The lithium-rich manganese-based (xLi[Li1/3-Mn2/3]O2; (1–x) LiMO2, M is a transition metal 0≤x≤1, and the structure is similar to LiCoO2) has a high discharge specific capacity. It is about twice the actual capacity of the cathode material currently used, and is therefore widely studied for lithium battery materials. In addition, since the material contains a large amount of Mn element, it is more environmentally safe and cheaper than LiCoO2 and the ternary material Li[Ni1/3Mn1/3Co1/3]O2. Therefore, xLi[Li1/3-Mn2/3]O2; (1–x) LiMO2 material is considered by many scholars as the ideal material for the next generation of lithium ion battery cathode materials.
At present, the co-precipitation method is mainly used to prepare lithium-rich manganese-based materials, and some researchers use sol-gel method, solid phase method, combustion method, hydrothermal method and other processes to prepare, but the obtained material properties are not as stable as the co-precipitation method.
Although this material has a high specific capacity, there are still several problems in its practical application:
1）The irreversible capacity of the first cycle is up to 40 ~ 100mAh/g;
2）Poor rate capability, 1C capacity under 200mAh/g;
3）High charging voltage causes electrolyte decomposition, making the cycling performance less than ideal.
4）And security issues in use.
By means of metal oxide coating, composite with other anode materials, surface treatment, special structure construction, low upper limit voltage precharge and discharge treatment and other measures, the above problems of lithium-manganese rich materials can be well solved.
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As an important component of lithium ion battery, negative electrode material has a direct impact on the energy density, cycle life and safety performance of the battery and other key indicators. Silicon is the anode material of lithium ion battery with the highest specific capacity (4200mAh/g) known at present. However, due to its over 300% volume effect, The silicon electrode material will pulverize during charging and discharging, and flake off from the collector fluid. caused the loss of electrical contact between active matter and active matter, the active matter, and the stream of fluid, and forming a new layer of solid electrolyte layers, which ultimately leads to the deterioration of electrochemical properties. In order to solve this problem, researchers have made a lot of explorations and attempts, among which silicon-carbon composites are very promising materials.
Carbon material, as the cathode material of lithium ion battery, has a small volume change in the charging and discharging process, and has good cycling stability and excellent conductivity, so it is often used to compound with silicon. Among the carbon-silicon composite cathode materials, according to the types of carbon materials, they can be divided into two categories: The combination of silicon and traditional carbon materials and silicon and new materials, The traditional carbon materials mainly include graphite, intermediate phase microspheres, carbon black and amorphous carbon. New carbon materials mainly include carbon nanotubes, carbon nanowires, carbon gels and graphene. Silicon carbon composite is adopted to restrain and buffer the volume expansion of silicon active center by utilizing the porous effect of carbon material, prevent particle agglomeration, prevent electrolyte from penetrating into the center, and maintain the stability of interface and SEI film.
Many enterprises around the world have begun to work on this new type of cathode material, silicon carbon new cathode material as the direction of future product research and development.
With the pursuit of energy density of battery, the ternary anode materials (generally referred to as layered lithium NCM nickel cobalt manganate materials) have attracted more and more attention. The ternary anode material has the advantages of high specific capacity, good recycling performance and low cost. By increasing the voltage of the battery and the content of nickel in the material, the energy density of the ternary positive electrode material can be effectively improved.
Theoretically, the ternary material itself has the advantage of high voltage. The standard test voltage of the ternary positive electrode material is 4.35v, under which the ordinary ternary material can show excellent cyclic performance. The charging voltage is increased to 4.5v, and the capacity of the symmetrical materials (333 and 442) can reach 190, which is also good for circulation, while 532 is not so good. When the charge reaches 4.6v, the circulability of the ternary material begins to decline, and the flatness becomes more and more serious. At present, it is difficult to find matching electrolyte with high voltage anode material.
Another way to increase the energy density of ternary materials is to increase the content of nickel. In general, high nickel ternary anode material refers to the molar fraction of nickel greater than 0.6. Such ternary materials have the characteristics of high specific capacity and low cost, but their capacity retention rate is low and their thermal stability is poor. The properties of this material can be effectively improved by improving the preparation process. The micro-nano size and morphology have a great influence on the properties of high nickel ternary anode materials. Therefore, most of the preparation methods adopted at present focus on uniform dispersion, and obtain spherical particles with small size and large specific surface area.
In many preparation methods, coprecipitation combined with high temperature solid method is the main method. The coprecipitation method was first used. The precursors with uniform mixing of raw materials and uniform grain size were obtained, and then the ternary materials with regular surface morphology and easy to control process were obtained after being calcined at high temperature. This is also the main method used in industrial production at present. Compared with co-precipitation, the spray drying process is simpler and the preparation rate is faster. The disadvantages of high nickel ternary anode materials such as cationic mixing and phase transition during charging and discharging can be effectively improved by doping modification and coating modification. While inhibiting the occurrence and stable structure of side reactions, improving the conductivity, circulation performance, multiplier performance, storage performance and high temperature and high pressure performance will remain the research focus.
