Dual-Salt Electrolyte Composition for NCM Battery Thermal Stability
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Solution Overview
Problem
Lithium nickel cobalt manganese-based secondary batteries face thermal instability issues due to exothermic reactions, leading to potential battery rupture and ignition, especially when using a carbonate-based solvent and graphite negative electrode, which limits their safe application in high-capacity devices like electric vehicles.
Innovation Solution
An electrolyte solution with a specific combination of lithium salts, such as lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and solvents like ethylene carbonate and dimethyl carbonate, optimized in concentration and ratio, is used to enhance the thermal stability of lithium nickel cobalt manganese-based batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel cobalt manganese-based positive electrode active material is used to achieve high capacity, then battery capacity is improved, but thermal stability deteriorates leading to thermal runaway
Solution Approach 1:
The patent applies parameter changes by modifying the electrolyte composition parameters - specifically using a dual lithium salt system (LiPF6 and LiFSO3CF3) with optimized concentration ratios, and selecting specific solvent combinations (cyclic carbonate and chain carbonate) with controlled proportions. These parameter adjustments transform the electrolyte's thermal properties to prevent exothermic reactions while maintaining high capacity operation of lithium nickel cobalt manganese-based cathodes
Solution Approach 2:
The patent employs composite materials by creating a composite electrolyte system that combines two different lithium salts (LiPF6 and LiFSO3CF3) with complementary properties, and mixing two types of carbonate solvents (cyclic and chain). This composite electrolyte composition synergistically improves thermal stability while preserving the high capacity characteristics of nickel-rich cathode materials
2Quantity of substance
If graphite negative electrode is used with lithium nickel cobalt manganese-based positive electrode, then battery capacity is improved, but vulnerability to heat increases leading to thermal runaway
Solution Approach 1:
The patent introduces the improved electrolyte composition as an intermediary between the graphite negative electrode and lithium nickel cobalt manganese-based positive electrode. This electrolyte acts as a thermal buffer that prevents direct heat transfer and exothermic reactions between the heat-vulnerable graphite anode and the high-capacity cathode, thereby mediating the thermal interaction while preserving capacity benefits
3Ease of operation
If conventional electrolyte solution is used with lithium nickel cobalt manganese-based positive electrode, then battery operation is simplified, but thermal runaway occurs due to exothermic reactions
Solution Approach 1:
The patent modifies the electrolyte parameters by incorporating a specific dual-salt system (LiPF6 and LiFSO3CF3) with optimized concentration ratios and selecting particular solvent combinations. These parameter changes suppress exothermic decomposition reactions that occur with conventional electrolytes, while maintaining adequate ionic conductivity for simplified battery operation
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 electrolyte solution significantly improves the thermal stability of lithium nickel cobalt manganese-based batteries, preventing deformation or explosion at temperatures up to 170°C or higher, ensuring safer and more reliable high-capacity energy storage.
Implementation Method 1
electrical energy is produced by oxidation and reduction reactions when lithium ions are intercalated/deintercalated at the positive and negative electrodes
Implementation Method 2
improving the thermal stability of the lithium secondary battery by adjusting the type and ratio of salts and solvents included in the electrolyte solution
Data Source
AI summary
Disclosed is an electrolyte solution for a lithium secondary battery that can improve the thermal stability of a lithium secondary battery comprising a lithium nickel cobalt manganese-based positive electrode active material by adjusting the type and ratio of salt and solvent comprised in the electrolyte solution, and a lithium secondary battery comprising the same. It is characterized in that the electrolyte solution for the lithium secondary battery includes: a lithium salt including a first lithium salt and a second lithium salt; and a solvent, and the first lithium salt contains lithium hexafluorophosphate, and the second lithium salt contains lithium bis(fluorosulfonyl)imide or lithium bis(trifluorosulfonyl)imide.