Introduces several kinds of lithium ion battery with the forefront of technology

1, all solid state lithium ion battery

Currently commercial lithium ion battery electrolytes are liquid and are therefore also referred to as liquid lithium ion batteries. In simple terms, an all-solid-state lithium-ion battery means that all components in the battery structure are in solid form, replacing the liquid electrolyte and diaphragm of a conventional lithium-ion battery with a solid electrolyte.

Compared with liquid lithium ion battery, all solid state electrolyte has the following advantages: high security/excellent thermal stability, long-term work under the condition of 60-120 ℃;Wide electrochemical window, can reach more than 5 v, can match the high voltage materials; Conducting lithium ion conduction electrons not only; The cooling system is simple, high energy density; Can be used in the field of thin flexible batteries. But the shortcomings are obvious: the unit area of ionic conductivity is low, the power worse than normal temperature; Cost is very expensive; Industrialized production of big capacity battery.

Electrolyte material performance to a large extent determines the all solid state lithium ion battery power density, cycle stability, safety performance, high and low temperature performance and service life. Solid electrolyte can be divided into class polymer electrolytes (generally is a mixture of PEO and lithium salt LITFSI electrolyte base material) and inorganic electrolytes, such as the oxide and sulfide) two kinds big. All solid state battery technology is generally accepted that the next generation of battery technology focus on the development of innovation, believe that technology is more and more mature in the near future, these problems can be solved.

2, high energy density batteries ternary material

As people pursuit of the battery energy density, the ternary cathode material more and more get the attention of people. Ternary cathode material with high specific capacity and good cycle performance, low cost advantages, generally refers to the layer structure of nickel cobalt manganese acid lithium materials. By improving the battery voltage and nickel element content in the material, can effectively improve the energy density of ternary cathode material.

In theory, the ternary material itself has the advantage of high voltage: the standard test voltage of the ternary cathode material is 4.35V, and the ordinary ternary material can exhibit good cycle performance under this voltage; The voltage is increased to 4.5V, the symmetrical materials (333 and 442) can have a capacity of 190, the cycle is also good, 532 is less cyclic; when charged to 4.6V, the cyclization of the ternary material begins to decrease, flatulence The phenomenon is getting worse. At present, the factor that restricts the practical use of high-voltage ternary cathode materials is that it is difficult to find a matching high-voltage electrolyte.

Another way to increase the energy density of ternary materials is to increase the content of nickel in the material. Generally, a high-nickel ternary cathode material means that the molar fraction of nickel in the material is greater than 0.6, and such a ternary material has a high ratio. Capacity and low cost, but its capacity retention rate is low and thermal stability is poor. The performance of this material can be effectively improved by the improvement of the preparation process. Micro-nano size and morphology have great influence on the performance of high-nickel ternary cathode materials. Therefore, most of the preparation methods currently used focus on uniform dispersion, and spherical particles with small size and large specific surface area are obtained.

Among the many preparation methods, the combination of the coprecipitation method and the high temperature solid phase method is the mainstream method. Firstly, the coprecipitation method is used to obtain a precursor with uniform raw material and uniform particle size, and then subjected to high temperature calcination to obtain a ternary material with regular surface morphology and easy control of the process, which is the main method used in industrial production. The spray drying method is simpler than the coprecipitation method, and the preparation speed is fast. The obtained material morphology is no less than the coprecipitation method, and has the potential for further research. The shortcomings of the high-nickel ternary cathode material during cation mixing and phase change during charge and discharge can be effectively improved by doping modification and coating modification. Improving the conductivity, cycle performance, rate performance, storage performance, and high temperature and high pressure performance while suppressing the occurrence of side reactions and stabilizing structures will remain a hot topic of research.

3, high volume silicon carbon negative

As an important part of lithium ion battery anode materials, directly affects the battery energy density, cycle life and safety performance and other key indicators. Silicon is given a known (4200mah/g), the highest lithium ion battery cathode material, but because of its more than 300% of the volume effect, silicon electrode materials in the process of charging and discharging will pulverization and peeling from the collection of fluid, make active substances and active substances, loss of electrical contact between the active materials, at the same time constantly forming new solid electrolyte layer SEI, eventually lead to the deterioration of the electrochemical properties. In order to solve this problem, the researchers conducted a large number of explorations and attempt, the silicon carbon composite material is of great application prospect.

As a negative electrode material for lithium ion batteries, carbon materials have small volume change during charge and discharge, good cycle stability and excellent electrical conductivity, so they are often used for recombination with silicon. In the carbon-silicon composite anode material, according to the type of carbon material, it can be divided into two categories: silicon and traditional carbon materials and silicon and new carbon materials, among which the traditional carbon materials mainly include graphite, mesophase microspheres, carbon black. And amorphous carbon; new carbon materials mainly include carbon nanotubes, carbon nanowires, carbon gels and graphene. The silicon-carbon composite is utilized to utilize the porous action of the carbon material to restrain and buffer the volume expansion of the active center of the silicon, prevent the agglomeration of the particles, prevent the electrolyte from penetrating into the center, and maintain the stability of the interface and the SEI film.

