Layered Graphite Anode Sheet for Low-Expansion Li-Ion Cycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium batteries face issues of short cycle life and low volumetric energy density due to problems with negative electrode materials, including expansion during cycling and low capacity.
Innovation Solution
A negative electrode sheet with distinct active layers, where the first active layer includes a first graphite and the second active layer includes a second graphite, with a capacity ratio greater than 1, and optionally incorporating silicon materials, to enhance cycle life and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mixing methods are used to disperse silane-modified polyethylene crosslinking agent in polyethylene resin, then the mixing process is simple, but the crosslinking agent aggregates and disperses unevenly leading to inconsistent crosslinking degree
Solution Approach 1:
The mixing process is divided into multiple stages: first mixing the crosslinking agent with a plasticizer to form a uniform mixture, then adding this mixture to the polyethylene resin. This segmentation ensures uniform dispersion without requiring complex mixing equipment.
Solution Approach 2:
A plasticizer is introduced as an intermediary substance to facilitate uniform dispersion of the crosslinking agent. The plasticizer acts as a medium that prevents aggregation and enables homogeneous distribution before the crosslinking agent contacts the polyethylene resin.
2Reliability
If silane-modified polyethylene crosslinking agent is not uniformly dispersed in polyethylene resin, then the mixing process is simple, but the crosslinked polyethylene has inconsistent crosslinking degree affecting product quality
Solution Approach 1:
The crosslinking agent is pre-mixed with the plasticizer before being added to the polyethylene resin. This preliminary action ensures uniform distribution of the crosslinking agent, guaranteeing consistent crosslinking degree in the final product while maintaining process simplicity.
Solution Approach 2:
The plasticizer content is controlled within a specific range (1-10 parts by weight per 100 parts of crosslinking agent) to optimize dispersion uniformity. By adjusting this parameter, reliable product quality is achieved without complicating the manufacturing process.
3Manufacturing precision
If excessive plasticizer is used to improve crosslinking uniformity, then crosslinking uniformity improves, but resin aggregate formation increases and mechanical properties deteriorate
Solution Approach 1:
The plasticizer content is precisely controlled within the range of 1-10 parts by weight per 100 parts of crosslinking agent. This parameter optimization achieves uniform crosslinking while preventing resin aggregate formation, thereby maintaining excellent mechanical properties.
Solution Approach 2:
Instead of using excessive plasticizer, the invention applies a controlled, moderate amount that is sufficient for uniform dispersion but not enough to cause aggregate formation. This partial action approach balances crosslinking uniformity with mechanical property preservation.
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 improves cycle life and reduces expansion, increasing the volumetric energy density and meeting high energy requirements.
Implementation Method 1
utilizing a silane-modified polyethylene crosslinking agent and a condensation reaction therefor to perform gel crosslinking
Data Source
Figure 1~2
AI summary
A negative electrode sheet, a fabricating method, and a battery are provided. The negative electrode sheet includes: a current collector; a first active layer is provided on a surface of at least one side of the current collector, and a second active layer is provided on a surface of one side of the first active layer away from the current collector, the first active layer is different from the second active layer, the first active layer includes a first active material including a first graphite, and the second active layer includes a second active material including a second graphite; a ratio of capacity per unit mass of the first active material to specific surface area of the first active material is a first capacity ratio, and a ratio of capacity per unit mass of the second active material to specific surface area of the second active material is a second capacity ratio, a ratio of the second capacity ratio to the first capacity ratio being greater than 1. In the negative electrode sheet of the present application, different active layers are coated on the current collector, thereby increasing the cycle life of the negative electrode material, reducing the expansion rate, increasing the capacity and volumetric energy density of the battery, and prolonging the cycle life.