Lithium Nickel Cathode Material With Stable Surface Lithium Distribution
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Solution Overview
Problem
Lithium nickel composite oxide positive electrode active materials for lithium secondary batteries face issues with lithium ion deficiencies due to incomplete reaction during calcination, leading to low initial charging and discharging efficiency and cycle characteristics.
Innovation Solution
A positive electrode active material with a lithium metal composite oxide containing Ni and elements like Co, Mn, or Fe, with a layered rock-salt structure, where the lithium compound is evenly distributed to minimize lithium ion deficiencies, achieved through a calcining and mixing process that ensures adequate BET specific surface area and lithium distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If water wash treatment is applied to remove unreacted lithium compound, then purity is improved, but lithium ion deficiencies occur on crystal surface leading to deteriorated capacity
Solution Approach 1:
The invention changes the washing parameters by controlling the washing temperature to be 90°C or higher, which selectively removes unreacted lithium compound while preserving the lithium ions in the crystal structure. This temperature parameter change resolves the contradiction by enabling effective purification without causing lithium ion deficiencies on the crystal surface.
2Reliability
If no washing treatment is applied, then cycle characteristics are improved, but unreacted lithium compound remains leading to low initial charging and discharging efficiency
Solution Approach 1:
The invention introduces temperature as a critical parameter for the washing process, specifying 90°C or higher. This parameter change enables the washing treatment to selectively remove unreacted lithium compound without damaging the crystal structure, thereby achieving both high initial charging and discharging efficiency and good cycle characteristics.
3Productivity
If calcination is performed to produce positive electrode active material, then reaction completeness is improved, but unreacted lithium compound remains due to incomplete reaction
Solution Approach 1:
The invention extracts the unreacted lithium compound from the positive electrode active material through a controlled washing process. By using water at 90°C or higher, the unreacted lithium compound is selectively dissolved and removed, achieving high purity material while maintaining the integrity of the crystal structure and lithium ion content.
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 results in lithium secondary batteries with improved initial charging and discharging efficiency and high cycle retention rates by maintaining a stable lithium distribution and increasing the reaction area for ion insertion and desorption.
Implementation Method 1
In the calcining step, the metal composite compound reacts with the lithium compound, and a positive electrode active material is produced
Implementation Method 2
increasing the reaction area for ion insertion and desorption
Data Source
AI summary
In a spectrum obtained by X-ray photoelectron spectroscopy measurement of surfaces of particles of the positive electrode active material for the lithium secondary battery, the positive electrode active material has a peak X derived from a Li element having a peak top at 54.5±3.0 eV; when, upon waveform separation of the peak X derived from the Li element into a peak (A) having a peak top at 53.5±1.0 eV and a peak (a) having a peak top at 55.5±1.0 eV, an atomic ratio calculated from the peak (A), a peak derived from the Ni element, and a peak derived from the element M is defined as Li(A)/(Ni+M), and the BET specific surface area of the positive electrode active material for the lithium secondary battery measured by a nitrogen adsorption method is defined as PS, the value of {Li(A)/(Ni+M)}/PS is 0.4 to 2.6 g/m2.