Layered Graphite Anode Structure for Fast-Charging Li-Ion Batteries
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving high energy density and fast charging performance, particularly in applications requiring rapid energy delivery and efficient charging.
Innovation Solution
The negative electrode plate is designed with distinct regions, where the region closer to the current collector has a lower Raman value ID/IG and higher graphitization degree, while the region further away has a higher Raman value ID/IG and lower graphitization degree, along with specific density and particle size distributions, to enhance lithium-ion transfer and charge exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the negative electrode film layer uses uniform active material throughout, then the manufacturing process is simple, but the fast charging performance and energy density cannot be optimized simultaneously
Solution Approach 1:
The negative electrode film layer is divided into multiple regions (first region, second region, third region) with different active materials arranged in sequence from the current collector outward. This segmentation allows each region to perform specialized functions: the first region provides stable lithium ion insertion/extraction, the second region enhances fast charging kinetics, and the third region contributes to energy density, thereby resolving the contradiction between fast charging performance and structural complexity.
Solution Approach 2:
Different regions of the negative electrode film layer are assigned different active materials with specific local properties tailored to their positions. The first region near the current collector uses material with suitable expansion characteristics, the second region uses material optimized for fast charging, and the third region uses material for high energy density. This local quality differentiation enables simultaneous optimization of fast charging performance while maintaining a structured but manageable design.
2Reliability
If high graphitization degree active material is used throughout the negative electrode, then the structural stability is improved, but the fast charging kinetics are limited
Solution Approach 1:
The patent applies different graphitization degrees at different locations within the negative electrode film layer. The first region near the current collector uses active material with higher graphitization degree (≥90%) for structural stability, while the second region uses active material with lower graphitization degree (80-89%) to enhance lithium ion transfer speed and fast charging kinetics. This spatial variation in graphitization degree resolves the contradiction between structural stability and fast charging performance.
Solution Approach 2:
The negative electrode film layer is segmented into regions with different graphitization characteristics. The first region provides a stable structural foundation with high graphitization, while the second region facilitates rapid lithium ion transport with moderate graphitization. This segmentation allows the electrode to simultaneously achieve both structural reliability and fast charging capability.
3Productivity
If the negative electrode film layer is designed with multiple regions of different active materials, then the fast charging performance and energy density are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The negative electrode film layer is divided into three distinct regions with different active materials applied in sequence. By defining clear boundaries and thickness ranges for each region (first region: 1-5 μm, second region: 5-15 μm, third region: 15-30 μm), the patent provides manufacturable specifications that balance the need for improved energy density with achievable manufacturing precision through controlled material deposition.
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 the fast charging performance and increases the energy density of lithium-ion batteries, optimizing the balance between kinetic performance and energy storage.
Implementation Method 1
a graphitization degree of the first negative electrode active material is greater than a graphitization degree of the second negative electrode active material
Implementation Method 2
a median Raman value ID/IG of the first negative electrode active material is denoted as R150, and a median Raman value ID/IG of the second negative electrode active material is denoted as R250, where R150 is less than R250
Data Source
AI summary
A secondary battery and an electric apparatus are provided. The secondary battery includes a negative electrode plate comprising a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer includes a lower region and an upper region. The lower region comprises a first negative electrode active material, and the upper region comprises a second negative electrode active material. A median Raman value I_D/I_G of the first negative electrode active material is denoted as R150, and a median Raman value I_D/I_G of the second negative electrode active material is denoted as R250, where R150<R250. The first negative electrode active material has a higher graphitization degree than the second negative electrode active material. The disclosed design improves the fast-charging performance and energy density of the secondary battery.