Carbon-Coated Graphite Particles for Better Li-Ion Cycle Stability
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Solution Overview
Problem
Conventional methods for producing carbonaceous substance-coated graphite particles for lithium ion secondary batteries often result in insufficient battery properties, such as initial charging-discharging efficiency and cycle characteristics.
Innovation Solution
A method involving the use of modified novolac-type phenolic resin to adhere to graphite particles, followed by heating in a non-oxidizing atmosphere to form a carbonaceous coating, with specific structural and compositional parameters to achieve enhanced battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods are used to produce carbonaceous substance-coated graphite particles, then the production process is simple, but the battery properties (initial charging-discharging efficiency and cycle characteristics) are insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the heating temperature (900-1500°C) and heating time (1-24 hours) during carbonization, as well as controlling the novolac resin content (1-30 parts by mass per 100 parts graphite). These parameter optimizations transform the simple conventional process into one that produces particles with specific surface area (4.0-15.0 m²/g) and pore structure (SAb/SAa ratio: 0.20-1.29), thereby improving battery properties without requiring complex equipment or processes
Solution Approach 2:
The patent creates a composite structure by coating graphite particles with carbonaceous substance derived from novolac resin. This composite material combines the high capacity of graphite with the protective and conductive properties of the carbonaceous coating, resulting in particles that exhibit both excellent initial charging-discharging efficiency and cycle characteristics while maintaining a relatively simple production process
2Area of stationary object
If the specific surface area is increased to improve battery performance, then the reaction area increases, but the particle size must be reduced which may affect structural stability
Solution Approach 1:
The patent resolves this contradiction by controlling the particle diameter D50 within 3.0-20.0 μm and the specific surface area within 4.0-15.0 m²/g through optimized carbonization parameters (temperature and time). This parameter control ensures that particles achieve sufficient surface area for good electrochemical performance while maintaining adequate size for structural stability and resistance to fragmentation during battery cycling
3Reliability
If the pore specific surface area ratio (SAb/SAa) is optimized to enhance lithium ion insertion-extraction performance, then the pore structure is controlled, but the manufacturing precision requirements increase
Solution Approach 1:
The patent achieves the desired pore structure (SAb/SAa ratio: 0.20-1.29) by controlling the carbonization temperature (900-1500°C) and time (1-24 hours), as well as the novolac resin content (1-30 parts by mass per 100 parts graphite). These parameter optimizations create a pore structure that facilitates lithium ion insertion-extraction without requiring extremely precise manufacturing control, as the process parameters naturally guide the formation of the desired pore characteristics
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 method produces carbonaceous substance-coated graphite particles with improved initial charging-discharging efficiency and cycle characteristics, optimizing battery performance by controlling particle diameter, specific surface area, pore structure, and crystallinity.
Implementation Method 1
obtaining resin-adhered graphite particles by causing a modified novolac-type phenolic resin to adhere to graphite particles
Implementation Method 2
coating at least part of surfaces of the graphite particles with a carbonaceous coating by heating the resin-adhered graphite particles in a non-oxidizing atmosphere at 900 to 1,500° C. to carbonize the modified novolac-type phenolic resin
Data Source
AI summary
Resin-adhered graphite particles are obtained by causing a modified novolac-type phenolic resin to adhere to graphite particles. At least part of surfaces of the graphite particles is coated with a carbonaceous coating by heating the resin-adhered graphite particles in a non-oxidizing atmosphere at 900 to 1,500° C. to carbonize the modified novolac-type phenolic resin. Arylene groups having hydroxy groups account for 5 to 95 mol % of arylene groups constituting the modified novolac-type phenolic resin. The obtained carbonaceous substance-coated graphite particles exhibit excellent battery properties when used as a negative electrode material for a lithium ion secondary battery.