Lithium-Ion Battery Electrolyte Additives for Low Impedance and Cycle Life
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Solution Overview
Problem
Lithium-ion batteries for electric vehicles face challenges in achieving low impedance, long calendar life, and cycle life due to interactions between the electrolyte and electrodes, which affect energy recovery, fuel efficiency, and reliability.
Innovation Solution
An electrolyte composition including a lithium salt, organic solvent, and additives such as cyclic sultones, cyclic sulfates, silane phosphate compounds, and fluoro-phosphate salts is used to form a stable film that reduces direct contact between active oxygen and nickel, lowering impedance and gas production, and enhancing thermal stability and oxidation stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte compositions are used, then the battery can operate, but the internal resistance is high and cycle life is limited due to unstable electrolyte-electrode interactions
Solution Approach 1:
The electrolyte additives perform preliminary action by forming stable protective films on the electrode surfaces during initial cycles. These films (SEI layers) are formed in advance to prevent subsequent degradation reactions, thereby reducing internal resistance growth and extending cycle life. The cyclic sulfate and sultone compounds specifically form stable surface films that protect the electrodes from harmful interactions.
Solution Approach 2:
The patent employs a composite electrolyte formulation combining multiple additive types (cyclic sulfate, sultone, silane phosphate/borate, and fluoro-phosphate salt) working synergistically. This composite approach creates a more robust and stable protective interface between electrolyte and electrodes, simultaneously addressing both internal resistance and cycle life issues through the combined effects of different additive mechanisms.
2Stability of the object's composition
If the electrolyte forms a stable protective film, then thermal stability improves, but gas production increases due to film formation reactions
Solution Approach 1:
The patent optimizes the concentration parameters of each additive component within specific ranges (e.g., cyclic sulfate 0.01-5%, sultone 0.01-0.5%). By precisely controlling these parameters, the electrolyte forms stable protective films with minimized gas-generating side reactions. The balanced composition ensures sufficient film formation for thermal stability while limiting excessive gas production.
Solution Approach 2:
The electrolyte additives act as intermediaries between the electrolyte and electrode surfaces. These additive molecules preferentially react to form stable surface films that mediate the interaction, preventing direct contact between the bulk electrolyte and electrodes. This intermediary layer provides thermal stability while the controlled composition minimizes gas-evolving reactions during film formation.
3Reliability
If additive concentrations are increased to improve film stability, then protection against oxygen-nickel contact improves, but impedance increases due to excessive film formation
Solution Approach 1:
The patent precisely optimizes the concentration parameters of each additive to achieve the minimum effective level for forming stable protective films. The cyclic sulfate (0.01-5%) and sultone (0.01-0.5%) concentrations are specifically tuned to provide sufficient oxidation stability and protection against oxygen-nickel contact while avoiding excessive film thickness that would increase impedance. This parameter optimization balances protection and conductivity.
Solution Approach 2:
The patent applies partial action by using small, optimized amounts of each additive rather than large excess concentrations. The synergistic combination of multiple additives at low concentrations (each 0.01-5% range) achieves the desired protective effect without the excessive film formation that would occur with high concentrations of single additives, thereby maintaining low impedance while providing oxidation stability.
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 results in lithium-ion batteries with low internal resistance, high capacity retention, and improved performance at high and low temperatures, extending cycle life and calendar life while maintaining reliability.
Implementation Method 1
form a stable film that reduces direct contact between active oxygen and nickel
Implementation Method 2
Interaction between the electrolyte and electrodes plays an important role
Implementation Method 3
low impedance, long calendar life and long cycle life. The low internal resistance improves acceleration and dynamic performance
Implementation Method 4
enhancing thermal stability and oxidation stability
Implementation Method 5
Long calendar life and cycle life can guarantee high reliability of batteries
Data Source
AI summary
The present application relates to the technical field of lithium-ion batteries and, specifically, relates to an electrolyte and a lithium-ion battery containing the electrolyte. The electrolyte of the present application comprises a lithium salt, an organic solvent and additives that include additive A, additive B and at least one of additive C and additive D; in which, the additive A is a cyclic sultone; the additive B is a cyclic sulfate; the additive C is a silane phosphate compound and/or a silane borate compound; and the additive D is a fluoro-phosphate salt. The battery of the present application has low gas production at high temperature, high capacity retention rate and high power at low temperature as a function of synergistic effects of additives.