Cathode Residual Lithium Analysis Beyond pH Titration Limits
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Solution Overview
Problem
Conventional methods for analyzing residual lithium compounds in cathode active materials of lithium secondary batteries are inadequate, as they fail to distinguish between Li2O and LiOH and cannot measure Li2SO4, leading to inaccurate performance evaluation.
Innovation Solution
A method involving ONH, CS, and ICP-OES analyses is employed to measure H, C, and S components, allowing separate quantification of LiOH, Li2CO3, and Li2SO4, with Li2O calculated by subtracting measured Li from total Li, correcting for moisture-induced LiOH changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wet pH titration method is used to analyze residual lithium compounds, then the measurement process is simple, but Li2O and LiOH cannot be distinguished and Li2SO4 cannot be measured
Solution Approach 1:
The patent divides the analysis into separate measurement steps: first measuring total lithium content, then measuring carbon and sulfur content, and finally calculating the amounts of different lithium compounds through systematic subtraction. This segmentation allows each compound to be analyzed independently rather than mixing them together in a single pH titration measurement.
Solution Approach 2:
The patent introduces intermediate measurement steps using carbon-sulfur analyzer and ICP-OES to measure total lithium and carbon/sulfur content separately. These intermediary measurements serve as bridges to calculate the specific amounts of Li2CO3, Li2SO4, LiOH, and Li2O without directly measuring each compound through pH titration.
2Ease of operation
If conventional pH titration is used, then the analysis method is straightforward, but multiple peaks appear when other metals are coated on the surface making accurate analysis difficult
Solution Approach 1:
The patent extracts the measurement of carbon and sulfur content separately from the pH titration process using a carbon-sulfur analyzer. This extraction removes the interference of metal coatings that cause multiple peaks in pH titration, allowing accurate measurement of Li2CO3 and Li2SO4 content without being affected by surface metal layers.
Solution Approach 2:
The patent replaces the mechanical/chemical pH titration system with instrumental analysis methods (ICP-OES for lithium, carbon-sulfur analyzer for C and S). These instrumental methods are less sensitive to surface metal coating interference and provide more reliable quantitative data for calculating residual lithium compounds.
3Ease of operation
If Li2O is measured in contact with water, then the measurement process is simple, but Li2O turns into LiOH making them indistinguishable
Solution Approach 1:
The patent performs preliminary measurement of total lithium content using ICP-OES before any water contact occurs. This preliminary measurement captures the total lithium including Li2O that has not yet converted to LiOH. By combining this with subsequent measurements of LiOH (after water contact) and calculations based on carbon and sulfur content, the patent can distinguish and quantify Li2O separately from LiOH.
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
Accurately determines the amounts of all four residual lithium compounds, enhancing the evaluation of cathode and battery performance by overcoming the limitations of wet pH titration.
Implementation Method 1
analyzing a cathode active material sample with an oxygen nitrogen hydrogen analyzer (ONH analyzer) and a Karl Fischer analyzer to measure the amount of an H component
Implementation Method 2
analyzing a cathode active material sample with an oxygen nitrogen hydrogen analyzer (ONH analyzer) and a Karl Fischer analyzer to measure the amount of an H component
Implementation Method 3
analyzing the sample with a carbon-sulfur analyzer (CS analyzer) to measure the amounts of C and S components
Implementation Method 4
analyzing the sample with an inductively coupled plasma optical emission spectrometer (ICP-OES) to measure the amount of a Li component
Data Source
AI summary
The present invention provides a method for analysis of residual lithium compounds in a positive electrode active material for a lithium secondary battery, the method for analysis comprising the steps of: analyzing a sample of a positive electrode active material using an oxygen/nitrogen/hydrogen analyzer (ONH analyzer) and a Karl Fischer analyzer to determine the amount of the H component; analyzing the sample using a carbon/sulfur analyzer (CS analyzer) to determine the amount of the C component and the S component; analyzing the sample using an inductively coupled plasma optical emission spectrometer (ICP-OES) to determine the amount of the Li component; and calculating the amount of each of LiOH, Li2CO3, and Li2SO4 in the sample using the quantification results of the H, C, and S components, and calculating the amount of Li2O in the sample using the quantification result of the Li component. According to the method for analysis of the present invention, the amounts of all four residual lithium compounds present in the positive electrode active material, LiOH, Li2CO3, Li2SO4, and Li2O, can be analyzed.