Positive Electrode Crystal Orientation for Stable High-Ni Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional positive electrode active materials for lithium secondary batteries, particularly high-Ni-type materials, face challenges with structural instability leading to rapid deterioration at both high and room temperatures, coupled with issues of cation mixing and phase transformations during calcination.
Innovation Solution
The development of a positive electrode active material where the lithium ion diffusion path is directed to a specific crystal plane, such as the (012), (101), or (104) planes, with improved growth of these crystal planes, enhancing both electrochemical properties and stability. This is achieved through controlled calcination conditions and the use of fluxes during the synthesis of lithium composite oxides.
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 structural instability occurs due to Li/Ni cation mixing
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface region has different composition and properties from the core. The surface is enriched with Li and depleted of Ni compared to the bulk, forming a protective layer that prevents cation mixing at the surface while maintaining high Ni content in the core for high capacity. This local compositional variation resolves the contradiction by protecting the structurally unstable high-Ni core.
Solution Approach 2:
The patent creates a composite structure consisting of a high-Ni layered oxide core and a Li-rich surface layer. This composite material approach combines the high capacity advantage of high-Ni materials with the structural stability of Li-rich surfaces, effectively resolving the contradiction between capacity and stability.
2Stability of the object's composition
If a single-crystal lithium composite oxide is synthesized by excessively increasing or extending the calcination temperature to achieve single crystallization, then the crystallinity is improved, but cation mixing phenomenon increases
Solution Approach 1:
The patent applies preliminary action by forming a precursor structure with controlled composition before final calcination. The surface is pre-enriched with Li and depleted of Ni before the high-temperature treatment, so that even when single crystallization occurs at high temperature, the cation mixing is limited because the surface composition is already optimized. This preliminary compositional adjustment prevents excessive cation mixing during the crystallization process.
Solution Approach 2:
The patent changes the compositional parameters during synthesis, specifically creating a gradient in Li and Ni content from core to surface. By controlling the Li/Ni ratio as a function of position and synthesis conditions, the patent achieves single crystallization while minimizing cation mixing through parameter optimization.
3Ease of manufacture
If excessive lithium composite oxides with metastable or rock-salt phase are formed due to increased cation mixing, then the synthesis is simplified, but the electrochemical properties deteriorate
Solution Approach 1:
The patent applies preliminary anti-action by creating a Li-rich surface composition that prevents the formation of metastable or rock-salt phases during calcination. The surface Li enrichment acts as a protective barrier that suppresses unwanted phase transformations even when high-temperature treatment is applied, thereby maintaining electrochemical properties while allowing simplified synthesis conditions.
4Ease of manufacture
If the crystal plane growth is not controlled, then the synthesis process is simpler, but the lithium ion diffusion path is not optimized
Solution Approach 1:
The patent changes the synthesis parameters (calcination temperature, time, and atmosphere) to control crystal plane growth orientation. By optimizing these parameters, the patent promotes growth of specific crystal planes that expose surfaces with favorable lithium ion diffusion pathways, thereby improving ion diffusion speed while maintaining a relatively simple synthesis process.
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 proposed solution maintains high electrochemical properties while improving structural stability, reducing the likelihood of side reactions with the electrolyte and enhancing thermal stability, thus extending the lifespan and performance of lithium secondary batteries.
Implementation Method 1
a lithium secondary battery storing electrical energy due to a difference in chemical potential when lithium ions are intercalated/deintercalated into/from a positive electrode and a negative electrode
Implementation Method 2
a positive electrode active material which is formed such that a lithium ion diffusion path in a lithium composite oxide constituting a positive electrode active material is directed to a specific crystal plane, and has improved electrochemical properties and stability by improving the growth of the crystal plane to which the lithium ion diffusion path is directed
Implementation Method 3
This is achieved through controlled calcination conditions and the use of fluxes during the synthesis of lithium composite oxides
Data Source
Figure 1~2
Figure 3~6
AI summary
The present invention relates to a positive electrode active material which is formed such that a lithium ion diffusion path in a lithium composite oxide constituting a positive electrode active material is directed to a specific crystal plane, and has improved electrochemical properties and stability by improving the growth of the crystal plane to which the lithium ion diffusion path is directed, and a lithium secondary battery using the same.