Positive Electrode Coating and Electrolyte for High-Rate Secondary Batteries
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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 controlling the areal density and particle size distribution of active materials, along with a suitable molar ratio of organic and inorganic lithium salts, to enhance ionic conductivity and reduce impedance.
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 dynamic performance and rate performance deteriorate due to increased ion transmission resistance
Solution Approach 1:
The patent applies parameter changes by optimizing the areal density of the positive electrode film layer to a specific range (15-35 μg/cm²) and controlling the particle size distribution of the active material. This balanced parameter selection ensures sufficient energy density while maintaining adequate ion transmission pathways, thereby resolving the contradiction between energy density and dynamic performance.
2Quantity of substance
If the coating thickness of the positive electrode is increased to improve energy density, then the energy density is improved, but the lithium ion migration resistance increases and dynamic performance decreases
Solution Approach 1:
The patent applies local quality by creating a non-uniform particle size distribution within the electrode coating, where smaller particles (0.5-5 μm) are distributed throughout the coating layer. This local optimization ensures that ion migration pathways are maintained even in thicker coatings, allowing high energy density to be achieved without compromising lithium ion migration 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
The design improves both energy density and dynamic performance by optimizing ion transmission and reducing electrode polarization, resulting in a battery with enhanced rate and cycle performance.
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
form a stable passivation film with good ionic conductivity on the electrode surface, and improve the interface stability
Implementation Method 3
The organic lithium salt in the electrolyte solution can improve the transmission rate of lithium ions in the positive electrode film layer
Data Source
Figure 1~2
Figure 3
AI summary
A secondary battery is provided. 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.