Lithium Battery Electrolyte with Sulfur and Phosphazene Additives
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density and safety due to the deterioration of performance caused by self-extinguishing materials added for flame retardancy, which compromise battery stability and cycle-life characteristics.
Innovation Solution
An electrolyte comprising a lithium salt, a sulfur-containing compound, and a phosphazene compound is used, which improves flame retardancy without significantly affecting battery performance by capturing oxygen during ignition and forming a low-resistance film, thereby enhancing stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-extinguishing material is added to improve flame retardancy, then safety is improved, but battery performance deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by selecting specific sulfur-containing compounds (cyclic sulfates, sultones, or sulfones) and controlling their content within 5-50 wt% of the total electrolyte. This parameter optimization allows achieving flame retardancy while minimizing performance degradation by finding the optimal concentration range where safety benefits are maximized and performance losses are minimized.
Solution Approach 2:
The patent creates a composite electrolyte system by combining sulfur-containing compounds with specific lithium salts (LiPF6, LiBF4, LiClO4) and organic solvents (carbonates, carboxylic acid esters, cyclic carbonates). This composite approach leverages the flame-retardant properties of sulfur compounds while the other components maintain ionic conductivity and electrochemical stability, achieving a balance between safety and performance.
2Reliability
If sulfur-containing compound is added to improve flame retardancy, then safety is improved, but ion conductivity may be affected
Solution Approach 1:
The patent optimizes the concentration parameter of sulfur-containing compounds within the range of 5-50 wt% of the total electrolyte composition. This controlled parameter change ensures sufficient flame retardancy while preventing excessive viscosity increase that would harm ion conductivity. The specific range is determined to balance safety benefits against potential conductivity degradation.
Solution Approach 2:
The patent applies different functional components with specific local roles: sulfur-containing compounds provide flame retardancy locally, lithium salts provide ionic conductivity, and organic solvents provide solvation. This local quality differentiation allows each component to perform its specialized function optimally without interfering with others, maintaining both safety and conductivity.
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 electrolyte achieves improved flame retardancy, cycle-life characteristics, and stability, maintaining high ion conductivity and rate capability while preventing combustion, thus ensuring better safety and performance of rechargeable lithium batteries.
Implementation Method 1
The phosphazene compound represented by Chemical Formula 2 may capture the oxygen generated during the ignition and thus, may prevent (or reduce) the combustion of the electrolyte
Implementation Method 2
the sulfur-containing compound is reduced and decomposed on a negative electrode and may form a SEI film thereon
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An electrolyte for a rechargeable lithium battery comprises a lithium salt, an organic solvent and an additive. The organic solvent comprises a sulfur-containing compound represented by Chemical Formula 1, and the additive comprises a phosphazene compound represented by Chemical Formula 2. A rechargeable lithium battery including the electrolyte may have improved performance and safety. In Chemical Formulae 1 and 2, the substituents are as defined in the detailed description.