Safety Coating for High-Nickel Positive Electrode Plates
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Solution Overview
Problem
High-nickel ternary materials in lithium ion batteries suffer from poor thermal stability, leading to safety issues such as fire and explosion under abnormal conditions, limiting their application in electric vehicles due to their tendency to release substances that oxidize non-aqueous electrolytes and deteriorate high-temperature performance.
Innovation Solution
A positive electrode plate with a safety coating comprising a polymer matrix, conductive material, and inorganic filler is introduced between the metal current collector and the positive electrode active material layer, where the inorganic filler stabilizes the coating and enhances its response speed, preventing direct contact between the current collector and active material layer, thus improving safety and electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-nickel ternary materials are used as positive electrode active material, then energy density is improved, but thermal stability deteriorates leading to safety issues
Solution Approach 1:
A safety coating layer comprising polymer matrix, conductive material, and inorganic filler is introduced between the current collector and the high-nickel ternary material. This intermediary layer prevents direct contact between the active material and current collector during thermal runaway, blocking the propagation of oxidizing substances while maintaining electrical conductivity through the conductive material component.
Solution Approach 2:
The safety coating is designed as a composite material system combining polymer matrix (for structural integrity and thermal stability), conductive material (for maintaining electrical conductivity), and inorganic filler (for enhanced thermal resistance and mechanical strength). This composite structure allows the coating to simultaneously provide electrical conductivity and thermal safety protection.
2Reliability
If safety coating is added between current collector and active material layer, then safety performance is improved, but device complexity increases
Solution Approach 1:
The positive electrode is segmented into distinct functional layers: the safety coating layer and the active material layer. This segmentation allows the safety coating to independently perform its protective function while the active material layer maintains its electrochemical function, with each layer optimized for its specific purpose.
Solution Approach 2:
The safety coating performs multiple functions simultaneously: it provides thermal stability, maintains electrical conductivity through the conductive material, offers mechanical support, and prevents direct contact between the current collector and active material. This multi-functionality reduces the need for additional separate components.
3Reliability
If inorganic filler content in safety coating is increased, then thermal stability is improved, but electrical conductivity may deteriorate
Solution Approach 1:
The content of inorganic filler in the safety coating is precisely controlled within the range of 10-60 wt% to optimize the balance between thermal stability and electrical conductivity. This parameter optimization ensures sufficient thermal resistance while maintaining adequate electrical conductivity through the conductive material network.
Solution Approach 2:
The composite structure of the safety coating combines inorganic filler (for thermal stability) with conductive material (for electrical conductivity). The conductive material forms a continuous network within the composite that compensates for the insulating effect of the inorganic filler, maintaining overall electrical conductivity while providing thermal protection.
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 safety coating effectively increases resistance at high temperatures, preventing short circuits and improving nail penetration safety, while maintaining electrochemical performance, thereby enhancing the safety and electrical performance of lithium ion batteries.
Implementation Method 1
the safety coating effectively increases resistance at high temperatures
Data Source
AI summary
This application relates to a positive electrode plate and an electrochemical device. The positive electrode plate comprises a metal current collector, a positive electrode active material layer and a safety coating disposed between the metal current collector and the positive electrode active material layer; the safety coating comprises a polymer matrix, a conductive material and an inorganic filler; the positive electrode active material layer comprises Li1+xNiaCobMe(1−a−b)O2, wherein −0.1≤x≤0.2, 0.6≤a<1, 0<b<1, 0<(1−a−b)<1, and Me is at least one of Mn, Al, Mg, Zn, Ga, Ba, Fe, Cr, Sn, V, Sc, Ti and Zr; and the metal current collector is a porous aluminum-containing current collector. The positive electrode plate can improve safety and electrical performances of an electrochemical device (such as a capacitor, a primary battery, or a secondary battery).