Positive Electrode Piece Coating for Contact Short-Circuit Impedance
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Solution Overview
Problem
Lithium-ion batteries are prone to catching fire due to mechanical abuse, such as squeezing and impact, which causes short-circuits between the positive electrode current collector and the negative electrode active material, resulting in excessive heat generation and safety hazards.
Innovation Solution
A positive electrode piece with a first coating layer containing nano-scale particles and a conductive agent, which increases the impedance of the contact short-circuit site, reducing heat generation and preventing fires while maintaining the energy density and electrochemical performance of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer is added to increase contact short-circuit impedance, then safety performance is improved, but electrochemical performance and energy density are degraded
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size of the first material to be ≤800 nm and the sheet resistance of the first coating layer to be within 500-13000 mΩ/□. These specific parameter ranges optimize the balance between safety performance (increased contact short-circuit impedance) and electrochemical performance (minimal impact on energy density and charge-discharge rates), resolving the technical contradiction between reliability and energy efficiency.
Solution Approach 2:
The patent employs composite materials by creating a first coating layer that contains both a first material (such as aluminum oxide, barium sulfate, silicon dioxide, or their carbon-coated versions) and a conductive agent. This composite structure allows the coating to simultaneously provide high contact short-circuit impedance for safety while maintaining sufficient electrical conductivity for electrochemical performance, thus resolving the contradiction between safety and energy density.
2Reliability
If the sheet resistance of the first coating layer is increased to reduce short-circuit heat, then safety is improved, but electrical performance is degraded
Solution Approach 1:
The patent applies parameter changes by optimizing the sheet resistance of the first coating layer to fall within the specific range of 500-13000 mΩ/□. This parameter optimization ensures that the coating layer provides sufficient impedance to reduce short-circuit heat generation and improve safety, while simultaneously maintaining adequate electrical performance by preventing excessive resistance that would degrade power delivery and charge-discharge rates.
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 effectively reduces the risk of battery cell fires caused by mechanical abuse by enhancing the impedance of the contact short-circuit site, ensuring safety performance while minimizing the impact on electrical and energy density.
Implementation Method 1
a sheet resistance of the first coating layer is not less than 500 μmΩ/□... improve the impedance of a contact short-circuit site... reduce the heat generated by the short circuit
Data Source
AI summary
The present disclosure provides a positive electrode piece and a lithium-ion battery. The positive electrode piece includes: a positive electrode current collector, a first coating layer disposed on at least one surface of the positive electrode current collector, and a positive electrode active material layer disposed on a surface of the first coating layer, where the first coating layer contains a first material and a conductive agent, a particle diameter of the first material is ≤800 nm, and a sheet resistance of the first coating layer is not less than 500 mΩ/□. The positive electrode piece provided by the present disclosure can improve the impedance of a contact short-circuit site between the positive electrode current collector and a negative electrode active material, and reduce the heat generated by the short circuit, thereby effectively reducing safety problems such as battery cell catching fire caused by the short circuit.