What is Natural Graphite Crushing for Anode Material

What is Natural Graphite and Why Use It for Batteries?

To understand graphite crushing, we first need to know what graphite is. If you’ve ever used a pencil, you’ve already encountered graphite – it’s the main component of pencil lead. This seemingly ordinary black material actually has an amazing microscopic structure.

Natural graphite has a very special structure, like a mille-feuille pastry – it’s layered one on top of another. Each layer is as thin as paper, with relatively loose connections between layers. This structure has a technical term called “layered structure,” but you can simply think of it as “pages stacked like a book.” It’s precisely this unique structure that gives graphite excellent electrical conductivity and chemical stability.

So why choose graphite for batteries? There are several important reasons:

First, graphite has excellent electrical conductivity, like a highway where electric current can flow rapidly. This superior conductivity comes from graphite’s special structure, where electrons can move freely between layers. Second, graphite is abundant and relatively inexpensive – Earth has large graphite reserves, unlike rare metals, making it ideal for industrial production. Third, graphite is chemically stable and doesn’t easily undergo unwanted chemical reactions, which is crucial for battery safety and longevity.

According to Mordor Intelligence’s 2025 market research report, while synthetic graphite dominates the global graphite anode market with approximately 73% market share in 2024, natural graphite still holds an important position, particularly in cost-sensitive applications. More notably, the natural graphite anode material market is projected to grow from $1.5 billion in 2024 to $3.5 billion by 2033, with a compound annual growth rate of 8.5%.

In batteries, graphite plays the role of a “parking lot” for lithium ions. When you charge your phone, lithium ions travel from the positive electrode to “park” in the graphite negative electrode; when you use your phone, lithium ions “drive” back from the graphite to the positive electrode. This back-and-forth process is the principle behind battery charging and discharging. Graphite’s layered structure provides ideal intercalation space for lithium ions, forming LiC6 compounds with a theoretical capacity of 372 mAh/g.

While natural and synthetic graphite have the same chemical composition, they differ significantly in performance and cost. Natural graphite is mined from underground and used after purification, with relatively lower costs but slightly inferior quality stability compared to synthetic graphite. Synthetic graphite is manufactured in factories through high-temperature graphitization processes, offering more stable quality and higher purity, but at higher production costs. These differences make each material advantageous in different application scenarios.

Why Do We Need to Crush Graphite?

Now you might ask: why is it necessary to crush graphite? Can’t we just use large chunks directly? The answer to this question involves understanding battery working principles and performance requirements.

This is like using salt in cooking. If you use large rock salt chunks, they won’t dissolve evenly in your dish – some parts might be too salty while others have no flavor. But if you grind the salt finely, it distributes evenly throughout the dish, making the entire meal taste good. The mechanism of graphite action in batteries follows the same principle.

Large graphite chunks face several fundamental problems in battery applications:

Space limitation issues: Modern lithium batteries pursue high energy density, with electrode layer thickness typically only tens to hundreds of micrometers. Large graphite chunks simply cannot be effectively arranged in such limited space – it’s like trying to park a large truck in a compact parking space.

Insufficient reaction contact area: Lithium ion intercalation and deintercalation reactions mainly occur on graphite particle surfaces. Large graphite chunks have very small specific surface areas, meaning lithium ions can’t find enough reaction sites. According to Bettersize research data, graphite with particle sizes around 20μm shows optimal energy storage performance within the 13-80μm range.

Transport kinetic limitations: During charging and discharging, lithium ions need to diffuse within graphite particles. The larger the particles, the longer the ion transport pathways, significantly affecting battery charging/discharging speed and power performance.

Therefore, the industry has established strict particle size control standards. According to NEI Corporation’s commercial specifications, high-quality natural graphite anode materials must meet the following particle size distribution requirements:

These seemingly tiny numbers contain precise scientific considerations. One micrometer equals 0.001 millimeters, meaning these graphite powders are much finer than human hair (approximately 70 micrometers in diameter)!

