High-Ni Positive Electrode with Doping Gradient
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Solution Overview
Problem
High-Ni type positive electrode active materials for lithium secondary batteries face challenges with low structural stability and rapid deterioration at both high and room temperatures, despite exhibiting high capacity characteristics, due to Li/Ni cation mixing and the generation of Li by-products like LiOH and Li2CO3, which cause gelation and gas generation during charging and discharging.
Innovation Solution
A positive electrode active material with secondary particles formed by aggregating primary particles, where a concentration gradient of the doping metal is established from the grain boundary towards the center of the primary particle, reducing the surface area for side reactions and stabilizing the crystal structure, thereby enhancing structural stability and electrochemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the Ni content in the positive electrode active material is increased to achieve high capacity characteristics, then the discharge capacity is improved, but the structural stability deteriorates due to Li/Ni cation mixing
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of doping metal (Al, Ti, Zr, V, or B) within the particle structure, with higher concentration at the surface and lower concentration toward the center. This non-uniform distribution allows the surface region to provide structural stability and suppress cation mixing, while the interior maintains high Ni content for capacity, thus resolving the contradiction between capacity and stability.
Solution Approach 2:
The patent creates a composite structure by combining high-Ni lithium composite oxide with doping metals in a gradient distribution. The multi-component system (Li-Ni-Co-Me-O) with spatially varying composition enables simultaneous achievement of high capacity from Ni-rich core and high stability from doped surface layer, effectively addressing the structural instability problem.
2Quantity of substance
If the Ni content is increased to improve capacity characteristics, then the electrochemical performance is enhanced, but the rate characteristics deteriorate due to cation mixing
Solution Approach 1:
The doping metal concentration gradient creates a surface region with suppressed cation mixing, which improves ion transport kinetics at the particle surface. This local modification of surface properties enhances rate characteristics without sacrificing the high capacity potential of the Ni-rich bulk material.
3Quantity of substance
If the Ni content is increased to achieve high capacity, then the battery characteristic is improved, but Li by-products are generated causing gelation and gas generation
Solution Approach 1:
The doping metal enrichment at the particle surface creates a protective surface layer that suppresses side reactions with the electrolyte. This surface modification reduces the generation of Li by-products (LiOH and Li2CO3) that cause gelation and gas generation, while the high-Ni core maintains capacity performance.
4Quantity of substance
If the Ni content is increased to improve capacity characteristics, then the energy storage is enhanced, but the thermal safety and stability at room temperature deteriorate
Solution Approach 1:
The doping metal concentration gradient creates a thermally stable surface layer that suppresses exothermic reactions and structural degradation. This surface engineering approach improves thermal safety and room temperature stability while preserving the high capacity characteristics of the high-Ni bulk material.
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 concentration gradient in the doping metal within the secondary particles improves the structural stability and electrochemical performance of the high-Ni type positive electrode active material, reducing the risk of phase transformation and side reactions, leading to improved charging/discharging and storage stability, and maintaining high capacity characteristics.
Implementation Method 1
a concentration gradient of the doping metal is formed from a grain boundary between the primary particles toward a center portion of the primary particle
Implementation Method 2
when lithium ions are intercalated/deintercalated into/from a positive electrode and a negative electrode
Implementation Method 3
reducing the surface area for side reactions and stabilizing the crystal structure
Data Source
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AI summary
The present invention relates to a positive electrode active material with improved electrochemical properties and stability and a lithium secondary battery using a positive electrode comprising the same, wherein secondary particles formed by aggregation of a plurality of primary particles are provided as aggregates of primary particles in which a concentration gradient of the doping metal is formed from a grain boundary between the primary particles toward a center portion of the primary particle.