In 2002, in a laboratory of Shenzhen University, Liu Jianhong, then director of the Science and Technology Department and head of the Department of Chemistry of Shenzhen University, led a team to synthesize a low molecular polymer and gradually synthesize a monolayer graphite. At that time, there was no relevant literature available, and Jianhong Liu only thought it was a monolayer graphite.

It was not until 2004, when a paper by British physicist Derek Heim reported graphene, that Jianhong Liu realized that the monolayer graphite molecule he had synthesized was also a graphene from a physical point of view.

Jianhong Liu was very excited, and after systematically sorting out the synthesis process and modifying it, Jianhong Liu opened the door to its "treasure" of applications.

Because of the excellent characteristics of the graphene material in the field of battery electrodes, diaphragms, etc. 11 years later, that is, in 2015, he got the power battery ternary precursor leading enterprise Greenmax 20 million yuan investment.

In 2021, the leading company of graphene industry chain back-end, CNNC Titanium White, also invested in them. Soon, the construction of a 10,000-ton capacity graphene-coated graphite anode material production line began. Later this year, the 1,000-ton capacity graphene-covered silicon anode material also entered into production.

"Upholding original innovation, integrating resources, and building up a strong foundation, just in time for the national support policy for new energy industry, standing on the wind, we will make a good development." Liu Jianhong envisioned.

01

Synthetic monolayer graphite is actually graphene

"At that time, we did not realize it was graphene, and there was no concept of graphene." Jianhong Liu somewhat regrettably told The Great Nation that the single layer of graphite prepared by the team in the laboratory 20 years ago turned out to be graphene, not realizing that it would have a series of excellent physical properties.

After seeing Dreyer Heim's paper being reported, Jianhong Liu realized that the monolayer graphite synthesized by his team was graphene and began to systematically explore its synthesis process, structural characterization by transmission electron microscopy, scanning electron microscopy, X diffraction, and Raman spectroscopy, as well as attempts to modify its structure and applications.

Unlike Nobel laureate André Heim's transparent glue repeatedly para-adhesive method and the mainstream CVD chemical vapor deposition method, redox method and other preparation paths, Jianhong Liu's team uses liquid-phase oligomers to synthesize graphene.

Jianhong Liu told "Da Guo Zhi Zhi" that chemical vapor deposition is to use natural gas as the carbon source, hydrocarbon cracking at about 1200 degrees Celsius, carbon deposited onto copper foil, thus catalyzing the graphene structure, and then the structure is transferred out to prepare a graphene film. However, Jianhong Liu believes that this structure may contain non-graphene carbon structures such as amorphous carbon.

The other is graphene oxide reduction, which uses concentrated sulfuric acid and potassium permanganate as strong oxidants to oxidize on the graphite surface. However, the strong oxidizing agent will destroy the conjugate structure of graphite, which is a structure with alternating single and double bonds between carbon and carbon atoms. After the oxidation is completed, a graphene oxide dispersion is obtained, and finally it is reduced in a complicated process. "Once the co-structure is destroyed, it is difficult to restore it back intact."

"The synthesis of single-atomic layer graphene by liquid-phase oligomer method is an original path for us." Jianhong Liu told The Big Country Material that only the intrinsic equation can produce single-layer graphene by this way, and only products based on single-layer or two-layer graphene can truly reflect the various advantages of graphene.

The liquid-phase oligomer undergoes a gradual thermochemical reaction to transform from a linear molecule to a trapezoidal molecule, then to a planar molecule, and finally to carbonize it. This process makes the graphene structure very complete, and the graphene content of the obtained monoatomic layer is as high as 97% from the structure of Raman spectra.

In order to demonstrate its monolayer characteristics, Jianhong Liu's team spent several years devoted to which, through the selective oxidation reaction of carbon atoms on the edges of graphene planar molecules, the monatomic layer graphene showed surfactant properties and could dissolve in water, oil and organic solvents to form a transparent solution, solving the problem of graphene powder molding.

This method unlocks many new application scenarios for graphene, such as the possibility of preparing transparent graphene films in large quantities and at low cost. In addition, dissolving graphene in motor oil has excellent lubricating properties and also has restorative properties.

