Electrolyte for lithium secondary battery and lithium secondary battery including the same
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Solution Overview
Problem
Lithium secondary batteries face issues with decreased output and capacity due to damage to nickel-based lithium metal oxide cathodes, side reactions with the electrolyte, and performance degradation in high-temperature environments, leading to swelling, increased internal resistance, and reduced lifespan.
Innovation Solution
The electrolyte for lithium secondary batteries includes an additive with a specific chemical structure, such as bis(dimethylamino)dimethylsilane, and an auxiliary additive comprising cyclic carbonate and fluorine-substituted cyclic carbonate compounds, forming a robust solid electrolyte interphase (SEI) that reduces decomposition and facilitates Li ion movement, improving low and high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional electrolytes are used in lithium secondary batteries with nickel-based lithium metal oxide cathodes, then the battery can operate at high voltage and high energy density, but the output and capacity decrease due to side reactions between the cathode and electrolyte during repeated charging and discharging
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance that mediates between the nickel-based lithium metal oxide cathode and the conventional electrolyte. This compound forms a protective interface layer that prevents direct contact and harmful side reactions, while still allowing lithium ion transport. The fluorinated compound acts as a buffer that stabilizes the electrode-electrolyte interface, thereby maintaining high output and capacity over repeated charge-discharge cycles without compromising operational stability.
Solution Approach 2:
The patent employs a composite electrolyte system consisting of conventional electrolyte components combined with fluorinated cyclic carbonate compounds. This composite approach creates a multi-functional electrolyte that simultaneously provides ionic conductivity, electrochemical stability, and protective interface formation. The combination of different materials allows the system to maintain high power output while improving operational reliability through the synergistic effects of the composite composition.
2Duration of action of moving object
If the lithium secondary battery is placed in a high-temperature environment with repetitive charging/discharging, then the battery can maintain operation, but swelling phenomenon occurs due to gas generation, internal resistance increases, and life-span deteriorates
Solution Approach 1:
The fluorinated cyclic carbonate compound performs preliminary protective action by forming a stable interface layer on the cathode surface before harmful high-temperature reactions can occur. This pre-formed protective layer acts as a barrier that prevents gas-generating side reactions during subsequent high-temperature charging and discharging cycles. By establishing this protective interface in advance, the system prevents swelling and internal resistance increase before they can develop, thereby extending battery life-span while maintaining continuous operation capability.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating fluorinated cyclic carbonate compounds with specific molecular structures and properties. This parameter change alters the electrochemical window, interfacial stability, and thermal characteristics of the electrolyte system. The fluorinated compounds change the physical-chemical parameters at the electrode interface, creating a more stable environment that resists high-temperature degradation, reduces gas generation, and maintains lower internal resistance throughout the battery's operational life.
3Temperature
If additives are added to the non-aqueous electrolyte to improve high and low temperature characteristics, then temperature performance improves, but operational reliability decreases
Solution Approach 1:
The patent applies local quality enhancement by introducing fluorinated cyclic carbonate compounds specifically at the electrode-electrolyte interface rather than uniformly throughout the bulk electrolyte. This localized modification creates a protective interface layer with specialized properties that improve temperature performance precisely where it is most needed - at the reaction interface. The bulk electrolyte maintains its original good properties while the local interface region gains enhanced thermal stability and reduced reactivity, thereby improving temperature characteristics without compromising overall operational reliability.
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 enhances discharge capacity at low temperatures, suppresses gas generation and thickness increase at high temperatures, and improves capacity retention, thereby extending the battery's lifespan and operational stability.
Implementation Method 1
forming a robust solid electrolyte interphase (SEI) that reduces decomposition and facilitates Li ion movement
Implementation Method 2
an electrolyte in which the electrode assembly is impregnated
Data Source
Figure 1~2
AI summary
An electrolyte for a lithium secondary battery according to exemplary embodiments includes an additive represented by Formula 1 below; an organic solvent; and a lithium salt: wherein in Formula 1, R1 to R4 are each independently hydrogen, or a substituted or unsubstituted C1-C10 alkyl group, and R5 and R6 are each independently hydrogen, a substituted or unsubstituted C1-C10 alkyl group, or a substituted or unsubstituted amine group. Accordingly, a lithium secondary battery including the electrolyte for a lithium secondary battery having a specific composition may have improved low and high temperature characteristics.