Silicon-Gradient Anode Layers for Deep-Cycle Li-Ion Stability
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Solution Overview
Problem
Lithium-ion batteries face issues with volume swelling and contraction of silicon materials, leading to SEI film rupture, electrolyte consumption, and cycle decay due to lithium ion migration, which affects their service life and deep discharge cycling performance.
Innovation Solution
A multi-layer coating method is applied to the negative electrode film layer with varying silicon material percentages and the addition of a substance A with a specific structure in the electrolyte, enhancing the SEI film flexibility and inhibiting swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon material is used as negative electrode material to increase theoretical specific capacity, then battery capacity is improved, but volume swelling and contraction occurs during cycling leading to SEI film rupture and cycle decay
Solution Approach 1:
The negative electrode is divided into multiple layers with different silicon content. The first layer (near current collector) has lower silicon content while the second layer (farther from current collector) has higher silicon content. This segmentation allows the electrode to achieve high overall capacity while the lower-silicon first layer provides structural stability and reduces volume swelling during cycling.
Solution Approach 2:
Different regions of the negative electrode are assigned different silicon concentrations to optimize local functions. The region closer to the current collector (first layer) has lower silicon content for structural stability, while the region farther away (second layer) has higher silicon content for maximum capacity utilization. This local quality differentiation resolves the contradiction between high capacity and cycle stability.
2Stability of the object's composition
If composite silicon-graphite materials are used to reduce volume swelling, then structural stability is improved, but lithium ion migration occurs during relaxation process causing electrolyte decomposition and service life degradation
Solution Approach 1:
The composite silicon-graphite material is segmented into layers with different silicon contents. This segmentation creates a gradient structure that reduces lithium ion migration during relaxation by providing a more uniform distribution of lithium insertion sites, thereby reducing electrolyte decomposition and extending service life while maintaining volume stability.
Solution Approach 2:
The silicon content parameter is changed across different layers of the negative electrode. By creating a gradient in silicon concentration (lower in the first layer, higher in the second layer), the electrode achieves both volume stability and reduced lithium ion migration, thus extending service life without sacrificing structural stability.
3Productivity
If deep discharge cycling is performed to increase energy utilization, then battery efficiency is improved, but decomposition reaction intensifies causing continuous degradation and reconstruction of protective film
Solution Approach 1:
The segmented layer structure with varying silicon content distributes the electrochemical reactions more uniformly during deep discharge cycling. This reduces localized stress and minimizes protective film degradation, thereby reducing electrolyte consumption while maintaining high energy utilization efficiency.
Solution Approach 2:
Different layers with different silicon contents perform different functions during deep discharge cycling. The lower-silicon first layer provides structural support that prevents excessive film degradation, while the higher-silicon second layer maximizes energy utilization. This local quality differentiation allows deep discharge cycling without excessive electrolyte consumption.
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
Improves deep discharge cycling performance and high-temperature storage performance by reducing electrolyte consumption and silicon swelling, thereby extending the battery's service life.
Implementation Method 1
a substance A with a structure shown in formula I is further synergistically added to an electrolyte in this application. This can improve the deep discharge cycling performance of the electrochemical apparatus and the electronic device and take the high-temperature performance into account
Implementation Method 2
during continuous charging and discharging, the silicon material is very prone to volume swelling and contraction, creating gaps between silicon materials, ultimately leading to the rupture of an SEI film
Implementation Method 3
during the relaxation process after charging and discharging to a cutoff voltage, lithium ion migration occurs in composite silicon-graphite materials
Implementation Method 4
during continuous charging and discharging, the silicon material is very prone to volume swelling and contraction, creating gaps between silicon materials
Data Source
AI summary
An electrochemical apparatus includes a negative electrode plate and an electrolyte. The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. In a direction facing away from the negative electrode current collector, the negative electrode film layer sequentially includes a first active substance layer and a second active substance layer, where a mass percentage of a silicon material in the first active substance layer is less than a mass percentage of the silicon material in the second active substance layer. The electrolyte includes a substance A with a structure shown in formula I.