Gradient Lithium Nickel Manganese Cobalt Oxide Cathode Material
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Solution Overview
Problem
Current lithium secondary battery positive electrode materials, such as LiCoO2, face challenges with thermal stability, high cost, toxicity, and limited reserves, while alternative materials like LiNi1−xCoxO2 and LiaCobMncMdNi1−(b+c+d)O2 lack satisfactory thermal stability, and existing concentration gradient methods result in discontinuous metal composition changes and low tap density.
Innovation Solution
A positive electrode active material with a first concentration gradient portion, a first concentration maintained portion, and a second concentration gradient portion, featuring gradients and constant concentrations of nickel, manganese, and cobalt, optimized through a coprecipitation process with controlled pH and ammonia addition to achieve continuous and high concentration gradients, enhancing thermal stability and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiCoO2 is used as positive electrode material, then charge and discharge characteristics and stability are improved, but cost increases and thermal stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a concentration gradient structure where the composition varies spatially within the particle. The center region has higher Ni content for capacity while the outer region has higher Co content for stability, allowing different regions to fulfill different functions simultaneously.
Solution Approach 2:
The patent creates a composite material structure by combining Ni-rich and Co-rich regions within a single LiNi1-x-yCoxMnyO2 particle. This composite approach leverages the high capacity of Ni-based materials and the high stability of Co-based materials in a unified structure.
2Quantity of substance
If Ni content is increased to achieve high capacity, then energy density improves, but thermal stability deteriorates
Solution Approach 1:
The patent uses local quality by concentrating high Ni content (x=0.7-0.9) in the center region for maximum capacity while placing higher Co content (y=0.05-0.2) in the outer region for thermal stability. This spatial differentiation allows the material to achieve both high capacity and improved thermal stability simultaneously.
3Ease of manufacture
If conventional double layer synthesis method is used, then production is simplified, but metal composition changes discontinuously and tap density decreases
Solution Approach 1:
The patent applies periodic action by using sequential coprecipitation with controlled pH stages. The process involves adding ammonia in a controlled manner to create distinct growth phases: first forming the inner core, then forming the outer shell with different composition, achieving continuous gradient through periodic compositional adjustment during synthesis.
Solution Approach 2:
The patent uses feedback control by monitoring and controlling pH during the coprecipitation process. The pH is adjusted to specific ranges (8.5-9.5 for inner layer, 9.5-10.5 for outer layer) to control the precipitation sequence and achieve the desired continuous concentration gradient 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 material exhibits improved charge and discharge characteristics, thermal stability, and high capacity, with a high nickel content and optimized Ni:Mn:Co ratio, reducing residual lithium issues and enhancing battery safety and energy density.
Implementation Method 1
A positive electrode active material with a first concentration gradient portion, a first concentration maintained portion, and a second concentration gradient portion, featuring gradients and constant concentrations of nickel, manganese, and cobalt, optimized through a coprecipitation process with controlled pH and ammonia addition
Data Source
AI summary
The inventive concepts relate to a positive electrode active material for lithium secondary battery, and more particularly, relate to a positive electrode active material which includes a first concentration gradient portion, a second concentration gradient portion, and a first concentration maintained portion. The first and second concentration gradient portions have gradients of concentrations of nickel, manganese, and cobalt in the direction from the center to the surface, and the first concentration maintained portion has constant concentrations of nickel, manganese, and cobalt between the first concentration gradient portion and the second concentration gradient portion.