Cellulose Nanocrystal Battery Separator for Strength Without Weight
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Solution Overview
Problem
Existing separators for electrochemical devices are heavy due to the use of high-density inorganic materials, which hinders weight reduction and energy density improvement, and lack sufficient mechanical strength and binding properties.
Innovation Solution
A separator comprising a porous polymer base with cellulose nanocrystals, which have a density of 0.1 g/m3 to 2.0 g/m3, a Young's modulus of 50 GPa to 80 GPa, and a diameter of 30 nm or less, integrated with a coating layer containing inorganic particles and a polymer binder, enhancing mechanical properties and ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-density inorganic materials are used in the separator, then mechanical strength is improved, but weight increases and energy density decreases
Solution Approach 1:
The patent uses a composite structure combining organic polymer matrix with inorganic nanoparticles (alumina, boehmite, or silica) having density of 2.0 g/cm³ or less. This composite approach provides mechanical strength through the inorganic reinforcement while maintaining low weight through the lightweight polymer matrix and low-density inorganic fillers, resolving the contradiction between strength and weight.
Solution Approach 2:
The separator employs a porous structure with controlled pore size and distribution, allowing the use of lightweight materials while maintaining mechanical integrity through the porous network architecture. The porous structure reduces overall density and weight while the interconnected framework provides structural support, addressing the strength-weight tradeoff.
2Reliability
If inorganic matter is added to the coating layer, then flame resistance and heat resistance are improved, but binding characteristic becomes weak
Solution Approach 1:
The patent introduces a polymer binder as an intermediary substance that chemically or physically bonds the inorganic matter particles to each other and to the substrate. This binder layer mediates between the inorganic flame-resistant particles and the separator structure, providing strong binding characteristics while maintaining the flame resistance benefits of the inorganic materials.
Solution Approach 2:
The coating layer is designed as a composite material system combining inorganic matter (for flame resistance), polymer binder (for binding strength), and potentially organic matrix. This multi-component composite approach allows simultaneous optimization of flame resistance, binding characteristics, and other properties by adjusting composition ratios and interactions between components.
3Strength
If inorganic matter with high density is used, then mechanical strength is improved, but energy density of battery decreases
Solution Approach 1:
The patent specifies using inorganic matter with density of 2.0 g/cm³ or less (such as alumina, boehmite, or silica) in the composite separator structure. This low-density inorganic reinforcement provides necessary mechanical strength while minimizing weight addition, thereby preserving or improving the battery's energy density by reducing the mass fraction of non-active components.
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 separator achieves reduced weight, improved energy density, and enhanced mechanical strength through strong hydrogen bonding, while maintaining high ion conductivity and electrolyte wettability.
Implementation Method 1
enhanced mechanical properties and stiffness by including cellulose nanocrystals in a porous polymer base
Implementation Method 2
a polymer base having a porous structure that is disposed between a positive electrode and a negative electrode, and plays a role to separate the positive electrode and a negative electrode, to prevent an electrical short-circuit between the two electrodes, and to transmit an electrolyte and ions
Implementation Method 3
physical properties of the separator, such as wettability for the electrolyte, a degree of porosity, and a thermal shrinkage ratio, affect performance and safety of the electrochemical device
Data Source
AI summary
Disclosed is a separator for an electrochemical device and an electrochemical device including the same. The separator for the electrochemical device can reduce the weight of the separator, can improve the energy density of a battery, and can enhance stiffness because cellulose nanocrystals are included in a porous polymer base.