HNBR Binder for All-Solid-State Battery Cathodes
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Solution Overview
Problem
Conventional lithium secondary batteries, especially those with sulfide-based solid electrolytes, face issues with binder reactivity leading to hardening and interface resistance due to the use of nitrile butadiene rubber (NBR), which limits their performance in all-solid-state lithium ion batteries.
Innovation Solution
A cathode for all-solid-state lithium ion batteries is developed using hydrogenated nitrile butadiene rubber (HNBR) with a residual double bond of 0-5.5% and nitrile content of 20-30%, dissolved in a solvent mixture of cyclopentyl methyl ether and a ketone-based solvent, such as acetone or methyl ethyl ketone, to reduce reactivity and ensure uniform dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If NBR is used as a binder in all-solid-state lithium ion batteries with sulfide-based solid electrolyte, then the binder can effectively bind electrode materials, but the NBR causes chemical reaction with sulfide-based compound leading to hardening and increased interface resistance
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by using HNBR with specific residual double bond content (0-5.5%) and nitrile content (20-30%). This parameter modification reduces the reactivity between the binder and sulfide-based solid electrolyte, preventing hardening and maintaining low interface resistance while preserving binding functionality.
Solution Approach 2:
The patent employs HNBR as a composite binder material that combines the beneficial properties of nitrile butadiene rubber with hydrogenation treatment. This composite approach maintains the adhesion strength of NBR while reducing its chemical reactivity with sulfide-based compounds, thus resolving the contradiction between binding strength and interface stability.
2Strength
If conventional NBR binder is used, then the electrode materials are well bound, but the binder hardens during charge and discharge cycles due to chemical reaction with sulfide-based solid electrolyte
Solution Approach 1:
The patent modifies the binder's chemical structure by controlling the hydrogenation degree, specified by residual double bond content (0-5.5%). This parameter change reduces the binder's susceptibility to chemical reactions with sulfide-based solid electrolyte during charge-discharge cycles, preventing hardening and extending battery service life while maintaining binding strength.
3Reliability
If HNBR with low residual double bond content is used, then reactivity with sulfide-based compound is reduced, but the binder may not dissolve uniformly in the solvent
Solution Approach 1:
The patent optimizes multiple parameters of HNBR simultaneously: residual double bond content (0-5.5%), nitrile content (20-30%), and molecular weight distribution. These coordinated parameter adjustments ensure both low reactivity with sulfide-based compounds and adequate solubility in the solvent mixture of cyclopentyl methyl ether and ketone-based solvent, achieving uniform dispersion and stable composition.
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 HNBR binder exhibits low reactivity with sulfide-based compounds, reducing curing during charge and discharge, enhancing discharge capacity and service life of the battery.
Implementation Method 1
The slurry may further include a solvent which dissolves the binder. The solvent may include a mixture of cyclopentyl methyl ether (CPME) and a ketone-based solvent.
Implementation Method 2
The binder may be a hydrogenated nitrile butadiene rubber (HNBR) having a residual double bond, an amount thereof is more than 0% and equal to or less than 5.5%
Data Source
AI summary
A cathode of an all-solid-state lithium ion battery is prepared by applying a slurry, in which an active material, a conductive material, a sulfide-based solid electrolyte, and a binder are mixed, to a substrate. The binder is a hydrogenated nitrile butadiene rubber (HNBR) having a residual double bond, an amount thereof is more than 0% and equal to or less than 5.5%.