Graphite Negative Material With Through-Layer Channels
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Solution Overview
Problem
The high-rate charge-discharge performance of lithium-ion batteries using conventional graphite negative electrodes is limited due to the small diffusion coefficient of lithium ions, leading to surface concentration, metal lithium crystallite formation, and reduced cycle life, along with security risks from lithium dendrites.
Innovation Solution
A graphite negative material with channels through its layers is developed by loading a catalyst such as Ti, Zr, or Mn onto graphite layers and reacting it with a gas like CO2 or H2O at elevated temperatures to create pores with diameters ranging from 0.2 nm to 1.5 μm, allowing free passage of lithium ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite material is used as negative electrode, then good reversibility and low potential plateau are achieved, but lithium ion diffusion coefficient is small restricting high-rate performance
Solution Approach 1:
The patent applies porous materials by constructing a three-dimensional porous conductive network using carbon nanotubes and graphite flakes. The porous structure provides numerous channels for lithium ion transport, significantly increasing the diffusion coefficient while maintaining the good reversibility characteristics of graphite material.
Solution Approach 2:
The patent uses composite materials by combining carbon nanotubes with graphite flakes to form a hybrid conductive network. This composite structure leverages the high aspect ratio and conductivity of carbon nanotubes together with the intercalation properties of graphite, achieving both fast ion transport and good reversibility.
2Power
If high current density charge-discharge is performed, then power output increases, but lithium ions concentrate on surface forming metal lithium crystallite and dendrite
Solution Approach 1:
The patent introduces carbon nanotubes as an intermediary conductive network between lithium ions and graphite layers. This intermediary structure facilitates uniform lithium ion distribution across the electrode surface, preventing local concentration that would lead to metal lithium crystallite and dendrite formation, thereby maintaining safety and cycle life at high power rates.
Solution Approach 2:
The patent transitions from a two-dimensional planar graphite structure to a three-dimensional porous network incorporating carbon nanotubes. This dimensional enhancement provides additional pathways for lithium ion transport, enabling uniform distribution and preventing surface concentration even at high charge-discharge rates.
3Volume of stationary object
If graphite layers are made compact, then density increases, but channels for lithium ion passage are reduced
Solution Approach 1:
The patent deliberately incorporates a porous structure into the graphite material by integrating carbon nanotubes with graphite flakes. This porous architecture maintains high density while providing numerous interconnected channels for efficient lithium ion transport, resolving the contradiction between compactness and ion accessibility.
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
This approach enhances the cycle stability and high-rate charge-discharge performance of lithium-ion batteries by shortening lithium ion diffusion distances and preventing dendrite formation, thereby extending cycle life and ensuring safety.
Implementation Method 1
a catalyst is loaded on a graphite material including a number of graphite layers to form a graphite material loading the catalyst. And then, the graphite material loading the catalyst is reacted with a reaction gas to transform the carbon of the graphite material to a gaseous product
Implementation Method 2
the graphite material loading the catalyst is reacted with a reaction gas to transform the carbon of the graphite material to a gaseous product
Data Source
AI summary
A graphite negative material for a lithium-ion battery includes a number of graphite layers parallel to each other. A number of channels are through the graphite layers. And the channels are capable of allowing lithium ions to pass therethrough freely. A method for preparing the graphite negative material and a lithium-ion battery including the graphite negative material are also provided.