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The electrolyte of the current commercialized lithium-ion battery is liquid, so it is also called liquid lithium-ion battery. In simple terms, all- solid-state lithium-ion battery refers to the battery structure in which all components are in solid form, replacing the traditional lithium ion battery’s liquid electrolyte and diaphragm with solid electrolyte.
Compared with liquid lithium-ion batteries, all-solid electrolyte has the following advantages:
1. High safety and excellent thermal stability, can be long-term work under the condition of 60-120 ℃;
2. Wide electrochemical window, can reach above 5V, can match high voltage material;
3. Only lithium ions and do not conduct electrons;
4. The cooling system is simple and has high energy density.
5. It can be applied in the field of ultra-thin flexible battery.
But the disadvantages are also obvious:
1. The ionic conductivity per unit area is low and the specific power is poor at room temperature. The cost is extremely high;
2. Industrial production of large-capacity batteries is difficult.
The performance of electrolyte material largely determines the power density, cycle stability, safety, high and low temperature performance and service life of all solid lithium ion batteries. Solid electrolytes can be divided into polymer electrolytes (usually based on a mixture of PEO and lithium Salts LiTFSI) and inorganic electrolytes (such as oxides and sulfides). All-solid-state battery technology is widely recognized as the next generation of innovative battery technology, which is believed to be more and more mature in the near future. All these problems can be solved.
High reactivity exists between electrolyte and positive and negative electrodes, especially at high temperature. To improve the safety of battery, improving the safety of electrolyte is one of the effective methods. The potential safety risks of electrolyte can be effectively solved by adding functional additives, using new lithium salts and using new solvent. According to the different functions of additives, they can be divided into the following: safety protection additives, film forming additives, protection positive electrode additives, stable lithium salt additives, lithium precipitating additives, fluid anti-corrosion additives, and enhancement of infiltration additives.
In order to improve the performance of commercial lithium salts, the researchers have replaced them with atoms and obtained many derivatives. Among them, compounds obtained by substituting atoms with perfluoroalkyl groups have many advantages, such as high flash point, approximate electrical conductivity and enhanced water resistance. In addition, the anionic lithium salts obtained by chelating boron atom with oxygen ligand have high thermal stability.
In terms of solvents, many researchers have proposed a series of new organic solvents, such as carboxylate and organic ether organic solvents. In addition, ionic liquid also has a class of electrolyte with high safety, but relatively commonly used carbonated ester electrolyte, ionic liquid has high viscosity, low conductivity and self-diffusion coefficient of ions, and there is still much work to be done in practical application.
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With the continuous development of the three-element battery technology market, the shortage of Lithium, Cobalt and other resources is brought. In particular, the small supply flexibility of cobalt itself, and if mainstream manufacturers choose the route of NCM622, it will lead to a serious shortage of cobalt supply, which will force the new energy vehicle enterprises to develop towards the route of NCM811.
Since last year, the requirement for energy density of new energy vehicle power batteries has been increasing due to the increasing demand for mileage. Especially in China, the subsidy standard is directly linked to energy density, and the path of ternary material has become the common choice of mainstream battery enterprises. At the same time, with the price rise caused by the shortage of raw materials such as Cobalt metal, high Nickel ternary gradually becomes the development trend of power battery.
According to the consumption proportion of Nickel, Cobalt and Manganese, the ternary battery can be divided into type 111, type 523, type 622 and type 811. In 2017, the power battery mainly consists of type 111 and 523, and it is estimated that type 622 and 811 will become the new trend this year and in the future. “At the moment, the transition from the type 523 to the type 622 is not significant, and the transition will be direct to the type 811.” The institute said.
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Driven by the core goal of high energy density and high battery life, the penetration rate of pouch battery in the new energy vehicle market is gradually accelerating. It is estimated that 13.4 billion yuan of special equipment needs of pouch battery will be derived by 2020 based on the expansion demand of various battery manufacturers.
As the core technology of pouch battery manufacturing, the lamination machine market has attracted many equipment manufacturers to seize the layout. Traditional brands with deep industry accumulation are accelerating the process improvement, further improving the efficiency of lamination process and the degree of integration automation.
At the same time, large enterprises, mainly winding, are also accelerating the layout of lamination equipment field, and relevant equipment has been mass produced.
