Polymer Binder for Inorganic Solid Electrolyte
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Solution Overview
Problem
All-solid state secondary batteries face challenges with increased interface resistance and deteriorated cycle characteristics due to restricted interfacial contact between solid particles, particularly in low temperature environments, and the instability of inorganic solid electrolytes when exposed to moisture during manufacturing.
Innovation Solution
An inorganic solid electrolyte-containing composition is developed, featuring a polymer binder with specific surface energy and SP value characteristics, dissolved in a dispersion medium, which enhances dispersibility and adhesion, reducing interface resistance and moisture-induced deterioration, while maintaining high ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a constitutional layer is composed of solid particles such as inorganic solid electrolyte, active material, and conductive auxiliary agent, then the battery structure is simple and energy density is high, but the interfacial contact state between solid particles is restricted and interface resistance increases
Solution Approach 1:
A polymer binder is introduced as an intermediary substance between solid particles (inorganic solid electrolyte, active material, conductive auxiliary agent) to improve interfacial contact. The polymer binder fills gaps between particles and creates conductive pathways, reducing interface resistance while maintaining the high energy density structure of solid particle-based constitutional layers.
Solution Approach 2:
The constitutional layer is transformed from a simple mixture of solid particles to a composite material system comprising solid particles embedded in a polymer binder matrix. This composite structure combines the high energy density advantage of solid particles with the excellent interfacial contact properties of the polymer binder, resolving the contradiction between energy density and interface resistance.
2Reliability
If inorganic solid electrolyte is used to achieve high ion conductivity comparable to organic electrolytic solution, then ion conductivity is improved, but the inorganic solid electrolyte is easily deteriorated by water during manufacturing
Solution Approach 1:
The polymer binder serves as a protective intermediary between the moisture-sensitive inorganic solid electrolyte and the manufacturing environment. It forms a barrier that prevents direct contact between water and the inorganic solid electrolyte particles, reducing deterioration during manufacturing while allowing the inorganic solid electrolyte to maintain its high ion conductivity functionality.
Solution Approach 2:
The polymer binder matrix creates a protected micro-environment around inorganic solid electrolyte particles, effectively isolating them from moisture in the manufacturing atmosphere. This protective environment allows handling and processing of moisture-sensitive inorganic solid electrolytes without requiring extreme inert atmosphere conditions.
3Reliability
If particle-shaped polymer binder is used to suppress interface resistance increase, then interfacial contact is improved, but the battery performance and ion conductivity are not sufficiently improved in low temperature environments
Solution Approach 1:
The invention changes the physical state parameter of the polymer binder from particle-shaped to dissolved state. When dissolved in the dispersion medium, the polymer forms a continuous matrix that provides excellent interfacial contact between solid particles. This dissolved state polymer maintains flexibility and ionic conductivity even at low temperatures, overcoming the limitations of particle-shaped binders in cold environments.
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 composition achieves improved ion conductivity and cycle characteristics in both normal and low temperature environments, with reduced interface resistance and moisture sensitivity, leading to more reliable and efficient all-solid state secondary batteries.
Implementation Method 1
a polymer binder containing a polymer having a surface energy of 20 mN/m or less and an SP value of 14 to 21.5 MPa1/2, and dissolved in the dispersion medium
Implementation Method 2
a polymer binder containing a polymer having a surface energy of 20 mN/m or less and an SP value of 14 to 21.5 MPa1/2, and dissolved in the dispersion medium
Data Source
AI summary
There are provided an inorganic solid electrolyte-containing composition that exhibits excellent dispersibility and hardly deteriorates an inorganic solid electrolyte and is capable of forming a constitutional layer that exhibits a high ion conductivity even in a low temperature environment, a sheet for an all-solid state secondary battery and an all-solid state secondary battery, in which this inorganic solid electrolyte-containing composition is used, and manufacturing methods for a sheet for an all-solid state secondary battery and an all-solid state secondary battery. The inorganic solid electrolyte-containing composition contains an inorganic solid electrolyte, a polymer binder, and a dispersion medium, in which the polymer binder contains a polymer having a surface energy of 20 mN/m or less and an SP value of 14 to 21.5 MPa1/2, and the polymer binder is dissolved in the dispersion medium.