Dissection and test of lithium batteries

Lithium-ion battery is a new generation of green high-energy battery with excellent performance, which has become one of the key points of high-tech development. With the rapid development of new energy vehicles, lithium battery materials will fully benefit. The lithium battery has superior performance, wide application and broad prospects. Lithium batteries have high energy density, long cycle life, low self-discharge rate, no memory effect and green environmental protection. China's new energy vehicles will develop rapidly during the 13th Five-Year Plan period, which will drive the rapid growth of lithium battery materials.

Jinjian detection can provide SEM test of lithium battery electrode material, particle size measurement, argon ion polishing sample preparation of lithium battery material, provide a good R&D test platform for lithium battery electrode material industry, promote the development of lithium battery industry, and respond the state supports the call for new energy.

Lithium-ion batteries have the following characteristics: high voltage, high capacity, low consumption, no memory effect, no pollution, small volume, small internal resistance, less self-discharge, and more cycles. Due to the above characteristics, lithium-ion batteries have been applied to many civil and military fields such as mobile phones, notebook computers, video cameras, and digital cameras.

The main constituent materials of the lithium ion battery include an electrolyte, a separator, a positive and a negative material, and the like. The positive electrode material occupies a large proportion (the mass ratio of the positive and negative materials is 3:1 to 4:1), because the performance of the positive electrode material directly affects the performance of the lithium ion battery, and the cost directly determines the battery cost. In the middle of the positive and negative electrodes is the battery electrolyte and diaphragm.

Common lithium battery cathode materials: lithium cobaltate, lithium manganate, lithium iron phosphate, lithium nickelate, ternary, lithium-rich phase, lithium iron silicate, lithium manganese phosphate, lithium iron sulphate.

Common lithium battery anode materials: Among the four major materials of lithium batteries, the technology of anode materials is relatively mature. Lithium battery anode materials are generally divided into two categories: carbon materials and non-carbon materials. Among them, carbon materials are divided into graphite and amorphous carbon, such as natural graphite, artificial graphite, mesophase carbon microspheres, soft carbon (such as coke) and some hard carbon; other non-carbon anode materials are nitride, silicon-based materials, Tin-based materials, titanium-based materials, alloy materials, and the like.

Case 1: Cathode material - SEM test:

Case 2: Scanning electron microscopy surface morphology of lithium iron phosphate:

SEM effect diagram of the pole piece of lithium battery material coated with lithium iron phosphate after argon ion polishing:

Case 3: Identification of argon ion cross-section polishing anatomical lithium battery material pole piece artificial graphite and natural graphite (graphite inspection)

In the past 20 years of development of lithium-ion batteries, theoretical and academic circles have not conducted in-depth analysis of the identification methods of carbon (graphite) anode materials for lithium-ion batteries: natural graphite and artificial graphite anode materials, and have clearly defined the methods of scientific identification and determination. The industry has experienced the unclear boundary between natural graphite and artificial graphite anode materials, and the mixed market has greatly affected the rational and effective use of materials.

The natural graphite anode material is made of natural scaly crystal graphite, which is obtained by pulverization, spheroidization, classification, purification, surface treatment, etc., and its high crystallinity is naturally formed. The artificial graphite anode material is obtained by calcining easily graphitizable carbon such as petroleum coke, needle coke, pitch coke, etc. at a certain temperature, followed by pulverization, classification, high temperature graphitization, and high crystallinity is formed by high temperature graphitization. of. It is precisely because of the essential difference between the two materials in the raw materials and preparation process that there are significant differences in microscopic morphology, crystal structure, electrochemical performance and processing properties. In order to unify standards, scientifically distinguish and correctly determine natural and artificial graphite anode materials, it will be explored, repeatedly verified and practical scientific methods after years of research:

1. Differences in microscopic morphology between natural graphite and artificial graphite anode materials - SEM profile analysis

2. Crystal structure difference between natural graphite and artificial graphite anode materials - X-ray diffraction method

3. Difference in the degree of disorder (ID/IG) between natural graphite and artificial graphite anode materials - Raman spectroscopy

Comparison of natural graphite and artificial graphite:

At present, the negative electrode materials are mainly composed of natural graphite and artificial graphite, and the two kinds of graphite have advantages and disadvantages. The natural graphite has a high capacity, simple process and low price, but the liquid absorption and circulation performance are poor; the artificial graphite process is more complicated and expensive, but the cycle and safety performance are better. Through the technical improvement of various means, both graphite anode materials can be 'strengthened and avoided short', but for the moment, artificial graphite has certain advantages in power batteries.

Differences in Microscopic Morphology of Natural Graphite and Artificial Graphite Anode Materials——SEM Profile Analysis

Customer service: graphite material purchaser, graphite material supplier, lithium battery manufacturer, lithium battery.

In the microstructure, natural graphite is a layered structure, and its SEM cross-section retains the layered structure of flake graphite, and there are a large number of voids between the flake structures; while the artificial graphite anode material is coke and mesophase in high temperature graphite. During the process, the crystal structure is rearranged according to the ABAB structure, and the polymerization shrinks, and the inside is dense and seamless.

(1) SEM sectional view: The SEM cross-section of the natural graphite negative electrode material which has not been subjected to high-temperature graphitization has voids between the sheet-like structures, and the SEM sectional view of the artificial graphite negative electrode material is dense and seamless.

(2) Comparison of natural graphite anode materials and artificial graphite negative materials treated by high temperature (2400-3300 °C) graphitization (different natural and artificial, composite type for description)

SEM profile: The SEM profile of the pure natural graphite anode material treated by high temperature graphitization has voids between the sheet structures. The SEM profile of the pure artificial graphite anode material is dense and seamless, and the composite graphite is treated by high temperature graphitization. In the SEM cross-sectional view of the negative electrode material, the gap between the natural graphite sheet-like structure and the dense structure of the artificial graphite coexist.

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