ThePastandPresentLivesofLithiumCobalt

Cobalt is a hard metal with a steel gray and metallic luster. Cobalt (Co) has an atomic number of 27 and is located in the eighth group of the periodic table. Its atomic weight is 58.93. Its main physical and chemical parameters are similar to those of iron and nickel, and it belongs to the iron group element. Cobalt is a magnetic hard metal with high melting point and good stability. It is an important raw material for manufacturing heat-resistant alloys, hard alloys, anti-corrosion alloys, magnetic alloys, and various cobalt salts, widely used in aviation, aerospace, electrical appliances, mechanical manufacturing, chemical, and ceramic industries. Therefore, it is an important strategic material.

The cobalt industry chain mainly consists of upstream cobalt ore mining, beneficiation, midstream smelting and processing, and downstream terminal applications. In terms of downstream consumption, although cobalt is widely used in fields such as high-temperature alloys, hard alloys, and magnetic materials, about 60% of cobalt is used in the battery industry.

Upstream cobalt deposits: Individual cobalt deposits are generally divided into three types: arsenic cobalt deposits, sulfide cobalt deposits, and cobalt earth deposits. Except for individual deposits, cobalt is widely dispersed in skarn type iron ore, vanadium titanium magnetite, hydrothermal polymetallic ore, various types of copper ore, sedimentary cobalt manganese ore, sulfide copper nickel ore, silicate nickel ore and other deposits. Although its grade is low, its scale is often large, and it is the main source of cobalt extraction. Cobalt resources in China are mainly distributed in Gansu, Shandong, Yunnan, Qinghai, Hebei, and Shanxi.

Mid stream smelting: A major feature of mid stream smelting of cobalt is the abundance of products and the existence of multiple processing chains, such as "cobalt concentrate cobalt sulfate cobalt tetroxide", "cobalt concentrate cobalt chloride cobalt tetroxide", "cobalt concentrate cobalt chloride cobalt carbonate cobalt tetroxide", "cobalt concentrate cobalt chloride cobalt carbonate cobalt powder", and "cobalt concentrate cobalt chloride cobalt oxalate cobalt powder". Among these cobalt products, cobalt sulfate and cobalt chloride are important intermediates. Among them, cobalt sulfate can also be directly applied to the production of lithium cobalt oxide batteries used in 3C production. Cobalt tetroxide is an important downstream product mainly used as a positive electrode material and magnetic material for lithium-ion batteries, and for lithium-ion power batteries in new energy vehicles.

钴产品工艺流程图

Battery grade cobalt oxide is mainly used in the production of lithium cobalt oxide as the positive electrode material for lithium-ion batteries. Its performance has a significant impact on the performance of lithium cobalt oxide material, and subsequently on the charging and discharging capacity, service life, and other aspects of the battery. Cobalt oxide used in batteries not only has strict chemical composition requirements, but also has special requirements for physical indicators, especially particle size composition and distribution, and loose density. Taking the synthesis process of preparing precursor by carbonate precipitation and preparing cobalt oxide after oxidation and calcination as an example:

 

 

The experimental results show that different amounts of cobalt and carbonate ratios, the selection of crystal form changing agents, temperature, reaction time, and cobalt solution concentration can all affect the particle size and morphology of cobalt carbonate. In addition, existing research suggests that the morphology of cobalt salt precursor particles determines the morphology of cobalt powder particles, and the latter has a great dependence and inheritance on the former.

 

Figure 1: Surface morphology of cobalt carbonate at low magnification (left) and high magnification (right)

 

Scanning electron microscopy, as a tool for material characterization, can be used to observe the particle size and surface characteristics of cobalt carbonate particles effectively; As shown in Figure 1, the images were taken using Thermo Apreo2 field emission scanning electron microscopy.

