Lithium Sulfide Core Shell Coatings for Battery Conductivity
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Solution Overview
Problem
Lithium-sulfur (Li/S) batteries face challenges due to poor electrical conductivity of elemental sulfur and the intrinsic polysulfide shuttle, leading to low energy efficiency and short cycle life in high power applications.
Innovation Solution
A composite core shell material is developed, comprising a lithium sulfide core encapsulated by a diffusion barrier shell of Li4P2S7 and a conductive shell of Li4P2S7 and carbon, which reduces polysulfide shuttle and enhances ionic and electronic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If elemental sulfur is used in lithium-sulfur batteries, then theoretical capacity is high (1675 mAhg−1), but electrical conductivity is poor
Solution Approach 1:
The patent uses composite materials by combining lithium sulfide core particles with conductive carbon matrices and sulfide-based solid electrolyte coatings (Li3PS4, Li2SiO3). This composite structure maintains the high capacity of sulfur while adding electrical conductivity through carbon and ionic conductivity through the solid electrolyte coating, directly resolving the contradiction between theoretical capacity and electrical conductivity
Solution Approach 2:
The patent applies local quality by creating a heterogeneous structure where different materials serve different functions: the lithium sulfide core provides capacity, the carbon matrix provides electrical conductivity, and the solid electrolyte coating provides ionic conductivity and polysulfide containment. Each local region has optimized properties for its specific function, resolving the overall conductivity issue while maintaining high capacity
2Power
If lithium-sulfur batteries are designed for high power applications, then energy output is improved, but polysulfide shuttle causes short cycle life
Solution Approach 1:
The patent extracts the harmful polysulfide species from the electrolyte by containing them within the solid electrolyte coating on the electrode surface. The sulfide-based solid electrolyte (Li3PS4, Li2SiO3) acts as a physical barrier that prevents polysulfide dissolution into the liquid electrolyte, thereby eliminating the polysulfide shuttle effect while maintaining high power output and extending cycle life
Solution Approach 2:
The sulfide-based solid electrolyte coating serves as an intermediary layer between the lithium sulfide active material and the liquid electrolyte. This intermediate coating allows lithium ion transport while blocking polysulfide diffusion, mediating the interaction between the electrode and electrolyte to prevent the harmful shuttle effect while maintaining electrochemical performance
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 composite core shell material improves the ionic conductivity of lithium sulfur batteries, reducing polysulfide shuttle and enhancing cycle life and energy efficiency, making them suitable for high power applications.
Implementation Method 1
forming a first mixture including a solid component of a first portion of lithium sulfide (Li2S) and diphosphorus pentasulfide (P2S5) in a ratio ranging from 0.75:1 to 1.25:1 with a liquid solvent comprising carbon and hydrogen to form a first shell on a core material
Implementation Method 2
The liquid solvent may then be removed
Data Source
AI summary
Method of forming lithium-containing electrolytes are provided using wet chemical synthesis. In some examples, the lithium containing electrolytes are composed of β-Li3PS4 or Li4P2S7. The solid electrolyte may be a core shell material. In one embodiment, the core shell material includes a core of lithium sulfide (Li2S), a first shell of β-Li3PS4 or Li4P2S7, and a second shell including one of β-Li3PS4 or Li4P2S7 and carbon. The lithium containing electrolytes may be incorporated into wet cell batteries or solid state batteries.