Fluorinated Polycationic Polymer Binder for Battery Electrodes
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Solution Overview
Problem
Conventional binders for lithium-ion and lithium-air batteries, such as PVDF and Nafion, do not provide optimal performance in terms of capacity and resistance for NMC cathodes and air electrodes, respectively.
Innovation Solution
A composition comprising a mixed oxide of lithium, nickel, manganese, and cobalt combined with a fluorinated anion salt of a polycationic polymer, specifically with repeating units and fluorinated counterions like imide anions or perfluoroalkyl sulfonates, is used as a binder to enhance performance in lithium-ion and lithium-air batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binders PVDF or Nafion are used for cathode electrodes in Li-ion and Li-air batteries, then the structural integrity of the electrode is maintained, but the overall resistance of the cell increases and capacity performance is suboptimal
Solution Approach 1:
The patent changes the chemical and physical parameters of the binder by using polymeric ionic liquids with specific repeating units (formulae 1 and 2) and fluorinated anions instead of conventional PVDF or Nafion. This parameter change results in a binder that provides both structural integrity and enhanced ionic conductivity, thereby reducing cell resistance while maintaining electrode stability.
Solution Approach 2:
The invention employs a composite binder system consisting of polymeric ionic liquids with specific cationic repeating units and fluorinated anions. This composite material combines the structural properties needed for electrode integrity with the ionic conductivity required to reduce resistance, achieving both functions simultaneously rather than relying on conventional single-material binders.
2Reliability
If conventional binders PVDF or Nafion are used for cathode electrodes, then the electrode structure is maintained, but the battery capacity and performance are suboptimal
Solution Approach 1:
The patent modifies the binder's ionic conductivity parameter by selecting polymeric ionic liquids with specific repeating units (formulae 1 and 2) and fluorinated anions. This parameter enhancement allows the binder to facilitate greater lithium ion transport, directly increasing battery capacity while the polymer structure maintains electrode stability.
Solution Approach 2:
The polymeric ionic liquid binder acts as an intermediary between the electrode structure and the electrolyte, facilitating efficient lithium ion transport. The fluorinated anions and cationic repeating units create pathways for ion conduction, thereby enhancing capacity while the polymer matrix maintains structural stability.
3Reliability
If polymeric ionic liquids with fluorinated anions are used as binders, then capacity and resistance performance are significantly improved, but the device complexity increases due to specific polymer structure requirements
Solution Approach 1:
The patent defines specific parameter ranges for the polymeric ionic liquid structure (formulae 1 and 2 with fluorinated anions) that optimize both performance and manufacturability. By establishing clear structural parameters, the invention balances performance improvement with practical synthesis considerations, avoiding excessive complexity.
Solution Approach 2:
The invention applies local quality by specifying particular structural features (formulae 1 and 2 with fluorinated anions) at critical locations within the polymer chain where they most effectively enhance ionic conductivity and electrode adhesion, while allowing flexibility in other regions of the polymer structure.
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 proposed binder composition significantly improves the performance of lithium-ion and lithium-air batteries by enhancing capacity and reducing resistance, as demonstrated by galvanostatic discharge-charge tests and resistance measurements.
Implementation Method 1
Conventional binders for cathode electrodes in Li-ion and Li-air batteries are PVDF and Nafion respectively. These polymers do not have any lithium conductivity and thus increase the overall resistance of the cell.
Implementation Method 2
Lithium-ion batteries are widely used in many technologies. On the positive side of the battery, acting as the cathode during discharge, cathode materials are known which comprise a lithium nickel manganese cobalt oxide (NMC)
Implementation Method 3
Non-Patent Literature Reference (1) discloses the manufacturing and material composition of a solid electrolyte for a Li-ion battery. A polyionic liquid such as PDADMA-TFSI is mentioned as a possibility to be used at the interface between cathode and solid electrolyte
Data Source
AI summary
Composition includes: (A) a mixed oxide of lithium, nickel, manganese and cobalt and (B) a fluorinated anion salt of a polycationic polymer. The fluorinated anion salt of the polycationic polymer contains repeating units represented by one of formula (1) or formula (2):wherein, in the formula (1), N+ is a nitrogen atom constituting a quaternary ammonium cation, R1 and R2 being each independently a substituent containing a carbon atom bonded to the nitrogen atom,wherein, in the formula (2), R3 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.