Many global companies already committed to this kind of new anode materials, such as, Shenzhen terry and Jiangxi Zichen has pioneered many silicon carbon anode materials products, Shanghai Shanshan is in silicon carbon negative electrode materials in the process of industrialization, star city graphite has silicon carbon anode materials for future new product development direction.

4, high voltage high capacity lithium materials

Li-rich manganese-based (xLi[Li1/3-Mn2/3]O2; (1–x)LiMO2, M is a transition metal 0≤x≤1, structure similar to LiCoO2) has a high discharge specific capacity and is currently used The actual capacity of the positive electrode material is about 2 times, and thus it has been 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, mainly using the method of coprecipitation preparation rich lithium manganese base material, there are also some researchers the sol - gel method, solid phase method, burning method and hydrothermal method and process for the preparation of, but the material performance than steady coprecipitation method. Although the material has high specific capacity, but its application still has a few problems: for the first time cycle the irreversible capacity of up to 40 ~ 100mah/g; Performance ratio is poor, 1 c capacity under 200mah/g; High charging voltage cause the electrolyte decomposition, makes the cycle performance is not ideal, and the use of security problems. By using metal oxide coating, and other positive electrode materials for composite, surface treatment, construct the special structure of upper limit of low voltage, the charge and discharge process, measures such as rich lithium manganese base material of the above problem can get a good solution.

In 2013, Ningbo materials have developed a novel gas-solid interface modification, and let the rich lithium manganese anode material particles form a uniform oxygen vacancy, thus greatly improving the initial charge-discharge efficiency, discharge specific capacity of the materials and cycle stability, powerfully impelled the rich lithium manganese anode material in the practical process.

5, the electrolyte of high voltage tolerance

Although the high voltage with more attention paid to the lithium battery materials, but in actual production application, the high voltage anode material still cannot achieve good effect. The biggest constraints is, carbonate electrolyte electrochemical stability window is low, when the battery voltage at 4.5 (VS.LI/Li +), the electrolyte began to severe oxidation decomposition, in which lithium battery set off reactions not normal. Tolerance of high voltage electrolysis system become to promote this new material is an important link in practical application.

Improving the stability of the electrode/electrolyte interface by developing and applying new high-pressure electrolyte systems or high-pressure film-forming additives is an effective way to develop high-voltage electrolytes, which are often favored economically. Such additives which increase the ability of the electrolyte to withstand voltage generally include boron-containing, organophosphorus, carbonate, sulfur-containing, ionic liquids and other types of additives. The boron-containing additives include tris(trimethylalkane)borate, lithium bis(oxalate)borate, lithium difluorooxalate borate, tetramethylborate, trimethyl borate, and trimethylcyclotriborane. Organophosphorus additives include phosphites and phosphates. Carbonate-based additives include fluorine-containing mercapto compounds. Sulfur-containing additives include 1,3-propane sultone, dimethoyl methane, trifluoromethyl phenyl sulfide, and the like. Ionic liquid additives include imidazole and quaternary phosphonium salts.

From already publicly reported at home and abroad research, the introduction of high pressure additive can make 4 electrolyte tolerance.4 ~ 4.5 v voltage, however, when the charging voltage reaches 4.More than 8 v or 5 v, must be developed to a higher voltage resistance of the electrolyte.

6, resistance to high temperature diaphragm

Lithium battery diaphragm in the lithium ion battery mainly conducting lithium ion and isolation is the role of the electrical contact between the cathodes, is one of the important components supporting completed battery charge-discharge electrochemical process. In the process of lithium battery, when the battery overcharge or at higher temperatures, the diaphragm need to have enough thermal stability (thermal deformation temperature > 200 ℃), to effectively isolate the battery positive and negative electrode contact, prevent short circuit, such as thermal runaway and even explosion accidents. Currently widely used polyolefin diaphragm, its melting point and low softening temperature (< 165 ℃), it is difficult to effectively guarantee the safety of the battery, and the low porosity and low surface energy, limiting the battery performance ratio. Therefore vigorously develop high resistance to high temperature diaphragm safety is very important.

Ningbo materials power lithium battery engineering lab and Dalian institute of chemical physics energy storage technology research, using a wet process molding technology, have developed a new type of high temperature resistant porous membrane, the preparation of porous membrane of low cost, easy to quantify the production. Preliminary study results show that thermal deformation temperature of the diaphragm is much higher than 200 ℃, and the thermal stability of the commercialization of non-woven diaphragm, can effectively guarantee the battery safety. At the same time, this kind of porous membrane with high porosity and high curvature of pore structure, to ensure the battery capacity of play at the same time effectively avoid micro short circuit and battery self-discharge phenomenon. In addition, Ningbo materials also developed with ultra-thin ion exchangeable function layer of heat-resistant composite diaphragm, based on the three dimensional heat-resistant skeleton gel composite membrane and ceramic membrane.

