Electrode Coating with Different Isoelectric Points
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Solution Overview
Problem
Lithium secondary batteries face challenges in improving input-output density due to increased internal resistance caused by surface coatings on active materials, leading to poor input-output characteristics.
Innovation Solution
An electrode design featuring a collector with an electrode mix layer containing active materials A and B, where the coat material A has an isoelectric point of 7 or lower and coat material B has an isoelectric point of 7 or higher, creating nonuniform surface charges, enhancing charge carrier ion affinity and wettability, and optimizing the distribution of these materials to reduce internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the surface of active material is coated with metal oxide, then contact between electrolyte and active material is reduced and side reactions are inhibited, but internal resistance increases and input-output characteristic deteriorates
Solution Approach 1:
The patent applies local quality by using two different coat materials (A and B) with distinct isoelectric points on different portions of the active material surface. Coat material A (isoelectric point ≤7) provides one type of surface charge while coat material B (isoelectric point ≥7) provides an opposite or different charge, creating locally differentiated surface properties that simultaneously reduce side reactions and maintain good input-output characteristics
Solution Approach 2:
The patent employs composite materials by combining two coat materials with different isoelectric points on the active material surface. This composite coating structure leverages the complementary properties of both materials: one providing protection against side reactions while the other maintains ion transport efficiency, thereby resolving the contradiction between reliability and power
2Reliability
If uniform coat material is applied on active material surface, then protection is provided, but charge distribution becomes uniform and charge carrier ion attraction decreases
Solution Approach 1:
The patent creates local quality differences on the particle surface by applying two distinct coat materials (A and B) with different isoelectric points in specific proportions (70-95 wt% of one material, 5-30 wt% of the other). This results in different surface charge densities in different regions, generating localized electric fields that effectively attract charge carrier ions while maintaining overall surface protection
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 electrode design results in superior input and output characteristics by reducing internal resistance and enhancing charge carrier ion movement, leading to improved battery performance and power density.
Implementation Method 1
The coat material A has an isoelectric point, based on an electrophoretic method, of 7 or lower; the isoelectric point of the coat material B is 7 or higher
Implementation Method 2
the affinity between the charge carrier ions and the electrode becomes higher, and the wettability of the electrolyte towards the electrode is enhanced
Data Source
AI summary
One aspect of the present invention provides an electrode having a collector and an electrode mix layer disposed on the collector. The electrode mix layer contains an active material A having a core portion A and a coat material A, and an active material B having a core portion B and a coat material B. The isoelectric point of the coat material A is 7 or lower. The isoelectric point of the coat material B is 7 or higher. The isoelectric point of at least one of the coat material A and the coat material B is not 7.