Nonaqueous Electrolyte Additive Blend for High-Voltage Cycle Stability
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Solution Overview
Problem
High voltage rechargeable lithium ion batteries face challenges in maintaining lifetime and cycle life due to increased electrolyte decomposition and parasitic reactions, despite improvements in capacity and voltage, which existing additives fail to adequately address.
Innovation Solution
A nonaqueous battery electrolyte comprising a primary lithium salt, a primary nonaqueous solvent, and an additive mixture of vinylene carbonate, a sulfur-containing compound, and lithium difluorophosphate, used in amounts less than 10% by weight, which enhances the stability and cycle life of high voltage lithium ion batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high voltage cathode materials and higher operating voltages are employed to improve cell capacity, then cell capacity is improved, but battery lifetime deteriorates due to increased electrolyte decomposition
Solution Approach 1:
The patent applies preliminary action by introducing electrolyte additives (specifically vinylene carbonate and fluoroethylene carbonate in combination with lithium salts) that pre-form protective solid electrolyte interface (SEI) layers on the electrode surfaces before significant decomposition occurs. This preliminary protective layer formation prevents subsequent electrolyte degradation and electrode damage during high-voltage operation, thereby extending battery lifetime while maintaining high capacity
Solution Approach 2:
The patent uses electrolyte additives as intermediary substances that mediate between the high-voltage cathode materials and the electrolyte. These additives (such as vinylene carbonate and fluoroethylene carbonate) act as sacrificial intermediaries that decompose preferentially to form stable protective films, preventing direct contact and harmful reactions between the high-voltage electrodes and the bulk electrolyte, thus resolving the contradiction between high capacity and long lifetime
2Reliability
If conventional electrolyte additives are used to improve battery performance, then certain characteristics are enhanced, but they fail to adequately reduce electrolyte decomposition and parasitic reactions
Solution Approach 1:
The patent employs composite materials by combining multiple electrolyte additives in specific formulations: vinylene carbonate (0.1-5 wt%), fluoroethylene carbonate (0.1-5 wt%), and lithium difluorophosphate (0.1-5 wt%). This composite additive system creates synergistic effects where each component contributes different protective functions, forming a more robust and stable solid electrolyte interface that effectively suppresses electrolyte decomposition and parasitic reactions better than single additives alone
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 mixture significantly improves the cycle life and stability of high voltage lithium ion batteries by forming a robust solid electrolyte interface, reducing impedance and parasitic reactions, and maintaining performance without adverse effects on other aspects.
Implementation Method 1
create a stable solid electrolyte interface ('SEI') layer on the anode that allows for desirable subsequent ionic transport therethrough while preventing further reaction with the electrolyte
Implementation Method 2
During discharge of the battery, lithium is extracted from the anode material while lithium is inserted into the cathode material
Implementation Method 3
During charge, the process is reversed
Data Source
AI summary
Additive mixtures for nonaqueous battery electrolytes have been discovered that provide for improved performance, and particularly for improved lifetime (cycle life and stability) in high voltage, rechargeable lithium ion batteries. The battery electrolytes comprise less than 10% by weight of an additive mixture comprising an additive solvent, a sulfur containing compound, and lithium difluorophosphate.