Lithium industry 8 can not know the forefront of lithium technology!

- Jul 25, 2017-

With the extensive use of lithium-ion batteries in people's daily life and military industry, many universities, research institutes and enterprises are committed to the development of new technologies for lithium-ion batteries, perhaps in the near future more secure, higher capacity, Faster lithium-ion batteries will become a reality. Next, please follow the mini-disk inventory of lithium battery near the field of the most popular eight research technology.

1, all solid-state lithium-ion battery1500887765126071190.png

The current commercial lithium-ion battery electrolyte is liquid, it is also known as liquid lithium-ion battery. In simple terms, all solid-state lithium-ion battery means that all components in the battery structure are in solid form, the traditional lithium-ion battery liquid electrolyte and diaphragm replaced with solid electrolyte.

Lithium industry 8 can not know the forefront of lithium technology!

Compared with the liquid lithium-ion battery, all solid electrolyte has the following advantages: high safety / thermal stability is excellent, long-term normal work in the 60-120 ℃ conditions; wide electrochemical window, can reach more than 5V, Can match the high voltage material; only conduction lithium ion does not conduct electrons; cooling system is simple, high energy density; can be used in ultra-thin flexible battery field. But the shortcomings are more obvious: the unit area of the ionic conductivity is lower, the temperature is lower than the power; the cost is extremely expensive; industrial production of large capacity battery is difficult.

Lithium industry 8 can not know the forefront of lithium technology!1500887768574081585.png

The performance of the electrolyte material to a large extent determine the 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 polymer electrolyte (usually PEO and lithium salt LiTFSI and other mixtures for the electrolyte substrate) and inorganic electrolytes (such as oxides and sulfides) two categories. All solid-state battery technology is recognized as the next generation focus on the development of innovative battery technology, I believe in the near future more and more mature technology, these problems can be solved.

2, high energy density ternary material battery

With the pursuit of energy density of the battery, ternary cathode materials more and more people's attention. Ternary cathode material with high specific capacity, good cycle performance, low cost advantage, generally refers to the layered structure of nickel cobalt manganese oxide material. By increasing the battery voltage and nickel content in the material, can effectively improve the energy density of ternary cathode materials.

Lithium industry 8 can not know the forefront of lithium technology!

In theory, the ternary material itself has the advantage of high voltage: ternary cathode material half-cell standard test voltage is 4.35V, in this voltage under the ordinary ternary material can show a good cycle performance; will charge Voltage increases to 4.5V, symmetrical type of material (333 and 442) capacity can reach 190, the cycle is also good, 532 cycle worse; charge to 4.6V, ternary material circulation began to decline, flatulence The phenomenon is more serious. At present, it is difficult to find the high voltage electrolyte which is suitable for the high voltage ternary cathode material.

Lithium industry 8 can not know the forefront of lithium technology!

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

Among the many preparation methods, the coprecipitation method combined with the high temperature solid phase method is the mainstream method. First, the coprecipitation method is used to obtain the precursors with uniform homogeneous material and uniform particle size. Then, after the high temperature calcination, the ternary materials with easy surface control and easy to control are obtained. This is also the main method used in industrial production. The method of spray drying is simple and the preparation speed is faster than that of coprecipitation method. The morphology of the obtained material is not as good as coprecipitation method, and has the potential of further research. High nickel ternary cathode materials cationic mixing and charge and discharge process phase change and other shortcomings, by doping modification and coating modification can be effectively improved. It is still a hot topic to improve the conductivity, cycle performance, magnification performance, storage performance and high temperature and high pressure performance while suppressing the occurrence and stability of side reactions.

3, high-capacity silicon carbon anode

As an important part of lithium-ion battery, anode material, a direct impact on the battery energy density, cycle life and safety performance and other key indicators. Silicon is currently known as the highest specific capacity (4200mAh / g) of the lithium ion battery anode material, but because of its more than 300% of the volume effect, the silicon electrode material in the charge and discharge process will be pulverized from the current collector peeling, Substances and active substances, active substances and the loss of electrical contact between the collector, while the formation of new solid electrolyte layer SEI, and ultimately lead to deterioration of electrochemical performance. In order to solve this problem, the researchers conducted a lot of exploration and try, of which silicon-carbon composite material is very promising materials.

Lithium industry 8 can not know the forefront of lithium technology!

Carbon material as a lithium ion battery anode material in the charge and discharge process changes in volume smaller, with good cycle stability and excellent conductivity, it is often used to complex with silicon. In the carbon-silicon composite anode material, according to the type of carbon material can be divided into two categories: silicon and traditional carbon materials and silicon and new carbon composite materials, including traditional carbon materials, including graphite, mesophase microspheres, carbon black And amorphous carbon; new carbon materials mainly include carbon nanotubes, carbon nanowires, carbon gels and graphene. The use of silicon and carbon composite, the use of carbon material porous role, the constraints and buffer the active center of the volume expansion, to prevent the agglomeration of particles to prevent the electrolyte to the center of penetration, to maintain the interface and SEI membrane stability.

