All-Solid-State Battery Cathode Interface with Titanium Oxide Buffer
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Solution Overview
Problem
Existing secondary batteries face issues with side reactions at the interfaces between positive and negative electrode active material layers and solid electrolyte layers, leading to reduced charge and discharge capacity and safety concerns, particularly in lithium-ion secondary batteries using liquid electrolytes.
Innovation Solution
Incorporating a buffer layer made of titanium compounds between the positive electrode active material layer and the solid electrolyte layer, and optionally a base film, to stabilize the crystal structure and inhibit side reactions, using a sputtering method for layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a liquid electrolyte is used in lithium-ion secondary batteries, then high ionic conductivity and ease of manufacture are achieved, but safety risks increase due to volatility, low flash point, and potential for explosion or fire
Solution Approach 1:
The patent changes the physical state of the electrolyte from liquid to solid, fundamentally altering the safety parameters while maintaining ionic conductivity. The solid electrolyte eliminates volatility and flash point issues inherent in liquid electrolytes, directly resolving the safety contradiction.
Solution Approach 2:
The patent introduces a buffer layer as an intermediary between the positive electrode active material layer and the solid electrolyte layer. This buffer layer mediates the interface interaction, preventing direct contact that would cause side reactions and crystal structure breakdown, thereby maintaining reliability without sacrificing manufacturing feasibility.
2Duration of action of moving object
If charge and discharge cycles are repeated in secondary batteries, then energy storage and release functions are performed, but the crystal structure of the positive electrode active material breaks down leading to reduced charge and discharge capacity
Solution Approach 1:
The buffer layer serves as a protective cushioning layer that is positioned in advance between the positive electrode active material and the solid electrolyte. This layer prevents direct mechanical and chemical stress during charge-discharge cycles, cushioning the positive electrode material from degradation and preserving its charge and discharge capacity over extended cycling.
Solution Approach 2:
The buffer layer acts as an intermediary that mediates the mechanical and chemical interactions at the interface during charge-discharge cycles. It allows ionic transport while preventing direct contact that would lead to crystal structure breakdown, thus maintaining both cycle performance and capacity.
3Reliability
If side reactions occur at the interface between positive electrode active material layer and solid electrolyte layer, then chemical instability is generated, but charge and discharge capacity is reduced
Solution Approach 1:
The buffer layer functions as a chemical intermediary that prevents direct reaction between the positive electrode active material and the solid electrolyte. It allows ionic conduction while blocking harmful chemical interactions, thus maintaining both chemical stability and charge-discharge capacity.
Solution Approach 2:
The buffer layer extracts or removes the harmful interface reaction problem by introducing a third material that is chemically inert to both the positive electrode active material and the solid electrolyte. This extraction of the problematic direct interface prevents side reactions while maintaining functional ionic transport.
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 the likelihood of side reactions, enhances cycle performance, and maintains high charge and discharge capacity, resulting in a safer and more reliable secondary battery.
Implementation Method 1
incorporating a buffer layer made of titanium compounds between the positive electrode active material layer and the solid electrolyte layer, and optionally a base film, to stabilize the crystal structure and inhibit side reactions, using a sputtering method for layer formation
Data Source
AI summary
A secondary battery with excellent cycle performance is provided. The secondary battery is an all-solid-state battery including a positive electrode current collector layer, a base film, a positive electrode active material layer, a buffer layer, and a solid electrolyte layer. The base film contains titanium nitride. The positive electrode active material layer contains lithium cobalt oxide. The buffer layer contains titanium oxide. The solid electrolyte layer contains a titanium compound. By using titanium oxide for the buffer layer, a side reaction between the positive electrode active material layer and the solid electrolyte layer can be suppressed, and cycle performance can be improved.