Dual-Additive Lithium Battery Electrolyte for SEI and CEI Stability
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Solution Overview
Problem
Lithium secondary batteries face degradation in life characteristics and high-temperature stability due to side reactions between the electrolyte and electrodes, particularly when using organic electrolytes with lithium salts, leading to increased internal resistance and gas generation.
Innovation Solution
An electrolyte composition for lithium secondary batteries is introduced, incorporating a lithium salt, an organic solvent, and specific additives represented by Formulas 1 and 2, which form a solid electrolyte interface (SEI) film and cathode electrolyte interphase (CEI) film, reducing internal resistance and suppressing side reactions, thereby enhancing high-temperature stability and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If organic electrolytes including lithium salt are used, then ionic conductivity and high voltage operation are achieved, but life characteristics and high-temperature stability are degraded due to side reactions
Solution Approach 1:
The patent introduces a specific additive compound (Formula 1 with X1 being F, Cl, Br, or I; R1-R6 being various organic groups; n being 0 or 1) as an intermediary substance between the lithium salt/organic solvent electrolyte and the electrodes. This additive forms protective interface films (SEI on negative electrode, CEI on positive electrode) that mediate the interaction, preventing direct harmful side reactions while allowing ionic transport, thus resolving the contradiction between maintaining ionic conductivity and improving stability.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating the specific additive compound with defined structural parameters (X1 substituent type, R1-R6 organic groups, n value) at controlled concentrations (0.01-5 wt%). This parameter change transforms the electrolyte system from one that directly reacts with electrodes to one that forms stable protective interfaces, improving life characteristics and high-temperature stability while preserving ionic conductivity.
2Use of energy by moving object
If conventional organic electrolyte is used, then high energy density is achieved, but internal resistance increases and gas generation occurs during storage
Solution Approach 1:
The patent converts the potentially harmful side reactions between conventional organic electrolytes and electrodes into a beneficial process by using the additive compound to control the reaction pathway. The additive directs the formation of stable, low-resistance protective films (SEI and CEI) instead of allowing uncontrolled decomposition and gas-generating reactions. This transforms the harmful effect of chemical reactivity into a beneficial protective interface formation, reducing internal resistance and preventing gas generation while maintaining high energy density.
3Temperature
If stable organic solvents are used, then high voltage operation is enabled, but viscosity increases and permittivity decreases
Solution Approach 1:
The patent creates a composite electrolyte system combining the stable organic solvent (enabling high voltage operation) with the specific additive compound (Formula 1). This composite approach allows the solvent to provide high voltage stability while the additive compound compensates for increased viscosity and adjusted permittivity by forming conductive interface films. The synergistic combination maintains overall ionic conductivity and optimizes the balance between voltage stability and transport properties.
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 composition significantly reduces internal resistance, prevents gas generation, and improves the cycle life and high-temperature stability of lithium secondary batteries by forming protective films that inhibit undesired reactions and thermal decomposition.
Implementation Method 1
incorporating a lithium salt, an organic solvent, and specific additives represented by Formulas 1 and 2, which form a solid electrolyte interface (SEI) film and cathode electrolyte interphase (CEI) film
Implementation Method 2
form a solid electrolyte interface (SEI) film and cathode electrolyte interphase (CEI) film
Implementation Method 3
prevents gas generation, and improves the cycle life and high-temperature stability of lithium secondary batteries by forming protective films that inhibit undesired reactions and thermal decomposition
Data Source
AI summary
Provided are an electrolyte for a lithium secondary battery including a lithium salt, an organic solvent; and an additive, wherein the additive includes a first compound represented by Formula 1 and a second compound represented by Formula 2 below, and a mixing weight ratio of the first compound to the second compound is in a range of 1:9 to 9:1, and a lithium secondary battery including the same.In Formula 1, X1, R1 to R6, and n in Formula 1 and A1 and A2 in Formula 2 are as defined in the detailed description.