Ketone Polymer Additive for Stable SEI in High-Voltage Batteries
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Solution Overview
Problem
Conventional electrolytes in lithium-ion batteries face challenges at high voltages and temperatures, leading to decomposition, poor mechanical and electrochemical stability, and limited cycle life due to non-uniform solid electrolyte interphase (SEI) formation, which affects the performance and safety of high-energy cathode materials like LiCoO2 and LiNi-based compounds.
Innovation Solution
A lithium-ion battery electrolyte formulation incorporating a ketone-containing polymer additive, such as poly(vinyl methyl ketone), which forms a stable solid electrolyte interphase (SEI) on the cathode, preventing oxidative decomposition and enhancing the battery's stability and cycle life at high voltages and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytes are used in lithium-ion batteries, then the batteries can operate with standard components and manufacturing processes, but the electrolytes decompose at high voltages and temperatures leading to poor cycle life and safety issues
Solution Approach 1:
The patent applies preliminary action by introducing a polymer additive that pre-forms a protective film on the cathode surface before operational degradation can occur. This film is formed during initial cycles through controlled decomposition of the polymer additive, creating a stable interface that prevents subsequent electrolyte decomposition at high voltages and temperatures, thereby extending cycle life and improving safety.
Solution Approach 2:
The patent uses a polymer additive as an intermediary substance between the electrolyte and the cathode. This intermediary forms a protective interphase layer that mediates the interaction between the electrolyte and high-voltage cathode materials, preventing direct contact and chemical reactions that would otherwise lead to electrolyte decomposition and capacity fade.
2Reliability
If organic compounds with polymerizable functional groups are used to form SEI on the cathode, then passivation films can be formed, but the in situ polymerization cannot be controlled precisely resulting in non-uniform SEIs with heterogeneous molecular weight and composition
Solution Approach 1:
The patent applies parameter changes by carefully controlling the molecular weight, composition, and structure of the polymer additive used in the electrolyte. By optimizing these parameters, the polymer decomposes in a controlled manner to form a uniform SEI film with consistent properties. The polymer's predetermined characteristics ensure reproducible film formation rather than uncontrolled in situ polymerization.
Solution Approach 2:
The patent uses a composite approach by combining the polymer additive with conventional electrolyte components (carbonate solvents and lithium salts). This composite electrolyte system leverages the benefits of both the polymer (controlled film formation) and conventional electrolytes (ionic conductivity), resulting in a uniform SEI with homogeneous composition and structure.
3Productivity
If batteries are operated at higher voltages above 4.2V to obtain higher capacity from high-energy cathode materials, then capacity increases, but conventional electrolytes degrade leading to significant deterioration of cycle life and generation of gas and acidic products
Solution Approach 1:
The patent applies preliminary anti-action by using the polymer additive to preemptively counteract the harmful effects of high-voltage operation. The polymer decomposes first to form a stable protective film that prevents the electrolyte from undergoing oxidative decomposition at high voltages, thereby eliminating the generation of gas and acidic products that would otherwise occur and damage the battery.
4Temperature
If conventional electrolytes are used at high temperatures, then the batteries can operate in elevated temperature environments, but the electrolytes decompose by oxidation or reduction leading to poor stability analogous to high voltage degradation
Solution Approach 1:
The patent applies this principle by using a small amount of polymer additive that sacrificially decomposes during initial cycles to form a stable protective film. The polymer additive acts as a consumable component that is used up in the formation process, creating a long-lasting stable interface that protects the electrolyte from thermal degradation during subsequent high-temperature 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 ketone-containing polymer additives improves the mechanical and chemical stability of the SEI, leading to increased cycle life and capacity retention, especially in high-energy cathode materials like NMC, by forming a uniform and protective film on the cathode, thereby enhancing the battery's performance and safety.
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
At high voltages, conventional electrolytes can decompose, for example, by catalytic oxidation in the presence of cathode materials
Implementation Method 3
these additives likely undergo polymerization during cell charging to form passivation films on the electrodes
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.