Flame Retardant Electrolyte for Lithium Battery
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Solution Overview
Problem
Phosphoric acid-based flame retardants in lithium rechargeable batteries cause reductive decomposition, reducing available capacity and increasing cell resistance, and excessive amounts degrade cycle-life characteristics.
Innovation Solution
A flame retardant electrolyte solution comprising a lithium salt, a linear carbonate-based solvent, an ammonium cation, a phosphoric acid-based solvent, and an oxalatoborate additive, which improves thermal stability and flame retardancy by minimizing decomposition and maintaining high rate and cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If phosphoric acid-based flame retardant is added to improve flame retardancy, then flame retardancy is improved, but reductive decomposition occurs causing decreased available capacity and increased cell resistance
Solution Approach 1:
The patent introduces an ionic liquid as an intermediary substance between the phosphoric acid-based flame retardant and the electrode. The ionic liquid forms a protective interface layer that prevents direct contact and reductive decomposition reactions between the flame retardant and the negative electrode, while still allowing the flame retardant to function. This mediator approach resolves the contradiction by enabling flame retardancy without the harmful reductive decomposition that would otherwise occur.
Solution Approach 2:
The patent creates a composite electrolyte system combining conventional carbonate-based electrolyte with ionic liquid and phosphoric acid-based flame retardant. This composite formulation allows the components to work synergistically: the carbonate provides baseline conductivity, the ionic liquid provides thermal stability and acts as a protective barrier, and the phosphoric acid-based flame retardant provides flame suppression. The composite structure enables flame retardancy while preventing direct harmful interactions between components.
2Object-affected harmful factors
If excessive amount of phosphoric acid-based flame retardant is added, then flame retardancy is enhanced, but cycle-life characteristics are significantly decreased
Solution Approach 1:
The patent optimizes the concentration parameters of all electrolyte components, specifically limiting the phosphoric acid-based flame retardant to 0.1-5 wt% and ionic liquid to 10-50 wt%. By precisely controlling these compositional parameters, the system achieves adequate flame retardancy while preventing the excessive flame retardant accumulation that would cause severe cycle-life degradation. The parameter optimization ensures the flame retardant functions effectively without causing harmful side effects over extended cycling.
Solution Approach 2:
The ionic liquid serves as a buffer and protective intermediary that allows the system to tolerate higher flame retardant concentrations without severe cycle-life penalties. The ionic liquid's protective interface prevents excessive flame retardant from directly decomposing at the electrode surface during cycling, thereby extending the battery's operational lifespan even when flame retardant is present at higher levels needed for adequate flame suppression.
3Object-affected harmful factors
If phosphoric acid-based flame retardant is used, then flame retardancy is improved, but gas generation and passivation film collapse occur reducing high rate characteristics
Solution Approach 1:
The ionic liquid acts as a protective intermediary that forms a stable interface layer between the electrode and electrolyte. This interface layer prevents gas generation reactions and stabilizes the passivation film, eliminating the sources of high-rate performance degradation. The mediator approach allows the phosphoric acid-based flame retardant to function while preventing the gas evolution and film collapse that would otherwise occur during high-rate charging and discharging operations.
Solution Approach 2:
The composite electrolyte formulation creates a synergistic system where the ionic liquid component specifically addresses the high-rate performance issues by providing superior interfacial stability and gas suppression. This composite structure allows the flame retardant to be present without suffering from gas generation and passivation film collapse, thereby maintaining high rate characteristics while achieving flame retardancy.
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 enhances thermal stability, flame retardancy, and electrochemical performance by preventing gas generation and passivation film collapse, maintaining high rate and cycle-life characteristics while reducing internal pressure and battery swelling.
Implementation Method 1
the phosphoric acid-based retardant causes reductive decomposition during reaction of the negative electrode and the electrolyte solution
Implementation Method 2
a mixture of cyclic and linear carbonate solvents and an additive amount of a phosphoric acid-based retardant has been suggested
Implementation Method 3
Various carbon-based materials (such as artificial graphite, natural graphite, and hard carbon) capable of intercalating and deintercalating lithium ions
Implementation Method 4
A lithium salt dissolved in a carbonate-based solvent has been generally used as the electrolyte solution
Data Source
AI summary
Flame retardant electrolyte solutions for rechargeable lithium batteries and lithium batteries including the electrolyte solutions are provided. The flame retardant electrolyte solution includes a lithium salt, a linear carbonate-based solvent, at least one ammonium cation, a phosphoric acid-based solvent, and an additive including oxalatoborate.