Silicon Battery Electrolyte Additives for Stable SEI and High-Voltage Cycling
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Solution Overview
Problem
Lithium-ion batteries with silicon-based anodes and high-voltage nickel-rich cathodes face challenges in long-term cycling stability due to volumetric expansion, unstable solid electrolyte interphase (SEI) layers, and oxidative instability of conventional electrolytes, leading to reduced cycle life and capacity retention.
Innovation Solution
The development of electrolyte additives, such as carboxylic ethers, carboxylic acid-based salts, and acrylates, which form stable, electronically insulating but ionically conducting SEI layers on silicon anodes and protective cathode electrolyte interphase (CEI) films, enhancing mechanical strength, thermal stability, and reducing flammability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anodes are used to increase energy density, then capacity is improved, but volumetric expansion during lithiation leads to disintegration and reduced cycling stability
Solution Approach 1:
The patent employs flexible polymer coatings and thin film encapsulation layers around silicon anode particles. These flexible shells accommodate the volumetric expansion and contraction during lithiation/delithiation cycles, preventing particle disintegration while maintaining structural integrity and electrical contact throughout cycling.
Solution Approach 2:
The patent utilizes composite material structures combining silicon with other materials (such as carbon matrices, metal oxides, or polymer binders) to create mechanically robust anodes. These composites provide structural support during expansion, maintain electrical conductivity pathways, and prevent silicon particle isolation, thereby preserving cycling stability while utilizing high-capacity silicon.
2Power
If conventional electrolytes are used with high-voltage cathodes, then operating voltage is improved, but oxidative instability occurs beyond 4.5 V leading to accelerated decay
Solution Approach 1:
The patent modifies electrolyte composition parameters by incorporating advanced additives (such as fluoroethylene carbonate, lithium difluorophosphate, or novel cyclic carbonates) that shift the electrochemical stability window to higher voltages. These compositional changes enable the electrolyte to remain stable at operating voltages exceeding 4.5 V, preventing oxidative decomposition and maintaining cycling performance.
Solution Approach 2:
The patent introduces protective interfacial layers (such as artificial solid electrolyte interphase films or surface coatings on cathode materials) that act as intermediaries between the high-voltage cathode and conventional electrolyte. These intermediary layers prevent direct contact and oxidative reactions, enabling high-voltage operation while protecting the electrolyte from decomposition.
3Duration of action of moving object
If silicon anodes undergo repeated lithiation/delithiation, then capacity cycling is improved, but unstable SEI layer formation leads to continuous electrolyte decomposition and irreversible capacity loss
Solution Approach 1:
The patent employs preliminary formation cycles or pre-treatment processes that establish a stable solid electrolyte interphase (SEI) layer on silicon anodes before full cycling begins. This preliminary action creates a robust, low-resistance SEI that prevents continuous electrolyte decomposition during subsequent cycling, reducing irreversible capacity loss and improving long-term cycle life.
Solution Approach 2:
The patent utilizes sacrificial coating materials or disposable protective layers on silicon anodes that decompose during initial cycles to form stable SEI structures. These sacrificial layers consume themselves to create durable interfaces, preventing ongoing electrolyte decomposition and capacity fade during extended cycling operations.
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
These additives improve the electrochemical stability and safety of lithium-ion batteries by stabilizing the SEI and CEI layers, reducing capacity fade, and increasing cycle life, while also enhancing thermal stability and safety by minimizing electrolyte decomposition and transition metal ion dissolution.
Implementation Method 1
an unstable solid electrolyte interphase (SEI) layer can develop on the surface of the cycled anodes, and leads to an endless exposure of Si particle surfaces to the liquid electrolyte. This results in an irreversible capacity loss at each cycle due to the reduction at the low potential where the liquid electrolyte reacts with the exposed surface of the Si anode
Implementation Method 2
form stable, electronically insulating but ionically conducting SEI layers on silicon anodes
Implementation Method 3
form stable, electronically insulating but ionically conducting SEI layers on silicon anodes
Implementation Method 4
protective cathode electrolyte interphase (CEI) films, enhancing mechanical strength, thermal stability, and reducing flammability
Data Source
AI summary
Electrolytes and electrolyte additives for energy storage devices comprising a carboxylic ether, a carboxylic acid based salt, or an acrylate electrolyte are disclosed. The energy storage device comprises a first electrode and a second electrode, wherein 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, an electrolyte, and at least one electrolyte additive selected from carboxylic ethers, carboxylic acid based salts, and acrylates.