Borate-Additive Electrolyte for High-Temperature Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges with high-temperature stability and cycle-life characteristics due to the decomposition of commonly used lithium salts like LiPF6, leading to electrolyte depletion and poor safety performance.
Innovation Solution
An electrolyte composition for lithium secondary batteries is developed, incorporating a non-aqueous organic solvent, a lithium salt, and specific borate-based lithium salts and compounds, such as lithium tetrafluoroborate (LiBF4) and a compound represented by Chemical Formula 1, which form an adsorptive and reactive SEI film to suppress thermal decomposition and enhance ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as the lithium salt in the electrolyte, then the battery can achieve good initial performance, but the LiPF6 decomposes at high temperatures causing electrolyte depletion and poor safety
Solution Approach 1:
The patent introduces LiBF4 as an intermediary substance that mediates between the electrode and the main electrolyte. LiBF4 forms a protective interface layer that prevents direct contact and harmful reactions between LiPF6 and the electrolyte solvent, thereby suppressing decomposition while maintaining ionic conductivity. This intermediary layer acts as a barrier that allows beneficial ion transport while blocking harmful chemical reactions.
Solution Approach 2:
The patent employs a composite electrolyte system combining multiple lithium salts (LiPF6 and LiBF4) with specific additives. This composite approach leverages the high conductivity of LiPF6 while using LiBF4 and additives to form a stable protective matrix that suppresses decomposition. The composite material strategy creates synergistic effects where each component contributes specific properties to overcome the limitations of individual substances.
2Productivity
If LiPF6 is used to achieve good conductivity, then the battery shows high rate capability, but LiPF6 decomposition leads to poor cycle-life characteristics
Solution Approach 1:
The patent applies preliminary action by having LiBF4 and additives form a stable protective film on the electrode surfaces during initial cycles. This pre-formed protective layer prevents subsequent decomposition of LiPF6 during charging and discharging cycles. The preliminary formation process creates a stable interface that protects against electrolyte depletion and maintains performance over extended cycling, thereby extending cycle life while preserving rate capability.
3Reliability
If conventional electrolyte composition is used to maintain simplicity, then the manufacturing process remains straightforward, but high-temperature performance and safety are compromised
Solution Approach 1:
The patent applies parameter changes by modifying the electrolyte composition parameters - specifically adjusting the types and ratios of lithium salts and additives. By changing these compositional parameters (adding LiBF4 at specific concentrations and selecting appropriate additives), the electrolyte achieves enhanced high-temperature stability and safety. These parameter adjustments optimize the balance between performance improvement and manufacturing complexity, maintaining relative simplicity while achieving superior reliability.
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 solution significantly improves high-temperature stability and cycle-life characteristics, reducing internal resistance and maintaining battery performance by forming a low-resistance SEI film that prevents electrolyte decomposition, thereby enhancing the battery's overall performance.
Implementation Method 1
an adsorptive and reactive SEI film to suppress thermal decomposition of LiPF6
Implementation Method 2
enhancing ion conductivity
Data Source
AI summary
This disclosure relates to an electrolyte for a lithium secondary battery and a lithium secondary battery including the same.For example, the electrolyte for a lithium secondary battery includes a non-aqueous organic solvent, a lithium salt, and an additive, wherein the additive includes at least one borate-based lithium salt selected from lithium tetrafluoroborate (LiBF4), lithium bis(oxalate)borate (LiBOB), lithium difluoro(oxalato)borate (LiFOB), lithium bis(2-methyl-2-fluoro-malonato)borate, and a combination thereof; and a compound represented by Chemical Formula 1.The detailed description of Chemical Formula 1 is the same as that defined in the specification.