Lithium Battery Electrolyte Additives for High-Temperature CEI Stability
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Solution Overview
Problem
Lithium secondary batteries using organic electrolytes face degradation in lifetime and high-temperature stability due to side reactions between electrodes and the electrolyte, with existing additives not providing sufficient performance.
Innovation Solution
An electrolyte for lithium secondary batteries incorporating a lithium salt, organic solvent, and specific additives represented by Formulas 1 or 2, which include sulfolane and cyclic phosphite or phosphate groups, forming a cathode electrolyte interface film to stabilize the positive electrode and enhance thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If organic electrolytes are utilized in lithium secondary batteries, then high energy density and fast charging capability are achieved, but lifetime and high-temperature stability are degraded due to side reactions between electrodes and electrolyte
Solution Approach 1:
The patent introduces a novel additive compound as an intermediary substance between the electrode and organic electrolyte. This additive forms a protective interface film that mediates the interaction, preventing direct harmful contact while allowing beneficial ionic transport, thus resolving the contradiction between maintaining high energy density and improving stability.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte system by incorporating specific additive compounds with particular functional groups. This parameter change transforms the electrolyte's interfacial properties, reducing side reactions while preserving the core performance characteristics of organic electrolytes.
2Reliability
If conventional additives are used in electrolytes to compensate for stability issues, then some improvement in lifetime is achieved, but sufficient high-temperature stability is not provided
Solution Approach 1:
The patent employs a composite additive strategy, combining multiple functional groups (sulfolane, cyclic phosphite, cyclic phosphate) within a single molecular structure. This composite approach creates synergistic effects that simultaneously address lifetime extension and high-temperature stability, overcoming the limitations of conventional single-function additives.
Solution Approach 2:
The patent designs the additive molecule with specific local functional regions: the sulfolane portion provides thermal stability, while the cyclic phosphite/phosphate groups contribute to lifetime extension through SEI formation. This local quality differentiation within the additive structure enables simultaneous improvement of both parameters.
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 electrolyte additive improves high-temperature stability by reducing gas generation and resistance increase, thereby extending the battery's lifespan and performance under high-temperature conditions.
Implementation Method 1
the electrolyte undergoes oxidation during formation to form a cathode electrolyte interface (CEI) film on a positive electrode
Implementation Method 2
the electrolyte undergoes oxidation during formation to form a cathode electrolyte interface (CEI) film on a positive electrode
Data Source
AI summary
An electrolyte for a lithium secondary battery and a lithium secondary battery including the same are provided. The electrolyte may include a lithium salt, an organic solvent, and an additives (e.g., sulfolane, cyclic phosphate, cyclic phosphite) that form a cathode electrolyte interface film to protect the surface of a positive electrode. Utilization of the additives may improve cycle-life characteristics and suppress or reduce increases to resistance during high-temperature storage of the lithium secondary battery.