Multilayer Carbon Negative Electrode for Li-Ion Battery
Solution Overview
Problem
Conventional lithium ion secondary batteries face challenges in improving both initial efficiency and cycle characteristics, particularly due to the expansion and contraction of carbon-containing negative electrodes during charge and discharge, which affects energy density, large-current charge-discharge behavior, and durability.
Innovation Solution
A multilayer-structured carbon material is developed for the negative electrode, treated under specific cracking conditions to reduce fine agglomeration and increase surface oxygen content, resulting in improved paste properties, initial efficiency, and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If graphite particles are subjected to mechanochemical treatment to hydrophilize surfaces, then fast charging characteristic is improved, but initial efficiency and cycle characteristics deteriorate
Solution Approach 1:
The invention applies different surface treatments to different regions of the graphite particles. The surface is selectively hydrophilized through controlled oxidation to improve fast charging, while the bulk structure maintains its graphitic properties for good cycle characteristics. This local differentiation allows simultaneous optimization of surface reactivity and bulk stability.
Solution Approach 2:
The invention changes the surface chemical parameters of graphite particles by controlling the degree of oxidation and surface functional group content. By adjusting these parameters, the surface becomes sufficiently hydrophilic for fast charging while maintaining structural integrity for good cycle life, resolving the contradiction between speed and reliability.
2Reliability
If tapping density is increased by changing spheroidicity or average particle size, then cycle characteristics are improved, but total friction between particles decreases causing other problems
Solution Approach 1:
The invention changes the surface chemical composition and physical structure of graphite particles through controlled oxidation and surface treatment. This modifies surface properties to maintain adequate friction between particles while achieving high tapping density through improved particle packing, thus improving cycle characteristics without excessive friction loss.
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 multilayer-structured carbon material enhances the trade-off relationships between paste properties, initial efficiency, cycle characteristics, and low-temperature output, leading to better performance in lithium ion secondary batteries.
Implementation Method 1
treating a multilayer-structured carbon material under specific cracking conditions to reduce fine agglomeration and increase surface oxygen content
Implementation Method 2
reacting it with a surrounding atmosphere by imparting energy having a certain power or less to the multilayer-structured carbon material
Data Source
AI summary
An object of the present invention is to provide a nonaqueous electrolytic solution secondary battery that can improve trade-off relationships and exhibit good performance in paste properties, initial efficiency, cycle characteristics, low-temperature output, and the like. The present invention resolves the problem by using a multilayer-structured carbon material, as a nonaqueous electrolytic solution secondary battery negative electrode, which satisfies the following (a) and (b): (a) (Void fraction calculated from DBP oil absorption)/(Void fraction calculated from tapping density) is less than 1.01; and (b) Surface oxygen content (O/C) determined by X-ray photoelectron spectroscopy is 1.5 atomic % or more.