Siloxane Polymer Electrolyte Additives for High-Temperature Battery Stability
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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 concerns due to the formation of non-uniform solid electrolyte interphases (SEIs) and parasitic reactions.
Innovation Solution
Incorporation of siloxane-containing homopolymers or copolymers, such as poly(dimethylsiloxane-co-methylphenylsiloxane), poly(methylphenylsiloxane), and poly(vinylmethoxysiloxane), into the electrolyte formulation to form stable and uniform SEIs that inhibit oxidative decomposition at high voltages and temperatures, enhancing the stability and performance of high-energy cathode materials like NMC.
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 and temperatures, 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 introducing siloxane-containing polymers with specific molecular structures and functional groups. These compositional changes enable the electrolyte to maintain stability at elevated temperatures and voltages, expanding the operating temperature range from standard conditions to high-temperature operation while improving reliability
Solution Approach 2:
The patent creates a composite electrolyte system by combining siloxane-containing polymers with conventional electrolyte components. This composite approach integrates the thermal stability and film-forming capabilities of siloxane polymers with the ionic conductivity of conventional electrolytes, achieving both high-temperature stability and reliable performance
2Productivity
If conventional electrolytes are used at high voltages above 4.2V, then higher capacity can be achieved, but the electrolyte degrades producing gas and acidic products that damage the battery
Solution Approach 1:
The siloxane-containing polymers in the electrolyte proactively form protective films on electrode surfaces before high-voltage operation begins. These pre-formed films act as barriers that prevent subsequent decomposition reactions, stopping the generation of harmful gas and acidic products before they can occur during high-voltage charging above 4.2V
Solution Approach 2:
The patent converts the potential harm of polymer decomposition into a beneficial outcome by designing siloxane-containing polymers that decompose preferentially to form stable, protective solid electrolyte interphase (SEI) films. This controlled decomposition at lower voltages creates a protective layer that prevents further degradation at high voltages, turning what would be a harmful process into a protective mechanism
3Reliability
If in situ polymerization is used to form SEI on cathode, then passivation films can be formed, but the polymerization cannot be controlled precisely resulting in non-uniform SEIs with heterogeneous composition
Solution Approach 1:
The siloxane-containing polymers are pre-synthesized with controlled molecular weights, uniform compositions, and specific functional groups before being incorporated into the electrolyte. This preliminary preparation ensures that when these polymers form SEI films during battery operation, they do so in a controlled and uniform manner, avoiding the heterogeneous composition problems of in situ polymerization
Solution Approach 2:
The siloxane-containing polymers act as intermediary substances that mediate between the electrode surfaces and the conventional electrolyte components. These pre-formed polymer structures serve as templates that guide the formation of uniform SEI films, controlling the composition and structure of the passivation layer to achieve homogeneous films with consistent properties
4Reliability
If organic polymers are used as solid electrolytes, then volatility and safety improve, but ionic conductivity becomes poor
Solution Approach 1:
The patent creates a composite electrolyte system that combines the safety advantages of polymeric materials with the ionic conductivity of conventional liquid electrolyte components. The siloxane-containing polymers provide the safety benefits of low volatility and high thermal stability, while the conventional electrolyte components maintain ionic conductivity, achieving both safety and performance
Solution Approach 2:
The patent applies different material properties to different functional requirements: the siloxane-containing polymers are positioned to provide safety and stability functions where needed, while conventional electrolyte components are maintained in regions where ionic conductivity is critical. This spatial and functional differentiation allows the system to simultaneously achieve both safety and high ionic conductivity
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 siloxane-containing polymers significantly improves the cycle life and coulombic efficiency of lithium-ion batteries by forming stable SEIs, allowing operation at higher voltages and temperatures without significant capacity fade, thereby enhancing the overall performance and safety of the batteries.
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
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. The polymer additives can be homopolymers or copolymers.