Silyl Ester Phosphinates for High Voltage Battery Stability
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Solution Overview
Problem
Secondary lithium batteries with high energy/high voltage cathode materials face challenges in maintaining capacity retention, long-term performance, low gas evolution, and low impedance build-up, particularly in high-temperature environments.
Innovation Solution
Non-aqueous electrolyte compositions containing aprotic organic solvents, silyl ester phosphinates, and lithium ion conducting salts, optionally with additional additives, are used to enhance the performance and safety of electrochemical cells, particularly those with high specific energy and high working voltage cathode materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high energy/high voltage cathode materials are used to increase specific energy and working voltage, then energy density and power output are improved, but capacity retention and long-term performance deteriorate
Solution Approach 1:
The patent introduces silyl ester phosphinates as intermediary compounds that form protective films on the cathode surface. These films act as mediators between the high voltage cathode material and the electrolyte, preventing direct harmful interactions while allowing lithium ion transport. The protective film stabilizes the electrode-electrolyte interface, enabling high voltage operation without sacrificing capacity retention.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating silyl ester phosphinates with specific molecular structures (formula I and II). These compositional changes alter the electrochemical window and stability characteristics of the electrolyte, allowing it to withstand higher voltages while maintaining good capacity retention through optimized film-forming properties.
2Quantity of substance
If high cut-off voltages are used during charging to obtain high specific energies, then energy density is improved, but gas evolution and impedance build-up increase
Solution Approach 1:
The silyl ester phosphinates perform preliminary protective action by forming stable surface films on the cathode before gas evolution can occur. These pre-formed films prevent electrolyte decomposition and oxygen release at high voltages, counteracting the harmful effects before they manifest. The films act as barriers that suppress gas-generating side reactions during high voltage charging.
Solution Approach 2:
The patent converts the potentially harmful high voltage stress into a beneficial effect by using it to form stable protective films through controlled initial decomposition of silyl ester phosphinates. This controlled decomposition creates a protective layer that subsequently prevents further harmful decomposition and gas evolution, turning the initial harmful effect into a protective mechanism.
3Quantity of substance
If high cut-off voltages are used during charging to obtain high specific energies, then energy density is improved, but impedance build-up increases
Solution Approach 1:
The silyl ester phosphinates serve as intermediary substances that form stable interfacial films between the high voltage cathode and electrolyte. These films mediate the interaction by providing a stable interface that prevents impedance-increasing side reactions while maintaining lithium ion conductivity. The intermediary layer protects against transition metal dissolution and electrolyte decomposition that would otherwise increase impedance.
Solution Approach 2:
The patent changes the electrochemical parameters of the system by introducing silyl ester phosphinates that modify the interface stability and conductivity characteristics. These parameter changes result in lower impedance growth rates during high voltage cycling while maintaining the high specific energy benefits, achieving a favorable balance between energy density and impedance stability.
4Adaptability or versatility
If conventional electrolyte compositions are used with high voltage cathode materials, then compatibility is maintained, but performance and safety deteriorate in high-temperature environments
Solution Approach 1:
The patent creates a composite electrolyte system by combining conventional electrolyte components with silyl ester phosphinates. This composite composition maintains the beneficial properties of conventional electrolytes (compatibility with standard electrodes) while adding high-temperature stability through the phosphinate additives. The composite formulation achieves both adaptability and high-temperature reliability.
Solution Approach 2:
The silyl ester phosphinates act as intermediary compounds that enhance high-temperature performance by forming thermally stable protective films. These intermediaries prevent direct contact between the electrolyte and electrode at elevated temperatures, reducing decomposition reactions and maintaining performance. The mediators enable the system to withstand high temperatures while preserving electrochemical activity.
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 proposed electrolyte compositions result in electrochemical cells with improved capacity retention, long-term performance, reduced gas generation, and decreased cell resistance, ensuring high safety and stability even at elevated temperatures.
Implementation Method 1
film forming additives which react during first charge/discharge cycle on the electrode surface thereby forming a film on the electrode
Implementation Method 2
organic carbonates, ethers, esters and ionic liquids are used as sufficiently polar solvents for solvating the conducting salt(s)
Implementation Method 3
reversible conversion of chemical energy into electrical energy and vice versa
Data Source
AI summary
A non-aqueous electrolyte composition containing (i) at least one aprotic organic solvent; (ii) a compound of formula (I) (iii) at least one ion containing conducting salt; and (iv) optionally one or more additives.