Secondary Battery Electrolyte-Anode Matching to Limit Charging Polarization
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Solution Overview
Problem
Existing secondary battery technologies do not adequately address the issues of large polarization, cycling performance, and storage performance, particularly under high current charging and high temperature conditions, without considering the relationship between negative electrodes and electrolytes.
Innovation Solution
A secondary battery design incorporating a specific negative electrode and electrolyte relationship, using a low-viscosity solvent, high-dielectric-constant solvent, and electrolyte salt, with a defined relational expression to optimize parameters such as solvent percentage, electrolyte salt concentration, porosity, and coating weight of the negative electrode active material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high current charging is used to improve rate performance, then charging speed increases, but polarization inside the battery increases causing battery swelling
Solution Approach 1:
The patent changes the physical and chemical parameters of the electrolyte by selecting specific solvents with low viscosity (0.3-0.6 mPa·s at 25°C) and high dielectric constant (30-100 F/m), and by optimizing the electrolyte salt concentration (10-23 wt%). These parameter changes reduce internal resistance and polarization, enabling high-rate charging without battery swelling.
Solution Approach 2:
The patent uses a composite electrolyte system combining multiple components: low-viscosity solvents (dimethyl carbonate, ethyl acetate, methyl acetate, or acetonitrile), high-dielectric-constant solvents (cyclic carbonates), electrolyte salts, and film-forming additives. This composite approach synergistically reduces polarization while maintaining safety and performance.
2Speed
If the electrolyte viscosity is reduced to improve ion transport and rate performance, then charging rate improves, but the electrolyte may become less stable
Solution Approach 1:
The patent creates a composite electrolyte system where low-viscosity solvents (providing fast ion transport) are combined with high-dielectric-constant solvents (providing stability and solvation). The synergistic interaction between these components maintains electrolyte stability while achieving low overall viscosity and high ion conductivity.
Solution Approach 2:
The patent introduces film-forming additives as intermediaries that form protective films on electrode surfaces. These films stabilize the electrolyte-electrode interface, preventing degradation reactions while allowing the bulk electrolyte to maintain low viscosity for fast ion transport.
3Power
If the dielectric constant of the electrolyte is increased to improve ion dissociation, then conductivity improves, but the viscosity may increase
Solution Approach 1:
The patent optimizes the dielectric constant parameter of the electrolyte by selecting solvents with dielectric constants in the range of 30-100 F/m. This parameter change improves ion dissociation and conductivity while the low viscosity of the selected solvents prevents excessive viscosity increase.
Solution Approach 2:
The patent applies the concept of local quality by having different solvent components perform different functions: high-dielectric-constant solvents provide local ion dissociation enhancement near the electrolyte salt, while low-viscosity solvents provide bulk fluidity and fast ion transport throughout the electrolyte volume.
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 rate performance, cycling performance, and storage performance by reducing polarization and maintaining battery integrity under high-rate charging conditions.
Implementation Method 1
a viscosity of the low-viscosity solvent at 25°C is 0.3 mPa·s-0.6 mPa·s
Implementation Method 2
a dielectric constant of the high-dielectric-constant solvent is 30 F/m-100 F/m
Data Source
Figure 1~3
Figure 4~6
AI summary
This application relates to a secondary battery, and a battery module, a battery pack, and an electric apparatus containing the same. The secondary battery includes: an electrolyte having a specific percentage of a low-viscosity solvent, a specific percentage of a high-dielectric-constant solvent, and a negative electrode having a negative electrode active material layer, and the secondary battery satisfies the relational expression: 1×10−4≤B×C×POI×CW≤1×10−3, where B is the percentage of the low-viscosity solvent in total solvent in the electrolyte by mass; C is a percentage of an electrolyte salt in the electrolyte by mass; P is a porosity of the negative electrode active material layer; CW is a coating weight of the negative electrode active material layer, measured in mg/cm2; and OI is an orientation index of the negative electrode active material layer, where OI=C004/C 110, C004 is a peak area of a 004 characteristic diffraction peak in an X-ray diffraction pattern of the negative electrode active material layer, and C110 is a peak area of a 110 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material layer.