Lithium Composite Particles Surface Purification
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Solution Overview
Problem
Current lithium ion secondary batteries using LiNiO2 as positive electrode active substances face issues with thermal stability and cycle durability due to surface impurities, leading to undesirable side reactions and battery degradation.
Innovation Solution
Lithium composite compound particles with a specific compositional formula (Li1+xNi1-y-zCOyMzO2) are developed, where x, y, and z are within defined ranges, and undergo a process involving water washing and heat treatment to control surface impurities and crystal structure, resulting in improved cycle characteristics and high-temperature storage properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiNiO2 is used as positive electrode active substance to achieve large charge/discharge capacity, then battery capacity is improved, but thermal stability and cycle durability are deteriorated due to surface impurities
Solution Approach 1:
The patent applies the extraction principle by removing surface impurities (excess lithium, carbonates, sulfates) from the LiNiO2 particles through washing treatments. This extraction of harmful surface components resolves the contradiction by maintaining the high-capacity bulk material while eliminating the impurities that cause thermal instability and poor cycle durability.
Solution Approach 2:
The patent applies local quality by treating only the surface region of the particles differently from the bulk. The surface is cleaned and modified to remove impurities and control composition, while the bulk retains the high-capacity LiNiO2 structure. This localized treatment resolves the contradiction between high capacity and stability.
2Ease of manufacture
If excess lithium is present on particle surface to simplify synthesis, then manufacturing is easier, but gelation occurs during electrode formation and battery swelling occurs due to carbonation
Solution Approach 1:
The patent applies preliminary action by performing washing treatments during the synthesis process to remove excess lithium and prevent subsequent gelation and carbonation issues. By addressing the impurity problem early in the manufacturing process rather than after electrode formation, the patent prevents harmful effects while maintaining synthesis simplicity.
Solution Approach 2:
The patent converts the potentially harmful excess lithium into a beneficial process feature by using controlled washing to remove only the harmful surface excess while preserving the bulk composition. The washing process transforms what would be a manufacturing defect into a controlled purification step that improves battery performance.
3Ease of manufacture
If sulfates are present on particles to accept as synthesis byproduct, then manufacturing is simpler, but resistance value increases during storage
Solution Approach 1:
The patent applies extraction by specifically removing sulfate impurities from the particle surface through washing treatments. This selective removal of sulfates resolves the contradiction by maintaining simple synthesis processes while eliminating the specific impurity that causes resistance increase during storage.
4Reliability
If water washing is performed to remove surface impurities, then cycle characteristics and storage property are improved, but water may penetrate into particle interior and cause structural degradation
Solution Approach 1:
The patent applies partial action by performing controlled washing treatments that remove surface impurities without excessive water exposure that would penetrate the particle interior. The washing is sufficient to remove harmful impurities but controlled to avoid structural degradation, resolving the contradiction between purification and structural integrity.
Solution Approach 2:
The patent applies parameter changes by controlling washing conditions (water amount, washing time, temperature) to optimize the balance between impurity removal and structural preservation. By adjusting these parameters, the patent achieves effective purification while preventing water penetration that would cause structural degradation.
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 lithium composite compound particles exhibit excellent cycle characteristics and high-temperature storage properties, effectively suppressing side reactions and enhancing the performance of secondary batteries.
Implementation Method 1
treating lithium composite compound particles with a water solvent to remove impurities therefrom
Implementation Method 2
subjecting the lithium composite compound particles obtained in the step (1) to heat treatment... in an air or oxygen atmosphere having a carbonate concentration of not more than 100 ppm
Data Source
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Figure 4~5
AI summary
The present invention relates to lithium composite compound particles having a composition represented by the formula: Li1+xNi1-y-zCoyMzO2 (M = B or Al), wherein the lithium composite compound particles have an ionic strength ratio A (LiO-/NiO2-) of not more than 0.3 and an ionic strength ratio B (Li3CO3+/Ni+) of not more than 20 as measured on a surface of the respective lithium composite compound particles using a time-of-flight secondary ion mass spectrometer. The lithium composite compound particles of the present invention can be used as a positive electrode active substance of a secondary battery which has good cycle characteristics and an excellent high-temperature storage property.