Ester Polymer Additives for Stable SEI Films
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Solution Overview
Problem
Conventional electrolytes in lithium-ion batteries degrade at high voltages and temperatures, leading to poor mechanical and electrochemical stability, limited cycle life, and safety issues due to non-uniform solid electrolyte interphase (SEI) formation and decomposition.
Innovation Solution
Incorporation of ester-containing polymer additives, such as poly(vinyl acetate) and poly(1,4-butylene adipate), into the electrolyte formulation to stabilize the SEI and prevent oxidative decomposition at high voltages and temperatures, forming a more uniform and stable film on the cathode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytes are used in lithium-ion batteries, then the batteries can operate at standard conditions, but the electrolytes decompose at high voltages and temperatures leading to poor stability and limited cycle life
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolyte by incorporating polymer additives with specific functional groups (carboxylic acid, hydroxyl, amine) to change the decomposition behavior and stability characteristics of the electrolyte system, enabling operation at higher temperatures and voltages
Solution Approach 2:
The patent creates a composite electrolyte system by combining conventional electrolyte components with polymer additives, forming a hybrid system that exhibits enhanced thermal and electrochemical stability compared to conventional electrolytes alone
2Productivity
If conventional electrolytes are used at high voltages above 4.2V, then higher capacity can be achieved, but the electrolyte degrades leading to significant deterioration of cycle life
Solution Approach 1:
The polymer additives perform preliminary protective action by decomposing first during initial charging cycles to form a stable SEI film on the electrode surfaces, which then prevents subsequent degradation of the bulk electrolyte during high-voltage operation and extended cycling
Solution Approach 2:
The polymer additives act as sacrificial components that decompose during initial cycles to form protective films, consuming themselves in the process while protecting the main electrolyte system from degradation during prolonged high-voltage operation
3Reliability
If organic compounds with polymerizable functional groups are used to form SEI on cathode, then passivation films are formed, but in situ polymerization cannot be controlled precisely resulting in non-uniform SEI with heterogeneous composition
Solution Approach 1:
The patent changes the molecular weight parameters of the polymer additives and controls their concentration in the electrolyte to regulate the polymerization process, achieving more uniform SEI formation with controlled molecular weight distribution and homogeneous composition
4Use of energy by moving object
If batteries are operated at high temperatures, then thermal energy is increased, but conventional electrolytes decompose by oxidation or reduction leading to poor stability
Solution Approach 1:
The patent converts the potentially harmful thermal energy that would cause electrolyte decomposition into a beneficial effect by using heat-stable polymer additives that decompose at controlled temperatures to form thermally stable SEI films, transforming thermal stress into a protective mechanism
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 ester-containing polymer additives significantly improves the cycle life and coulombic efficiency of lithium-ion batteries by enhancing the mechanical and chemical stability of the SEI, maintaining performance at high temperatures and voltages.
Implementation Method 1
solvents, salts, or additives have been incorporated into the electrolyte to decompose on the electrode to form a protective film called a solid electrolyte interphase (SEI)
Implementation Method 2
A liquid electrolyte serves to transport ions between electrodes in a battery
Implementation Method 3
These additives likely undergo polymerization during cell charging to form passivation films on the electrodes
Implementation Method 4
At high voltages, conventional electrolytes can decompose, for example, by catalytic oxidation in the presence of cathode materials
Implementation Method 5
Conventional electrolytes may also be degraded by reduction by the anodes when the cells are charged
Data Source
AI summary
Described herein are additives for use in electrolytes that provide a number of desirable characteristics when implemented within batteries, such as high capacity retention during battery cycling at high temperatures. In some embodiments, a high temperature electrolyte includes a base electrolyte and one or more polymer additives, which impart these desirable performance characteristics.