Lithium Battery Electrolyte Additive for High-Temperature Stability
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Solution Overview
Problem
Rechargeable lithium batteries face performance deterioration and safety issues due to electrolyte decomposition and side reactions, particularly at high temperatures, leading to increased internal resistance and gas generation, which affect stability and cycle-life.
Innovation Solution
Incorporating a specific additive represented by Chemical Formula 1 into the electrolyte, which forms a stable solid electrolyte interface film on the negative electrode, suppressing electrolyte decomposition and side reactions, and including a carbon nanotube in the positive active material layer to enhance conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LiPF6 is used as lithium salt in the electrolyte, then high conductivity is achieved, but electrolyte decomposition and gas generation occur at high temperature
Solution Approach 1:
A cyclic carboxylate compound is introduced as an intermediary substance between LiPF6 and the electrode/electrolyte interface. This additive preferentially reacts to form a stable solid electrolyte interface (SEI) film that acts as a protective barrier, preventing direct contact and harmful reactions between LiPF6 and the electrode materials at high temperatures, thus maintaining both conductivity and stability
Solution Approach 2:
The chemical composition and structure of the solid electrolyte interface film are modified by introducing cyclic carboxylate compounds with specific molecular structures (containing carbonyl groups and heteroatoms). This changes the film's properties to be more thermally stable and less prone to decomposition, thereby improving high-temperature performance while maintaining ionic conductivity
2Reliability
If electrolyte volume is increased to improve impregnation of positive electrode, then initial resistance is reduced, but battery size increases
Solution Approach 1:
The electrolyte composition is optimized by selecting specific non-aqueous organic solvents with appropriate dielectric constants and viscosity, combined with cyclic carboxylate additives. This formulation enhances the electrolyte's ability to form conductive pathways and impregnate the electrode structure efficiently, achieving low initial resistance with reduced electrolyte volume
Solution Approach 2:
The electrolyte is formulated as a composite system combining multiple non-aqueous organic solvents (such as cyclic carbonates and chain carbonates) with cyclic carboxylate additives. This composite approach creates synergistic effects that improve both conductivity and electrode impregnation efficiency, allowing reduced electrolyte volume while maintaining performance
3Use of energy by moving object
If high voltage range is used to expand capacity, then energy density is increased, but positive electrode performance deteriorates due to electrolyte oxidization
Solution Approach 1:
The cyclic carboxylate compound serves as a protective intermediary that forms a stable interface layer on the positive electrode surface. This layer acts as a barrier that prevents direct oxidization reactions between the electrolyte (particularly LiPF6) and the positive electrode materials at high voltages, thereby preserving electrode performance while enabling high energy density operation
Solution Approach 2:
The potential harmful oxidization reactions at high voltage are converted into a beneficial process where the cyclic carboxylate additive preferentially reacts with the electrolyte to form a protective film. This transforms the harmful high-voltage environment into a condition that generates a protective barrier, preventing further degradation and enabling stable high-voltage 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 solution reduces gas generation, minimizes internal resistance, and improves battery stability and high-temperature storage characteristics, thereby enhancing the cycle-life and safety of rechargeable lithium batteries.
Implementation Method 1
Incorporating a specific additive represented by Chemical Formula 1 into the electrolyte, which forms a stable solid electrolyte interface film on the negative electrode
Implementation Method 2
including a carbon nanotube in the positive active material layer to enhance conductivity and stability
Data Source
Figure 1
AI summary
Provided a rechargeable lithium battery including a positive electrode including a positive active material; a negative electrode including a negative active material; and an electrolyte including a non-aqueous organic solvent, a lithium salt, and an additive represented by Chemical Formula 1, wherein a volume thereof is 5 cm3 to 200 cm3. Details of Chemical Formula 1 are as described in the specification.