3D Negative Electrode Structure for Expansion and Dendrite Control
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Solution Overview
Problem
Existing electrochemical devices face challenges in maintaining high energy density while improving cycle performance due to volume expansion of high-capacity negative active materials, leading to issues like delamination and reduced safety from lithium dendrite formation.
Innovation Solution
A negative electrode plate with a three-dimensional framework structure composed of fibers and rigid particles with a Mohs hardness ≥2 and elastic modulus ≥40 GPa, which stabilizes the structure, facilitates lithium deposition, and reduces dendrite formation by distributing lithium-wetting rigid particles to mitigate volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-capacity negative active materials (such as lithium metal and silicon-based materials) are used to increase energy density, then the energy density of the electrochemical device is improved, but the cycle performance deteriorates due to significant volume expansion during cycling
Solution Approach 1:
The patent employs a flexible binder film that envelops rigid particles to create a composite negative electrode structure. This flexible film accommodates volume expansion of high-capacity materials during lithium insertion/extraction cycles while maintaining structural integrity, thereby resolving the contradiction between achieving high energy density and maintaining cycle performance
Solution Approach 2:
The patent creates a composite structure combining rigid particles (with specific hardness and elastic modulus requirements) and a flexible binder film. This composite material design allows the electrode to simultaneously achieve high energy density from the rigid particles and good cycle performance from the flexible matrix that absorbs expansion stress
2Use of energy by moving object
If high-capacity negative active materials are used to achieve high energy density, then the energy storage capacity is improved, but structural stability deteriorates leading to delamination of the negative active material layer
Solution Approach 1:
The flexible binder film acts as a stabilizing matrix that maintains structural integrity during volume changes. This film prevents delamination of the negative active material layer by providing mechanical support and adhesion, while allowing the high-capacity materials to achieve their full energy density potential
Solution Approach 2:
The composite structure of rigid particles embedded in a flexible binder creates a synergistic system where the rigid phase provides high capacity and the flexible phase provides structural stability, preventing delamination while maintaining high energy density
3Ease of manufacture
If conventional negative electrode structures are used, then the manufacturing process is simple, but lithium dendrite formation occurs reducing safety and cycle performance
Solution Approach 1:
The patent introduces rigid particles with specific local properties (hardness ≥2, elastic modulus ≥40 GPa) distributed within the binder film. These particles create localized nucleation sites that guide uniform lithium deposition, preventing dendrite formation while maintaining a relatively simple manufacturing process
Solution Approach 2:
The rigid particles act as intermediaries between the electrolyte and the flexible binder matrix, providing controlled lithium deposition sites. This intermediary structure promotes uniform lithium plating and prevents dendrite formation without significantly complicating the manufacturing process
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 three-dimensional framework structure enhances structural stability, reduces lithium dendrite generation, and improves cycle performance and safety by accommodating lithium deposition and dispersing current density.
Implementation Method 1
the rigid particles help to stabilize the three-dimensional framework structure and can serve as a lithium wetting material to induce lithium to deposit inside the three-dimensional framework
Data Source
AI summary
A negative electrode plate includes a three-dimensional framework structure. The three-dimensional framework structure includes fibers and rigid particles. Mohs hardness of the rigid particles is greater than or equal to 2, and an elastic modulus of the rigid particles is greater than or equal to 40 Gpa. The three-dimensional framework structure can mitigate volume expansion of the negative active material during cycling. On the other hand, the rigid particles help to stabilize the three-dimensional framework structure and can serve as a lithium wetting material to induce lithium to deposit inside the three-dimensional framework, thereby reducing the generation of lithium dendrites and improving safety performance and cycle performance of the formed electrochemical device.