Solid-State Battery Cathode Coating for Low-Pressure Contact Stability
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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 increases interface resistance, and high restraining pressure is required to prevent this, but it reduces energy density.
Innovation Solution
A novel all-solid-state battery design with a restraining pressure of 0.5 MPa or less, where the positive electrode active material particle is covered with a sulfide solid electrolyte, allowing it to follow shrinking behavior and maintaining contact integrity, using a composite particle with a specific chemical composition (LiaNixMe1-xO2) and a high-nickel material with 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 prevent contact failure between active material and solid electrolyte, then contact integrity is improved, but energy density decreases due to larger restraint member volume
Solution Approach 1:
The patent changes the physical-chemical parameters of the solid electrolyte by introducing a glass component (specifically boron oxide-based glass) to modify its mechanical properties. This allows the solid electrolyte to have lower modulus and better flexibility, enabling it to withstand volume changes of the active material without requiring high restraining pressure, thus resolving the contradiction between contact integrity and energy density
Solution Approach 2:
The patent uses a composite solid electrolyte made by combining inorganic glass particles (boron oxide-based glass) with a sulfide solid electrolyte matrix. This composite structure provides both the ionic conductivity of sulfide electrolytes and the mechanical flexibility of glass, allowing the electrolyte to accommodate active material volume changes while maintaining contact integrity without high pressure
2Stability of the object's composition
If the solid electrolyte is rigid to maintain structural stability, then structural stability is improved, but contact failure occurs during active material volume changes
Solution Approach 1:
The patent creates a composite solid electrolyte combining rigid sulfide solid electrolyte particles with flexible glass component particles. The sulfide particles provide structural stability and ionic conductivity, while the glass component provides flexibility to accommodate volume changes, thus simultaneously achieving structural stability and contact integrity
Solution Approach 2:
The patent modifies the mechanical parameters of the solid electrolyte by incorporating glass with specific composition (boron oxide-based) that has lower modulus and higher flexibility. This parameter change allows the electrolyte to deform with the active material during volume changes while maintaining structural integrity and preventing contact failure
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 battery operates effectively with reduced contact resistance and stress, maintaining performance while achieving lower energy density losses, even at low restraining pressures, by using a high-nickel material with a sulfide solid electrolyte covering layer.
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
Data Source
AI summary
An all-solid-state battery comprises a power generation element and a restraint member. The restraint member applies a pressure of 0.5 MPa or less to the power generation element. The power generation element includes a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. The solid electrolyte layer is interposed between the positive electrode layer and the negative electrode layer. The positive electrode layer includes a composite particle. The composite particle includes a positive electrode active material particle and a covering layer. The covering layer covers at least part of a surface of the positive electrode active material particle. The covering layer includes a sulfide solid electrolyte.