Solid-State Battery Cathode Coating for Low-Pressure Interface Contact
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Solution Overview
Problem
All-solid-state batteries face performance degradation due to contact failure between the active material and sulfide solid electrolyte, which is exacerbated by high restraining pressures that increase interface resistance and reduce energy density.
Innovation Solution
The battery design incorporates a positive electrode active material particle covered with a sulfide solid electrolyte, applying a restraining pressure of 0.5 MPa or less, allowing the SSE to follow the shrinking behavior of the active material particle and maintaining interface contact, with a composite particle structure and specific chemical composition (Li a Ni x Me 1-x O 2) and a covering layer that disperses stress and forms an ion conduction path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high restraining pressure is applied to maintain interface contact, then contact failure is reduced, but energy density decreases due to increased component volume
Solution Approach 1:
A covering layer comprising a sulfide solid electrolyte is introduced as an intermediary between the positive electrode active material particle and the external environment. This covering layer acts as a mediator that follows the shrinking behavior of the active material particle during charging, thereby maintaining interface contact without requiring high restraining pressure from the restraint member.
Solution Approach 2:
The restraining pressure is reduced from conventional high levels (e.g., 20 MPa) to 0.5 MPa or less by changing the mechanism of contact maintenance. Instead of relying solely on external mechanical pressure, the system utilizes the covering layer's ability to deform and follow the active material particle's volume changes, fundamentally altering the pressure parameter requirements.
2Reliability
If the covering layer completely covers the active material particle to maintain contact, then interface stability improves, but ion conduction efficiency may decrease
Solution Approach 1:
The covering layer comprises a sulfide solid electrolyte that provides different functional properties at different locations: it maintains mechanical contact stability while its ionic conductivity properties enable efficient ion transport at the interface, resolving the contradiction between contact stability and ion conduction efficiency.
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 configuration reduces contact resistance and maintains battery performance under low restraining pressure, achieving reduced stress and increased energy density while preventing cracks and maintaining ion conduction efficiency.
Implementation Method 1
The positive electrode active material particle may shrink during charging. It is considered that, under a low restraining pressure, SSE cannot follow the shrinking behavior of the positive electrode active material particle and thereby may cause a contact failure.
Implementation Method 2
The covering layer includes a sulfide solid electrolyte... forms an ion conduction path... maintaining ion conduction efficiency
Data Source
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AI summary
An all-solid-state battery (100) comprises a power generation element (50) and a restraint member (70). The restraint member (70) applies a pressure of 0.5 MPa or less to the power generation element (50). The power generation element (50) includes a positive electrode layer (10), a solid electrolyte layer (30), and a negative electrode layer (20). The solid electrolyte layer (30) is interposed between the positive electrode layer (10) and the negative electrode layer (20). The positive electrode layer (10) includes a composite particle (5). The composite particle (5) includes a positive electrode active material particle (1) and a covering layer (2). The covering layer (2) covers at least part of a surface of the positive electrode active material particle (1). The covering layer (2) includes a sulfide solid electrolyte.