Modified Graphite Anode Coating to Limit Electrolyte Penetration
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Solution Overview
Problem
Conventional natural graphite used in lithium ion batteries has high void structures that lead to increased side reactions with the electrolytic solution, resulting in reduced cycle performance and lifespan due to volume expansion caused by co-intercalation of anions and solvent molecules, which existing core-shell structures fail to adequately address.
Innovation Solution
A graphite negative electrode material with a carbon coating layer containing modifying groups such as B, N, or P, applied through a thermal polymerization and carbonization process, which reduces side reactions and prevents electrolyte infiltration, improving cycle performance and volume expansion properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional natural graphite is obtained by mechanically crushing flake graphite, then high capacity and low price are achieved, but rich void structures are retained which increase side reactions with electrolytic solution and accelerate battery attenuation
Solution Approach 1:
The patent applies parameter changes by controlling the spheroidization process parameters (ball milling time, ball-to-graphite ratio, classification particle size) to transform flake graphite into spherical particles with reduced void structures. This changes the physical state and morphology parameters of the graphite, achieving both high capacity and improved cycle performance by eliminating the harmful void structures while preserving the beneficial graphite properties.
Solution Approach 2:
The patent creates a composite structure by coating the spherical graphite particles with a carbon-containing polymer coating layer. This composite material combines the high capacity of natural graphite with the protective and performance-enhancing properties of the polymer coating, resulting in improved cycle performance and reduced side reactions while maintaining the advantages of natural graphite.
2Reliability
If spherical natural graphite is coated with soft carbon to construct core-shell structure, then direct contact between electrolytic solution and natural graphite is reduced, but the first efficiency remains relatively low due to side reactions of the shell with electrolytic solution
Solution Approach 1:
The patent optimizes the coating parameters including the type and concentration of polymer monomers, crosslinking agent ratios, and coating process conditions to create a coating layer with controlled thickness and porosity. This optimized coating structure reduces side reactions while maintaining lithium ion transport efficiency, thereby improving both expansion properties and first efficiency simultaneously.
Solution Approach 2:
The patent creates a coating layer with spatially varying properties - the coating is designed to have different characteristics at different locations and depths. The crosslinked polymer network provides protective properties at the surface while maintaining controlled porosity and conductivity in the coating structure, allowing the coating to perform multiple functions: protecting the graphite core while enabling efficient lithium ion transport.
3Object-generated harmful factors
If conventional core-shell structure is used, then initial side reactions are reduced, but electrolytic solution continuously infiltrates and reacts with inner core natural graphite during cycle, causing violent volume expansion and cycle deterioration
Solution Approach 1:
The patent employs a flexible, crosslinked polymer coating film that can dynamically adapt to volume changes of the graphite core during lithium insertion and extraction. This flexible coating maintains structural integrity during cycling, preventing electrolyte infiltration while accommodating the natural expansion and contraction of the graphite particles, thereby extending battery life span without compromising cycle performance.
Solution Approach 2:
The patent applies beforehand cushioning by creating a pre-crosslinked protective coating layer before the graphite particles undergo volume expansion during cycling. This pre-formed protective shell acts as a buffer that prevents direct contact between the electrolyte and graphite surface during subsequent expansion events, cushioning against the harmful effects of continuous side reactions and extending the battery's operational life.
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 modified graphite negative electrode material enhances the first efficiency and cycle performance by reducing irreversible reactions and preventing electrolyte penetration, thereby extending the battery's service life and reducing production costs.
Implementation Method 1
the carbon coating layer includes an M element-containing modifying group, where M is at least one selected from the group consisting of B, N, and P
Implementation Method 2
performing a thermal polymerization treatment on a mixture containing graphite, a coating agent, and a modifying additive
Implementation Method 3
performing a carbonization treatment on the precursor under a protective atmosphere
Data Source
AI summary
The present disclosure relates to a graphite negative electrode material and a preparation method thereof and a lithium ion battery, wherein the graphite negative electrode material includes spherical graphite and a carbon coating layer, the carbon coating layer includes an M element-containing modifying group, where M is at least one selected from the group consisting of B, N, and P. The preparation method of a graphite negative electrode material includes performing a thermal polymerization treatment on a mixture containing spherical graphite, a coating agent, and a modifying additive, to obtain a precursor, wherein modifying additive includes an element M-containing compound, and M is at least one selected from the group consisting of B, N, and P; and performing a carbonization treatment on the precursor under a protective atmosphere, to obtain the graphite negative electrode material.