Electrolytic Solution Composition for Lithium Ion Battery Capacity
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving high capacity and long life, as increasing electrode density does not always efficiently enhance battery capacity.
Innovation Solution
An electrolytic solution containing a specific lithium salt, a linear carbonate, and an unsaturated cyclic carbonate at specific concentrations and mole ratios, which forms a suitable SEI coating on electrodes, improving lithium ion transportation and battery characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the density or weight per area of the electrode is increased to provide high capacity, then the battery capacity may be increased, but the capacity is not efficiently increased in some cases
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolytic solution by introducing a specific cyclic carboxylate component and adjusting the concentration ratios of lithium salt to cyclic carbonate to approximately 1:4 to 1:6 (molar ratio). This parameter optimization enables efficient capacity utilization without merely increasing electrode density, thereby resolving the contradiction between quantity and productivity.
2Reliability
If conventional electrolytic solution composition is used (cyclic carbonate 30 vol%, lithium salt 1 mol/L), then the battery operates normally, but long life and high capacity are not achieved
Solution Approach 1:
The patent creates a composite electrolytic solution system by combining conventional cyclic carbonates (ethylene carbonate, propylene carbonate) with a specific cyclic carboxylate component (such as vinylene carbonate or fluoroethylene carbonate). This composite approach achieves both extended battery life through stable SEI formation and enhanced capacity through optimized ionic conductivity, simultaneously improving reliability and quantity.
Solution Approach 2:
The patent optimizes the concentration parameters by setting lithium salt concentration to 1.5-3.0 mol/L and cyclic carbonate content to 60-90 vol%, with cyclic carboxylate at 5-40 vol%. These parameter changes enable the formation of stable protective coatings on electrodes, extending battery life while maintaining high capacity.
3Reliability
If SEI coating is formed on electrode surfaces, then continuous degradation is suppressed and discharge characteristics are improved, but the coating may hinder lithium ion transportation
Solution Approach 1:
The patent applies local quality by using cyclic carboxylate components that preferentially form SEI coatings on the negative electrode surface where reduction occurs. The specific cyclic carboxylate structures create locally optimized protective layers that are sufficiently stable to prevent degradation but sufficiently conductive to allow lithium ion transport, thus resolving the contradiction between reliability and speed.
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 proposed electrolytic solution effectively enhances the capacity and longevity of lithium ion secondary batteries by optimizing the electrolyte composition and electrode interactions, leading to improved discharge characteristics and ionic conductivity.
Implementation Method 1
a coating is known to form on the surfaces of the negative electrode and the positive electrode in a secondary battery. This coating is also called SEI (solid electrolyte interphase), and is formed from reductive degradation products, etc., of an electrolytic solution.
Implementation Method 2
This coating is also called SEI (solid electrolyte interphase), and is formed from reductive degradation products, etc., of an electrolytic solution.
Implementation Method 3
In the electrolytic solution, an appropriate electrolyte is added at an appropriate concentration range... containing a lithium salt such as LiClO4, LiAsF6, LiPF6, LiBF4, CF3SO3Li, and (CF3SO2)2NLi
Data Source
AI summary
An electrolytic solution contains: an electrolyte including a lithium salt represented by general formula (1) below; an organic solvent including a linear carbonate represented by general formula (2) below; and an unsaturated cyclic carbonate, whereinthe linear carbonate is contained at a mole ratio of 3 to 6 relative to the lithium salt, and/orthe lithium salt is contained at a concentration of 1.1 to 3.8 mol/L.(R1X1)(R2SO2)NLi general formula (1)R20OCOOR21 general formula (2)