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At this time, Cao Xun and Zhang Liu had already arrived at the laboratory, and they were sitting in a position at this time, waiting for Shang Yiyun's arrival.

"Cao Xun and Zhang Liu, I didn't expect you to come so early, and now there are still five minutes before two o'clock in the afternoon. ”

Hearing Shang Yiyun's words, Cao Xun stood up from his seat and said.

"We were new here, so we came five minutes early, so we didn't have to wait too long. ”

However, Shang Yiyun has not forgotten the purpose of coming to the laboratory.

"Okay, we're here to do experiments, not to explore when to come to the labs, now that we're all here, let's start experimenting. ”

After saying these words, Shang Yiyun came to the experimental table, put some materials that could be used in the experiment on the experimental table, and then started the experiment according to the steps of the experiment.

However, before doing the experiment, he still recalled some knowledge related to graphene batteries.

Graphene batteries are made by improving existing lithium-ion batteries, which is achieved by adding graphene to the electrodes, which can change the chemical and physical properties of the electrodes, resulting in improved charge-discharge rate characteristics and capacity, and the improved discharge rate means that the graphene battery has a higher maximum output power.

There are two main types of graphene batteries that Shangyiyun wants to study, one is graphene vanadium oxide battery, and the other is graphene iron phosphate lithium-ion battery.

The main component of the first graphene vanadium oxide battery is a mixture of vanadium oxide (VO2) and graphene, and this hybrid power supply can be used for the cathode of lithium-ion batteries, and the measurement results show that this hybrid cathode can be fully charged and discharged in 20 seconds and can withstand more than 1000 charge cycles. After 1000 cycles, the capacity is still better than the nominal 90%.

Vanadium oxides have a high energy capacity in lithium-ion batteries because they collect lithium ions like a sponge, and one of the drawbacks of using vanadium oxide (VO2) or vanadium pentoxide (VO5) is that oxides are usually bad conductors, and low conductivity leads to slower charge-discharge rates.

So Shangyiyun has found a way to use graphene as the structural framework of vanadium oxide, graphene is an excellent conductor, this hybrid material inherits good capacity characteristics from vanadium oxide, and good conductivity from graphene, so that it can be charged quickly.

The process consists of graphite oxide nanosheets mixed with VO5 powder, the mixture suspended in water and heated to high temperatures. At these temperatures, vanadium pentoxide is reduced to VO2, while graphite oxide is reduced to graphene, and when VO2 crystallizes, it forms a thickness of about 10 nanometers, 600 nm wide nanoribbons and with a single atom thickness of graphene coating, these with tens of microns long, they have a very large specific surface area, due to the ionic immersion properties of VO2 and the high conductivity of graphene, which makes the diffusion of electrons and lithium ions very fast, the combination of these two characteristics enables fast charge-discharge rates, as well as high maximum power output of these batteries.

The real technical difficulty in manufacturing graphene batteries lies in the actual manufacture of VO2-graphene hybrid materials, in order to produce this mixture, the process conditions such as temperature, pressure and mixture concentration must be very precisely controlled.

The second type of graphene battery is a graphene iron phosphate lithium-ion battery.

Lithium iron phosphate lithium-ion battery, also known as lithium iron phosphate (LFP), is a rechargeable battery with lithium iron phosphate as the cathode, LFP battery is a rechargeable lithium-ion battery, although their energy density is lower than some other consumer lithium-ion batteries, but their power density is higher, power density is the rate of energy supplied by the battery.

Due to its high power density, it can be well used in new energy vehicles, and the LiFePO4 battery has better thermal and chemical stability, and it is safer than other lithium-ion batteries. They are difficult to ignite during charging, and LFP batteries are more likely to be misused than other lithium-ion batteries before they fail to be charged.

Graphene batteries not only charge many times faster than lithium-ion batteries, but also have a larger capacity, exceeding the theoretical maximum capacity of traditional LFP batteries.

LiFePO4 nanoparticles were mixed with graphene oxide nanosheets, and processes such as spray drying and annealing were used to fabricate a material consisting of LiFePO4 primary nanoparticles embedded in secondary spherical particles, which were loosely wrapped together through a three-dimensional network of graphene sheets. 、

Graphene is an excellent conductive material, its application greatly improves the mobility and mobility of electrons, the nanopores on the graphene sheet can add the Li+ mobility of the entire three-dimensional graphene matrix, and what they create is basically an ionic sponge that can absorb lithium ions while allowing electrons to move freely in the matrix.

When applied to graphene batteries, this new type of LiFePO4-graphene composite material has produced good results, so that the battery has some good performance, and the weight reduction is a warmly welcomed progress for new energy vehicles.

These improved LFP graphene batteries can be charged at 10C and discharged 1000 times at 20C with a capacity decay rate of just less than 15%.

The charging temperature of ordinary lithium-ion batteries is 0.5-0.8C, and the discharge temperature can reach 1C. On the other hand, these improved graphene batteries are able to reliably charge and discharge at up to 20 times faster than conventional lithium-ion batteries. The peak discharge rate is safely increased to 70C, which is a 70-fold increase in battery power density.

In this experiment, the graphene battery that Shang Yiyun wants to make is a graphene vanadium oxide battery, as for the other one, wait until the first one is successfully developed, and then consider the second one.

Shang Yiyun treated each experimental step very cautiously, not daring to be careless, just like that, after a while, he looked at the things on the test bench and wanted to cry without tears.

Shang Yiyun didn't expect that he had already understood the production principle of graphene vanadium oxide batteries, but he didn't expect the experiment to fail, he didn't know what affected the success or failure of the experiment, so he could only sit on the stool and start thinking about the steps of the experiment just now.

If you don't figure out why, even if you try it again, you may end up failing.

At this time, Cao Xun and Zhang Liu were not idle, and they also saw the steps of the experiment just now, so they also fell into contemplation.

At this moment, Shang Yiyun recalled the steps of the experiment and did not let go of the slightest detail, because in the experiment, the details determine the success or failure, and the failure of many experiments is because of the details of the problem.

In this way, time passed minute by minute, Shang Yiyun's frowning brows also relaxed, he had already grasped some clues, although he still didn't know the real reason for the failure of the experiment, but he believed that if he was given a while, he would definitely be able to figure out the reason for the failure.