Sulfone-Based Electrolyte for High-Rate Lithium-Ion Battery
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving high rate characteristics and cycle performance due to the limitations of carbonate-based solvents in the electrolytic solution, particularly with graphite as the negative electrode active material.
Innovation Solution
The use of an electrolytic solution containing a salt with an alkali metal, alkaline earth metal, or aluminum cation and an organic solvent with a heteroelement, combined with a negative electrode active material layer featuring graphite with a G/D ratio not lower than 3.5, carbon materials with crystallite sizes not larger than 20 nm, silicon or tin elements, and metal oxides, to enhance battery characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbonate based solvents (ethylene carbonate, propylene carbonate) are used in the electrolytic solution, then the battery can operate with graphite as negative electrode active material, but the activation barrier of electrode reaction is large and rate characteristics are poor
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolytic solution by introducing sulfone-based solvents (dimethyl sulfone, diethyl sulfone) and specific lithium salts (LiClO4, LiBF4, LiPF6) to replace or supplement traditional carbonate solvents. This parameter change reduces the activation barrier of electrode reactions while maintaining battery operation stability, thereby improving rate characteristics without sacrificing reliability
Solution Approach 2:
The patent creates a composite electrolytic solution system combining sulfone-based solvents with carbonate solvents and specific lithium salts. This composite approach leverages the benefits of both solvent types: the stability and graphite compatibility of carbonates with the reduced activation barrier of sulfones, achieving both reliable operation and high rate characteristics simultaneously
2Duration of action of stationary object
If graphite is used as negative electrode active material, then the battery achieves good cycle performance, but the combination with carbonate based solvents limits rate characteristics improvement
Solution Approach 1:
The patent modifies the electrolytic solution parameters by adding sulfone-based solvents and specific lithium salts that are compatible with graphite. This enables graphite to maintain its good cycle performance while the new electrolyte composition reduces activation barriers, allowing high-speed charging/discharging capability to be achieved without compromising cycle life
3Productivity
If the electrolytic solution composition is optimized for high rate characteristics, then charging/discharging speed improves, but electrode degradation risk increases
Solution Approach 1:
The patent employs a composite electrolytic solution formulation combining sulfone-based solvents (for high rate characteristics) with carbonate solvents and specific lithium salts (for electrode stability). This composite material approach achieves fast charging/discharging speeds while the stabilizing components protect against electrode degradation, balancing productivity and 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
This combination improves the rate capacity and cycle characteristics of the nonaqueous electrolyte secondary battery, leading to better energy density and charging/discharging efficiency, while reducing the risk of electrode degradation and maintaining capacity during high-rate charging/discharging cycles.
Implementation Method 1
The batteries operate when lithium ions move through an electrolytic solution sealed between the two electrodes
Implementation Method 2
carbon materials such as graphite are widely used. In order to enable reversible insertion and elimination of lithium ions with respect to the negative electrode active material
Data Source
AI summary
An electrolytic solution of a nonaqueous electrolyte secondary battery contains a metal salt, and an organic solvent having a heteroatom and satisfies Is>Io, when an intensity of an original peak of the solvent is represented as Io and an intensity of a peak resulting from shifting of the original peak is represented as Is. For the negative electrode, (1) a graphite whose G/D ratio of G-band and D-band peaks in a Raman spectrum is not lower than 3.5; (2) a carbon material whose crystallite size, calculated from a half width of a peak appearing at 2θ=20 degrees to 30 degrees in a X-ray diffraction profile is not larger than 20 nm; (3) silicon element and/or tin element; (4) a metal oxide configured to occlude and release lithium ions; or (5) a graphite whose ratio (long axis/short axis) is 1 to 5.