Composite Graphite Coating for High-Capacity Stable Battery Anodes
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Solution Overview
Problem
Current graphite materials in secondary batteries do not achieve their theoretical gravimetric capacity without compromising other electrochemical performances, and existing methods to improve capacity often lead to adverse effects on battery performance.
Innovation Solution
A composite graphite material is developed with a core material coated by a layer containing a cyclic structure moiety, achieved through a process of mixing a cyclizable polymer with graphite, drying, and heat treating, which results in a weight-loss rate of 0.1% to 0.55% when heated in an inert gas, enhancing gravimetric capacity, cycle performance, and kinetic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If current approaches to improve the gram capability of graphite material are used, then the gram capability is improved, but other electrochemical performances are compromised
Solution Approach 1:
The patent applies local quality by coating only the surface of graphite particles with a specific coating material containing cyclic structure moieties, rather than modifying the entire bulk material. This localized modification improves electrochemical performance at the surface where reactions occur, while preserving the bulk graphite structure and its high gram capability
Solution Approach 2:
The patent creates a composite material system consisting of graphite core particles coated with a coating material containing cyclic structure moieties (such as polyacrylonitrile-derived structures). This composite structure combines the high capacity of graphite with the beneficial surface properties of the coating material, achieving both high gram capability and improved electrochemical performance
2Quantity of substance
If the gram capability of graphite material is increased, then the energy density is improved, but the expansion rate of electrode plate increases
Solution Approach 1:
The patent uses a thin film coating material containing cyclic structure moieties that conformally coats the graphite particles. This flexible thin film layer accommodates volume changes during lithium insertion/extraction cycles, reducing electrode plate expansion while maintaining high gram capability
Solution Approach 2:
The composite structure of graphite core with coating material shell creates a mechanically stable system where the coating layer restrains graphite expansion during cycling, solving the contradiction between high capacity and structural stability
3Reliability
If a coating layer is added to improve performance, then electrochemical performance is improved, but the device complexity increases
Solution Approach 1:
The patent optimizes parameters including the thickness of the coating layer, the molecular weight of the coating material, and the heat treatment temperature (300-400°C) to achieve the desired cyclic structure formation. By controlling these parameters, the patent achieves improved performance with a relatively simple two-step process (coating and heat treatment)
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 composite graphite material improves gravimetric capacity, reduces electrode expansion, and enhances cycle and kinetic performance by controlling the cyclization and carbonization degrees of the polymer coating, providing a more stable and efficient battery performance.
Implementation Method 1
heat treating the powder at a temperature between 300° C. and 400° C. to obtain the composite graphite material comprising a core material and a coating layer that coats at least a portion of the surface of the core material, wherein the core material comprises the graphite, and the coating layer comprises a coating material containing a cyclic structure moiety
Implementation Method 2
heat treating the powder at a temperature between 300° C. and 400° C. to obtain the composite graphite material
Implementation Method 3
the composite graphite material has a weight-loss rate of from 0.1% to 0.55% when the composite graphite material is heated in an atmosphere of an inert non-oxidative gas at a temperature rising from 40° C. to 800° C.
Data Source
AI summary
The present application discloses a composite graphite material and a method for preparing the same, a secondary battery, and an apparatus. The composite graphite material includes a core material and a coating layer that coats at least a portion of the surface of the core material, the core material including graphite, and the coating layer including a coating material containing a cyclic structure moiety, wherein the composite graphite material has a weight-loss rate of from 0.1% to 0.55% when the composite graphite material is heated in an atmosphere of an inert non-oxidative gas at a temperature rising from 40° C. to 800° C. The composite graphite material can enhance the gram capability and reduce the expansion rate of an electrode plate, and more preferably, can improve the cycle performance and kinetic performance of a battery as well.