Battery Separator Coating With Polymer Protrusions for Cycle Stability
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Solution Overview
Problem
Secondary batteries face challenges in maintaining high energy density, cycle performance, and safety due to large distances between positive and negative electrode sheets during charging and discharging, leading to battery capacity decay.
Innovation Solution
A separator with a coating comprising a first region of inorganic ceramic particles and a first polymer, and a second region of a second polymer, where the second region forms a protrusion in an electrolytic solution, ensuring close contact between electrode sheets and enhancing lithium ion transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used, then the battery structure is simple, but the distance between positive and negative electrode sheets is large during charging and discharging, leading to capacity decay
Solution Approach 1:
The coating is divided into two distinct regions: a first region containing inorganic ceramic particles and a first polymer, and a second region containing a second polymer. This segmentation allows different functional zones to address specific problems - the first region provides structural stability and thermal resistance, while the second region forms protrusions that reduce electrode distance and enhance lithium ion transmission.
Solution Approach 2:
Different regions of the coating are given different compositions and properties. The first region with inorganic ceramic particles provides localized thermal and mechanical stability, while the second polymer-rich region creates localized protrusions at critical areas (corners of the innermost circle) to ensure close electrode contact and improve lithium ion transmission where it is most needed.
2Reliability
If the separator coating is made thicker to improve safety, then safety performance improves, but the distance between electrodes increases, reducing lithium ion transmission efficiency
Solution Approach 1:
The coating thickness is optimized by controlling the weight content of inorganic ceramic particles (50%-99% in the first region) and the weight content of the second polymer (20%-100% in the second region). These parameter adjustments allow the coating to provide adequate safety protection while maintaining sufficient lithium ion transmission capability through the protrusion structure.
Solution Approach 2:
The coating uses composite materials combining inorganic ceramic particles with polymers (first polymer and second polymer). This composite structure provides both safety (through the thermally stable inorganic particles) and transmission efficiency (through the polymer matrix that allows ion passage and forms protrusions), resolving the contradiction between protection and conductivity.
3Reliability
If the second polymer content in the second region is increased to form protrusions, then electrode contact improves and cycle performance increases, but the manufacturing complexity increases
Solution Approach 1:
The weight content of the second polymer in the second region is controlled within a specific range (20%-100%) to ensure protrusion formation. By optimizing this parameter, the coating automatically forms the desired protrusion structure during assembly without requiring complex post-processing or additional manufacturing steps, balancing performance improvement with manufacturing simplicity.
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 improves cycle and safety performance of secondary batteries by promoting normal lithium ion transmission and maintaining battery capacity over extended cycles.
Implementation Method 1
In an electrolytic solution, the second region forms a protrusion relative to the first region, and the protrusion may make a positive electrode sheet and a negative electrode sheet here in close contact, so as to promote a normal transmission of a lithium ion
Data Source
AI summary
The present application relates to a separator, including a porous substrate, and a coating on at least one surface of the porous substrate. The coating may include a first region and a second region, the first region including an inorganic ceramic particle and a first polymer, the second region including a second polymer, and the first region having a same thickness as the second region, where a weight content of the second polymer in the second region may be 20%-100%, based on a total weight of the second region.