Lithium Nickel Cobalt Cathode Material With Two-Step Firing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing lithium nickel-based composite oxides for cathode active materials in lithium ion secondary batteries are inefficient and result in degraded battery performance due to issues like cation mixing and uneven distribution of lithium, leading to reduced cycle characteristics and discharge capacity.
Innovation Solution
A two-step firing process is employed, involving preliminary firing at 500° C. to 600° C. for 30 minutes to 5 hours, followed by final firing at 680° C. to 780° C. for 3 to 6 hours, to produce spherical particles of lithium nickel cobalt composite oxide with uniform lithium distribution and high crystallinity, using a mixture of nickel cobalt composite and lithium compounds with specific bulk density and particle size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-step high-temperature firing process is used to produce lithium nickel-based composite oxide, then the production time is short and productivity is high, but cation mixing occurs and lithium distribution becomes uneven, degrading battery performance
Solution Approach 1:
The single-step firing process is divided into two distinct stages: a first firing at lower temperature (450-650°C) to form intermediate particles with controlled lithium distribution, followed by a second firing at higher temperature (650-800°C) to achieve final crystallization. This segmentation allows each stage to optimize for its specific function, preventing cation mixing while ensuring uniform lithium distribution throughout the composite oxide structure.
Solution Approach 2:
The first firing treatment serves as a preliminary action that pre-establishes a favorable lithium distribution pattern and forms an intermediate structure before the final high-temperature firing. By performing this preparatory step at lower temperature, the lithium ions are positioned optimally within the crystal lattice, preventing subsequent cation mixing during the second firing stage and ensuring high manufacturing precision without sacrificing productivity.
2Reliability
If high temperature firing is applied to improve crystallinity and battery performance, then discharge capacity increases, but energy consumption increases and production efficiency decreases
Solution Approach 1:
The energy-intensive firing process is segmented into two temperature zones: a low-energy first firing (450-650°C) that performs preliminary lithium distribution and structure formation, and a higher-energy second firing (650-800°C) that completes crystallization. This segmentation reduces total energy consumption by performing most of the structural work at lower temperatures, while still achieving high crystallinity and battery performance through the optimized two-stage approach.
Solution Approach 2:
The firing temperature parameter is dynamically changed between two distinct levels rather than maintaining a constant high temperature. The first firing uses lower temperature (450-650°C) to minimize energy consumption while achieving lithium distribution, then the temperature is increased to (650-800°C) for final crystallization. This parameter change strategy achieves the necessary crystallinity for high battery performance while significantly reducing overall energy consumption compared to continuous high-temperature firing.
3Manufacturing precision
If extended firing time is used to ensure complete reaction and uniform lithium distribution, then manufacturing precision improves, but productivity decreases
Solution Approach 1:
The extended firing time is segmented into two distinct time periods at different temperatures: a first firing duration (3-10 hours) at lower temperature for thorough lithium distribution, and a second firing duration (0.5-5 hours) at higher temperature for rapid crystallization. This segmentation allows the reaction to proceed to completeness through the prolonged low-temperature stage, while the high-temperature stage completes the process quickly, maintaining high productivity despite the need for complete reaction and uniform lithium distribution.
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
This method enhances battery performance by ensuring uniform lithium distribution and high crystallinity, resulting in improved discharge capacity and cycle characteristics while maintaining high productivity.
Implementation Method 1
subjecting the mixture to preliminary firing by maintaining a firing temperature at 500° C. or higher and 600° C. or lower for 30 minutes or longer and 5 hours or shorter
Implementation Method 2
ensuring uniform lithium distribution and high crystallinity
Data Source
AI summary
The cathode active material for a lithium ion secondary battery is produced from spherical particles made of lithium nickel cobalt composite oxide represented by general formula: LizNi1−x−yCoxMyO2 (wherein M is at least one element selected from among Mn, V, Mg, W, Mo, Nb, Ti, and Al and x, y, and z satisfy 0<x≤0.35, 0≤y≤0.35, and 0.97≤z≤1.20, respectively) and having a volume average particle diameter MV in a range of preferably 8 to 30 μm, wherein an area ratio of a lithium compound unevenly distributed on surfaces of the particles in a SEM image is 5% or less. The spherical particles preferably have a crystallite diameter in a range of 50 to 200 Å as determined from a full width at half maximum, FWHM of diffraction peak of (003) plane obtained by X ray diffraction by using Sherrer formula.