Inventory of the ten most promising new materials for lithium batteries
Publish：Sino Energy Corporation Time：2017-04-26
[lithium engineering comprehensive report]
The development of lithium battery is in a bottleneck period, and the energy density is close to its physical limit.We need new materials or technology to achieve a breakthrough in lithium batteries, the following battery materials have been optimistic about the industry, or will become a breakthrough in lithium battery breach.
1, silicon carbon composite anode material
Digital terminal products, large screen, functional diversification, the battery life of the new requirements. The grams of low capacity lithium battery materials can not meet the end, growing demand for batteries.
As one of the future anode materials, the theoretical capacity of silicon carbon composite is about 4200mAh/g, which is 10 times higher than that of Shi Molei‘s 372mAh/g, which will greatly enhance the capacity of the battery. At present the major material manufacturers in the development of silicon carbon composite materials, such as BTR, leather, Shanshan, nano Xin HUAWEI, Samsung etc.. Now the main problems of silicon carbon composites:
1, charging and discharging, the volume expansion, imbibition ability;
2, poor cycle life. At present, silicon dioxide, nano silicon, carbon coating, doping and other means to solve the above problems, and some enterprises have made some progress.
2, lithium titanate
In recent years, the domestic research and development of lithium titanate is high, the main advantages of lithium titanate:
1, long cycle life (up to more than 10000 times), belong to zero strain material (volume change is less than 1%), does not produce the traditional meaning of the SEI film;
2, high security. The potential of lithium insertion is high, the dendrite is not formed, and the thermal stability is very high when charging and discharging;
3, can quickly charge.
At present, the main factor limiting the use of lithium titanate is the price is too high, higher than the traditional graphite, and the capacity of lithium titanate is very low, about 170mAh/g. Only by improving the production process and reducing the cost of production, the long cycle life and fast charging of lithium titanate can play an important role. Combined with the market and technology, lithium titanate is more suitable for the space requirements of the bus and storage areas.
3, Shi Moxi
Graphene has received worldwide attention since 2010, especially in china. Domestic set off a boom of graphene research and development, which has many excellent properties, such as good transparency, excellent conductivity, high thermal conductivity, high mechanical strength. Potential applications of graphene in lithium ion batteries:
1, as the anode material. Graphene has a higher capacity and a reversible capacity of about 700mAh/g, which is higher than that of graphite anode. In addition, the thermal conductivity of graphene good to ensure that its battery system stability, and the graphene layer spacing is larger than that of graphite, the lithium ion diffusion in smooth graphene layers, is conducive to improve the performance of power battery. The production process of graphene is not mature, the structure is unstable, leading to graphene as anode materials there are still some problems, such as the first discharge efficiency is relatively low, about 65%; poor cycle performance; the higher the price, significantly higher than that of the traditional graphite anode.
2, as positive and negative additives, can improve the stability of the lithium battery, prolong the cycle life, increase the internal conductivity.
In view of the current mass production process of graphene is not mature, the price is high, the performance is not stable, graphene will be the first positive and negative additives used in lithium-ion batteries.
4, lithium rich manganese based cathode materials
High capacity is one of the development direction of lithium battery, but the energy density of lithium iron phosphate is 580Wh/kg, and the energy density of nickel cobalt lithium manganate is 750Wh/kg. The theoretical energy density of lithium rich manganese can reach 900Wh/kg, becoming a hot spot of research and development.
The advantages of lithium rich manganese based materials as follows: 1, high energy density; 2, the main raw material rich. Due to the development of a relatively short time, the rich lithium manganese base has a series of problems: 1, the first discharge efficiency is low; 2, material in the circulation process of oxygen evolution, bring security risks; 3, the life cycle is very poor; 4, the low rate performance.
At present, the methods to solve these problems include coating, acid treatment, doping, pre circulation, heat treatment and so on. Although the lithium rich manganese base has obvious advantages in capacity and potential, but it is limited to the slow progress of technology, it will take time for the mass market.
