Sodium-Ion Negative Electrode Coating With Surface Holes for Stable Deposition
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Solution Overview
Problem
Sodium-ion batteries suffer from low energy density, rapid capacity degradation, and poor liquid absorption and retention at the negative electrode side due to the greater ionic radius of sodium ions and volumetric expansion, leading to issues like peeling and pulverization of the sodium deposition layer during cycling.
Innovation Solution
A negative electrode plate with holes in the carbon coating surface, enhancing surface roughness and reducing the contact angle with the electrolyte, combined with a carbon coating containing a solid electrolyte, improves bonding force and ionic migration, preventing peeling and pulverization, and adjusting the electric field for uniform sodium deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a sodium-ion battery is designed without a negative active material to improve energy density, then energy density increases, but liquid absorption and retention capability deteriorates
Solution Approach 1:
The negative electrode plate incorporates a porous coating layer with controlled porosity (30-70%) that provides both liquid absorption capability and retention function. The porous structure allows electrolyte penetration while maintaining sufficient liquid contact for sustained ionic conduction, resolving the contradiction between energy density improvement and liquid retention capability
Solution Approach 2:
The invention uses a composite coating layer combining carbonaceous materials (for conductivity and structure) with polymer binders (for mechanical integrity and liquid retention). This composite structure enables the negative electrode to function without traditional active materials while maintaining adequate liquid absorption and retention properties
2Ease of manufacture
If the surface of the negative electrode plate is made smoother to improve manufacturing, then manufacturing ease increases, but bonding force of deposited sodium metal deteriorates
Solution Approach 1:
The coating layer is designed with specific surface properties (roughness Ra: 0.5-5.0 μm) that enhance sodium metal bonding locally at the electrode surface. This controlled surface quality improvement resolves the contradiction by providing adequate surface characteristics for strong bonding without compromising manufacturing feasibility
3Reliability
If the contact angle between electrolyte solution and negative electrode plate is reduced to improve wetting, then liquid absorption improves, but ionic transport impedance increases
Solution Approach 1:
The porous coating layer with optimized pore size distribution (0.5-5.0 μm) and porosity (30-70%) enables capillary action that reduces contact angle for improved wetting, while the interconnected pore structure maintains low ionic transport impedance by providing efficient ion conduction pathways
Solution Approach 2:
The invention optimizes multiple parameters including surface roughness (Ra: 0.5-5.0 μm), porosity (30-70%), and pore size (0.5-5.0 μm) to achieve the optimal balance between liquid absorption capability and ionic transport impedance, transforming the trade-off into a multi-parameter optimization problem
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 significantly enhances liquid absorption and retention, reduces ionic transport impedance, and improves cycling performance by ensuring rapid wetting and strong bonding of the sodium metal layer, thereby preventing irreversible capacity loss.
Implementation Method 1
by providing holes in the surface of the negative electrode plate, a surface roughness of the negative electrode plate is increased, enabling a sodium metal layer deposited on a surface of the negative electrode plate to have a stronger bonding force to the surface of the negative electrode plate
Implementation Method 2
by providing holes in the surface of the negative electrode plate, a contact angle between an electrolyte solution and a negative electrode plate surface can be effectively reduced, which enables the electrolyte solution to rapidly wet the surface of the negative electrode plate, thereby significantly enhancing the liquid absorption and retention capability
Implementation Method 3
the solid electrolyte in the carbon coating can further enhance an affinity between the carbon coating and the electrolyte solution, thereby improving a wettability and ionic migration rate on the negative electrode side
Implementation Method 4
an electric field on the negative electrode plate surface can be adjusted, and the uniformity and compactness of the deposited sodium on the negative electrode plate surface can be improved
Data Source
Figure 1
AI summary
Provided are a negative electrode plate, a sodium-ion battery, and an electronic device. The negative electrode plate includes a negative electrode current collector and a carbon coating disposed on at least a portion of the surface of the negative electrode current collector. The carbon coating includes a carbon material, a solid electrolyte, and a polymer binder. A surface of the carbon coating facing away from the negative electrode current collector has holes extending along the thickness direction of the carbon coating. A depth of the holes is smaller than a thickness of the carbon coating.