Phosphorus Additives Stabilize Silicon Anode SEI Layers
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Solution Overview
Problem
Conventional lithium-ion batteries with silicon-based anodes face challenges such as large volume changes, unstable solid electrolyte interphase (SEI) formation, and electrolyte decomposition, leading to reduced cycle life and energy density, especially when paired with high-voltage cathodes like Ni-rich NCM or LCO.
Innovation Solution
Incorporation of phosphorus-containing compounds as additives in the electrolyte or electrode compositions to form stable, electronically insulating but ionically conductive SEI layers on silicon anodes and passivation layers on high-voltage cathodes, which mitigate volume changes, SEI instability, and electrolyte decomposition, thereby enhancing cycle performance and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anodes are used to increase energy density, then battery capacity is improved, but volume changes and SEI instability occur reducing cycle life
Solution Approach 1:
Phosphorus-containing compounds are introduced as intermediary substances that mediate between the silicon anode and the electrolyte. These compounds form stable interfacial layers (SEI) that act as protective intermediaries, preventing direct harmful interactions between the electrolyte and silicon while maintaining ion transport, thus resolving the contradiction between high capacity and cycle stability
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolyte by incorporating phosphorus-containing compounds. This parameter change transforms the properties of the formed SEI layer, making it more stable and less prone to decomposition, thereby enabling silicon anodes to maintain both high capacity and long cycle life
2Quantity of substance
If high-voltage cathodes are used to increase energy density, then battery capacity is improved, but electrolyte decomposition occurs reducing stability
Solution Approach 1:
The phosphorus-containing compounds perform preliminary protective action by forming stable interfacial layers on the cathode surface before the electrolyte can decompose. This preliminary formation of protective films prevents subsequent electrolyte decomposition that would otherwise occur at high voltages, allowing high-capacity cathodes to operate stably
3Ease of manufacture
If conventional electrolyte compositions are used with silicon anodes, then manufacturing is simple, but SEI instability and impedance increase occur
Solution Approach 1:
The invention modifies the electrolyte composition parameters by adding phosphorus-containing compounds to conventional electrolytes. This parameter change enhances SEI stability and reduces impedance growth during cycling, while maintaining the simplicity of the manufacturing process as the additive is easily incorporated into standard electrolyte formulations
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 phosphorus-containing compounds improves the cycle life, energy density, and safety of lithium-ion batteries by stabilizing the SEI and cathode surfaces, reducing impedance, and preventing electrolyte decomposition, leading to more efficient and durable battery performance.
Implementation Method 1
form stable, electronically insulating but ionically conductive SEI layers on silicon anodes
Implementation Method 2
passivation layers on high-voltage cathodes, which mitigate volume changes, SEI instability, and electrolyte decomposition
Data Source
AI summary
Additives for energy storage devices comprising phosphorus-containing compounds are disclosed. The energy storage device comprises a first electrode and a second electrode, where at least one of the first electrode and the second electrode is a Si-based electrode, a separator between the first electrode and the second electrode, and an electrolyte composition. Phosphorus-containing compounds may serve as additives to the first electrode, the second electrode and/or the electrolyte, as well as the separator.