Many companies around the world have begun to devote to this new type of anode materials, for example, Shenzhen Beitui and Jiangxi purple Chen has been the first to introduce a variety of silicon carbon anode material products, Shanghai Shanshan is in the process of industrialization of silicon anode material, Star City graphite Silicon anode has been a new type of negative materials as a future product development direction.

4, high-voltage high-capacity lithium-rich materials

(XLi [Li1 / 3-Mn2 / 3] O2; (1-x) LiMO2, M is the transition metal 0≤x≤1, the structure is similar to LiCoO2) has a high discharge specific capacity, The actual capacity of the cathode material about 2 times, and therefore widely studied for lithium battery materials. In addition, because the material contains a lot of Mn elements, and LiCoO2 and ternary materials Li [Ni1 / 3Mn1 / 3Co1 / 3] O2 compared to more environmentally friendly and safe. Therefore, xLi [Li1 / 3-Mn2 / 3] O2; (1-x) LiMO2 materials are considered by many scholars as ideal for the next generation of lithium ion battery cathode materials.1500887772302013764.png

Lithium industry 8 can not know the forefront of lithium technology!

At present, some coprecipitates are used to prepare fumed lithium manganese-based materials, and some researchers use sol-gel method, solid phase method, combustion method and hydrothermal method to prepare, but the obtained material is less stable than coprecipitation method. Although this material has a high specific capacity, but its practical application there are still several problems: the first cycle of irreversible capacity up to 40 ~ 100mAh / g; magnification performance is poor, 1C capacity of 200mAh / g below; high charge voltage caused by electrolyte Decomposition, making the cycle performance is not ideal, and the use of security issues. The above problems of lithium-rich manganese-based materials can be solved satisfactorily by adopting metal oxide coating, compounding with other cathode materials, surface treatment, constructing special structure and low upper limit voltage precharge and discharge treatment.

In 2013, Ningbo Materials developed a novel gas-solid interface modification technology, so that the surface of lithium-rich lithium-based cathode material to form a uniform oxygen vacancy, which greatly improved the material of the first charge and discharge efficiency, discharge capacity and cycle Stability, and effectively promote the lithium-manganese-based cathode material practical process.

5, high voltage withstand electrolyte

Although the high-voltage lithium battery materials more and more attention, but in the actual production applications, these high-voltage cathode materials still can not achieve good results. The biggest limiting factor is that the electrochemical stabilization window of the carbonate-based electrolyte is low, and when the battery voltage reaches about 4.5 (vs.Li/Li+), the electrolyte begins to undergo severe oxidative decomposition, resulting in lithium The reaction does not proceed normally. The development of high-voltage electrolytic solution system to promote the practical use of this new material an important part.

Lithium industry 8 can not know the forefront of lithium technology!

It is an effective way to develop high-voltage electrolytes by developing and applying new high-pressure electrolyte systems or high-pressure film-forming additives to improve the stability of the electrode / electrolyte interface. The latter is often favored. Such additives for improving the withstand voltage of the electrolyte generally include boron-containing, organophosphorus, carbonate, sulfur-containing, ionic liquids and other types of additives. Boron-containing additives are tris (trimethyl) borate, lithium bis-oxalate, lithium bisfluoroborate, tetramethyl borate, trimethyl borate and trimethylcyclotrisborane. Organic phosphorus additives include phosphites and phosphates. Carbonate-based additives include fluorine-containing compounds. The sulfur-containing additives include 1,3-propanesultone, dimethanesulfonylmethane, trifluoromethylphenyl sulfide and the like. Ionic liquid additives include imidazoles and quaternary phosphonium salts.

From the domestic and foreign research has been publicly reported, the introduction of high pressure additives can make the electrolyte withstand 4.4 ~ 4.5V voltage, but when the charging voltage reaches 4.8V or even more than 5V, must be developed to withstand higher voltage Electrolyte.

6, high temperature diaphragm

Lithium battery separator in the lithium-ion battery mainly plays a role in conducting lithium ions and isolation between the positive and negative electronic contact is to support the battery to complete the charge and discharge of the important components of electrochemical process. In the use of lithium batteries, when the battery overcharge or temperature rise, the diaphragm needs to have sufficient thermal stability (heat distortion temperature> 200 ℃), to effectively isolate the battery between the positive and negative contact to prevent short circuit, heat Out of control or even explosion and other accidents. The polyolefins membrane, which is widely used today, has a low melting point and softening temperature (<165 ° C), which is difficult to ensure the safety of the battery, while its low porosity and low surface energy limit the battery performance. Therefore, it is very important to develop high safety and high temperature resistance.

Lithium industry 8 can not know the forefront of lithium technology!

Ningbo Institute of Materials Power Lithium Battery Engineering Laboratory and Dalian Institute of Chemical Physics Energy Research Institute, the use of wet process a molding technology, jointly developed a new type of high temperature porous membrane, the porous membrane preparation costs are low, easy to quantify produce. The preliminary results show that the heat distortion temperature of the diaphragm is much higher than 200 ℃, which is equivalent to the thermal stability of the commercial nonwoven fabric separator, which can effectively guarantee the safety of the battery. At the same time, this porous membrane has a high porosity and high curvature of the pore structure, to ensure that the battery capacity to play at the same time to effectively avoid the battery micro short circuit and self-discharge phenomenon. In addition, Ningbo Materials has also developed a ultra-thin ion exchangeable functional layer of heat-resistant composite diaphragm, based on three-dimensional heat-resistant skeleton of the gel composite diaphragm and ceramic diaphragm.