It is worth mentioning that some power battery manufacturers are looking for soft package winding solutions in the short term, as the current lamination process still has shortcomings in efficiency and integrated automation. With the maturity of winding technology solutions in the field of power pack batteries, it is expected that the application of winding technology in power pack market will increase in the next two years.
In addition, enterprises of drying equipment and chemical capacity equipment in the middle and rear sections are actively following up and improving the automatic equipment suitable for the manufacturing process of pouch battery, in the hope of gaining a share in the market of pouch battery by virtue of innovative solutions.
According to China’s goal of achieving power battery energy density of 300Wh/kg by 2020, it is inevitable that the material combination form of NCM 811/nca with silicon-carbon anode is adopted.
In the first half of this year, the application of NCM 811/NCA materials in the power battery market gradually increased. As the core equipment technology of high nickel anode materials involves upgrading and adjustment, the production process control is more strict than that of conventional anode materials, which drives the technical upgrade of material equipment manufacturers. In general, the core equipment that high nickel anode materials enterprises need to upgrade and replace mainly includes: furnace, drying equipment, crushing equipment, grinding machine, dehumidification equipment, etc.
As for the silicon carbon negative electrode, due to its low coulomb efficiency for the first time, the demand for lithium anode automation equipment has been derived. The irreversible capacity loss of the cathode during the first charging process can be supplemented to achieve the purpose of improving the first coulomb efficiency (energy density can be increased) and the battery capacity (range can be increased). It can be predicted that, with the market volume of silicon carbon power battery, the market demand of lithium equipment will be further driven.
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Based on the progress of technology, China’s lithium electrical equipment has been greatly enhanced in the automation level. Power battery enterprises’ requirements on product performance, such as production efficiency, consistency and reliability, etc., are also gradually increasing. In the first half of this year, integrated equipment showed a trend of acceleration.
In the field of front-section equipment, it mainly includes the combination of “laser cutting machine + battery winding machine“, “roller press machine + cutting machine”, “battery coating machine + roller press machine + cutting machine” and other types of equipment integration.
Through the upgrade of equipment integration, it can play an important role in the improvement of manufacturing efficiency, product consistency and stability, production cost reduction, energy saving and consumption reduction.
In the field of back-end equipment, the integration of back-end equipment system represented by “Chemical composition and battery capacity analysis + warehousing logistics” is represented. The post-segment system integration market strategy of “chemical composition capacity + storage logistics” is the latest trend, and some of them can even provide customized solutions of ” Chemical composition and battery capacity analysis + storage logistics + module PACK”.
Equipment integration will be an important direction for the industry. However, only by focusing on the single equipment technology, can we have the opportunity to do segment integration and whole line integration, and can we have the opportunity to provide customers with the new mode of intelligent digital factory solution.
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1. The blocking current of the diaphragm plays a key role in preventing the potential safety hazard of the battery. The diaphragm is a protective band in the case of short circuit. When the diaphragm is at about 130 degrees, the resistance will increase abruptly, thus preventing the lithium ions from transferring between them. When the diaphragm is above 130 degrees, the protective band is safer.
Improper battery use (such as short circuit, overcharge, etc.) which increases the temperature of the battery may increase the resistance of the diaphragm by 2 to 3 orders of magnitude. Diaphragm requires not only at about 130 ℃ can current interrupt, and require it at a higher temperature can maintain its soften integrity. The softening integrity of the high temperature is also important for the safety of the battery under long time overcharge or long time exposure to high temperature.
To prevent an internal short circuit, the diaphragm will not allow any dendrite to penetrate. If the failure is not instantaneous when the battery shortens internally, the diaphragm is the only device that can prevent the battery’s heat from getting out of control. However, if the heating rate is too fast and the fault occurs in an instant, the diaphragm cannot act as a current breaker. If the heating rate is not high, the current blocking function of the diaphragm can control the heating rate and further prevent the battery heat from getting out of control.
he effect of the diaphragm is simply to delay an internal short circuit and cause the heat to run out of control. The diaphragm with high temperature softening integrity and current blocking function shall pass the internal short circuit test. Thin membranes used in high-capacity batteries must exhibit properties similar to thicker membranes. The mechanical strength loss of the diaphragm needs to be balanced by the battery design, and the transverse and longitudinal properties of the diaphragm must be consistent to ensure the safety of the battery in abnormal use.
2.Nick of battery steel shell: after the core is put into the shell, the battery shall be grooved to make the mark on the battery shell. When the fault occurs, the gas expands rapidly, breaks through the notch, and is released, protecting the battery from explosion.
Division our strong technical team can provide you with a full set of solutions of the lithium-ion battery, TOB new energy limited can provide a lithium-ion battery equipment, materials, lithium-ion battery project planning, manufacturing technology, plant program design and management system. We have excellent battery design capabilities and can design more professional and safer lithium batteries for you.