Solid-State Battery Sheet Binder for Low-Resistance Electrode Strength
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Solution Overview
Problem
The existing methods for producing solid-state secondary battery sheets using fibrillated polytetrafluoroethylene (PTFE) as a binder often result in high electrical resistance and uneven distribution of components, leading to decreased strength and flexibility, while mixing PTFE with conductive aids can cause lithium dissolution and battery capacity issues.
Innovation Solution
A method involving a binder composed of a powder mixture of PTFE and a conductive aid, such as ketjen black or carbon nanotubes, is used, which is free of active materials and is homogeneously mixed to reduce electrical resistance and enhance strength, using a process that includes spray drying to achieve optimal fibrillation and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fibrillated PTFE is used as a binder in the electrode, then the electrode structure is maintained, but the electrical resistance increases and strength decreases
Solution Approach 1:
The patent applies composite materials by combining PTFE binder with conductive aids (such as carbon black or metal particles) to create a multi-functional binder system. This composite approach simultaneously provides structural maintenance from PTFE and electrical conductivity from the conductive aids, resolving the contradiction between structure maintenance and electrical resistance reduction.
Solution Approach 2:
The patent merges the functions of binder and conductive additive by integrating conductive aids into the PTFE binder matrix. This combination allows the binder to perform both its traditional structural role and an additional electrical conductivity function, thereby reducing electrical resistance while maintaining electrode structure.
2Stability of the object's composition
If PTFE and conductive aid are mixed separately, then component distribution can be controlled, but lithium dissolution occurs and battery capacity decreases
Solution Approach 1:
The patent uses composite materials by forming a pre-mixed composite powder of PTFE and conductive aid before incorporating it into the electrode. This composite powder prevents direct contact between lithium and separate PTFE/conductive aid components, thereby preventing lithium dissolution while maintaining homogeneous distribution through the composite structure.
Solution Approach 2:
The composite powder acts as an intermediary between PTFE and conductive aids, preventing direct interaction with lithium that would cause dissolution. The composite structure serves as a protective barrier while still allowing electrical conductivity and homogeneous distribution.
3Stability of the object's composition
If vigorous kneading is applied to eliminate uneven distribution, then homogeneity improves, but excessive PTFE fibrillation occurs reducing flexibility and strength
Solution Approach 1:
The patent applies preliminary action by pre-mixing PTFE and conductive aids to form a composite powder before incorporating it into the electrode. This pre-mixing ensures homogeneous distribution of components, eliminating the need for vigorous kneading that would cause excessive PTFE fibrillation and damage electrode flexibility and strength.
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
This approach effectively decreases the electrical resistance of the solid-state secondary battery sheet while maintaining high strength and flexibility, preventing lithium dissolution and improving battery performance.
Implementation Method 1
a binder that is a powder which comprises a polytetrafluoroethylene resin and a conductive aid homogeneously mixed
Implementation Method 2
using a process that includes spray drying to achieve optimal fibrillation and distribution
Data Source
AI summary
A method for producing a solid-state secondary battery sheet, which includes: (1) preparing a composition for producing a secondary battery sheet by using a binder that is a powder which comprises a polytetrafluoroethylene resin and a conductive aid homogeneously mixed and which is free of an active material, and (2) preparing the composition into a sheet by applying shear stress to the composition in solvent content of 10% mass or less relative to the composition. Also disclosed is a binder for a solid-state secondary battery, that is a powder which is composed of a composition essentially including a polytetrafluoroethylene resin and a conductive aid in a weight ratio proportion of 90:10 to 65:35 and which is free of an electrode active material. Also disclosed is a binder for a solid-state secondary battery electrode including a mixed powder of a polytetrafluoroethylene resin and ketjen black and/or a carbon nanotube.