Non-aqueous Electrolyte Battery High Density Porosity Control
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in achieving high volume energy density while maintaining even electrolyte distribution and cycle life, as increasing active material density reduces porosity and electrolyte permeability, leading to uneven electrolyte distribution and reduced capacity retention.
Innovation Solution
A non-aqueous electrolyte secondary battery design with a wound electrode group, where the positive and negative electrodes have material mixture layers with controlled porosity and contact angles, ensuring a specific ratio of electrolyte volume to pore volume and minimizing the difference in contact angles between electrodes to enhance electrolyte distribution and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the density of active material in the material mixture layers is increased to achieve higher capacity, then the volume energy density is improved, but the porosity of the material mixture layers is reduced, causing the non-aqueous electrolyte to be less likely to permeate into the material mixture layers
Solution Approach 1:
The patent applies parameter changes by precisely controlling the porosity of the positive electrode material mixture layer (20-30%) and negative electrode material mixture layer (25-35%), along with controlling the volume ratio of non-aqueous electrolyte (0.9-1.3) and contact angles (positive electrode: 5-20°, negative electrode: 10-30°). These parameter optimizations resolve the contradiction by finding the optimal balance point where high active material density coexists with sufficient electrolyte permeability, achieving volume energy density of 650 Wh/L or more while maintaining good discharge characteristics.
2Quantity of substance
If the amount of non-aqueous electrolyte is reduced to achieve higher volume energy density, then the volume energy density is improved, but the non-aqueous electrolyte becomes unevenly distributed between the positive and negative electrodes
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the volume ratio of non-aqueous electrolyte (0.9-1.3) and controlling the contact angles of both electrodes. The positive electrode contact angle is controlled at 5-20° and the negative electrode at 10-30°, ensuring that even with reduced electrolyte volume for high energy density, the electrolyte distributes evenly between electrodes, preventing capacity loss and maintaining cycle stability.
Solution Approach 2:
The patent employs feedback mechanisms by controlling the contact angles of the positive and negative electrodes within specific ranges. This feedback control ensures that the electrolyte wets both electrodes appropriately, maintaining uniform distribution even when the total electrolyte volume is reduced for high volume energy density applications.
3Quantity of substance
If the porosity of the material mixture layers is reduced to increase active material density, then the volume energy density is improved, but the discharge characteristics deteriorate due to reduced electrolyte permeability
Solution Approach 1:
The patent applies parameter changes by optimizing the porosity of the positive electrode material mixture layer to 20-30% and the negative electrode material mixture layer to 25-35%. These specific porosity ranges, combined with controlling the electrolyte volume ratio (0.9-1.3) and contact angles, resolve the contradiction by maintaining sufficient electrolyte access to active material while maximizing active material density, thereby achieving high volume energy density with good discharge characteristics.
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 battery achieves high volume energy density with improved cycle life and capacity retention by ensuring even electrolyte distribution and efficient battery reactions, despite reduced porosity and electrolyte volume, effectively utilizing densely packed active material.
Implementation Method 1
the permeability of the non-aqueous electrolyte into the material mixture layers
Implementation Method 2
the contact angle of a positive electrode and a negative electrode with respect to the non-aqueous electrolyte
Data Source
AI summary
Provided is a non-aqueous electrolyte secondary battery having a high capacity and an improved cycle life. The battery includes an electrode group and a non-aqueous electrolyte, and has a volume energy density of 650 Wh/L or more. The electrode group includes wound positive and negative electrodes with a separator interposed therebetween. The positive and negative electrodes each include a current collector and a material mixture layer adhering thereto. The positive and negative electrode material mixture layers each have a porosity Pp of 22% or less and porosity Pn of 25% or less. The ratio VE/VT of a volume VE of the electrolyte to a total VT of the pore volumes of the positive and negative electrode material mixture layers, and the separator is 1 to 1.5. The difference between contact angles CAp and CAn of the positive and negative electrodes with respect to the non-aqueous electrolyte is 23° or less.