Apreo 2 has strong low-voltage ultra-high resolution performance in the industry, with a resolution of up to 0.8nm (1kV), which can present the true morphology contrast of material surfaces. At the same time, it combines high-quality imaging and multifunctional analysis performance, making it an ideal analysis platform essential for scientific research and production quality control. Using the ETD probe inside the Apreo 2 warehouse, calculate the particle size of cobalt carbonate and obtain its spherical shape; At the same time, under low voltage of 800V, an irregular stepped shape was observed on the surface of cobalt carbonate using the high-resolution morphology detector T2 inside the mirror tube.

 After high-temperature calcination and drying, battery grade cobalt oxide raw materials can be obtained. Similarly, using Apreo 2 for observation, it was found that the particle size of cobalt oxide is similar to that of cobalt carbonate, as shown in Figure 2-a; Further magnification reveals an irregular distribution with a smooth surface, as shown in Figure 2-b; Three detectors can be placed simultaneously in the Apreo 2 mirror tube, and the sample surface can be observed using the composition detector T1 and morphology detector T2 respectively, as shown in Figure 2-c and Figure 2-d, to obtain the distribution of cobalt oxide composition and the surface characteristics of primary particles.

Figure 2: Morphological characteristics of cobalt oxide under different detections

   

Cobalt oxide, as an important raw material, is mainly used to synthesize lithium cobalt oxide as a positive electrode material for batteries. Lithium cobalt oxide (LiCoO2) is an early developed and widely used cathode material, which has the advantages of low production process difficulty, high working voltage, stable release current, and long cycle life. However, under high voltage, the internal stress of LiCoO2 lattice increases, causing structural collapse and severe interface side reactions, which can lead to irreversible deterioration of battery performance. Therefore, it is necessary to modify lithium cobalt oxide materials to improve their electrochemical performance.

Surface coating modification is a modification method that involves coating a layer of other materials on the surface to suppress defects on the material surface, improve the stability of the material structure, and improve the structural and battery performance of lithium cobalt oxide materials under high voltage due to defects caused by phase transition. Most types of oxides, various conductive graphite materials, phosphates and titanates in inorganic salts are extensively studied coating materials.

Observing the surface coating of lithium cobalt oxide positive electrode is an important method for analyzing the performance of modified materials. By utilizing the excellent performance of Apreo 2 at low voltage, combined with a highly sensitive T1 detector, the distribution of the coating on the particle surface can be clearly observed, as shown in Figure 3; The T2 detector is mainly used to observe the surface morphology details of particles.。

Figure 3: Distribution of Lithium Cobalt Composition (Left) and Morphological Characteristics (Right)

 

Battery materials are one of the main consumer materials of cobalt, and the consumption of metallic cobalt in the Chinese battery industry accounts for about 60% of the total consumption of metallic cobalt in China. In the production of battery materials, the main materials with a large amount of cobalt are lithium-ion battery materials, cathode materials, lithium cobalt oxide, and ternary materials. Other uses are used in hydrogen storage alloys, spherical nickel, and so on. Although lithium cobalt oxide poses a risk of being replaced as a positive electrode material in the battery industry, the demand for lithium batteries driven by new energy vehicles and the use of ternary materials will continue to increase, leading to a continued increase in demand for cobalt in the lithium-ion battery industry.

References

1. Introduction to the Cobalt Industry Chain - Xingye Economic Research and Consulting Co., Ltd., 2017

2. Liu Cheng. Development of battery grade cobalt oxide [J]. Non ferrous Metals, 2002

3. Dong Guiyou; Han Houkun; Wang Chao'an; Zhang Zhiping; Qu Peng. Study on the Effect of Particle Size of Cobalt Carbonate Raw Materials on the Morphology of Cobalt Powder [J]. Cemented Carbides, 2021

4. Liu Qiaoyun; Qi Xiuxiu; Hao Weiqiang. Research progress on the modification of lithium cobalt oxide as a positive electrode material for lithium batteries [J]. Power Supply Technology, 2022

5. Xu Aidong and Yang Xiaofei. Current Situation of the Global Cobalt Market [J]. Report of the China Cobalt Industry Branch, 2010

6. The global cobalt market has launched a "sweeping" model [J]. Modern Mining, 2018

7. Panorama of Cobalt Industry Chain - Powder Network, 2021