Secondary Battery Electrolyte for Thick Cathode Rate Performance
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Solution Overview
Problem
Secondary batteries face challenges in achieving both high energy density and dynamic performance, with thick coatings leading to increased lithium ion migration resistance and decreased dynamic performance.
Innovation Solution
A secondary battery design incorporating an electrolyte solution with an organic lithium salt and a positive electrode film layer optimized by specific areal density and particle grading, along with a balanced ratio of organic and inorganic lithium salts, enhances ionic conductivity and reduces impedance, thereby improving both energy density and dynamic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the areal density of the positive electrode film layer is increased to improve energy density, then the energy density is improved, but the lithium ion transmission rate decreases due to increased impedance
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing organic lithium salts (lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide) with specific molecular structures. These parameter changes in the electrolyte composition improve the transmission rate of lithium ions through the positive electrode film layer, allowing high energy density to be achieved without sacrificing ion transmission rate.
2Quantity of substance
If a thick positive electrode film layer is used to increase energy density, then the energy density is improved, but the dynamic performance decreases due to increased migration resistance
Solution Approach 1:
The organic lithium salt acts as an intermediary substance between the lithium ions and the positive electrode film layer. It facilitates the interaction by improving ion transmission through the thick film layer, thereby maintaining dynamic performance while achieving high energy density through increased areal density.
3Quantity of substance
If the areal density of the positive electrode film layer is increased, then the energy density is improved, but the rate performance decreases
Solution Approach 1:
The patent modifies the electrolyte composition parameters by incorporating organic lithium salts with specific molecular structures that enhance lithium ion conductivity. This parameter change in the electrolyte system enables the thick positive electrode film layer to maintain high rate performance despite increased areal density, resolving the contradiction between energy density and rate performance.
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 optimized battery design achieves high energy density and dynamic performance by balancing areal density, particle grading, and salt composition, resulting in improved ion transmission and reduced electrode polarization.
Implementation Method 1
The organic lithium salt in the electrolyte solution can effectively improve the ionic conductivity of the electrolyte solution, reduce the impedance of the electrolyte solution/electrode interface
Implementation Method 2
The organic lithium salt in the electrolyte solution can improve the transmission rate of lithium ions in the positive electrode film layer
Implementation Method 3
form a stable passivation film with good ionic conductivity on the electrode surface, and improve the interface stability
Data Source
Figure 1~2
Figure 3
AI summary
The present application provides a secondary battery. The secondary battery includes an electrolyte solution and a positive electrode. The electrolyte solution contains an organic lithium salt. The positive electrode includes a positive electrode film layer. The energy density per unit area of the positive electrode film layer on a single side is 18-37 mWh/cm2, and optionally 18-35.7 mWh/cm2. Through the cooperation of the electrolyte solution and the positive electrode, the energy density and the dynamic performance of the battery are both improved.