Layered Li-Ion Negative Electrode for Dendrite-Resistant Cycling
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Solution Overview
Problem
Lithium-ion batteries face issues with lithium dendrite formation due to nonuniform current density, leading to safety concerns, reduced cycle performance, and short service life, as lithium dendrites can penetrate separators and cause 'dead lithium', affecting energy density and stability.
Innovation Solution
A lithium-ion battery design featuring a laminated composite negative electrode with a lithiophilic layer, a main body layer, and a lithiophobic layer stacked along the current collector, where the lithiophilic layer induces lithium ion deposition towards the current collector, the main body layer provides storage space and adapts to volume changes, and the lithiophobic layer enhances surface conductivity, preventing dendrite growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-ion batteries use conventional negative electrodes, then energy density can be increased, but lithium dendrites form due to nonuniform current density, causing safety issues and reduced cycle performance
Solution Approach 1:
The negative electrode is segmented into three distinct layers with different lithiophilicity: a lithiophilic layer (first layer) that promotes uniform lithium deposition, a main body layer (second layer) that provides storage capacity, and a lithiophobic layer (third layer) that prevents dendrite growth. This segmentation allows each layer to perform its specific function, resolving the contradiction between energy density and safety.
Solution Approach 2:
Different regions of the negative electrode are given different local qualities through the three-layer structure. The lithiophilic layer has high lithium affinity to guide deposition, the main body layer has moderate affinity for storage, and the lithiophobic layer has low affinity to block dendrites. This local differentiation enables the electrode to simultaneously achieve high energy density and prevent dendrite formation.
2Quantity of substance
If lithium dendrites are allowed to grow, then battery capacity may increase temporarily, but dendrites penetrate separators and form dead lithium, reducing service life
Solution Approach 1:
The lithiophobic layer is positioned as the third layer (outermost layer) to perform preliminary anti-action against dendrite growth. This layer creates a lithiophobic barrier that prevents lithium dendrites from penetrating the separator before they can cause damage, thereby protecting the battery's service life while allowing the main body layer to maintain high capacity.
Solution Approach 2:
The three-layer structure provides beforehand cushioning by creating a controlled environment for lithium deposition. The lithiophilic layer cushions the initial deposition process to ensure uniformity, the main body layer cushions volume changes during cycling, and the lithiophobic layer cushions against dendrite penetration, collectively extending service life while maintaining capacity.
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
This design improves energy density and cycle life by ensuring uniform current density and preventing lithium dendrite formation, enhancing the safety and stability of lithium-ion batteries.
Implementation Method 1
the lithiophilic layer induces lithium ion deposition towards the current collector
Implementation Method 2
the lithiophobic layer enhances surface conductivity, preventing dendrite growth
Implementation Method 3
the main body layer provides storage space and adapts to volume changes
Data Source
AI summary
A lithium-ion battery includes a negative electrode including a current collector, a lithiophilic layer, a main body layer, and a lithiophobic layer laminated in sequence. A ratio of a discharge negative electrode capacity to a discharge positive electrode capacity of the lithium-ion battery is less than 1.