Cylindrical Li-Ion Battery Electrolyte for Fast Charging and Low Heat
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Solution Overview
Problem
Large-sized cylindrical lithium secondary batteries face challenges in electrolyte impregnability, rapid charging, and high-temperature lifespan due to differences in internal structure and space arrangement compared to small-sized batteries, leading to lithium precipitation and heat generation during rapid charging.
Innovation Solution
A cylindrical lithium secondary battery design that includes a specific electrolyte composition of cyclic and linear carbonates, adjusted ion conductivity and cation transport rate, and a tab-less structure with uncoated electrode portions, optimizing electrolyte impregnability and rapid charging properties without increasing electrolyte injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rapid charging is performed at high voltage, then charging speed is improved, but lithium precipitates in the negative electrode causing battery deterioration
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by specifying precise proportions of cyclic carbonate (15-30 wt%) and chain carbonate (70-85 wt%), along with controlled amounts of lithium salt (0.5-2.0 M) and additives (0.1-5 wt%). This parameter optimization enables rapid charging at high voltage while preventing lithium precipitation and maintaining battery reliability
2Speed
If rapid charging is performed at high voltage, then charging speed is improved, but heat is generated in large amounts causing battery deterioration or ignition
Solution Approach 1:
The patent optimizes electrolyte composition parameters including cyclic carbonate content (15-30 wt%), chain carbonate content (70-85 wt%), lithium salt concentration (0.5-2.0 M), and additive amounts (0.1-5 wt%). This balanced composition enables rapid charging while controlling heat generation through improved ionic conductivity and reduced resistance
Solution Approach 2:
The patent creates a composite electrolyte system combining multiple carbonate solvents (cyclic and chain types) with lithium salts and functional additives. This composite formulation achieves synergistic effects that enable high-speed charging while maintaining thermal stability and preventing overheating
3Quantity of substance
If electrolyte injection amount is increased, then electrode assembly impregnability is improved in typical cylindrical batteries, but internal space arrangement and structure differ in large-sized batteries
Solution Approach 1:
The patent changes the quality parameters of the electrolyte (composition, viscosity, conductivity) rather than relying on quantity increases. By optimizing cyclic carbonate (15-30 wt%) and chain carbonate (70-85 wt%) ratios along with lithium salt concentration (0.5-2.0 M), the electrolyte achieves improved impregnation efficiency without requiring increased injection amounts, making it adaptable to large-sized battery configurations
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
Improves electrolyte solution impregnability, rapid charging capabilities, and high-temperature lifespan by preventing lithium plating and heat generation, enhancing overall battery performance.
Implementation Method 1
C is the ion conductivity of the electrolyte
Implementation Method 2
a diffusion of ions in a battery (DIB) value
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The present invention relates to a cylindrical lithium secondary battery including an electrode assembly in which a positive electrode, a separator, and a negative electrode are sequentially stacked and wound in one direction, an electrolyte, and a battery case in which the electrode assembly and the electrolyte are accommodated, wherein the electrolyte includes one or more selected from the group consisting of a cyclic carbonate-based solvent and a linear carbonate-based solvent, a diffusion of ions in a battery (DIB) value defined by Equation 1 below is 150 mS/mm2 to 160 mS/mm2, and the viscosity of the electrolyte at 25 °C is 3.23 cP or less. DIBDiffusionofIoninaBattery=hR×1r×C×t+×1000 In Equation 1 above, h (unit: mm) is the height of the cylindrical lithium secondary battery, R (unit: mm) is the diameter of the cylindrical lithium secondary battery, r (unit: mm) is the radius of a winding central portion of the electrode assembly, C (unit: mS/mm) is the ion conductivity of the electrolyte, and t+ is the cation transport rate of the electrolyte.