Layered Carbon Negative Electrode for Fast-Charging Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high power and rate capability due to inadequate orientation of negative electrode active materials, leading to poor electrolyte impregnation and increased electron resistance, which affects charge and discharge efficiency.
Innovation Solution
A negative electrode design featuring a current collector with a layered structure of carbon-based active materials, where the first layer has a Degree of Divergence (DD) value of 30% to 90% of the total, optimized through XRD measurements and magnetic field orientation, enhancing the orientation and adhesion of the second layer, thereby improving electrolyte impregnation and lithium ion transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer negative electrode structure is used, then the manufacturing process is simple, but the electrolyte impregnation is poor and electron resistance is high
Solution Approach 1:
The negative electrode active material layer is divided into two distinct layers: a first layer with carbon-based active material having specific crystal orientation (DD value of 10-30) that provides excellent electrolyte impregnation, and a second layer with carbon-based active material having different orientation (DD value of 30-50) that provides high lithium ion capacity. This segmentation allows each layer to perform its specialized function, resolving the contradiction between simple structure and effective electrolyte impregnation.
Solution Approach 2:
Different regions of the negative electrode are given different properties through the two-layer structure. The first layer near the current collector has optimized orientation for electrolyte penetration and adhesion, while the second layer has orientation optimized for lithium ion insertion/extraction. This local quality differentiation allows the electrode to simultaneously achieve good electrolyte impregnation and high capacity without requiring complex overall restructuring.
2Stability of the object's composition
If the first layer has high adhesion to current collector, then the electrode stability is improved, but the lithium ion transfer capability may be reduced
Solution Approach 1:
The functional segmentation separates adhesion stability (first layer with DD value 10-30) from lithium ion transfer capability (second layer with DD value 30-50). The first layer's lower DD value indicates more random orientation that enhances adhesion to the current collector, while the second layer's higher DD value provides better lithium ion transfer pathways, thus resolving the contradiction between stability and productivity.
3Quantity of substance
If a thick negative electrode active material layer is used, then the battery capacity is increased, but the charge-discharge rate capability deteriorates
Solution Approach 1:
The thick active material layer is structured with local quality variations through the two-layer configuration. The first layer provides stable adhesion and electrolyte distribution, while the second layer's specific orientation (DD value 30-50) creates efficient lithium ion transfer channels. This allows the overall layer to be thick for high capacity while maintaining fast charge-discharge rates through the optimized second layer structure.
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 design results in improved high-rate capability and cycle-life characteristics by ensuring effective electrolyte impregnation and reduced electron resistance, making the battery suitable for high-power applications.
Implementation Method 1
various carbon-based materials capable of intercalating/deintercalating lithium ions such as artificial graphite, natural graphite
Implementation Method 2
measured by XRD using a CuKα ray
Implementation Method 3
measured by XRD using a CuKα ray
Implementation Method 4
optimized through XRD measurements and magnetic field orientation
Data Source
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AI summary
The present invention relates a negative electrode for a lithium secondary battery, and a lithium secondary battery comprising same, wherein the negative electrode for a lithium secondary battery comprises a current collector, and a negative electrode active material layer including a first layer formed on the current collector and a second layer formed on the first layer, the first layer containing a first carbon-based negative electrode active material, and the second layer containing a second carbon-based negative electrode active material, wherein the degree of divergence (DD) value of the first layer is 30-90% of the DD value of the negative electrode active material layer, the DD value is defined by formula 1 below. DDDegreeofDivergence=Ia/Itotal*100 (In formula 1, Ia is the sum of peak intensities of peaks at out-of plane angles as measured by XRD with CuKα, and Itotal is the sum of peak intensities of peaks at all angles as measured by XRD with CuKa).