Beyond size control, graphite particle shape is equally critical. We want to preserve graphite’s natural flaky structure as much as possible during crushing, like thin fish scales. This flaky morphology helps form good conductive networks and provides more intercalation channels for lithium ions. Research shows that graphite particles with circularity between 0.862-0.896 have better packing performance.

Through precise particle size control, optimized natural graphite anode materials can ultimately achieve satisfactory electrochemical performance. MSE Supplies’ product data shows that high-quality natural graphite can achieve >360 mAh/g first discharge capacity and 95% first discharge efficiency.

How to Crush Graphite? Common Equipment Introduction

After understanding why graphite needs to be crushed, let’s examine how this goal is specifically achieved. Graphite crushing is a multi-stage process, like cooking a complex dish that requires multiple steps – each stage has its specific purpose and requirements.

Stage 1: Coarse Crushing (Like Cracking Walnuts)

The first step in the entire crushing process is coarse crushing, aimed at breaking fist-sized graphite ore into peanut or pea-sized chunks. This stage typically uses jaw crushers.

Jaw crushers work on a simple yet effective principle: they consist of a fixed jaw plate and a reciprocating movable jaw plate, like a giant mouth chewing food. When graphite chunks enter the crushing chamber between the two jaw plates, the movable jaw plate periodically approaches the fixed jaw plate, crushing graphite blocks through compression and shearing action. According to RETSCH’s technical parameters, laboratory-grade jaw crushers typically operate at speeds between 550-950 rpm to balance crushing effectiveness and equipment lifespan.

Notably, jaw crusher reduction ratios (ratio of feed size to discharge size) can typically reach 8:1, meaning if the feed is 80mm graphite chunks, the discharge can reach around 10mm. For large industrial applications, the largest jaw crushers can reach 1600×2514mm specifications with 250-400kW motors.

Stage 2: Intermediate Fine Crushing (Like Grinding Soy Milk)

After coarse crushing, graphite chunks have been broken down to several millimeters to centimeters, but this is still far from battery-grade requirements. The next stage requires intermediate fine crushing, where ball mills become the main equipment.

A ball mill is a cylindrical device filled with steel balls, ceramic balls, or other grinding media. When the cylinder rotates around a horizontal axis, the grinding media, under the action of centrifugal and gravitational forces, impacts, grinds, and shears graphite particles. This process is like ancient stone grinding for soy milk, but with greatly improved efficiency and precision.

The key to ball milling lies in controlling the balance of multiple parameters. According to Ball Mill Classifier System process description, the ball mill feeds material through a controllable feeding device, where grinding media repeatedly impacts and grinds the material using kinetic energy obtained from mill rotation. Ground material is discharged through the mill tail into a suction tank, then transported to the classifier for classification under negative pressure.

Stage 3: Ultra-Fine Grinding (Particle Collision via Airflow)

To obtain ultra-fine graphite powder meeting battery requirements, traditional mechanical crushing can no longer meet demands, requiring more precise air jet milling technology.

Air jet milling works on a clever principle: it uses high-pressure gas (usually compressed air or inert gas) to generate high-speed airflow, accelerating graphite particles to very high speeds, then allowing these high-speed particles to collide with each other in the airflow for further grinding. The biggest advantage of this method is avoiding contamination from metal wear in traditional mechanical grinding.

CMS company’s specially designed graphite micronizing grinding systems typically operate at 150-400 horsepower, capable of producing standard graphite powder products with particle sizes down to ±5μm.

Final Stage: Precision Classification (Separating Good from Bad)

After crushing is complete, the resulting graphite powder inevitably contains particles of various sizes, requiring classification equipment to separate them by particle size.

Modern classification equipment primarily uses centrifugal force and airflow principles. In air classifiers, particles experience different centrifugal forces based on their size and mass under the action of high-speed rotating classifier wheels. Fine particles are easily carried away by airflow, while coarse particles are thrown out due to greater inertia and discharged from the classifier bottom for re-crushing.

This process can achieve very precise particle size cuts, ensuring final products strictly meet battery manufacturing requirements.

What Should Be Monitored During Crushing?

