Dry-Processed LNMO Cathodes With Conductive Web for Cycle Stability
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Solution Overview
Problem
Lithium nickel manganese oxide (LNMO) cathodes face challenges in commercialization due to poor cycling stability, low electronic conductivity, and high manufacturing costs, particularly when used in high voltage lithium-ion batteries, which limits their practical application in electric vehicles and electronic devices.
Innovation Solution
A dry binder fibrillation process is employed to fabricate cathodes using lithium transition metal oxide, fluoropolymer binder, and conductive carbon, forming a conducting structural web that enhances electronic conductivity and mechanical properties, thereby improving cycling stability and reducing parasitic reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LNMO cathode material is used for high voltage operation, then energy density is improved, but cycling stability deteriorates
Solution Approach 1:
A fluoropolymer binder is introduced as an intermediary substance between the LNMO cathode material and the electrolyte. This binder forms a protective interface layer that mediates the interaction between the high-voltage cathode and the electrolyte, preventing direct harmful reactions while maintaining electrochemical performance, thus improving cycling stability without sacrificing energy density
Solution Approach 2:
The invention changes the chemical composition parameters of the electrode by incorporating fluoropolymer binder with specific fluorine-containing functional groups. This parameter change modifies the interfacial chemistry between cathode and electrolyte, creating a more stable solid electrolyte interface (SEI) that can withstand high voltage operation, thereby resolving the cycling stability issue
2Reliability
If conductive carbon is added to improve electronic conductivity, then electronic conductivity is improved, but energy density deteriorates
Solution Approach 1:
The fluoropolymer binder acts as an intermediary conductive network that facilitates electron transport between LNMO particles without requiring excessive carbon additives. The binder's molecular structure provides electron pathways through the electrode, reducing the need for inactive carbon fillers and thereby maintaining higher energy density while achieving sufficient conductivity
3Reliability
If surface coating is applied to reduce cathode surface degradation, then cycling stability is improved, but manufacturing complexity increases
Solution Approach 1:
The invention merges the binder function and surface protection function into a single fluoropolymer component. The fluoropolymer simultaneously serves as the electrode binder holding particles together and as the protective surface coating preventing degradation, eliminating the need for separate coating processes and reducing manufacturing complexity
Solution Approach 2:
The fluoropolymer binder exhibits multi-functionality by simultaneously performing binding, conductivity enhancement, and surface protection roles. This universal material replaces multiple specialized components, simplifying the overall electrode structure and manufacturing process while maintaining improved cycling stability
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 enables high-loading cathodes with improved long-term cycling stability and reduced parasitic reactions, maintaining energy density and efficiency over 300 cycles, while being cost-effective and environmentally benign.
Implementation Method 1
the fluoropolymer binder is fibrillated; the carbon fibers and the fibrillated fluoropolymer binder forming a conducting structural web electronically connecting the cathode active particles
Implementation Method 2
the carbon fibers and the fibrillated fluoropolymer binder forming a conducting structural web electronically connecting the cathode active particles so as to enable electronic conductivity through the electrode layer
Implementation Method 3
A dry binder fibrillation process is employed to fabricate cathodes using lithium transition metal oxide, fluoropolymer binder, and conductive carbon, forming a conducting structural web that enhances electronic conductivity and mechanical properties
Data Source
AI summary
A cathode for a high voltage lithium-ion secondary battery is described, including: an electrode layer having an electrode composition containing cathode active particles, fluoropolymer binder and conductive carbon. The cathode active particles are high voltage lithium transition metal oxides, the fluoropolymer binder is a fibrillated tetrafluoroethylene polymer having high melt creep viscosity, and the conductive carbon is carbon fibers having a specific surface area of about 50 m2/g or less. The carbon fibers and the fluoropolymer binder form a conducting structural web electronically connecting the cathode active particles, enabling electronic conductivity through the electrode layer. The electrode layer is adhered to a current collector comprising aluminum having surface roughness and substantially no carbon surface coating other than the conductive carbon of the electrode layer. Further described is a dry binder process to fabricate such cathodes, and the utility of such cathodes in high voltage lithium-ion secondary batteries.