Jianhong Liu discovered that graphene can also be compounded with metal oxides to produce magical effects. By compounding trapezoidal polymer molecules with metal oxides, a trapezoidal molecule-wrapped oxide metal layer is formed, and the outer layer is sintered at high temperature to form graphene, which is reductive and can reduce the internal oxide metal to metal, and a graphene-coated metal monolith and various graphene-metal composite structures are obtained.

Photovoltaic solar power generation requires silver paste, and silver as a precious metal, its cost accounts for about 8% of the cost of photovoltaic solar cells. Liu Jianhong compounded graphene with metallic copper oxide to form graphene-coated copper nanoparticles, which solved the problem of easy oxidation of copper in air and realized the replacement of silver powder. "It can achieve lower resistance while reducing the cost of raw materials."

"We have successfully synthesized the graphene structure of iron, manganese and nitrogen." Liu Jianhong told "Da Guo Zhi Zhi" that some carbon atoms in graphene are replaced by metals, forming a structure that can make its ferromagnetism increase by 70%, with electron supply function, which can achieve the replacement of precious metals such as platinum and titanium, and can be used as catalysts for hydrogen fuel cell redox, significantly reducing costs, and also as high-performance hydrogen storage materials.

02

Can crack the pain point of lithium cathode

In 2015, Liu Jianhong's team got a strategic investment of 20 million RMB from Greenmax and established Shenzhen Benzheng Graphene Technology Co.

In a media interview, Xu Kaihua, Chairman of Greenmax, commented on Liu Jianhong, "Professor Liu Jianhong is a bull in the field of graphene, and we are very optimistic about his technological leadership and ability to transform the technology into industry."

Hui Kaihua's vision is venomous, and Jianhong Liu's obsession with original innovation is engraved in his bones, which has become the source of motivation for his profound exploration in graphene technology research and application.

For liquid trapezoidal molecules compounded with oxide metals, Jianhong Liu found that it is even possible to control the reduction of metals to different stages, such as copper oxide can be controlled to reduce to cuprous oxide. Jianhong Liu explained that the intermediate oxide state is generally very unstable and will return to a highly oxidized state when it meets air, with the protection of graphene, it can be very stable in the intermediate oxide state.

Graphene-coated cuprous oxide and manganese oxide have excellent anti-sea life adhesion properties and can be used in marine ship anti-fouling coatings with long-lasting anti-sea life adhesion effect. As early as 2006, Liu Jianhong cooperated with Wu Qi, an academician of the Chinese Academy of Sciences, to carry out research on the anti-sea life adhesion of marine vessels, which was funded by the National 863 Project.

"This is a unique material in China for anti-adhesion of sea creatures." Liu Jianhong told The Great Nation of Materials quite proudly.

Graphene also has excellent thermal and electrical properties. In 2008, the first year of China's development of new energy vehicles, Jianhong Liu collaborated with Professor Xueliang Sun, a member of the Royal Canadian Academy of Sciences, on a research project to synthesize single-atom layer graphene in lithium-ion batteries by liquid-phase oligomer.

Jianhong Liu's team decided to start with the positive and negative electrodes of the battery. The commercially available negative electrode material is usually graphite, and Jianhong Liu found that covering the surface of graphite with a single atomic layer of graphene would produce a series of surprising effects.

For lithium battery positive electrode material, high current charging will quickly take away the lithium ions from the positive electrode, which is equivalent to the pillar of a house, and once taken away, it will produce the collapse of the positive electrode and cause the destruction of the lithium battery. The doping and coating of graphene on the cathode material can stabilize the structure of the cathode material.

For lithium battery cathode material, an important pain point is that it is easy to produce lithium dendrites when carrying out high current charging or low temperature discharge, thus causing battery short circuit to produce combustion and explosion. After the graphite anode is coated with graphene, the lithium atoms will preferentially bond with the graphene surface and then insert into the graphite layer segment structure, which can avoid the generation of lithium dendrites.

In addition, the resistance of the battery can be reduced, and the full charge DC internal resistance is reduced by 20%-40%, which reduces the heat generation when the battery is charged and discharged.

