Lithium Ion Capacitor Binder with RED Value > 1 for High Temperature Stability
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Solution Overview
Problem
Lithium ion capacitors face challenges in retaining capacity and experiencing significant increases in internal resistance at high temperatures, particularly at 85°C, due to the oxidative deterioration of conventional binders and electrolytes used in automotive applications.
Innovation Solution
A lithium ion capacitor design incorporating a positive electrode with a binder having a polymer with a relative energy difference (RED) value greater than 1 based on Hansen solubility parameters, an organic solvent mixture of ethylene carbonate and propylene carbonate, and a lithium salt electrolyte with an imide structure to enhance durability and ionic conductance at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional aqueous binders like SBR are used in lithium ion capacitors, then environmental load in manufacturing is reduced, but oxidative deterioration occurs at high temperatures (85°C)
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by incorporating specific functional groups (carboxyl groups with density 0.01-0.5 mmol/g) into the polymer structure. This parameter modification enables the binder to resist oxidative deterioration at high temperatures while maintaining environmental compatibility through aqueous formulation.
Solution Approach 2:
The invention creates a composite binder system combining polymer base material with specific functional additives containing carboxyl groups. This composite structure provides both the mechanical binding function and the chemical resistance to oxidation at high temperatures, resolving the contradiction between environmental friendliness and durability.
2Ease of manufacture
If lithium hexafluorophosphate electrolyte is used in lithium ion capacitors, then it is commonly available and easy to manufacture, but capacity significantly decreases and internal resistance increases at 85°C
Solution Approach 1:
The invention changes the electrolyte composition parameters by introducing lithium salt compounds with imide structures (such as lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide) and adjusting the solvent mixture ratios. These parameter changes maintain ease of manufacture while dramatically improving capacity retention and reducing internal resistance increase at high temperatures.
3Quantity of substance
If lithium ion capacitor is designed for automotive applications, then large capacity and high output are achieved, but durability at 85°C is not secured
Solution Approach 1:
The invention systematically changes multiple parameters including binder composition (polymer type, carboxyl group density), electrolyte composition (lithium salt type with imide structure, solvent ratios), and active material characteristics. These coordinated parameter changes enable the capacitor to maintain large capacity and high output while achieving the required durability at 85°C for automotive applications.
Solution Approach 2:
The invention employs composite material strategies in both the electrode structure (active material + binder + conductor) and electrolyte formulation (multiple solvents + lithium salt). These composite structures provide synergistic effects that simultaneously deliver high capacity, high output, and exceptional high-temperature durability needed for automotive use.
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 solution effectively maintains capacity retention and reduces internal resistance increase under high temperature environments, ensuring reliable performance for automotive applications.
Implementation Method 1
a binder including a polymer having a RED value to the electrolytic solution of more than 1, the RED value representing a relative energy difference with respect to the electrolytic solution based on Hansen solubility parameters
Implementation Method 2
The electrolytic solution includes an organic solvent and a lithium salt electrolyte having an imide structure
Implementation Method 3
an electrode that physically adsorbs and desorbs ions by holding an active material such as activated carbon onto a collector foils
Implementation Method 4
an electrode that adsorbs and desorbs lithium ions by oxidation-reduction reaction
Data Source
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AI summary
Provided is a lithium ion capacitor that can retain a capacity under a high temperature environment and has small increase in internal resistance while using an aqueous binder for a positive electrode. A lithium ion capacitor includes: a positive electrode; a negative electrode; and an electrolytic solution contacting the positive electrode and the negative electrode. The electrolytic solution includes an organic solvent and a lithium salt electrolyte having an imide structure; the positive electrode includes a collector foil and a positive electrode active material; and the positive electrode active material is held onto the collector foil through a binder including a polymer having a RED value to the electrolytic solution of more than 1, the RED value representing a relative energy difference with respect to the electrolytic solution based on Hansen solubility parameters.