Ceramic Coated Battery Separators for Thermal Stability
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Solution Overview
Problem
Current Li-ion batteries face safety issues due to thermal shrinkage of porous polyolefin separators, which can cause shorts between electrodes, and existing ceramic coating methods struggle to uniformly apply ceramic particles thinner than four microns.
Innovation Solution
A method involving layer-by-layer coating of oppositely charged nano/micro-sized ceramic particles or using physical vapor deposition (PVD) to achieve a uniform ceramic coating with controlled thickness on separators, enhancing safety and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If printing techniques are used to coat ceramic particles on separators, then a ceramic coating can be applied, but the coating uniformity and thickness control are insufficient for achieving four microns or less
Solution Approach 1:
The patent replaces mechanical printing techniques with electrostatic field-based particle deposition. Ceramic particles are charged and attracted to the separator surface through electrostatic forces, enabling precise thickness control at the micron and sub-micron level without the limitations of mechanical printing methods.
Solution Approach 2:
The patent controls coating thickness by adjusting electrostatic field parameters such as voltage, particle charge density, and deposition time. By varying these parameters, the coating thickness can be precisely controlled to achieve four microns or less with high uniformity across the separator surface.
2Reliability
If a ceramic coating is applied to prevent thermal shrinkage, then safety is improved, but the coating process generates waste and has low yield
Solution Approach 1:
The electrostatic deposition process allows particles to self-align and self-assemble on the separator surface based on electrostatic attraction. This self-organizing mechanism minimizes material waste by ensuring that charged particles are efficiently captured on the separator rather than being lost during application, achieving high yield with minimal excess material.
3Reliability
If porous polyolefin separators are used, then ion conductivity is maintained, but thermal shrinkage occurs at elevated temperatures causing shorts
Solution Approach 1:
The patent creates a composite structure by coating ceramic particles on the porous polyolefin separator. The ceramic layer provides thermal stability and dimensional integrity at elevated temperatures, preventing shrinkage-induced shorts, while the underlying porous polyolefin maintains ion conductivity. This composite approach combines the advantages of both materials to eliminate their respective weaknesses.
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 method results in a denser, more uniform ceramic coating with improved thermal stability and ion conductivity, reducing waste and increasing yield, thereby enhancing the safety and efficiency of Li-ion batteries.
Implementation Method 1
Other embodiments of the invention utilize a dry process such as PVD for depositing a ceramic film on a porous polyolefin separator
Implementation Method 2
the controlled process comprises coating the separator with a first layer of ceramic particles having a first charge; coating the first layer with a second layer of ceramic particles having a second charge opposite the first charge
Data Source
AI summary
The present invention relates generally to electrochemical energy storage devices such as Li-ion batteries, and more particularly to a method of providing uniform ceramic coatings with controlled thicknesses for separators in such storage devices. Some embodiments of the invention utilize a layer by layer coating of nano/micro-sized particles dispersed in a solvent, which can be aqueous or non-aqueous. Other embodiments of the invention utilize a dry process such as PVD for depositing a ceramic film on a porous polyolefin separator. According to certain aspects of the invention, advantages of this approach include the ability to achieve a denser more uniform film with better controlled thickness with less waste and higher yield than current ceramic coating technology. An advantage of a ceramic coated separator is increased safety of cells.