Dithioester Electrolyte Additives for Fast-Charging Li-Ion Batteries
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Solution Overview
Problem
Lithium ion batteries face challenges in maintaining cycling lifetime and safety due to issues with the solid-electrolyte interface (SEI) stability and cell degradation, particularly during fast charging, which existing electrolytes fail to adequately address.
Innovation Solution
The use of electrolytes containing linear solvents, cyclic carbonates, lithium salts, and specific additives with dithioester functional groups that act as polymerization controlling agents, stabilizing the SEI and CEI, and scavenging oxygen species to prevent degradation, thereby enhancing the cycling lifetime and safety of lithium ion batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional electrolytes are used for fast charging, then charging speed is improved, but SEI stability deteriorates and cycling lifetime is reduced
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate additive as an intermediary substance that mediates between the electrolyte and electrode surfaces. This additive preferentially decomposes to form a stable fluorinated SEI layer that protects the electrode during fast charging, thereby maintaining SEI stability while enabling high charging speeds.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating fluorinated cyclic carbonate compounds with specific molecular structures (Formula I and II). These parameter changes in electrolyte composition lead to the formation of a more stable fluorinated SEI layer that can withstand the stress of fast charging conditions.
2Speed
If conventional electrolytes are used for fast charging, then charging speed is improved, but cell degradation increases and safety is compromised
Solution Approach 1:
The fluorinated cyclic carbonate additive acts as a protective intermediary that forms a stable interface layer between the electrolyte and electrodes. This intermediary layer prevents harmful degradation reactions during fast charging, thereby reducing cell degradation and improving safety while maintaining high charging speeds.
Solution Approach 2:
The patent applies beforehand cushioning by having the fluorinated cyclic carbonate additive decompose first during initial cycles to form a protective fluorinated SEI layer. This pre-formed protective layer cushions and protects the electrode surfaces from degradation during subsequent fast charging operations.
3Ease of manufacture
If existing electrolyte compositions are used, then manufacturing simplicity is maintained, but cycling lifetime is insufficient
Solution Approach 1:
The patent modifies the electrolyte composition by incorporating fluorinated cyclic carbonate additives at specific concentration ranges (0.1-5 wt%). These parameter changes in composition lead to the formation of a stable fluorinated SEI layer that significantly extends cycling lifetime while maintaining straightforward manufacturing processes.
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 composition significantly improves the cycling lifetime of lithium ion batteries by stabilizing the SEI and CEI, reducing degradation, and maintaining performance during fast charging, leading to enhanced battery efficiency and safety.
Implementation Method 1
additives with dithioester functional groups that act as polymerization controlling agents, stabilizing the SEI and CEI
Implementation Method 2
scavenging oxygen species to prevent degradation
Data Source
AI summary
Lithium ion batteries and electrolytes therefor are provided, which include electrolyte additives having dithioester functional group(s) that stabilize the SEI (solid-electrolyte interface) at the surfaces of the anode material particles, and/or stabilize the CEI (cathode electrolyte interface) at the surfaces of the cathode material particles, and/or act as oxygen scavengers to prevent cell degradation. The electrolyte additives having dithioester functional group(s) may function as polymerization controlling and/or chain transfer agents that regulate the level of polymerization of other electrolyte components, such as VC (vinyl carbonate) and improve the formation and operation of the batteries. The lithium ion batteries may have metalloid-based anodes—including mostly Si, Ge and/or Sn as anode active material particles.