Negative Electrode Carbon Blend for High-Temperature Cycle Resistance
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Solution Overview
Problem
Nonaqueous electrolyte energy storage devices, such as lithium ion batteries, experience a significant increase in power resistance during charge-discharge cycles, especially under high temperatures, when using graphite as the negative electrode material.
Innovation Solution
Incorporating a combination of graphite and graphitizable carbon in the negative electrode, with a specific mass ratio and particle size distribution, to enhance filling rate and conductivity, thereby suppressing the increase in power resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If only graphite is used as the negative electrode material, then the device achieves good initial performance, but the power resistance increases significantly during charge-discharge cycles under high temperature
Solution Approach 1:
The patent applies composite materials by combining graphite and graphitizable carbon in a specific mass ratio (94:6 to 60:40). This composite negative electrode material maintains the advantages of graphite while adding the benefits of graphitizable carbon, which forms a protective coating during initial cycles that prevents electrolyte decomposition and maintains low power resistance throughout charge-discharge cycles under high temperature conditions.
Solution Approach 2:
The patent applies parameter changes by optimizing the mass ratio of graphite to graphitizable carbon (94:6 to 60:40) and controlling the particle size distribution (D50 of graphite: 3-20 μm, D50 of graphitizable carbon: 1-10 μm). These parameter optimizations ensure that the composite material achieves the right balance between initial performance and cycle stability, preventing excessive power resistance increase during cycling at high temperatures.
2Productivity
If the negative electrode contains graphitizable carbon with small particle size, then the filling rate and conductivity are enhanced, but the mass ratio of graphitizable carbon must be precisely controlled
Solution Approach 1:
The patent applies parameter changes by defining specific ranges for the mass ratio of graphitizable carbon (6-40 mass%) and particle size distribution (D50 of graphite: 3-20 μm, D50 of graphitizable carbon: 1-10 μm). These parameter specifications optimize the filling rate and conductivity while providing clear manufacturing guidelines to control the complexity of mass ratio management during production.
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 use of graphite and graphitizable carbon in a controlled ratio and size distribution effectively reduces power resistance during charge-discharge cycles, even under high temperature conditions, by minimizing side reactions and maintaining conductivity.
Implementation Method 1
graphitizable carbon which has a median diameter of less than a median diameter of the graphite and a ratio (graphitizable carbon/graphite) of the median diameter of the graphitizable carbon to the median diameter of the graphite of 0.28 or less
Data Source
Figure 1~3
AI summary
Provided is a nonaqueous electrolyte energy storage device in which an increase in power resistance accompanying a charging/discharging cycle under a high temperature is suppressed. The nonaqueous electrolyte energy storage device according to an aspect of the present invention includes a negative electrode including graphite and graphitizable carbon, in which a ratio of a mass of the graphitizable carbon to a total mass of the graphite and the graphitizable carbon is less than 26% by mass, and a median diameter of the graphitizable carbon is smaller than a median diameter of the graphite.