Phosphazene Electrolyte Flame Retardancy Capacity Retention
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Solution Overview
Problem
Lithium ion secondary batteries face challenges with capacity retention and flame retardancy due to the reductive degradation of phosphazene compounds over long-term use, leading to increased resistance and decreased safety.
Innovation Solution
Incorporating a specific disulfonate ester and a sultone compound into the nonaqueous electrolyte solution, along with a phosphazene structure, to suppress the reductive degradation of phosphazene compounds on negative electrodes, thereby maintaining effective flame retardancy and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphazene compounds are used as flame retardants in electrolyte solutions, then flame retardancy is improved, but reductive degradation occurs over long-term use leading to increased resistance and decreased capacity retention
Solution Approach 1:
The patent introduces a boron-containing compound as an intermediary substance that mediates between the phosphazene flame retardant and the negative electrode. This compound forms a protective interface layer that prevents direct contact and reductive degradation between the phosphazene and the electrode, while still allowing the phosphazene to function as a flame retardant in the bulk electrolyte.
Solution Approach 2:
The patent modifies the chemical structure of the phosphazene compound by introducing boron-containing groups, changing its electrochemical stability parameters. This structural modification raises the reduction potential of the phosphazene, making it more resistant to reductive degradation at the negative electrode while maintaining its flame retardant properties.
2Object-affected harmful factors
If phosphazene compounds are used as flame retardants, then safety is improved, but reductive degradation leads to increased resistance
Solution Approach 1:
The boron-containing compound serves as a protective intermediary that forms a stable interface layer between the phosphazene flame retardant and the negative electrode. This interface prevents the reductive degradation that would otherwise increase electrical resistance, while allowing the phosphazene to maintain its flame retardant function in the electrolyte bulk.
Solution Approach 2:
The patent creates a composite electrolyte system combining phosphazene compounds with boron-containing compounds. This composite approach leverages the flame retardant properties of phosphazene while the boron-containing component provides electrochemical stability and prevents resistance increase through interface protection.
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 solution effectively suppresses reductive degradation, maintaining high flame retardancy and capacity retention rates over long periods, reducing gas generation during initial charging and improving battery safety.
Implementation Method 1
the reductive degradation of phosphazene compounds over long-term use, leading to increased resistance
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3
AI summary
There are provided a nonaqueous-type electrolyte solution having high flame retardancy and a good capacity retention rate, and a device comprising the nonaqueous-type electrolyte solution. The nonaqueous-type electrolyte solution is used in a device comprising a positive electrode, a negative electrode and the nonaqueous-type electrolyte solution, and contains a lithium salt and a compound having a Phosphazene structure, and further contains 0.05% by mass or more and 12.0% by mass or less of at least one disulfonate ester selected from a cyclic disulfonate ester and a chain disulfonate ester based on the total of the nonaqueous-type electrolyte solution.