Positive Electrode Porous Coating for Low Resistance and Self-Discharge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium ion secondary batteries face challenges in minimizing energy loss and self-discharge, particularly when using thin separators, which can lead to increased battery resistance and reduced energy density, while attempts to suppress self-discharge through inorganic-particle layers often deteriorate power performance.
Innovation Solution
A positive electrode with a porous layer containing inorganic particles is implemented, where the porous layer is stacked on the active material-containing layer, with a thickness of 3.0 μm or less, and a specific pore diameter ratio is maintained to balance lithium ion movement and self-discharge suppression, ensuring low battery resistance and effective self-discharge control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin separator is used to ensure high safety, then battery resistance increases and energy density decreases
Solution Approach 1:
The patent applies porous inorganic particles (such as alumina, silica, or titania) to form a porous coating layer on the separator surface. This porous structure allows lithium ions to pass through while maintaining the mechanical integrity and safety functions of the thin separator, thereby reducing battery resistance without compromising safety.
Solution Approach 2:
The patent creates a composite structure by combining the separator material with inorganic particles to form a composite coating layer. This composite material approach enables the separator to simultaneously achieve thin thickness for high energy density, low resistance for high power, and maintained safety through the protective inorganic particle network.
2Loss of energy
If an inorganic-particle layer is provided on the separator surface to suppress self-discharge, then energy density and power performance deteriorate
Solution Approach 1:
The patent applies inorganic particles selectively on specific regions of the separator surface rather than uniformly across the entire separator. This local application strategy suppresses self-discharge at the electrode-separator interface where it occurs most, while maintaining open pore structures and thin overall thickness to preserve lithium ion transport pathways and power performance.
Solution Approach 2:
The patent uses porous inorganic particles with controlled pore sizes and distributions that allow lithium ions to pass through while blocking electron transport that causes self-discharge. The porous nature of the inorganic particle layer maintains ion conductivity for high power performance while providing the electron-blocking function to suppress self-discharge.
3Quantity of substance
If the porous layer thickness is reduced to maintain energy density, then self-discharge suppression capability decreases
Solution Approach 1:
The patent employs porous inorganic particles with high surface area to volume ratio, which provide effective self-discharge suppression functionality even at reduced thicknesses. The porous structure allows the thin layer to maintain sufficient inorganic particle content for electron blocking while preserving lithium ion transport pathways, thereby achieving both low thickness for high energy density and adequate self-discharge suppression.
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 solution achieves a balance between low battery resistance and suppressed self-discharge, enhancing the battery's performance and safety by optimizing the porous layer's thickness and pore distribution, thereby improving energy density and power output.
Implementation Method 1
a porous layer provided on at least a part of the positive electrode active material-containing layer and containing inorganic particles
Implementation Method 2
A ratio X/Y, between a mode diameter X in a log differential pore volume distribution curve obtained by mercury porosimetry with respect to the positive electrode active material-containing layer and the porous layer, and a mode diameter Y in a log differential pore volume distribution curve obtained by mercury porosimetry with respect to the positive electrode active material-containing layer
Data Source
AI summary
According to one embodiment, provided is a positive electrode including a positive electrode current collector, a positive electrode active material-containing layer thereon, and a porous layer on at least a part of the positive electrode active material-containing layer and containing inorganic particles. A thickness of the porous layer is 3.0 μm or less. A ratio X/Y, between a mode diameter X in a log differential pore volume distribution curve according to mercury porosimetry with respect to the positive electrode active material-containing layer and the porous layer, and a mode diameter Y in the log differential pore volume distribution curve according to mercury porosimetry with respect to the positive electrode active material-containing layer, satisfies 1.0<X/Y<1.5.