SEI Composition for High-Voltage Lithium Secondary Batteries
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Solution Overview
Problem
Existing lithium-ion batteries face limitations in achieving high energy density, stability, and safety, particularly at higher operating voltages, with conventional electrolyte compositions leading to capacity fading and safety issues.
Innovation Solution
A solid electrolyte interphase (SEI) with a specific F:CF3 molar ratio of 0.00<x≤12.00 is applied to the anode, composed of lithium bis(trifluoromethansulfonyl)imide (LiTFSI), fluoroethylene carbonate (FEC), and sulfolane (SL), enhancing the SEI's ability to conduct lithium ions while preventing electron tunneling and electrolyte decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional electrolyte compositions are used, then the battery can operate at standard voltages, but the energy density and operating voltage are limited to 4.2-4.4 V
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing specific fluorinated cyclic carbonates with controlled F:CF3 molar ratios, enabling the battery to operate at higher voltages (4.4-4.5 V) while maintaining stability through the unique molecular structure of the fluorinated additives
2Object-affected harmful factors
If conventional electrolyte compositions are used, then the battery structure is simple, but safety issues arise due to inflammability
Solution Approach 1:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate additives with conventional carbonate solvents and lithium salts, forming a complex multi-component electrolyte composition that provides both safety (reduced inflammability) and performance benefits
3Power
If the battery operates at higher voltages above 4.4 V, then energy density increases, but capacity fading occurs with conventional electrolytes
Solution Approach 1:
The fluorinated cyclic carbonate additives perform preliminary action by forming a stable solid electrolyte interphase (SEI) layer on the electrode surfaces during initial cycles, which prevents subsequent electrolyte decomposition and capacity fading, enabling long cycle life at high operating voltages
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 SEI composition significantly increases coulombic efficiency to over 80% and enables stable operation at higher voltages up to 4.5 V, improving battery performance and safety.
Implementation Method 1
The electrolyte should conduct lithium ions, acting as a carrier between the cathode and the anode
Implementation Method 2
This interphase prevents further decomposition of the electrolyte in subsequent charge/discharge cycles, and is therefore also referred to as a passivation layer
Implementation Method 3
Electrolyte solvents according to the prior art partially decompose on initial charging and form a solid electrolyte interphase (SEI) layer
Data Source
AI summary
The present invention relates to a solid electrolyte interphase composition having a F:CF3 mol-ratio (x) of 0.00<x≤12.00; a negative electrode comprising a negative electrode material and a solid electrolyte interphase composition on a surface of said negative electrode material, wherein said solid electrolyte interphase composition has a molar ratio F:CF3 (x) of 0.00<x≤12.00, as determined by XPS; as well as its application in a lithium secondary battery cell.