Multilayer Silicon Anode Composition for High-Density Battery Cycling
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Solution Overview
Problem
Secondary batteries face challenges in achieving better cycle performance while maintaining higher energy density, as existing technologies struggle to optimize the composition and structure of their negative electrode layers to enhance both energy storage capacity and durability.
Innovation Solution
A secondary battery design featuring a negative electrode sheet with a silicon-based material content of at least 30% and a conductive agent content of at least 25%, along with specific thickness and binder ratios, to create a high-energy-density and long-cycle-performance battery, where the conductive agent includes materials like carbon black, graphene, and carbon nanotubes, and the second negative active material is predominantly artificial graphite.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the silicon-based material content in the negative electrode is increased to improve energy density, then the energy density is improved, but the cycle performance deteriorates due to volume expansion and structural instability
Solution Approach 1:
The negative electrode is divided into multiple film layers (first negative film layer with silicon-based material, second negative film layer with graphite, and optionally third negative film layer). This segmentation isolates the silicon-based material in a specific layer, allowing high energy density while protecting against overall electrode degradation through the protective effect of adjacent layers.
Solution Approach 2:
The negative electrode uses a composite structure combining silicon-based material (high capacity) with graphite (stable structure) and conductive agents (carbon black, graphene, carbon nanotubes). This composite approach leverages the high energy density of silicon while the graphite and conductive network provide structural stability and electrical conductivity, resolving the contradiction between energy density and cycle performance.
2Productivity
If the conductive agent content is increased to improve electrical conductivity and capacity utilization, then the capacity utilization is improved, but the energy density decreases due to increased non-active material content
Solution Approach 1:
The patent optimizes the concentration and distribution of conductive agents (carbon black, graphene, carbon nanotubes) within the negative electrode layers. By controlling the mass proportion and spatial distribution parameters of these conductive materials, the patent achieves sufficient electrical conductivity for high capacity utilization while minimizing the volume occupied by non-active materials, thus maintaining high energy density.
3Device complexity
If the negative electrode layer structure is simplified to reduce manufacturing complexity, then the manufacturing complexity is reduced, but the electrode layer separation risk increases
Solution Approach 1:
The negative electrode is segmented into multiple film layers (first negative film layer, second negative film layer, and optionally third negative film layer) with distinct functions. This segmentation, while adding structural complexity, actually simplifies manufacturing by allowing each layer to be optimized independently for its specific function (silicon-based material for capacity, graphite for stability, conductive agents for conductivity), reducing the need for complex post-processing to prevent separation.
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 proposed battery configuration significantly improves energy density and cycle performance by ensuring effective capacity utilization and reducing the risk of electrode layer separation, leading to enhanced durability and efficiency in energy storage.
Implementation Method 1
a first negative film layer provided on at least one surface of the negative electrode current collector; and a second negative film layer provided on a surface of the first negative film layer; wherein the first negative film layer includes a first negative active material and a first conductive agent, and the first negative active material includes a silicon-based material
Implementation Method 2
a first negative active material includes a silicon-based material; a mass proportion of the silicon-based material in the first negative film layer is greater than or equal to 30%
Implementation Method 3
the second negative active material is predominantly artificial graphite
Data Source
AI summary
The present disclosure provides a secondary battery including a negative electrode sheet. The negative electrode sheet includes: a negative electrode current collector; a first negative film layer provided on at least one surface of the negative electrode current collector; and a second negative film layer provided on a surface of the first negative film layer. The first negative film layer includes a first negative active material and a first conductive agent, and the first negative active material includes a silicon-based material. A mass proportion of the silicon-based material in the first negative film layer is greater than or equal to 30%, and a mass proportion of the first conductive agent in the first negative film layer is greater than or equal to 25%. The secondary battery of the present disclosure does not easily expand and has good cycle performance.