Positive Electrode Precursor With Oriented Shell for Side-Reaction Control
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving excellent capacity, life, and resistance characteristics due to unwanted material formation on the surface of positive electrode active materials during doping or surface coating processes, leading to degraded performance.
Innovation Solution
A positive electrode active material precursor is developed, comprising a spherical secondary particle structure with specific core and shell portions formed through co-precipitation reactions, maintaining primary particle orientation to enhance capacity, life, and resistance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doping element or surface coating is applied to improve battery performance, then battery performance and stability are improved, but unwanted material is formed on the surface and primary particle shape/orientation is modified, leading to degraded capacity, life, and resistance characteristics
Solution Approach 1:
The invention divides the positive electrode active material into distinct core and shell portions, where the core maintains randomly oriented primary particles and the shell contains oriented primary particles. This segmentation allows different regions to serve different functions: the core provides capacity while the shell provides stability, avoiding the trade-off between performance improvement and particle structure degradation.
Solution Approach 2:
The invention applies different structural characteristics to different parts of the positive electrode active material. The core portion has randomly oriented primary particles for high capacity, while the shell portion has oriented primary particles for stability. This local differentiation resolves the contradiction by allowing each region to optimize for its specific function without compromising the other.
2Reliability
If doping element or surface coating is applied to improve battery performance, then battery performance is improved, but unwanted material is formed on the surface, leading to degraded capacity characteristics
Solution Approach 1:
The invention extracts the unwanted side effects (unwanted material formation) by using a co-precipitation process that directly forms the desired core-shell structure without requiring subsequent doping or coating steps. The oriented primary particles are formed in-situ during the shell formation process, eliminating the need for separate surface treatment operations that cause harmful side reactions.
Solution Approach 2:
The invention performs the orientation of primary particles in advance during the shell formation process itself, rather than attempting to modify already-formed particles through doping or coating. The co-precipitation process inherently creates oriented primary particles in the shell portion, so the desired structure is established before any potential harmful reactions can occur.
3Reliability
If doping element or surface coating is applied to improve battery stability, then battery stability is improved, but primary particle orientation is modified, leading to degraded life characteristics
Solution Approach 1:
The invention segments the positive electrode active material into core and shell portions with different structural characteristics. The shell portion contains oriented primary particles that provide stability for long cycle life, while the core maintains randomly oriented particles for capacity. This segmentation allows the oriented structure to benefit cycle life without compromising overall battery performance.
Solution Approach 2:
The invention changes the structural parameters of the positive electrode active material by creating a shell portion with oriented primary particles. This parameter change (from random to oriented arrangement) specifically improves stability and cycle life characteristics without negatively affecting capacity, as the oriented structure is confined to the shell portion while the core retains its capacity-providing random 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 precursor's structure ensures improved capacity, life, and resistance characteristics in the final positive electrode active material, suppressing side reactions and increasing doping efficiency without degrading existing performance.
Implementation Method 1
forming a first core portion by a co-precipitation reaction while adding a transition metal-containing solution containing nickel (Ni), cobalt (Co), and manganese (Mn) ions, an ammonium cationic complexing agent, and a basic solution to a reactor
Implementation Method 2
a first shell portion which is formed on the first core portion and composed of the primary particles having a (001) plane oriented in a direction from a center of the secondary particle toward a surface thereof
Data Source
AI summary
A positive electrode active material precursor, a method of preparing the same, and positive electrode active material prepared from the same are disclosed herein. In some embodiments, a positive electrode active material precursor includes a spherical secondary particle formed by aggregation of primary particles and includes a core portion composed of randomly oriented primary particles, a first shell portion which is formed on the first core portion and composed of the primary particles having a (001) plane oriented in a direction from a center of the secondary particle toward a surface thereof, and a second shell portion which is formed on the first shell portion and composed of randomly oriented primary particles.