Core-Shell Positive Electrode Active Material for Secondary Batteries
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Solution Overview
Problem
Current lithium-ion secondary batteries face challenges in achieving high charge and discharge capacity, voltage, and long-term reliability, with limitations in energy density and durability, particularly in maintaining performance over multiple charge cycles and in reducing material costs.
Innovation Solution
A secondary battery design featuring a positive electrode active material with a core-shell structure, where the core and shell regions differ in transition metal concentrations, incorporating impurity layers to inhibit interdiffusion, and utilizing graphene as a conductive material to enhance conductivity and stability, thereby promoting lithium diffusion and reducing deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the positive electrode active material uses a core-shell structure with different transition metal concentrations, then the charge and discharge capacity and voltage are improved, but the manufacturing complexity increases
Solution Approach 1:
The positive electrode active material employs a core-shell structure where the core region contains a first transition metal concentration optimized for charge and discharge capacity, while the shell region contains a second transition metal concentration optimized for voltage. This local differentiation of material properties enables simultaneous optimization of both capacity and voltage without requiring complex manufacturing processes, as each region independently contributes its specific function.
2Reliability
If impurity layers are added to inhibit interdiffusion between core and shell regions, then the reliability and cycle performance are improved, but the device complexity increases
Solution Approach 1:
An impurity layer is introduced as an intermediary between the core and shell regions of the positive electrode active material. This intermediate layer prevents interdiffusion of transition metals between the core and shell during battery operation, thereby maintaining the distinct compositional profiles of each region. The impurity layer acts as a barrier that preserves the integrity of the core-shell structure over multiple charge cycles, improving reliability without requiring complex external control mechanisms.
3Reliability
If graphene is used as a conductive material, then the conductivity and stability are improved, but the manufacturing cost increases
Solution Approach 1:
Graphene is integrated into the positive electrode active material structure as a conductive additive, forming a composite material system. The graphene network provides enhanced electrical conductivity throughout the electrode, improving electron transport efficiency. Additionally, graphene's mechanical strength and chemical stability contribute to the overall structural integrity and long-term stability of the battery, reducing degradation over time.
4Quantity of substance
If the secondary battery uses high energy density materials, then the energy density is improved, but the weight increases
Solution Approach 1:
The positive electrode active material utilizes parameter changes in transition metal concentrations between the core and shell regions to optimize energy density. The core region is designed with a composition that maximizes lithium insertion/extraction capacity, while the shell region is optimized for voltage stability. By carefully controlling the concentration gradients and thickness ratios of each region, the material achieves high energy density without requiring excessive material quantity, thereby limiting weight increase.
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 solution provides a secondary battery with improved energy density, extended charge mileage, and enhanced reliability, enabling longer vehicle ranges with minimal weight increase and increased durability, while reducing cobalt usage for cost-effectiveness.
Implementation Method 1
the impurity layer has a function of inhibiting interdiffusion of elements contained in the first region and the second region
Implementation Method 2
utilizing graphene as a conductive material to enhance conductivity and stability, thereby promoting lithium diffusion
Implementation Method 3
thereby promoting lithium diffusion and reducing deterioration
Data Source
AI summary
A positive electrode active material with high charge and discharge capacity is provided. Alternatively, a positive electrode active material with high charge and discharge voltages is provided. Alternatively, a power storage device that hardly deteriorates is provided. Alternatively, a highly safe power storage device is provided. Alternatively, a novel power storage device is provided. Provided is a positive electrode active material containing lithium, a plurality of transition metals, oxygen, and an impurity element. The positive electrode active material has a first region including a surface portion and a second region provided in an inner portion; the first region and the second region differ in the concentration of a transition metal. An impurity layer is included between the first region and the second region.