All-solid-state battery interface resistance reduction
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Solution Overview
Problem
Sulfide-based solid electrolytes in all-solid-state batteries react with positive electrode active materials, increasing interface resistance due to high electric potential, leading to elevated battery resistance, which existing solutions like oxide-based Li ion conductors struggle to mitigate effectively during slurry preparation.
Innovation Solution
Adjusting stirring conditions during slurry preparation to control the ratio of detached to covering oxide-based Li ion conductor area (SB/SA) within a specific range (3% to 30%) and ensuring the oxide-based Li ion conductor is scattered across the sulfide-based solid electrolyte (SB/SC ≤ 5%) to reduce interface resistance and maintain low battery resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a sulfide-based solid electrolyte is used to achieve high lithium ion conductivity, then the battery can achieve high ion conductivity, but the sulfide-based solid electrolyte reacts with the positive electrode active material due to high electric potential, causing increased interface resistance and battery resistance
Solution Approach 1:
An oxide-based Li ion conductor is introduced as an intermediary layer between the sulfide-based solid electrolyte and the positive electrode active material. This intermediate layer prevents direct contact and chemical reaction between the sulfide electrolyte and the high-potential positive electrode material, thereby reducing interface resistance while maintaining lithium ion conductivity.
Solution Approach 2:
The positive electrode layer is designed as a composite structure containing both sulfide-based solid electrolyte particles and oxide-based Li ion conductor particles. This composite material approach allows the system to benefit from the high lithium ion conductivity of the sulfide electrolyte while the oxide component provides protection against interfacial reactions.
2Reliability
If a covering layer of oxide-based Li ion conductor is formed on the positive electrode active material to reduce interface resistance, then the number of contacts between sulfide-based solid electrolyte and positive electrode active material is reduced, but during slurry preparation the oxide-based Li ion conductor may detach from the positive electrode active material due to shearing load
Solution Approach 1:
Instead of forming a continuous covering layer that is prone to detachment, the oxide-based Li ion conductor is distributed as discrete particles within the positive electrode layer. This local distribution maintains the protective function at critical interfaces while reducing the overall structural stress and detachment risk during slurry preparation.
Solution Approach 2:
The oxide-based Li ion conductor is applied as a separate component in the slurry mixture rather than as a pre-formed continuous coating. This segmentation allows the oxide particles to be distributed throughout the slurry and integrate naturally during the forming process, reducing detachment issues associated with continuous covering layers.
3Reliability
If the oxide-based Li ion conductor is scattered across the sulfide-based solid electrolyte to reduce battery resistance, then interface resistance is minimized, but excessive scattering may lead to aggregation of conductive materials and electron conduction defects
Solution Approach 1:
The patent optimizes the concentration and distribution parameters of the oxide-based Li ion conductor in the slurry. By controlling the amount of oxide particles and their spatial distribution, the system achieves sufficient protection against interfacial reactions while preventing excessive scattering that would cause conductive material aggregation and electron conduction defects.
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 controlled detachment and scattering of the oxide-based Li ion conductor effectively reduce battery resistance by minimizing contacts between the sulfide-based solid electrolyte and the positive electrode active material, while preventing excessive aggregation of conductive materials that could cause electron conduction defects.
Implementation Method 1
a positive electrode active material (particles) is covered with an oxide-based Li ion conductor. Thus, a covering layer consisting of the oxide-based Li ion conductor is formed. The covering layer may reduce the number of contacts between the sulfide-based solid electrolyte and the positive electrode active material.
Implementation Method 2
Sulfide-based solid electrolyte has been a promising electrolyte for all-solid-state batteries. It is because sulfide-based solid electrolyte has a high lithium (Li) ion conductivity.
Implementation Method 3
During slurry preparation, a surface of the positive electrode active material is under shearing load. This shearing load can cause detachment of the oxide-based Li ion conductor from the positive electrode active material.
Data Source
AI summary
An all-solid-state battery includes a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. The solid electrolyte layer separates the positive electrode layer from the negative electrode layer. The positive electrode layer includes a positive electrode active material, a conductive material, an oxide-based lithium ion conductor, and a sulfide-based solid electrolyte. A cross section of the positive electrode layer satisfies a relational expression (1): 3%≤SB/SA≤30%. In the relational expression (1), “SA” represents a partial area of the oxide-based lithium ion conductor that is in contact with the positive electrode active material, and “SB” represents a partial area of the oxide-based lithium ion conductor that is surrounded by the sulfide-based solid electrolyte.