Low-Sodium Ceramic Separator Coating for Lower Cell Resistance
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Solution Overview
Problem
Existing ceramic-coated separators in lithium batteries have high internal resistance due to the influence of sodium content and the use of sodium carboxymethyl cellulose (CMC), which affects ion conductivity and increases capacity attenuation and power decay.
Innovation Solution
A low-sodium ceramic-coated separator is developed by using low-sodium boehmite powder and omitting CMC, with a ceramic layer having a sodium content of less than 1000 ppm, and adjusting the ceramic slurry composition and coating process parameters to achieve a peel strength of 20 N/m or above and an ionic conductivity of 1.4 mS/cm or higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based porous substrate is used as a separator to ensure chemical inertness and electrochemical stability, then reliability is improved, but internal resistance increases and electrochemical performance deteriorates
Solution Approach 1:
The patent applies composite materials by coating the polyolefin-based porous substrate with a ceramic layer comprising metal oxides (such as Mn3O4, MnO2, Fe2O3, Fe3O4, Co3O4, NiO, or CuO). This composite structure combines the chemical inertness and electrochemical stability of polyolefin with the electrical conductivity and catalytic activity of ceramic materials, thereby reducing internal resistance while maintaining reliability.
Solution Approach 2:
The patent changes the surface properties of the separator by introducing ceramic coatings with specific electrical conductivity parameters. The ceramic layer transforms the electrical characteristics of the separator from high resistance to low resistance, enabling efficient electron transfer and improving electrochemical performance while preserving the base material's stability.
2Ease of manufacture
If the separator surface is left as-is to maintain manufacturing simplicity, then ease of manufacture is improved, but electrode adhesion is insufficient and dendrite formation occurs
Solution Approach 1:
The ceramic coating creates a composite surface structure that enhances electrode adhesion through chemical interactions between the ceramic particles and electrode materials. This composite surface also prevents dendrite formation by providing a uniform deposition interface, thereby improving reliability without significantly complicating the manufacturing process.
Solution Approach 2:
The ceramic coating is applied as a porous layer that maintains the underlying substrate's porosity while providing enhanced surface properties. The porous structure allows electrolyte penetration and ion transport while the ceramic surface provides improved adhesion and dendrite prevention, achieving reliability enhancement with minimal manufacturing complexity.
3Productivity
If a ceramic coating is applied to reduce internal resistance and improve electrochemical performance, then productivity is improved, but coating uniformity and control become challenging
Solution Approach 1:
The patent uses a slurry as an intermediary medium to apply ceramic particles to the separator substrate. The slurry formulation (comprising ceramic particles, binder, and solvent in specific ratios) ensures uniform distribution and adhesion of the ceramic coating, achieving consistent electrochemical performance while simplifying the coating process.
Solution Approach 2:
The patent optimizes coating parameters including slurry composition (ceramic-to-binder ratio, solvent type), coating thickness (5-50 micrometers), and sintering conditions (temperature and time). These parameter adjustments ensure uniform coating formation while maintaining high electrochemical performance and facilitating scalable production.
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 significantly reduces internal resistance, improving power performance and discharge efficiency by minimizing sodium content and optimizing slurry viscosity, peel strength, and Gurley value, thereby enhancing ion conductivity.
Implementation Method 1
facilitating smooth ion transport, the separator may be coated with a layer of ceramic having high ion conductivity
Implementation Method 2
it is also necessary to maintain the electrical insulation properties of the separator to prevent electron transfer
Implementation Method 3
drying the slurry to form a coating layer
Implementation Method 4
sintering the coating
Data Source
Figure 1
AI summary
The present disclosure provides a low-internal-resistance ceramic-coated separator, a preparation method thereof, and a lithium battery. The low-internal-resistance ceramic-coated separator of the present disclosure includes a polymer base film, and a ceramic layer coated on one or two sides of the polymer base film. The ceramic layer adopts low-sodium boehmite and does not contain sodium carboxymethyl cellulose (CMC). A sodium content of the ceramic layer is less than 1000 ppm, so that a Gurley increase value of the separator is significantly lowered. When applied to the lithium battery, the ceramic layer can greatly reduce an internal resistance of a cell, thereby improving the power performance and discharge efficiency of the battery.