Inside the cell, the presence of graphene makes its structure stable and the expansion and contraction is partially controlled. The application of graphene in silicon-carbon cathode materials has achieved results that have excited Jianhong Liu. In the traditional silicon-carbon anode, when the anode is filled with lithium atoms, the silicon swells up to 300% and the graphite swells to 20%-30%, both of which tend to form a strong internal stress, and the surface of the silicon-carbon anode will collapse after more than 70-80 cycles. The use of graphene-coated silicon nanoparticles will effectively reduce the expansion and internal stress.

In terms of cathode material, especially ternary cathode material, its structure is layered, lithium atoms are hidden between layers, which will cause lithium atoms to escape when charging, but if all lithium atoms escape, it will lead to collapse phenomenon, graphene can be inserted into the ternary layered structure in the form of planar trapezoidal molecules, and form nickel carbide and cobalt carbide by compounding with metallic nickel and cobalt on the surface, to achieve stable structure of ternary material, and the impedance of pole piece The graphene can be inserted into the ternary structure to form nickel carbide and cobalt carbide on the surface.

The excellent performance of graphene in lithium batteries and other materials has led Jianhong Liu to conceive plans for industrialization.

03

Catching the wind of new energy industry development

"I can say that I am doing graphene with my life." Liu Jianhong joked to "The Great Material of China".

The full dedication has also brought about technological progress. Graphene-coated positive and negative electrode materials, if imported into the application, will bring an improvement to the battery technology. Liu Jianhong analysis, for the first is the improvement of safety performance, reduce internal stress, to avoid the occurrence of spontaneous combustion and self-detonation; secondly, enhance the ability of the battery to quickly charge and discharge, to avoid the generation of lithium dendrites destroy lithium batteries; in addition, also gives the battery low-temperature performance, "we achieved a soft pack laminated battery at minus 40 degrees discharge rate to 76% of the room temperature discharge rate - 80%."

In terms of cost, Liu Jianhong said that the cost of graphene synthesized from liquid-phase oligomers is not high. After the oligomer trapezoidal molecules are compounded with battery electrodes, the cost of the high-temperature sintering link is low and does not raise the cost of lithium.

Technology breakthrough in the university laboratory, but Liu Jianhong believes that the combination of this and industry is limited. 2015, after getting the investment from Greenmax, Liu Jianhong launched the engineering of the attack.

"From the laboratory to industrialization, there is a lot to do in between." Liu Jianhong recalled to The Big Country's Material, taking graphite anode as an example, there are various kinds of natural and artificial graphite, and detailed structural standard research on raw materials should be conducted in the early stage to ensure that graphene trapezoidal molecules can achieve solid bonding with the material surface.

For the introduction of battery materials for new energy vehicles, the verification process is very complicated. "It takes a long process for customers to understand the new product." From product and process validation to stability verification, it takes 10-15 years to launch each product. "Since I started doing graphene research and its application in my 30s, I am now 58 years old and almost retired." Jianhong Liu lamented.

Thick and thin is Liu Jianhong's high grasp of the life cycle of research and industrialization of the results, which also contains his expectations.

At the end of 2021, Xu Kaihua came to Benzheng Equation and told Liu Jianhong that the time was ripe for large-scale engineering. This made Liu Jianhong, who was waiting for the day, excited.

At the time of the interview with "The Big Country" at the 2022 Shenzhen International Graphene Forum, Liu Jianhong had just returned to Shenzhen from Jingmen, Hubei Province. It turns out that in November last year, Benevolent Equation and five other companies jointly invested in a production base for graphene-coated graphite anode materials in Jingmen City, with a capacity of 10,000 tons.

At the end of last year, Benzheng Fangcheng also completed another major event by introducing another major shareholder, CNNC Titanium White, and accepted its 75 million investment.

This year, the production line of 1000 tons of graphene covered silicon anode located in Pingshan, Shenzhen has been built, with a gram capacity of 1300, first discharge efficiency of over 90%, and 1C cycle of 1000 turns, and is currently undergoing batch trial production.

Around graphene technology, for the new energy industry, Liu Jianhong drew up a technology layout map. Positive and negative materials for power batteries, graphene copper paste for photovoltaics, and graphene electrochemical hydrogen storage.

"Our graphene team started the business together and has persisted until now, and now the light has dawned. We have caught up with the national policy of supporting the new energy industry again, which makes us stand at the mouth of the wind." Liu Jianhong expects that it is time for Benzheng Fangcheng to make a big show again.