Lithium Cobalt Oxide Doping Gradient for High-Voltage Cathode Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium cobalt oxide (LiCoO2) used in lithium secondary batteries experiences structural instability and reduced service life due to destabilization of its crystal structure under high voltage and high temperature conditions, leading to side reactions with the electrolyte.
Innovation Solution
A lithium cobalt-based oxide with a doping element M, such as Al, Ti, or Zr, is developed, where the doping element is uniformly doped in the bulk portion and has a concentration gradient in the surface portion, enhancing structural stability and surface stability by maintaining a constant concentration in the bulk and increasing it near the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If lithium cobalt oxide is used as a positive electrode active material to achieve high operating voltage and excellent capacity characteristics, then the battery voltage and capacity are improved, but the crystal structure becomes destabilized under high voltage conditions, leading to reduced thermal characteristics and structural stability
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of doping elements where the surface portion has a higher doping element concentration than the bulk portion. This localized variation in composition allows the surface to provide enhanced structural stability and surface stability under high voltage conditions, while the bulk maintains the electrochemical performance needed for high capacity. The surface portion acts as a protective layer that stabilizes the crystal structure during charging/discharging cycles at high voltages of 4.5V or more.
Solution Approach 2:
The patent employs parameter changes by modifying the doping element concentration distribution within the lithium cobalt oxide particles. Specifically, it creates a non-uniform concentration profile where the doping element concentration varies from the bulk to the surface, with the surface portion having a higher concentration. This parameter change in compositional distribution enables the material to maintain structural stability at high operating voltages while preserving excellent capacity characteristics.
2Quantity of substance
If the voltage is increased to 4.5 V or more to increase the capacity of lithium cobalt oxide, then the battery capacity is improved, but the surface stability deteriorates due to side reactions with the electrolyte
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of doping elements where the surface portion has a higher doping element concentration than the bulk portion. This localized variation in composition allows the surface to provide enhanced structural stability and surface stability under high voltage conditions, while the bulk maintains the electrochemical performance needed for high capacity. The surface portion acts as a protective layer that stabilizes the crystal structure during charging/discharging cycles at high voltages of 4.5V or more.
Solution Approach 2:
The patent creates a composite structure within the lithium cobalt oxide particles by incorporating doping elements with a specific concentration gradient. The surface portion with higher doping element concentration forms a composite-like structure that provides enhanced stability, while the bulk portion maintains the original lithium cobalt oxide composition for high capacity. This composite approach allows the material to achieve both high capacity and improved surface stability simultaneously.
3Stability of the object's composition
If uniform doping is applied throughout the lithium cobalt oxide particle, then the structural stability is improved, but the surface stability under high voltage conditions is not sufficiently enhanced
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of doping elements where the surface portion has a higher doping element concentration than the bulk portion. This localized variation in composition allows the surface to provide enhanced structural stability and surface stability under high voltage conditions, while the bulk maintains the electrochemical performance needed for high capacity. The surface portion acts as a protective layer that stabilizes the crystal structure during charging/discharging cycles at high voltages of 4.5V or more.
Solution Approach 2:
The patent transitions from uniform doping (zero-dimensional distribution) to a gradient doping approach that introduces a spatial dimension to the doping element distribution. By creating a concentration gradient from the bulk to the surface, the patent adds a dimensional aspect to the doping strategy, allowing different regions of the particle to have optimized compositions for their specific functions: bulk for capacity and surface for stability.
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 approach effectively prevents structural changes under high voltage and improves surface stability, extending the service life and maintaining stability at high temperatures and voltages, particularly at 4.5 V or more.
Implementation Method 1
a lithium cobalt-based oxide including a doping element M
Implementation Method 2
in a surface portion from the surface of the particle to 100 nm in a core direction, the doping element M is contained at a concentration equal to or higher than that in the bulk portion and has a concentration gradient gradually in which the concentration thereof is decreased in the core direction from the surface of the particle
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The present invention provides a positive electrode active material for a secondary battery, the positive electrode active material being a lithium cobalt-based oxide including a doping element M, wherein a lithium cobalt-based oxide particle containing the doping element M in an amount of 3,000 ppm or more, wherein in a bulk portion corresponding to 90% of a core side among the radius from a core of the particle to a surface thereof, the doping element M in the lithium cobalt-based oxide particle is contained at a constant concentration, and in a surface portion from the surface of the particle to 100 nm in a core direction, the doping element M is contained at a concentration equal to or higher than that in the bulk portion and has a concentration in which the concentration thereof is gradient gradually decreased in the core direction from the surface of the particle.