Electrode Functional Layer for Electrolyte Retention and Short-Circuit Safety
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Solution Overview
Problem
Secondary batteries face challenges with low electrolyte retention, uneven surface appearance, and safety concerns due to high compaction densities of electrode plates and internal short-circuits.
Innovation Solution
An electrochemical apparatus with an electrode assembly where the current collector region not coated with active material is coated with a functional layer comprising an organic polymer and inorganic particles, optimizing electrolyte retention and safety through controlled thickness and particle size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If compaction density of electrode plates is increased to improve energy density, then energy density is improved, but electrolyte retention amount decreases and appearance flatness deteriorates
Solution Approach 1:
The patent applies local quality by coating only the current collector regions without active material (edge regions) with a functional layer containing inorganic particles and binder. This localized treatment allows the functional layer to absorb excess electrolyte and maintain appearance flatness without interfering with the high compaction density active material regions, thus preserving energy density while improving electrolyte retention.
Solution Approach 2:
The functional layer is composed of composite materials including inorganic particles (such as aluminum oxide, silicon oxide, titanium oxide) and binder (such as polyvinylidene fluoride, carboxymethyl cellulose). This composite structure provides both electrolyte absorption capability and mechanical stability, enabling the system to maintain high energy density through proper material selection and composition ratios.
2Quantity of substance
If compaction density of electrode plates is increased to improve energy density, then energy density is improved, but appearance flatness deteriorates due to non-uniform free electrolyte in packaging bag
Solution Approach 1:
The functional layer is applied locally to the current collector edge regions where excess electrolyte accumulates, rather than uniformly across the entire electrode. This localized application targets the specific problem area causing appearance swelling while preserving the high energy density design of the active material regions.
Solution Approach 2:
The patent converts the harmful effect of excess free electrolyte causing appearance swelling into a beneficial effect by using the functional layer to deliberately absorb and retain this excess electrolyte. The inorganic particles and binder work together to capture the surplus electrolyte that would otherwise cause packaging bag swelling, transforming a problem into a solution.
3Reliability
If functional layer thickness is increased to improve electrolyte retention, then electrolyte retention amount is improved, but energy density decreases
Solution Approach 1:
The functional layer is applied only to the current collector edge regions without active material, not to the entire electrode surface. This localized application minimizes the total volume occupied by the functional layer, ensuring that electrolyte retention is improved without significantly reducing the energy density of the active material regions.
Solution Approach 2:
The patent applies the functional layer with controlled thickness (0.1-10 μm) that is sufficient to provide the required electrolyte retention function but not excessive. This partial action approach ensures adequate electrolyte absorption while minimizing the space occupied by the functional layer, thereby maintaining high energy density.
4Reliability
If inorganic particles size is increased to improve safety performance, then safety performance is improved, but functional layer thickness increases causing energy density loss
Solution Approach 1:
The patent optimizes the particle size parameter of inorganic particles within a specific range (Dv10: 0.1-0.8 μm, Dv50: 0.5-2.0 μm, Dv90: 1.0-4.5 μm). This parameter optimization ensures that the inorganic particles are large enough to provide effective puncture resistance and safety performance, yet small enough to maintain a thin functional layer thickness that does not significantly reduce energy density.
Solution Approach 2:
The functional layer uses composite materials with optimized particle size distribution, combining inorganic particles of specific sizes with binder materials. This composite approach allows the system to achieve adequate safety performance through proper particle size selection while maintaining thin layer thickness through efficient material composition and packing.
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 solution significantly increases electrolyte retention, improves appearance flatness, reduces energy density loss, and enhances safety performance by preventing internal short-circuits, while maintaining good cycle performance.
Implementation Method 1
the organic polymer in the functional layer can absorb a free electrolyte
Implementation Method 2
the inorganic particles in the functional layer can prevent the failure caused by an internal short-circuit caused when the electrochemical apparatus is pierced by an external force
Data Source
AI summary
An electrochemical apparatus includes an electrode assembly. The electrode assembly includes an electrode plate; the electrode plate includes a current collector; the current collector includes a first region and a second region; an active material layer is arranged on the first region; and a functional layer is arranged on the second region, and the functional layer includes an organic polymer and inorganic particles, where the thickness of the functional layer is H1, where 1 μm≤H1≤15 μm; and Dv90 of the inorganic particles satisfies: 1 μm≤Dv90≤4.5 μm.