PVDF-HFP Primer-Coated Electrode for Nail Penetration Safety
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to nail penetration, which causes short-circuit currents and IR-heating, leading to potential explosions, and existing solutions have not effectively addressed the need for improved interfacial resistance between the electrode active material layer and the current collector.
Innovation Solution
An electrode for lithium secondary batteries is designed with a primer coating layer containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as a binder and a conductive material, increasing interfacial resistance and reducing short-circuit currents during nail penetration, while maintaining adhesion and controlling swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the interfacial resistance between electrode active material layer and current collector is increased to reduce short-circuit current during nail penetration, then nail penetration safety is improved, but electrode adhesion and electrical conductivity may deteriorate
Solution Approach 1:
The primer coating layer is applied locally at the interface between the current collector and electrode active material layer, creating a zone with differentiated properties. This layer has higher resistance than the bulk electrode materials, which is desirable for safety, while maintaining sufficient adhesion and conductivity for normal operation. The localized application ensures that the safety-enhancing resistance increase does not compromise overall electrode performance.
Solution Approach 2:
The primer coating layer is composed of a composite formulation including binder and conductive material, creating a material with intermediate properties between the current collector and electrode active material layer. This composite structure provides a gradient of electrical resistance that increases safety during nail penetration while maintaining adequate adhesion and conductivity for normal battery operation.
2Reliability
If a primer coating layer is introduced to increase interfacial resistance and improve safety, then nail penetration resistance is enhanced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The electrode structure is segmented into distinct layers: current collector, primer coating layer, and electrode active material layer. This segmentation allows each layer to be optimized for its specific function - the primer coating layer specifically for interfacial resistance control - while maintaining overall structural integrity and simplifying the manufacturing process through standardized layering procedures.
3Temperature
If PVDF-HFP binder with specific HFP content is used in the primer coating layer to control swelling and improve safety, then thermal stability is enhanced, but binder performance and adhesion may be compromised
Solution Approach 1:
The chemical composition parameter of the PVDF-HFP binder is precisely controlled, specifically the HFP-derived repeating units content within 2-13 wt%. This parameter optimization achieves the right balance between thermal stability enhancement through controlled swelling and maintaining adequate adhesion performance. The specific compositional range ensures that the binder provides sufficient thermal resistance during nail penetration while retaining enough flexibility and bonding capability for normal electrode operation.
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 primer coating layer effectively reduces short-circuit currents and IR-heating during nail penetration, enhancing the safety and thermal stability of lithium secondary batteries by increasing interfacial resistance without degrading battery performance.
Implementation Method 1
it is important to increase the interfacial resistance between an electrode active material layer and an electrode current collector. This is because high-rate current flows due to a short-circuit caused by nail penetration
Implementation Method 2
explosion caused by nail penetration results from local IR-heating due to short-circuit current derived from the contact between a nail and an electrode current collector
Data Source
AI summary
The present disclosure relates to an electrode for a lithium secondary battery which includes: an electrode current collector; a primer coating layer disposed on at least one surface of the electrode current collector and including a binder and a conductive material; and an electrode active material layer disposed on the primer coating layer, wherein the binder includes poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) containing vinylidene fluoride (VDF)-derived repeating units and hexafluoropropylene (HFP)-derived repeating units, the content of HFP-derived repeating units in PVDF-HFP is 2-13 wt %, and the primer coating layer has a thickness of 0.8-10 μm.