In addition to Ningbo materials, in 2015, the Mitsubishi resin in the diaphragm coated with high heat resistance inorganic filler, so that the diaphragm at 220 ℃ temperature can still maintain the appropriate resistance value, blocking the current through.

7, lithium-sulfur battery

Lithium-sulfur battery is a lithium element as a battery cathode, metal lithium as a negative lithium battery. The biggest difference with the general lithium-ion battery is that the reaction mechanism of lithium-sulfur batteries is electrochemical reaction, rather than lithium ion de-embedded. The working principle of the lithium-sulfur battery is based on the complex electrochemical reaction, so far, the sulfur electrode in the charge and discharge process formed by the intermediate product has not been a breakthrough characterization. It is generally believed that the negative electrode reaction is lithium loss of lithium ions, the positive reaction is sulfur and lithium ions and electrons to produce sulfide, the positive and negative electrode reaction potential difference is the lithium-sulfur battery provided by the discharge voltage. In the role of external voltage, lithium-sulfur battery positive and negative reaction reverse, that is, the charging process.

Lithium industry 8 can not know the forefront of lithium technology!

Lithium-sulfur battery is the biggest advantage of its theoretical specific capacity (1672mAh / g) and specific energy (2600Wh / kg) is higher, much higher than the current widely used on the market of other types of lithium-ion battery, and because of the rich quality of sulfur This battery is inexpensive and environmentally friendly. However, the lithium-sulfur battery also has some drawbacks: the elemental sulfur has poor electrical conductivity and ionic conductivity; the intermediate discharge product of the lithium-sulfur battery dissolves into the organic electrolyte, and the polysulfide ions migrate between the positive and negative ions, resulting in activity Material loss; metal lithium negative charge and discharge process will occur in volume changes, and easy to form dendrites; sulfur cathode in the charge and discharge process up to 79% of the volume expansion / contraction.

Lithium industry 8 can not know the forefront of lithium technology!

The main method to solve the above problems generally from the electrolyte and cathode materials in two aspects: the electrolyte, the main use of ether electrolyte as the battery electrolyte, add some additives in the electrolyte, can be very effective in relieving lithium polysulfide The solution of the compound; the cathode material, mainly the sulfur and carbon material composite, or the combination of sulfur and organic compounds, sulfur can solve the problem of non-conductive and volume expansion.

Lithium-sulfur battery is still in the laboratory research and development stage, the Chinese Academy of Sciences, Nanyang Science and Technology, Stanford, Japan Industrial Technology Research Institute and the University of Tsukuba research in a leading position, and SionPower has been in the notebook, UAV field carried out a meaningful Application attempt.

8, lithium battery

Lithium battery is a new type of large-capacity lithium-ion battery, by the Japanese Industrial Technology Research Institute and the Japan Society for the Promotion of Science (JSPS) jointly developed. The battery is made of lithium metal as the negative electrode, the oxygen in the air is used as the positive electrode, and the two electrodes are separated by the solid electrolyte. The negative electrode adopts the organic electrolyte and the positive electrode uses the aqueous electrolyte.

Lithium industry 8 can not know the forefront of lithium technology!

In the discharge of the negative electrode in the form of lithium ions dissolved in organic electrolyte, and then through the solid electrolyte migration to the positive electrode of the aqueous electrolyte; electrons through the wire to the cathode, the air of oxygen and water in the micro-carbon surface reaction Hydrogen peroxide is formed and is combined with lithium ions in the aqueous electrolyte of the positive electrode to form water-soluble lithium hydroxide. At the time of charging, the electrons are transferred to the negative electrode through the wires. The lithium ions pass through the solid electrolyte from the solid electrolyte to the surface of the negative electrode, and the reaction occurs on the surface of the negative electrode to produce metal lithium. The hydrogen atoms of the positive electrode lose electrons.

Lithium industry 8 can not know the forefront of lithium technology!

Lithium battery through the replacement of positive electrolyte and negative lithium can not charge, discharge capacity up to 50000mAh / g, high energy density, theoretically 30kg of lithium metal and 40L gasoline release of the same energy; product lithium hydroxide easy to recover, environmentally friendly. But the cycle stability, conversion efficiency and magnification performance is its shortcomings.

In 2015, Cambridge University, Gray developed a high-energy density of lithium air, the number of charges "more than 2000 times", the energy efficiency of the theory of more than 90%, so that the practical use of lithium battery has taken a step forward. As early as 2009, IBM launched a sustainable transportation project to develop a lithium-ion battery suitable for home electric vehicles, hoping to charge about 500 miles a time, the recent Japanese Asahi Kasei and Central Glass Company also Joined the project, research institutions and well-known companies in the field of lithium-air battery research and development will greatly promote the application of this battery technology.