While the basic principles of graphite crushing appear relatively simple, achieving stable industrial production requires careful control of many critical factors. Just like an experienced chef needs to master timing, seasoning, and temperature while cooking, graphite crushing processes also require precise control of multiple parameters.

Precise Particle Size Distribution Control

Particle size distribution control is the core of the entire crushing process – this isn’t simply grinding graphite finer, but achieving precise size distribution. According to Bettersize’s in-depth research, the mixing ratio of different particle size graphite has a decisive impact on final battery performance.

Experimental data shows that when the proportion of fine particles (Sample A) increases in the mixture, D50 values decrease while tapped density increases. This occurs because small particles can fill voids between large particles, improving packing density. However, when fine powder proportion becomes too high, after voids between large particles are completely filled, only small voids between small particles remain, actually causing tapped density to decrease.

Further research indicates that ideal graphite anode material tapped density should exceed 1 g/mL. This seemingly simple number represents comprehensive optimization of particle size distribution, shape characteristics, and packing arrangements.

Importance of Temperature Control

Temperature control during crushing is often overlooked but extremely important. While graphite has good thermal stability, mechanical energy generated during crushing converts to heat energy. Poor temperature control can cause the following problems:

First is oxidation. Graphite easily oxidizes at high temperatures in oxygen-rich environments, producing CO2 or CO, which not only reduces graphite purity but also destroys its layered structure. Second is structural changes – excessive temperatures may cause microscopic structural changes in the graphite lattice, affecting electrochemical performance. Third is impurity introduction – high temperatures may promote reactions between graphite and equipment materials, introducing unwanted impurity elements.

Therefore, modern graphite crushing equipment typically includes cooling systems using circulating cooling water or cold air to control working temperatures, ensuring the entire process occurs within suitable temperature ranges.

Strict Purity Maintenance Requirements

Graphite anode materials have extremely strict purity requirements. Commercial-grade natural graphite anode materials typically require purity above 99%, with strict limits on specific impurity elements, such as iron content must be controlled below 50ppm.

To meet such purity requirements, crushing equipment material selection and process design require special attention. Key equipment components must be manufactured from wear-resistant, low-contamination materials like high-purity ceramics or special alloys. Additionally, the entire crushing system needs to operate in sealed environments to prevent external contaminant entry.

Quality Testing and Process Optimization

Quality control is the key link ensuring product stability. Modern graphite processing plants typically have comprehensive online testing systems that can monitor key product indicators in real-time.

Particle size analysis is one of the most important testing items. Using laser diffraction particle size analyzers like Bettersize’s Bettersizer 2600, D10, D50, D90, and other key particle size indicators can be precisely measured. This equipment, based on Mie theory, can accurately determine particle size distribution after 30 seconds of ultrasonic dispersion.

Morphology analysis is equally important. Through scanning electron microscope (SEM) observation, we can evaluate whether graphite particles maintain ideal flaky structures. Research shows that graphite particles with circularity between 0.862-0.896 have optimal electrochemical performance.

Electrochemical performance testing is the ultimate verification method. By making test batteries and conducting charge-discharge testing, we can directly evaluate actual graphite material performance. Optimized natural graphite materials can achieve 420.4 mAh/g reversible capacity and maintain 94.5% capacity retention after 500 cycles.

Common Problem Identification and Solutions

In actual production, experienced process engineers can quickly identify and solve various problems:

Over-crushing is one of the most common issues. When graphite is ground too finely, specific surface area increases significantly. While this can improve reaction activity, it also increases the possibility of side reactions, affecting battery first-cycle efficiency and cycling stability. The solution is optimizing crushing parameters, such as reducing grinding speed, shortening grinding time, or adjusting grinding media ratios.

Uneven particle size distribution is another common problem. When products contain too many both coarse and fine particles simultaneously, it affects electrode uniformity and performance consistency. This usually requires improved classification processes, such as multi-stage classification or adjusting classifier operating parameters.

Destruction of flaky structure seriously affects graphite’s conductive performance. When shear forces are too high during crushing, graphite’s natural layers may be destroyed, forming irregular fragments. Preventing this problem requires selecting appropriate crushing methods, controlling impact intensity, and optimizing process parameters.