Cathode Active Material Aspect Ratio Gradient to Reduce Particle Strain
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Solution Overview
Problem
Lithium secondary batteries face challenges with limited energy density, lifetime, and stability due to issues with existing positive electrode active materials such as LiCoO2, LiMnO2, and LiNiO2, which suffer from high costs, thermal safety concerns, and difficulties in synthesis, leading to reduced cycle life and capacity.
Innovation Solution
A positive electrode active material with primary particles exhibiting an aspect ratio gradient increasing from the core to the surface of secondary particles, optimized by doping with metal elements like niobium and adjusting calcination conditions, improves particle density and electrochemical characteristics, reducing strain during charging/discharging and enhancing energy density and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiCoO2 is used as positive electrode active material, then charge/discharge efficiency and lifetime characteristics are improved, but cost increases due to limited cobalt resource
Solution Approach 1:
The patent changes the compositional parameters by replacing cobalt with nickel and manganese in a controlled ratio (LiNi1-x-yCoxMnyO2), where x and y are optimized to balance cost and performance. This parameter adjustment reduces cobalt content while maintaining structural stability and electrochemical performance through the synergistic effect of nickel (high capacity) and manganese (thermal stability).
Solution Approach 2:
The patent creates a composite oxide material LiNi1-x-yCoxMnymO2 that combines the advantages of different metal elements. Nickel provides high discharge capacity, cobalt maintains structural integrity, and manganese improves thermal stability. This composite approach achieves a balance between cost reduction and performance maintenance by leveraging the complementary properties of multiple materials.
2Ease of manufacture
If LiMnO2 or LiMn2O4 is used as positive electrode active material, then thermal safety and cost are improved, but capacity and high-temperature characteristics deteriorate
Solution Approach 1:
The patent modifies the stoichiometric ratios of metal elements in the spinel structure by controlling the values of x and y in LiNi1-x-yCoxMnymO2. By optimizing these parameters, the material achieves enhanced capacity while maintaining the thermal safety benefits of manganese-based structures. The controlled substitution of nickel for manganese increases capacity without compromising the thermal stability provided by the spinel framework.
3Quantity of substance
If LiNiO2-based positive electrode active material is synthesized, then discharge capacity is improved, but rate characteristics deteriorate due to cation mixing between Li and transition metal
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of metal elements within the crystal structure. Through controlled doping and surface modification, the material achieves different compositional characteristics in different regions - the bulk provides high capacity through nickel content, while the surface or specific crystallographic sites are optimized to prevent cation mixing and facilitate rapid ion transport, thereby improving rate characteristics.
Solution Approach 2:
The patent changes the compositional parameters by introducing small amounts of aluminum or other elements as additional dopants in specific ratios. This parameter adjustment modifies the local crystal field and ionic radii, creating pathways that facilitate lithium ion diffusion while maintaining high nickel content for capacity. The optimized doping levels prevent cation mixing by stabilizing the layered structure against phase transitions.
4Ease of manufacture
If cation mixing between Li and transition metal is intensified, then synthesis difficulty increases, but Li by-products increase causing gelation and gas generation
Solution Approach 1:
The patent applies preliminary action by pre-doping the precursor materials with aluminum or other stabilizing elements before the main synthesis process. This preliminary modification of the starting materials prevents cation mixing during subsequent high-temperature treatment, thereby reducing the formation of LiOH and Li2CO3 by-products. The pre-established structural framework resists degradation and minimizes harmful by-product generation during battery operation.
Solution Approach 2:
The patent converts the potential harm of cation mixing into a benefit by utilizing controlled doping with aluminum. The aluminum doping, while modifying the composition, actually prevents excessive cation mixing by stabilizing the crystal structure. The controlled structural modification transforms what could be a harmful effect (structure degradation) into a beneficial outcome (enhanced stability and reduced by-products).
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 effectively improves the electrochemical characteristics and stability of lithium secondary batteries by minimizing strain and maintaining high energy density, charge capacity, and efficiency, while reducing the risk of cracking and extending cycle life.
Implementation Method 1
it is possible to improve the density of the primary particles in the secondary particle and the electrochemical characteristics by adjusting a gradient range of an average aspect ratio of the primary particles present in a core of the secondary particle and an average aspect ratio of the primary particles present in a surface region of the secondary particle, or by doping with metal elements such as niobium
Implementation Method 2
adjusting calcination conditions, improves particle density and electrochemical characteristics
Implementation Method 3
lithium ions are intercalated/deintercalated into/from a positive electrode and a negative electrode
Data Source
AI summary
The present invention relates to a positive electrode active material having improved electrical characteristics by adjusting an aspect ratio gradient of primary particles included in a secondary particle, a positive electrode including the positive electrode active material, and a lithium secondary battery using the positive electrode.