Ceramic Separator and Metallic Anode for Lithium Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face issues with short circuits and low capacity due to the use of carbonaceous anodes and polyolefin-based separators, which are prone to shrinkage and volume changes with metallic negative electrode active materials, leading to reduced conductivity and lifespan.
Innovation Solution
An electrode assembly with a negative electrode active material layer comprising SiO, SnO, or GeO, a ceramic-based porous separator, and a binder, where the separator's thickness is 7 to 20% of the negative electrode active material layer and the binder makes up 5 to 20% of the separator's weight, along with carbon nanofibers grown on the negative electrode active material, enhancing stability and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based separator is used, then the separator provides good initial separation, but the separator shrinks when pores are blocked due to heat generated during rapid discharging/charging, leading to short circuits
Solution Approach 1:
The patent changes the material composition parameter of the separator from polyolefin-based to ceramic material-based, which fundamentally alters the thermal behavior. The ceramic separator maintains dimensional stability at high temperatures and does not shrink when pores are blocked, thereby preventing short circuits while maintaining good separation capability.
Solution Approach 2:
The patent uses a composite structure where ceramic material particles are dispersed in a binder to form the separator. This composite approach combines the high-temperature stability of ceramic materials with the flexibility and adhesion properties of the binder, achieving both separation capability and dimensional stability.
2Stability of the object's composition
If a carbonaceous anode is used, then the anode provides high stability with little volume change during charging and discharging, but the battery has low capacity due to high porosity
Solution Approach 1:
The patent changes the active material parameter from carbonaceous material to metallic material (aluminum, germanium, silicon, tin, zinc, or lead). These metallic materials have much higher theoretical capacity densities (e.g., pure silicon has 4017 mAh/g compared to graphite's 372 mAh/g) while maintaining acceptable volume stability characteristics.
Solution Approach 2:
The patent applies a specific binder content ratio (5 to 20 wt%) to the separator to optimize its properties. This local optimization of binder content ensures the separator has sufficient adhesion and structural integrity while maintaining porosity for ion transport, balancing mechanical stability with electrochemical performance.
3Quantity of substance
If a metallic material is used as negative electrode active material, then the battery capacity and energy density increase, but the negative active material expands by 300 to 400% during charging, reducing conductivity and causing separation from current collector
Solution Approach 1:
The patent optimizes the binder content parameter in the separator to 5 to 20 wt% of the total weight of the porous layer. This parameter optimization ensures the separator maintains sufficient mechanical strength and adhesion to accommodate the expansion and contraction of the metallic negative electrode active material during charging and discharging cycles, preventing separation from the current collector.
Solution Approach 2:
The binder in the separator acts as an intermediary that provides mechanical cushioning and maintains electrical contact during the expansion and contraction of the metallic negative electrode active material. The binder absorbs the mechanical stress of volume changes while maintaining the structural integrity and conductivity of the electrode assembly.
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 provides a lithium secondary battery with improved resistance to short circuits, higher capacity, and extended lifespan by maintaining conductivity and stability during charging and discharging.
Implementation Method 1
a polyolefin-based separator shrinks when pores therein are blocked, due to heat generated during rapid discharging/ charging
Implementation Method 2
The metallic material included in the metallic negative electrode active material absorbs lithium during charging, and thus, the negative active material expands by approximately 300 to 400%
Implementation Method 3
A lithium secondary battery stores and releases electrical energy through the intercalation and deintercalation of lithium ions at positive and negative electrodes
Data Source
Figure 1
AI summary
A lithium secondary battery including an electrode assembly that includes a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, and a separator disposed between the negative electrode from the positive electrode. The negative electrode active material layer includes a metallic material capable of forming an alloy with lithium, and the separator including a porous layer comprising a ceramic material and a binder. The separator is formed to a thickness that is 7 to 20% of the thickness of the negative electrode active material layer. The binder makes up 5 to 20% of the weight of the separator.