Lithium Battery Positive Electrode Wettability Evaluation
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Solution Overview
Problem
Existing methods for evaluating the wettability of lithium secondary battery electrodes to electrolyte solutions are inadequate, as conventional contact angle methods fail due to penetration issues, and gas-jetting methods struggle with measuring the liquid-removed space effectively.
Innovation Solution
A positive electrode for lithium secondary batteries is designed with a metal foil and a mixture layer containing lithium/transition metal complex oxide, conductive agents, and binders, evaluated using a specific gas-jetting wettability test that measures the diameter of the liquid-removed space to assess wettability accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional contact angle methods are used to evaluate wettability, then the evaluation can be performed, but the measurement is inaccurate due to electrolyte solution penetration issues
Solution Approach 1:
The patent employs gas jetting (pneumatic method) to remove electrolyte solution from the electrode surface for wettability evaluation. Nitrogen gas is jetted at controlled pressure (10 kPa) to blow off the liquid, creating a liquid-removed space whose diameter serves as the evaluation metric. This pneumatic approach overcomes the penetration issue inherent in contact angle methods by actively removing the electrolyte rather than measuring its interaction with the surface.
Solution Approach 2:
The patent changes the evaluation parameter from contact angle to liquid-removed space diameter. By measuring the diameter of the space created when gas jetting removes the electrolyte solution (specifically, the average diameter during 0.5-1.5 seconds after jetting starts), the method provides accurate wettability assessment without suffering from penetration problems. The specific parameter range (6.5 mm or less) establishes clear evaluation criteria.
2Measurement precision
If gas-jetting methods are used to measure liquid-removed space, then wettability can be evaluated, but the measurement is difficult due to ineffective liquid removal
Solution Approach 1:
The patent optimizes the pneumatic jetting parameters to effectively remove electrolyte solution. Nitrogen gas is jetted at a specific pressure (10 kPa) from a nozzle positioned 8 mm above the liquid surface, with the jet direction perpendicular to the electrode surface. These controlled pneumatic conditions ensure sufficient liquid removal while maintaining measurement feasibility, resolving the difficulty of detecting and measuring the liquid-removed space.
Solution Approach 2:
The patent replaces complex visual or instrumental measurement systems with a simpler pneumatic-jetting-and-measurement approach. By using gas jetting to create a visible liquid-removed space and measuring its diameter directly, the method simplifies the detection and measurement process while maintaining accuracy, avoiding the difficulties associated with traditional liquid removal and measurement techniques.
3Reliability
If positive electrode structure is optimized for better wettability, then battery cyclic characteristics improve, but manufacturing complexity increases
Solution Approach 1:
The patent establishes specific parameter ranges for the positive electrode components to achieve optimal wettability and cyclic characteristics. The lithium/transition metal complex oxide contains transition metals (Ni, Co, Mn, Al) with specific composition ratios, the binder content is controlled at 0.1-5 mass%, and the conductive agent content is controlled at 0.1-5 mass%. These parameter specifications enable manufacturers to produce electrodes with consistent, optimized performance without requiring complex structural designs.
Solution Approach 2:
The patent uses composite materials strategy by combining lithium/transition metal complex oxide (containing multiple metal elements), conductive agents, and binders in specific proportions. This composite approach enhances wettability and cyclic characteristics through the synergistic effects of different materials, while the defined composition ranges keep the manufacturing process manageable and scalable.
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 approach allows for accurate evaluation of wettability and improves the cyclic characteristics of lithium secondary batteries by ensuring a liquid-removed space diameter of 6.5 mm or less, enhancing battery performance.
Implementation Method 1
nitrogen gas is jetted out perpendicularly to the surface of the positive electrode at a pressure of 10 kPa
Implementation Method 2
A lithium secondary battery, which charges and discharges by migration of lithium ions between a positive electrode and a negative electrode
Implementation Method 3
a lithium hexafluorophosphate solution in a solvent composed of ethylene carbonate and ethyl methyl carbonate is poured therein
Data Source
AI summary
A lithium secondary battery positive electrode with: a metallic foil; and a positive electrode mixture layer formed on a surface of the metallic foil and containing a binding agent, a conductive agent, and a positive electrode active material comprising a lithium-transition metal complex oxide, wherein the positive electrode has a diameter of the liquid-removed space of at most 6.5 mm as measured by a wettability evaluation test, wherein a positive electrode is placed inside a container, and a prescribed test solution is added to a prescribed liquid-surface level, and nitrogen is sprayed thereon from a prescribed pipe at a prescribed pressure. A measurement is taken of the diameter of a region from which the solution has been removed by the spraying, and a mean value of such diameters measured between 0.5 seconds and 1.5 seconds after the initiation of the spraying is used as the diameter of the liquid-removed space.