Nitrile-Based Electrolyte for Lithium Secondary Battery High-Temperature Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges with organic electrolytes due to volatility, flammability, and safety issues at high temperatures, leading to reduced storage characteristics and capacity retention, especially when using additives like biphenyl, which decompose over time.
Innovation Solution
An electrolyte composition for lithium secondary batteries incorporating a nitrile compound represented by Chemical Formula 1, along with a lithium salt and non-aqueous organic solvent, which includes additives such as oxalatophosphate-based and sulfinyl group-containing compounds, to enhance high-temperature and low-temperature characteristics while maintaining charge and discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If organic electrolyte is used in lithium secondary battery, then charge and discharge reactions can occur, but safety problems occur at high temperature due to volatility and flammability
Solution Approach 1:
A coating film is introduced as an intermediary layer between the organic electrolyte and the electrode. This coating film acts as a mediator that allows lithium ion transport while preventing direct contact between the flammable organic electrolyte and the electrode, thereby maintaining charge-discharge capability while improving high-temperature safety
Solution Approach 2:
The chemical composition and physical properties of the electrolyte system are modified by adding specific additives that change the parameters of the interface between electrolyte and electrode. These parameter changes result in the formation of a stable coating film with controlled ion conductivity and thermal stability, resolving the contradiction between energy usage and safety
2Reliability
If aromatic compound additives like biphenyl are used to prevent overcharge and thermal runaway, then safety is improved, but the additives decompose over time and storage characteristics are reduced
Solution Approach 1:
Instead of using single aromatic compound additives, a composite electrolyte system is employed containing multiple components including cyclic carbonate, chain carbonate, and specifically selected nitrile compounds. This composite formulation creates a more stable coating film that maintains safety benefits while improving long-term storage characteristics and reducing decomposition
Solution Approach 2:
The chemical structure parameters of the additives are optimized by selecting nitrile compounds with specific molecular structures (containing CN group and specific alkyl/aryl substituents). This parameter optimization changes the decomposition behavior and coating film stability, allowing the system to maintain safety functionality while improving storage characteristics over time
3Reliability
If SEI film is formed on anode surface to suppress side reactions, then battery performance is maintained, but high-temperature stability and low-temperature performance are insufficient
Solution Approach 1:
The chemical composition parameters of the electrolyte are changed by incorporating nitrile compounds with specific structures. These parameter changes modify the SEI film formation process and composition, creating a coating film that exhibits enhanced thermal stability at high temperatures and maintains ion conductivity at low temperatures, thereby improving adaptability across temperature ranges
Solution Approach 2:
The coating film is designed to have different local properties: at the electrode interface, it provides stable suppression of side reactions, while its outer layers are optimized for thermal stability and ion transport. This local quality differentiation allows the single coating film structure to address multiple performance requirements simultaneously
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 composition provides improved high-temperature stability, low-temperature performance, and extended lifespan by forming a stable coating film on the cathode surface, reducing internal resistance and maintaining battery performance over cycles.
Implementation Method 1
a surface of carbon particles, which are anode active materials, reacts with an electrolyte since lithium has high reactivity, and thus, a coating film called a solid electrolyte interface (SEI) film is formed on the surface of the anode
Implementation Method 2
when lithium ions are inserted into and removed from a cathode and an anode
Implementation Method 3
The lithium secondary battery generates electrical energy by oxidation and reduction reactions when lithium ions are inserted into and removed from a cathode and an anode
Data Source
AI summary
Provided are an electrolyte for a lithium secondary battery and a lithium secondary battery including the same, wherein the electrolyte for a lithium secondary battery of the present invention may improve DC-IR characteristic and battery storage characteristic, and may improve high-temperature stability, low-temperature characteristic, and lifespan characteristic to thereby be effectively used for manufacturing a secondary battery.