Polymer Additive Electrolytes for High-Voltage Cathode Stability
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Solution Overview
Problem
Conventional electrolytes in lithium-ion batteries are unstable at high voltages, leading to decomposition and deterioration of battery performance and safety, limiting the use of high energy cathode materials like LiCoO2 and LiNi0.33Mn0.33Co0.33O2 to only 50% of their theoretical capacity due to degradation above 4.3V.
Innovation Solution
A battery design incorporating a lithium salt, non-aqueous solvent, and polymer or copolymer additive compounds with nitrile, amide, or ester groups, which form a stable solid electrolyte interphase (SEI) on the cathode, preventing oxidative decomposition and enhancing cycle life and ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytes are used in lithium-ion batteries, then the batteries can operate at standard voltages, but the electrolytes become unstable and decompose at high voltages above 4.3V, leading to deterioration of performance and safety
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolyte by incorporating specific polymer additives (polyacrylonitrile, polyvinylidene fluoride, polyvinylene carbonate) at controlled concentrations (0.1-5 wt%). This changes the electrolyte's decomposition characteristics, raising the stable operating voltage from 4.3V to above 4.7V while maintaining reliability
Solution Approach 2:
The patent creates a composite electrolyte system by combining conventional electrolyte components (lithium salt, non-aqueous solvent) with polymer additive compounds. This composite approach integrates the benefits of conventional electrolytes with the high-voltage stability of polymer materials, enabling operation at elevated voltages without decomposition
2Quantity of substance
If high energy cathode materials like LiCoO2 and LiNi0.33Mn0.33Co0.33O2 are used to increase capacity, then the theoretical capacity increases, but the cycle life deteriorates significantly because conventional electrolytes degrade above 4.3V
Solution Approach 1:
The polymer additives act as intermediary substances that form protective interface films between the high energy cathode materials and the conventional electrolyte. These intermediary layers prevent direct contact and decomposition reactions, allowing high capacity materials to be used without sacrificing cycle life
Solution Approach 2:
The patent changes the electrochemical window parameters of the electrolyte system through additive incorporation, enabling stable operation at higher potentials required for high energy cathode materials. This parameter modification allows full utilization of cathode capacity while maintaining long cycle life
3Use of energy by moving object
If the electrolyte is operated at higher voltages to utilize more cathode capacity, then the battery energy increases, but gas and acidic products are generated that damage the battery
Solution Approach 1:
The patent converts the potentially harmful decomposition reactions into beneficial protective film formation. The polymer additives decompose preferentially at high voltages to form stable surface films that prevent further decomposition, transforming what would be harmful gas and acid generation into a protective mechanism
Solution Approach 2:
The polymer additives perform preliminary protective action by forming stable interface films before conventional electrolyte decomposition can occur. This preliminary protection prevents the generation of harmful decomposition products during 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 use of polymer additives significantly improves the cycle life and coulombic efficiency of lithium-ion batteries, allowing operation at higher voltages while maintaining stability and preventing gas and acidic product formation, thereby extending battery capacity and safety.
Implementation Method 1
solvents, salts, or additives have been incorporated into the electrolyte to decompose to form a protective film called a solid electrolyte interphase (SEI)
Implementation Method 2
At high voltages, conventional electrolytes can decompose, for example, by catalytic oxidation in the presence of cathode materials
Implementation Method 3
An electrolyte serves to transport ions and prevent electrical contact between electrodes in a battery
Implementation Method 4
organic compounds containing polymerizable functional groups such as alkenes, furan, thiophene, and pyrole had been reported to form an SEI on the cathode of lithium ion batteries. These additives likely undergo polymerization during cell charging to form passivation films on the electrodes
Data Source
AI summary
Described herein are materials for use in electrolytes that provide a number of desirable characteristics when implemented within batteries, such as high stability during battery cycling up to high temperatures, high voltages, high discharge capacity, high coulombic efficiency, and excellent retention of discharge capacity and coulombic efficiency over several cycles of charging and discharging. In some embodiments, a high voltage electrolyte includes a base electrolyte and an additive compounds.