5, power type nickel cobalt lithium manganate material
All along, there is a lot of controversy about the power line route, so lithium iron phosphate, lithium manganate, three yuan materials and other routes have been adopted. Domestic power battery route to lithium iron phosphate based, but with the global hot Tesla, the use of three yuan of material route caused an upsurge.
Although the safety of lithium iron phosphate is high, but its low energy density can not overcome the weakness, and new energy vehicles require longer mileage, so in the long term, G high capacity lithium iron phosphate materials will replace the line become the mainstream technology of the next generation.
Nickel cobalt lithium manganate three yuan material most likely to become the next generation of power battery mainstream materials. China has launched three Yuan line of electric vehicles, such as Beiqi E150EV, JAC IEV4, Chery EQ, blue and so on, the unit weight density is much greater than the lithium iron phosphate battery.
6, carbon nanotubes
Carbon nanotubes are not new, they have been widely used as hydrogen storage materials, but they are used in lithium batteries. Carbon nanotubes were sold in 2009, because the price is too high, almost nobody cares. Now with the process improvement, cost reduction, higher requirements and internal lithium battery system, carbon nanotube has been recognized core enterprise.
Today, the capacity and power of the lithium battery is getting higher and higher, the excellent performance of carbon nanotubes come in handy.
1, excellent conductive properties, the resistivity of 2-6*10-4..cm; 2, excellent thermal conductivity, thermal conductivity of carbon nanotubes at room temperature can reach 6000w/m/k, can gather effective transfer of battery charge and discharge the heat, especially under the condition of high rate, high capacity and high rate with the rise of batteries, carbon nanotubes will be obtained wide application.
7, coated diaphragm
The separator is very important to the safety of the lithium battery, which requires that the membrane has good electrochemical and thermal stability, as well as a high degree of infiltration of electrolyte in the process of repeated charging and discharging.
Refers to the coating on the substrate coated with PVDF or other adhesive or ceramic alumina. The effect of coated diaphragm is: 1, improve diaphragm heat shrinkage resistance, prevent the shrinkage of the diaphragm resulting in a large area of short circuit; 2, coating material with low thermal conductivity, prevent certain thermal battery out of control point to expand the formation of the overall thermal runaway.
8, ceramic alumina
In the coating membrane, ceramic coating membrane mainly for power battery system, so the market growth space is spreading more of its core material diaphragm, alumina market demand will rise three yuan of power battery increased significantly.
Ceramic membrane used for coating the purity, particle size, morphology have high requirements, Japan, SouthKorea‘s products are more mature, but the price is more than twice the cost of domestic. At present, there are a number of enterprises in the development of ceramic alumina, hoping to reduce dependence on imports.
9, high voltage electrolyte
To improve the energy density of battery is a lithium battery current trend, improve energy density method mainly has two kinds: one is to improve the traditional cathode material charge cutoff voltage, such as lithium cobalt acid to enhance the charging voltage to 4.35V and 4.4V. But by raising the cut-off voltage of charging method is limited, to further enhance the voltage will lead to the collapse of LiCoO2 structure, unstable nature; the other is the development of new cathode material discharging platform higher, such as lithium rich manganese based lithium nickel cobalt oxide, etc..
The voltage of the cathode material needs to be matched with the high voltage electrolyte, which plays a key role in the high voltage performance of the electrolyte.
10, water-based binder
At present, the cathode material is mainly made of PVDF and dissolved in organic solvent. The binder system of the negative electrode is SBR, CMC, fluorinated olefin polymer, etc., and also can be used as an organic solvent. In the production process of the electrode sheet, it is necessary to evaporate the organic solvent, which not only pollute the environment, but also endanger the health of employees. The evaporated solvent is collected and processed by special refrigerating equipment, and the price of the fluoropolymer and the solvent is high, which increases the cost of the lithium battery.
In addition, the SBR/CMC binder is easy to stick in the process, and it is difficult to be used for the preparation of positive electrode.
For environmental protection, reduce costs, increase the performance of the chip and other needs, the development of water-based binder is imperative.
