Silicon Battery Negative Electrode Porous Membrane Binding
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Solution Overview
Problem
Secondary batteries face issues with the detachment of non-conductive particles from porous membranes and the peeling of these membranes from the negative electrode active material layer, leading to increased short circuit possibilities and poor cycle properties, especially with silicon-based active materials that experience significant expansion and contraction during charging and discharging.
Innovation Solution
A secondary battery negative electrode design incorporating a current collector, a negative electrode active material layer with particulate polymer, and a porous membrane featuring non-conductive particles made from a (meth)acrylate polymer with a softening point of 175°C or higher, along with a cross-linked porous membrane polymer, enhances the binding properties and cycle reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used to increase battery capacity, then capacity is improved, but the large expansion and contraction during charging and discharging disconnects conductive paths, worsening cycle property
Solution Approach 1:
The patent employs a flexible porous membrane as a protective layer over the silicon-based active material. This membrane accommodates the volume expansion and contraction of silicon during lithiation and delithiation cycles, maintaining structural integrity and preventing conductive path disconnection while allowing ion transport.
Solution Approach 2:
The patent changes the physical and chemical parameters of the porous membrane, including using cross-linked polymer structures and controlling pore size and distribution. These parameter optimizations enable the membrane to withstand the mechanical stress from silicon expansion/contraction while maintaining electrical insulation and ionic conductivity.
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 results in a highly reliable secondary battery with improved cycle properties and reduced risk of short circuits, effectively addressing the detachment and expansion issues associated with silicon-based active materials.
Implementation Method 1
particles of a (meth)acrylate polymer with a softening starting point or a decomposition point equal to or higher than a specific temperature are used as the non-conductive particles
Implementation Method 2
the porous membrane contains non-conductive particles and a non-particulate cross-linked porous membrane polymer
Data Source
AI summary
A secondary battery negative electrode including a current collector, a negative electrode active material layer, and a porous membrane, wherein the negative electrode active material layer contains a negative electrode active material and a particulate negative electrode polymer, the porous membrane contains non-conductive particles and a porous membrane polymer that is a non-particulate cross-linked polymer, and the non-conductive particles are particles of a polymer that contains 50% by weight or more of a structural unit formed by polymerization of a (meth)acrylate, the polymer having a softening starting point or decomposition point of 175°C or higher.