Sulfide Solid Electrolyte Electron Conductivity Reduction
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Solution Overview
Problem
A sulfide-based solid electrolyte with a cubic crystal structure belonging to space group F-43m, represented by Compositional Formula: Li7-xPS6-xHa (Ha is Cl or Br), experiences high electron conductivity, which hinders the increase in charge/discharge efficiency and cycle characteristics in lithium ion batteries.
Innovation Solution
A sulfide-based solid electrolyte with a cubic crystal structure, where x in the Compositional Formula is between 0.2 and 1.8, and a high lightness L* value of 60.0 or more in the L*a*b* color system, is developed by mixing lithium sulfide, phosphorus sulfide, and lithium chloride or lithium bromide powders and firing them under specific conditions to reduce electron conductivity and enhance lithium ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sulfide-based solid electrolyte with cubic crystal structure (space group F-43m) and compositional formula Li7-xPS6-xHax is used, then high ionic conductivity is achieved, but electron conductivity becomes excessively high which deteriorates charge/discharge efficiency and cycle characteristics
Solution Approach 1:
The invention changes the chemical composition parameters by introducing halogen elements (Cl, Br, I) to replace sulfur atoms in the Li7-xPS6-xHax structure. This compositional modification alters the electronic structure and band gap, thereby reducing electron conductivity while maintaining lithium ion conductivity. The halogen substitution changes the valence electron configuration and creates a more favorable electronic environment for ionic conduction over electronic conduction.
Solution Approach 2:
The invention creates a composite solid electrolyte material by combining sulfide-based Li7-xPS6-xHax with halogen elements (Cl, Br, I) to form a new composite structure. This composite approach leverages the high ionic conductivity of the parent sulfide material while the halogen components suppress electron conductivity, achieving a balanced performance suitable for practical battery applications.
2Object-generated harmful factors
If the composition is adjusted to reduce electron conductivity, then charge/discharge efficiency improves, but lithium ion conductivity may be compromised
Solution Approach 1:
The invention applies local quality modification by selectively substituting sulfur atoms at specific lattice positions with halogen elements. This localized compositional change affects specific regions of the crystal structure, creating zones with suppressed electron conductivity while preserving the overall lithium ion conduction pathways. The non-uniform distribution of halogen atoms allows differential control over electronic and ionic transport properties.
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 proposed solid electrolyte achieves high lithium ion conductivity, low electron conductivity, and a high transport number of lithium ions, thereby improving charge/discharge efficiency and cycle characteristics in lithium ion batteries.
Implementation Method 1
a solid electrolyte that is used for a battery has high ionic conductivity and should be chemically or electrochemically stable
Implementation Method 2
there are no side reactions by the movement of anion. Therefore, it is expected that it leads to improve safety or durability
Data Source
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AI summary
Provided is a solid electrolyte with which charge/discharge efficiency and cycle characteristics can be increased by reducing the electron conductivity of a compound which has a cubic crystal structure belonging to a space group F-43m, and is represented by Compositional Formula: Li7-xPS6-xHax (Ha is Cl or Br). Proposed is a sulfide-based solid electrolyte for a lithium ion battery, which includes a compound having a cubic crystal structure belonging to a space group F-43m, and being represented by Compositional Formula: Li7-xPS6-xHax (Ha is Cl or Br), in which x in the above Compositional Formula is 0.2 to 1.8, and the value of the lightness L* thereof in the L*a*b* color system is 60.0 or more.