In addition to Ningbo Materials, in 2015, Mitsubishi resin coated high heat-resistant inorganic filler on the separator, so that the separator can maintain an appropriate resistance value at 220 ° C, blocking the passage of current.

7, lithium sulfur batteries

A lithium-sulfur battery is a lithium battery in which a sulfur element is used as a positive electrode of a battery and lithium metal is used as a negative electrode. The biggest difference from the general lithium-ion battery is that the reaction mechanism of the lithium-sulfur battery is an electrochemical reaction, not a lithium ion deintercalation. The working principle of lithium-sulfur batteries is based on complex electrochemical reactions. So far, the intermediate products formed during the charging and discharging of sulfur electrodes have not been able to be characterized. It is generally believed that the reaction of the negative electrode during discharge is that lithium loses electrons to become lithium ions, and the positive electrode reacts with sulfur to react with lithium ions and electrons to form sulfides. The potential difference between the positive electrode and the negative electrode is the discharge voltage provided by the lithium-sulfur battery. Under the action of the applied voltage, the positive and negative electrodes of the lithium-sulfur battery react in reverse, which is the charging process.

The biggest advantage of lithium-sulfur battery is its theoretical specific capacity (1672mAh/g) and specific energy (2600Wh/kg), which is much higher than other types of lithium-ion batteries widely used in the market, and due to abundant sulfur reserves. This battery is inexpensive and environmentally friendly. However, lithium-sulfur batteries also have some disadvantages: the electronic conductivity and ionic conductivity of elemental sulfur are poor; the intermediate discharge products of lithium-sulfur batteries are dissolved in the organic electrolyte, and the polysulfide ions can migrate between the positive and negative electrodes, resulting in activity. Material loss; metal lithium anode will undergo volume change during charge and discharge, and dendrites are easily formed; sulfur positive electrode has up to 79% volume expansion/contraction during charge and discharge.

Main methods to solve these problems generally from two aspects of the electrolyte and the anode material, electrolyte, mainly use ethers as electrolyte battery electrolyte, electrolyte, add some additives can be very effective to relieve lithium sulfur compounds dissolve problems. The anode material, mainly is the sulfur and carbon composite material, or the sulfur and organic compound, can solve the problem of non-conductive and volume expansion of sulfur.

Lithium-sulfur battery is still on the stage of laboratory research and development, Chinese academy of sciences, Nanyang Polytechnic, Stanford, Japan Industrial Technology Research Institute and University of Tsukuba are leading, and SionPower has been in the field of notebooks, unmanned aerial vehicle (uav) has conducted significant applications.

8, lithium air batteries

Lithium-air battery is a new type of large-capacity lithium ion battery, by the Japanese industrial technology research institute and the external academic organization in Japan (JSPS) jointly developed. Batteries with lithium metal as the anode, the oxygen in the air as the anode, between two electrodes separated by a solid electrolyte; The cathode using organic electrolyte, anode is used aqueous electrolyte.

At the time of discharge anode dissolve in organic electrolyte in the form of lithium ion, and then through the solid electrolyte aqueous electrolyte of migrated to the anode; Electronic through a wire transfer to the anode, oxygen in the air and water on ultra-micronization model. The generated after the reaction of carbon surface hydroxyl, in the aqueous electrolyte of the anode combined with lithium ions generated water-soluble lithium hydroxide. Electronic by wire transfer to the cathode, when charging from the anode aqueous electrolyte through solid state lithium ion electrolyte reach the surface of the anode, the cathode surface react to generate metal lithium. The positive of hydroxyl lose electronically generated oxygen.

Lithium air batteries by replacing the anode and the cathode electrolyte lithium can without charge, discharge capacity as high as 50000mah/g, high energy density, theoretically 30 kg metal lithium and 40 l gas release the energy of the same; Lithium hydroxide product easy to recycle, the environment friendly. But the cycle stability, conversion efficiency and the performance ratio are its shortcomings.

In 2015, Cambridge University Gray developed a high-energy density lithium air. The number of times of charging was “more than 2,000 times”, and the energy use efficiency theoretically exceeded 90%, making the practical use of lithium-air batteries a step forward. As early as 2009, IBM launched a sustainable transportation project to develop a lithium-air battery suitable for home electric vehicles. It hopes to travel about 500 miles on a single charge. Recently, Asahi Kasei and Central Glass Corporation of Japan also joining this project, the research and development of research institutes and well-known companies in the field of lithium air batteries will greatly promote the application of this battery technology.

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