Li-Exchanged Zeolite Composite Separator for Moisture and Ion Scavenging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion secondary batteries face issues with poor high-rate capability, safety concerns due to polyolefin membrane shrinkage and lithium dendrite growth, and degradation from malicious species like moisture and transition-metal ions, which affect their cycle and calendar life.
Innovation Solution
A composite separator is developed using Li-exchanged zeolites as scavenging agents combined with other inorganic particles and a polymeric binder, which absorbs malicious species and improves wetting and mechanical integrity, preventing degradation and enhancing cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyolefin membrane is used as separator, then electrical insulation and electrode separation are achieved, but high-rate capability deteriorates due to poor electrolyte wetting
Solution Approach 1:
The patent applies composite materials by combining polyolefin membrane with inorganic particles (alumina, silica, boehmite) to create a separator that maintains electrical insulation while improving electrolyte wettability. The inorganic particles form a coating layer on the polyolefin substrate, creating a composite structure that addresses both requirements simultaneously.
Solution Approach 2:
The patent utilizes porous inorganic particles with controlled pore structures to enhance electrolyte penetration and wettability. The porous nature of the inorganic coating layer allows better electrolyte access to the separator, improving high-rate capability while maintaining the separation function.
2Reliability
If polyolefin membrane is used as separator, then electrode separation is achieved, but safety deteriorates due to shrinkage at elevated temperatures
Solution Approach 1:
The patent creates a composite separator where inorganic particles (alumina, silica, boehmite) are dispersed in or coated on the polyolefin membrane. These inorganic materials have high thermal stability and do not shrink at elevated temperatures, thereby preventing the separator from shrinking and maintaining electrode separation under thermal stress.
Solution Approach 2:
The patent modifies the thermal properties of the separator by incorporating inorganic materials with different thermal expansion characteristics than polyolefin. This changes the overall thermal behavior of the separator, making it dimensionally stable at elevated temperatures while maintaining its separation function.
3Reliability
If polyolefin membrane is used as separator, then electrode separation is achieved, but safety deteriorates due to lithium dendrite penetration
Solution Approach 1:
The patent employs composite materials by combining polyolefin membrane with inorganic particles to create a separator with enhanced mechanical properties. The inorganic particle coating or dispersion creates a more robust structure that is harder for lithium dendrites to penetrate, while maintaining the fundamental electrode separation function.
Solution Approach 2:
The patent applies local quality by creating an inorganic particle-rich layer or coating on specific regions of the separator. This localized modification provides enhanced dendrite resistance at the interface where electrolyte contact occurs, while the bulk polyolefin structure maintains its separation function.
4Reliability
If Li-exchanged zeolites are added to separator, then scavenging of malicious species is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by selecting inorganic particles like alumina, silica, and boehmite that serve multiple functions: they provide thermal stability, improve wettability, and act as scavengers for malicious species. This multi-functionality reduces the need for additional specialized components, offsetting the complexity increase from adding multiple ingredients.
Solution Approach 2:
The patent utilizes parameter changes by controlling the particle size, concentration, and distribution of inorganic materials in the separator. By optimizing these parameters, the separator achieves effective scavenging of malicious species while maintaining manufacturability and avoiding excessive complexity in the formulation and processing.
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 composite separator extends the cycle life of lithium-ion batteries, improves high-rate capability, and maintains capacity retention by effectively scavenging moisture and transition-metal ions, while maintaining compatibility with non-aqueous electrolytes.
Implementation Method 1
Li-exchanged zeolites as inorganic scavenging agents or additives located along with a different or second-type of inorganic particles in a polymeric binder to form the separator
Implementation Method 2
Polyolefin membranes, however, are generally poorly wetted by the non-aqueous electrolyte, which increases the impedance for Li-ion transport
Data Source
AI summary
A separator for use in an electrochemical cell, such as a lithium-ion secondary battery, that includes a plurality of first inorganic particles, one or more second inorganic particles, a polymeric binder, wherein the weight ratio of the first inorganic particles to the second inorganic particles is in the range from 1:99 to 99:1 and the weight ratio of the combined first and second inorganic particles to the polymeric binder is in the range from 50:50 to 99:1. The inorganic particles being a type of Li-exchanged zeolite having a lithium (Li) concentration in the range of 0.1 wt. % to 20 wt. % and a sodium (Na) concentration that is lower than 5 wt. %, based on the overall weight of the Li-exchanged zeolite. The second inorganic particles being different in composition than the first inorganic particles and having a sodium (Na) concentration in the range of 0.005 wt. % to 1.0 wt. %.