LFP/LMFP Cathode Slurry Coating for Thick-Layer Crack Resistance
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Solution Overview
Problem
Existing cathode chemistries face issues with crack resistance as the thickness of the coating layers increases, leading to reduced integrity and accelerated parasitic reactions with electrolyte, hindering the increase in energy density of secondary batteries.
Innovation Solution
A dual binder and dual solvent slurry coating process is employed, using polyvinylidene fluoride and polytetrafluoroethylene with a combination of dry and wet conductive fillers, applied onto a cathode current collector to form a cathode with enhanced crack resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the cathode coating layer is increased to increase energy density, then the areal capacity is improved, but cracks grow in the drying process reducing coating integrity
Solution Approach 1:
The patent uses a composite binder system comprising both polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) in specific weight ratios (PVDF: 2-6 wt%, PTFE: 0.1-2 wt%). This composite binder formulation provides enhanced mechanical strength and crack resistance in thick coating layers while maintaining electrochemical performance, directly resolving the contradiction between increasing areal capacity and maintaining coating integrity.
2Quantity of substance
If the thickness of the cathode coating layer is increased to increase energy density, then the areal capacity is improved, but parasitic reactions with electrolyte are accelerated
Solution Approach 1:
The dual binder system (PVDF and PTFE) creates a more stable and intact coating structure that acts as a protective barrier, reducing direct contact between the active material and electrolyte. This composite approach minimizes parasitic reactions while enabling thicker coating layers for higher areal capacity.
3Ease of manufacture
If a single binder system is used in the slurry coating process, then the manufacturing process is simple, but crack resistance in thick coatings is insufficient
Solution Approach 1:
The patent employs a composite binder system combining PVDF and PTFE with optimized weight ratios. PVDF provides good adhesion and flexibility, while PTFE contributes exceptional mechanical strength and crack resistance. This composite approach enhances crack resistance in thick coatings while maintaining reasonable manufacturing complexity through standardized slurry preparation and coating processes.
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 process results in a cathode with improved crack resistance and increased areal capacity, enhancing the energy density and integrity of secondary batteries.
Implementation Method 1
The coatings often include the active materials, a binder, additives, and a solvent
Implementation Method 2
drying the coating and forming a cathode
Data Source
AI summary
A cathode electrode for a secondary battery, a vehicle battery including the cathode electrode, and a method of forming a cathode for a secondary battery. The cathode electrode includes a cathode disposed on a surface of a cathode current collector, wherein the cathode includes an active material including at least one of lithium iron phosphate and lithium manganese iron phosphate, a binder including polyvinylidene fluoride and polytetrafluoroethylene and a conductive filler.