Since the advent of graphene, although it has aroused numerous hot debates, it is still the focus of researchers in many fields, including lithium battery industry. At present, graphene is mainly used as conductive agent in lithium batteries.
In the production and subdivision process of lithium battery, the addition of conductive agent usually first considers the characteristics of the active substance of the battery material itself, and its direct function is to increase the conductivity. It is worth noting that the conductivity will directly affect the battery's discharge platform, Capacity Performance, cycle stability, internal resistance, high magnification performance, etc.
At present, conductive agents widely used in lithium batteries can be divided into three categories: Conductive carbon black, conductive graphite and new conductive agents, among which new conductive agents include carbon nanotubes, graphene, etc.
An insider said that from the research and development history of lithium battery conductive agent, it is going through three processes of graphite-carbon nanotubes-graphene, which indicates that the particle particles of conductive agent are getting smaller and smaller. This is because lithium battery has higher and higher requirements for capacity and cycle performance, and the electrical conductivity of materials greatly affects these factors. Adding conductive agent with smaller particles is the most direct way to solve this problem.
Which of the two new conductive agents, carbon nanotubes and graphene, has more advantages? It will be comprehensively compared and analyzed from the perspectives of performance, development bottleneck, price cost, etc.
Carbon nanotubes are microtubes with a diameter of only a few nanometers rolled up by a layer of graphite, which can also be formed by coaxial sleeve of microtubes with different diameters. According to the number of layers, it can be divided into single-walled carbon nanotubes and multi-walled carbon nanotubes; Graphene is a two-dimensional crystal which is stripped from graphite material and composed of carbon atoms with only one layer of atomic thickness, it is also divided into single-layer graphene and graphene micro-chip (multi-layer structure).
Essentially, carbon nanotubes and graphene belong to graphite materials, but the arrangement and combination of carbon atoms are different, forming spiral carbon nanotubes and Flake graphene, so they all have some of the same characteristics of graphite, such as electrical conductivity.
Specifically, carbon nanotubes become ideal material additives due to their small size, large specific surface area, different bond states on the surface and internal particles, incomplete coordination of surface atoms, etc. However, graphene electrodes have smaller pole resistance and can achieve greater compaction density.
The conductive agent usually needs to achieve the optimal conductivity with the minimum amount of addition. At present, carbon nanotubes and graphene for market-oriented applications are provided in the form of pre-dispersed conductive paste. From the perspective of conductivity, some insiders believe that as the third generation of conductive agent, the conductivity of graphene will undoubtedly be higher than that of other products.
Dr. Shen Jie of Qingdao Haoxin New Energy Technology Company (hereinafter referred to as "Haoxin Energy") said that graphene has good electrical conductivity, and the advantage of carbon nanotubes is that it has stronger liquid absorption ability in electrolyte.
However, another insider said that he was more optimistic about the application of carbon nano-tube conductive agent in lithium battery, because the ionic conductivity of pure graphene was not as good as that of carbon nano-tube, electrons added with pure graphene conductive agent will jump out after decades of cycle, which will affect the cycle stability of the battery.
For this, Dr. Liu Qing from the basic research and development department of Shenzhen Bick Power Battery Co., Ltd (hereinafter referred to as "Bick battery") agrees that the electronic conductivity and ionic conductivity of carbon nanotubes are relatively good, this is more conducive to improving the cycle of the battery.
From the analysis of conductive mechanism, graphene conducts electricity through point-surface contact, while carbon nanotubes transmit through point-line contact. Generally speaking, the larger the contact area is, the better the conductivity will be. Some insiders believe that graphene with thick lamination will hinder the diffusion of lithium ion and reduce the ionic conductivity of pole lamination, and 6-9 layers are the most suitable.
In fact, although each has its own advantages, carbon nanotubes and graphene, two kinds of conductive agents, both have development bottlenecks.
At present, there is a consensus in the industry on graphene that the production cost of graphene in the true sense is high and it is difficult to realize industrialization. For carbon nanotubes, the biggest problem is dispersion. In contrast, the dispersion "difficulties" of carbon nanotubes are easier to overcome than the "dystocia" of graphene, and the application of carbon nanotubes in conductive agents is more mature.
It is understood that OCSiAl has realized the large-scale production and application of single-walled carbon nanotubes, which is a multinational company specializing in the research and development and production of single-walled carbon nanotubes.
Grigory Gurevich, the president of the company in Hong Kong, said proudly that OCSiAl is an international big company with a lot of resources in the world, including hundreds or even thousands of partners, all of which have world-famous laboratories, universities and research institutes jointly research and develop the dispersion and application of additives. OCSiAl products are well dispersed and easily added to materials. Customers do not need to re-disperse or change the original process flow.
It is worth noting that although the industry has always felt uncertain about the industrialization of graphene, it has been confirmed through many investigations recently that Haoxin Energy has realized the industrialization production of graphene-like. Compared with dozens or even hundreds of layers of graphite micro-chips on the market, the graphene conductive agent products produced by Haoxin energy can reach 2 to 10 layers.
As the saying goes, "whether it is a black cat or a white cat, it is a good cat as long as a mouse is caught." from the perspective of enterprise profit, the purchase cost of carbon nanotubes and graphene is an important factor for its consideration and measurement. Which of these two products can achieve lower cost will undoubtedly add competitive advantages.
At present, the prices of carbon nanotubes and graphene are not much different in the market, but the prices of conductive agents of different models will vary greatly. It is understood that the price of conventional carbon nanotube conductive agent is 700-800 yuan/kg.
Grigory Gurevich said that as a product promotion, the first point is that the price should be attractive. In the past, the price of additives even exceeded that of the matrix itself. Compared with other companies, OCSiAl's products are not only low in price, but also more efficient and attractive, because its additive amount is much lower than other additives, from 0.001% to 0.1%.
According to the relevant person in charge of Haoxin new energy, the production capacity of graphene-like products produced by the company has been close to 200 tons, and BYD (002594) and Guoxuan hi-tech (002074) have become the users of this product, and the company plans to expand its production capacity to 1000 tons next year.
It is learned from BYD that this conductive agent of Haoxin Energy has better conductivity than similar products on the market, and its price is also relatively advantageous.
The above-mentioned person in charge of Haoxin New Energy introduced that compared with the conductive agent on the market, the price of the company's products is similar to that of the company, but the conductive performance is much better, and the conductive effect can be achieved even when the additive amount is reduced, for example, the same conductivity can be achieved under the condition of adding 25% carbon nanotubes.
GGII believes that carbon nanotubes and graphene are both made into conductive paste at present, and the price is much higher than that of ordinary carbon black SP. Carbon black is a very mature conductive agent with relatively stable price. However, there is much room for the price reduction of carbon nanotubes and graphene, and the price reduction rate of graphene is faster, with great application prospects. As for the application of lithium battery, different usage of two kinds of conductive agents will produce different effects, and it is difficult to judge which is better or worse.
