure is formed on core to maintain structure integrity, then structural stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent controls the sulfur content within a specific range (100-400 ppm) to achieve the desired functional layer with different crystal structure. By optimizing this parameter, the patent forms the protective functional layer that maintains structural stability while avoiding excessive manufacturing complexity. The controlled sulfur content enables precise control over the functional layer's crystal structure and properties.
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 proposed material achieves high capacity and improved cycle-life characteristics by maintaining the structure integrity during charging and discharging, resulting in enhanced battery performance.
Implementation Method 1
the positive active material may include about 100 ppm to about 400 ppm of sulfur... stabilize a structure of the positive electrode
Implementation Method 2
suppress (or reduce) a side reaction with an electrolyte solution... functional layer on a surface of the core
Implementation Method 3
having a structure capable of intercalating lithium ions... intercalate and deintercalate lithium ions
Data Source
AI summary
A positive active material for a rechargeable lithium battery includes a core including a compound represented by Chemical Formula 1 and a functional layer on a surface of the core. The functional layer has one kind of a crystal structure that is different from the crystal structure of the core. The positive active material includes about 100 ppm to about 400 ppm of sulfur:LiaNixCoyMezO2, Chemical Formula 1wherein in Chemical Formula 1, 0.9≤a≤1.1, 0.5≤x≤0.93, 0<y≤0.3, 0<z≤0.3, x+y+z=1, and Me is Mn or Al.