Dual-Layer Negative Electrode Structure for Separator Adhesion Balance
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Solution Overview
Problem
Existing electrochemical apparatuses, such as lithium-ion batteries, face challenges in achieving high energy density and good high-temperature stability while maintaining sufficient cycling and rate performance, particularly with the use of high-adhesion separators that hinder electrolyte transport at low and medium temperatures.
Innovation Solution
The electrochemical apparatus features a dual-layer negative electrode plate with a first active material layer of higher compacted density and a second active material layer of lower compacted density, combined with a highly adhesive separator, where the first active material layer has a smaller sphericity and the second active material layer has a larger sphericity, enhancing adhesion between the separator and the electrode plate to improve electrolyte transport and overall performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-adhesion separators are used to improve energy density and high-temperature stability, then adhesion between separator and electrode plate is improved, but electrolyte transport speed is reduced
Solution Approach 1:
The separator is designed with different adhesion strengths at different locations: the first end (facing negative electrode) has adhesion of 3-20 N/m, while the second end (facing positive electrode) has adhesion of 0.3-2 N/m. This local differentiation allows strong adhesion where needed for high-temperature stability while maintaining adequate electrolyte transport channels at the other end.
Solution Approach 2:
The adhesion parameter of the separator is precisely controlled within specific ranges (3-20 N/m at first end, 0.3-2 N/m at second end) to balance two opposing requirements: strong enough to prevent electrode deformation and ensure high-temperature stability, but not so strong as to block electrolyte transport and reduce kinetic performance.
2Quantity of substance
If separator adhesion is increased to improve energy density, then energy density is improved, but cycling performance at low and medium temperatures is reduced
Solution Approach 1:
Different adhesion strengths are applied at different ends of the separator to satisfy different functional requirements: strong adhesion at the negative electrode side for energy density, and moderate adhesion at the positive electrode side for cycling performance.
Solution Approach 2:
The adhesion parameter is optimized within specific ranges (3-20 N/m at first end, 0.3-2 N/m at second end) to achieve the best balance between energy density and cycling performance across different temperature conditions.
3Quantity of substance
If compacted density of active material layer is increased to improve energy density, then energy density is improved, but porosity and electrolyte access are reduced
Solution Approach 1:
The compacted density of the active material layer is precisely controlled within the range of 1.3-1.9 g/cm³ to achieve optimal balance: high enough to improve energy density, but not so high as to reduce porosity and hinder electrolyte access to active material particles.
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
This configuration enhances energy density, cycling performance, rate performance, and high-temperature stability by optimizing electrolyte transport and lithium ion kinetics, resulting in improved overall performance of the electrochemical apparatus.
Implementation Method 1
adhesion between the separator and the negative electrode plate is greater than or equal to 2 N/m and less than or equal to 20 N/m
Data Source
AI summary
An electrochemical apparatus, includes an electrode assembly having a positive electrode plate; a negative electrode plate including a negative electrode current collector, a second active material having a second active substance, and a first active material layer having a first active substance located between the negative electrode current collector and the second active material layer; and a separator disposed between the positive electrode plate and the negative electrode plate. Compacted density of the first active material layer is greater than compacted density of the second active material layer. Sphericity of the first active substance is smaller than sphericity of the second active substance. The separator includes a porous substrate layer and a first coating layer disposed on at least one surface of the porous substrate layer facing the second active material layer. 20 N/m≥Adhesion between the separator and the negative electrode plate≥2 N/m.