Lithium Battery Electrolyte for Uniform SEI and Dendrite Suppression
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Solution Overview
Problem
Conventional lithium secondary batteries experience a significant reduction in discharge capacity due to the formation of lithium dendrites and nonuniform SEI films during repeated charging and discharging, especially at high temperatures.
Innovation Solution
The lithium secondary battery incorporates a non-aqueous electrolyte containing a solvent mixture of non-fluorinated ether and fluorinated cyclic monoether, along with a lithium salt featuring an oxalate complex anion, which forms a uniform SEI film, suppressing dendrite formation and maintaining discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional non-aqueous electrolytes are used, then the battery can operate at high temperatures, but lithium dendrites form and discharge capacity reduces significantly
Solution Approach 1:
The fluorinated cyclic monoether acts as an intermediary substance between the lithium salt and the non-fluorinated ether solvent. It forms a uniform SEI film that mediates the interaction, preventing direct harmful contact between lithium ions and the bulk electrolyte, thereby suppressing dendrite formation while maintaining high-temperature operation
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolyte by introducing fluorinated cyclic monoether with specific molecular structure and properties. This parameter change modifies the SEI film formation characteristics, leading to more uniform lithium deposition and reduced dendrite growth at high temperatures
2Duration of action of moving object
If repeated charging and discharging occurs at high temperatures, then the battery can be used extensively, but nonuniform SEI films form and characteristics degrade
Solution Approach 1:
The fluorinated cyclic monoether performs preliminary action by forming a stable, uniform SEI film during initial charging cycles. This pre-formed protective layer prevents subsequent nonuniform SEI formation during repeated high-temperature cycling, thereby extending cycle life while maintaining composition stability
Solution Approach 2:
The invention applies local quality by creating a specifically engineered SEI film with uniform properties at the electrode-electrolyte interface. This localized uniform structure prevents the propagation of nonuniformity during repeated cycling, maintaining overall system stability over extended duration
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 battery exhibits a smaller reduction in discharge capacity even after repeated charging and discharging at high temperatures, thanks to the uniform SEI film formation and controlled lithium deposition.
Implementation Method 1
a non-aqueous electrolyte having lithium ion conductivity
Implementation Method 2
which forms a uniform SEI film, suppressing dendrite formation
Implementation Method 3
lithium metal is deposited in a negative electrode during charging
Implementation Method 4
the lithium metal is dissolved in a non-aqueous electrolyte during discharging
Data Source
AI summary
Disclosed is a lithium secondary battery (10) including a positive electrode (11), a negative electrode (12), and a non-aqueous electrolyte having lithium ion conductivity. In the negative electrode (12), lithium metal is deposited during charging, and the lithium metal is dissolved in the non-aqueous electrolyte during discharging. The non-aqueous electrolyte includes a solvent and a lithium salt. The solvent includes a non-fluorinated ether and a fluorinated cyclic monoether. The fluorinated cyclic monoether includes a cyclic structure having one ether bond. The lithium salt includes an anion of an oxalate complex.