Cathode Residual Lithium Analysis for Li2O and LiOH Separation
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Solution Overview
Problem
Conventional methods for analyzing residual lithium compounds in cathode active materials for lithium secondary batteries, such as LiOH, Li2CO3, Li2SO4, and Li2O, are limited as they fail to distinguish between Li2O and LiOH due to water contact and cannot measure Li2SO4, leading to inaccurate pH titration results.
Innovation Solution
A method involving an oxygen nitrogen hydrogen analyzer, a carbon-sulfur analyzer, and an inductively coupled plasma optical emission spectrometer (ICP-OES) to measure H, C, and Li components, allowing for separate analysis of LiOH, Li2CO3, and Li2SO4, with correction for moisture-induced changes in LiOH amounts, and calculating Li2O from total Li content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a wet method of stirring a cathode active material sample in water to elute a residual compound and then measuring the pH of the filtrate is performed, then the analysis process is simple and fast, but Li2O and LiOH cannot be distinguished and Li2SO4 cannot be measured
Solution Approach 1:
The analysis method is segmented into multiple independent measurement steps: pH measurement to detect LiOH and Li2CO3, thermal analysis (TG-DTA) to detect Li2O, and ICP-OES to detect Li2SO4. Each step targets specific compounds, allowing accurate distinction and quantification of all four residual lithium compounds without cross-interference.
2Reliability
If multiple metals are coated on the surface of the cathode active material, then the battery performance can be enhanced, but multiple peaks appear during pH titration which renders accurate analysis difficult
Solution Approach 1:
The patent uses an organic solvent (acetone or ethanol) as an intermediary to dissolve and remove metal coating layers from the cathode active material surface before analysis. This intermediary step eliminates the interference of metal coatings on pH titration and other analytical measurements, allowing accurate detection of residual lithium compounds without affecting the underlying battery performance characteristics.
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
Enables accurate measurement of all four residual lithium compounds, improving the evaluation of cathode performance by distinguishing Li2O and LiOH and measuring Li2SO4, thereby enhancing the assessment of lithium secondary battery performance.
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
A method for analysis of residual lithium compounds in a positive electrode active material for a lithium secondary battery comprises 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.