I Am the President of the University

Currently, commercially available batteries are mainly lead-acid batteries and lithium batteries, and lithium batteries are currently roughly divided into four categories: lithium-ion batteries, lithium-sulfur batteries, lithium-air batteries and lithium-oxygen batteries.

As for the lithium-air battery, it is a battery that uses lithium as the negative electrode and oxygen in the air as the positive reactant.

Compared with lithium-ion batteries, lithium-air batteries have higher energy density because their cathodes (mainly porous carbon) are light and oxygen is obtained from the environment rather than stored in the battery.

It sounds like it is better than common lithium-ion batteries, but the development of lithium-air batteries is still in the early research stage, and there are still many technical difficulties that cannot be solved before practical application and commercialization.

"Preparation and performance study of key materials for lithium-air batteries."

Chen Hao was now in front of the poster, looked at the title and read it again, but this time it attracted the attention of the stall owner nearby.

"Hey, mam, are you interested in lithium-air batteries?" The other party stood up excitedly and asked Chen Hao.

Chen Hao took a look at the other person. He was wearing a polo shirt and jeans, a very typical look for an engineering man.

He has a beard, some dark circles around his eyes, and looks to be in his thirties or forties.

"A bit interested." Chen Hao nodded slightly and continued to look at the other party's paper.

"What is your research direction?" The other party didn't seem to recognize Chen Hao, but asked curiously,

"me?"

The corners of Chen Hao's lips raised, "I study polymer materials."

"Polymer materials are also very good." The man responded, but he noticed that the other party was reading the paper carefully, so he didn't speak.

At first, Chen Hao was a little dismissive. After all, the technology of lithium-air batteries is far from mature.

It was still in 2012 that the lithium-air battery field published a paper in Nature and Science for the first time, which meant that lithium-ion air batteries were officially recognized by the world's top journals.

Prior to this, lithium-air batteries were not recognized by the scientific community.

But as he looked back, the contempt in Chen Hao's eyes gradually disappeared.

His eyes became serious.

"interesting."

This paper actually surprised him.

Twenty minutes later.

Chen Hao roughly scanned the entire text. Before he could say what he wanted, the man on the side couldn't wait to ask:

"how is it going?"

…

Peking University Yuanpei general education curriculum system

1. It has not been established since its inception. This is also an important reason why it was not envisioned when it was first launched and has not yet been realized, thus affecting the effectiveness of this experiment. The purpose of this experiment was to establish a general education system similar to the first-class liberal arts colleges in the United States, but after more than ten years of operation, this purpose has not been achieved. You can find many commentaries on Yuanpei General Education at Peking University online, with mixed reviews. But in a word, this experiment was not successful.

2. Peking University Yuanpei College focuses on general education, but its current training model does not set up its own general education courses, but adopts a platter-style general education method. Whether this method is good or not remains to be discussed, but currently domestic The educational environment makes it difficult to set up independent general education courses. This may be the "experimental failure" mentioned above.

The so-called platter-style general education means that students at Yuanpei College can take all professional courses at Peking University. Therefore, Yuanpei itself does not offer general education courses, but students can achieve general education by freely combining professional courses from different departments. The result of education. Majors will be divided into sophomore years. Students are free to choose any major within Peking University as their major (of course, they retain the right to change directions and take other professional courses). They can also choose Yuanpei's specialty majors: such as PPE (Politics). , Economics and Philosophy), Foreign Languages ​​and Foreign History, Paleontology, Integrated Science, etc. As the name suggests, these majors are a combination of relevant courses from various departments as your required courses.

A banner that launched undergraduate education and teaching reform in this century, Yuanpei College has been exploring a talent training model with a solid foundation and a wide range of talents for 13 years. It is one of the first colleges in China to test the waters of general education. The accidents, frustrations, embarrassments and even controversies that "Yuanpei" encountered in this talent experiment fully reflect the difficulty and pain of general knowledge.

Peking University Yuanpei is the earliest and relatively mature model in domestic general education reform. General education is now being rolled out in various universities, but the current results are not particularly good - but at least it has taken a step forward.

3. According to the talent training plan of Yuanpei College, after freshmen enroll, they can theoretically choose any course offered by the school and listen to whatever they want. The course study plan is all made by themselves; starting from the sophomore year, students can according to You are free to choose the direction of study according to your own interests, and there are no restrictions in theory.

"Spiritual freedom, academic freedom, and learning freedom." The first feeling almost all students feel after entering Yuanpei is "freedom", but then most people will start to feel "confused."

A student who enrolled in 2004 once published an article online complaining about Yuanpei's "free system." For example, the "tutoring system" that is supposed to be responsible for guiding students to choose courses and majors has limited effect. In fact, freshmen in Yuanpei Grade 04 can't even get a departmental course plan and have to go to the academic affairs department of each department. "Take a look."

Compared with these trivial matters, the freedom to choose courses becomes a bigger obstacle - you can listen to all the classes in the school, but what exactly do you listen to?

At Peking University, undergraduate course plans are mainly divided into two parts: professional courses and general elective courses. Generally speaking, professional courses are more difficult than general elective courses. According to the idea, after any Yuanpei student is in his sophomore year and chooses his own major, the courses he has taken in other departments can replace the general elective courses, and he can graduate with full credits.

For students, such regulations are tantamount to shackles in addition to "free treatment": they choose courses based on their interests. Once their test scores are not satisfactory, they will lose a certain degree of freedom when choosing a major.

…

Although the names are similar, "lithium-ion batteries" and "lithium-air batteries" are two completely different systems, and the principles involved are also very different.

The concept of "lithium-air battery" first appeared in the 1970s. Its core principle is to react lithium with oxygen in the air and convert the energy generated directly into electrical energy.

This is just like burning wood or coal. As the most common way for humans to obtain energy, direct reaction of raw materials and oxygen results in extremely high energy release. It is calculated that the energy density of lithium-air batteries can reach 12,000 watt-hours per kilogram, which is almost 10 times that of lithium-ion batteries and even close to the energy level of gasoline (13,000 watt-hours per kilogram) [1].

This seemingly simple combination of lithium and air has raised the physical ceiling of battery technology by an entire order of magnitude!

Moreover, the oxygen it uses comes from air, and this raw material is almost unlimited.