Energy, as the material basis for the progress of human civilization, has always played an important role. It is an indispensable guarantee for the development of human society. Together with water, air, and food, it constitutes the necessary conditions for human survival and directly affects human life. .

The development of the energy industry has undergone two major transformations from the “era” of firewood to the “era” of coal, and then from the “era” of coal to the “era” of oil. Now it has begun to change from the “era” of oil to the “era” of renewable energy change.

From coal as the main source in the early 19th century to oil as the main source in the middle of the 20th century, humans have used fossil energy on a large scale for more than 200 years. However, the global energy structure dominated by fossil energy makes it no longer far away from the depletion of fossil energy.

The three traditional fossil energy economic carriers represented by coal, oil and natural gas will be exhausted rapidly in the new century, and in the process of use and combustion, it will also cause the greenhouse effect, generate a large amount of pollutants, and pollute the environment.

Therefore, it is imperative to reduce dependence on fossil energy, change the existing irrational energy use structure, and seek clean and pollution-free new renewable energy.

At present, renewable energy mainly includes wind energy, hydrogen energy, solar energy, biomass energy, tidal energy and geothermal energy, etc., and wind energy and solar energy are current research hotspots worldwide.

However, it is still relatively difficult to achieve efficient conversion and storage of various renewable energy sources, thus making it difficult to effectively utilize them.

In this case, in order to realize the effective utilization of new renewable energy by human beings, it is necessary to develop convenient and efficient new energy storage technology, which is also a hot spot in current social research.

At present, lithium-ion batteries, as one of the most efficient secondary batteries, have been widely used in various electronic devices, transportation, aerospace and other fields. , the prospects for development are more difficult.

The physical and chemical properties of sodium and lithium are similar, and it has energy storage effect. Because of its rich content, uniform distribution of sodium source, and low price, it is used in large-scale energy storage technology, which has the characteristics of low cost and high efficiency.

The positive and negative electrode materials of sodium ion batteries include layered transition metal compounds, polyanions, transition metal phosphates, core-shell nanoparticles, metal compounds, hard carbon, etc.

As an element with extremely abundant reserves in nature, carbon is cheap and easy to obtain, and has gained a lot of recognition as an anode material for sodium-ion batteries.

According to the degree of graphitization, carbon materials can be divided into two categories: graphitic carbon and amorphous carbon.

Hard carbon, which belongs to amorphous carbon, exhibits a sodium storage specific capacity of 300mAh/g, while carbon materials with a higher degree of graphitization are difficult to meet commercial use due to their large surface area and strong order.

Therefore, non-graphite hard carbon materials are mainly used in practical research.

In order to further improve the performance of anode materials for sodium-ion batteries, the hydrophilicity and conductivity of carbon materials can be improved by means of ion doping or compounding, which can enhance the energy storage performance of carbon materials.

As the negative electrode material of sodium ion battery, metal compounds are mainly two-dimensional metal carbides and nitrides. In addition to the excellent characteristics of two-dimensional materials, they can not only store sodium ions by adsorption and intercalation, but also combine with sodium The combination of ions generates capacitance through chemical reactions for energy storage, thereby greatly improving the energy storage effect.

Due to the high cost and difficulty in obtaining metal compounds, carbon materials are still the main anode materials for sodium-ion batteries.

The rise of layered transition metal compounds is after the discovery of graphene. At present, the two-dimensional materials used in sodium-ion batteries mainly include sodium-based layered NaxMO4, NaxCoO4, NaxMnO4, NaxVO4, NaxFeO4, etc.

Polyanionic positive electrode materials were first used in lithium-ion battery positive electrodes, and were later used in sodium-ion batteries. Important representative materials include olivine crystals such as NaMnPO4 and NaFePO4.

Transition metal phosphate was originally used as a positive electrode material in lithium-ion batteries. The synthesis process is relatively mature and there are many crystal structures.

Phosphate, as a three-dimensional structure, builds a framework structure that is conducive to the deintercalation and intercalation of sodium ions, and then obtains sodium-ion batteries with excellent energy storage performance.

The core-shell structure material is a new type of anode material for sodium-ion batteries that has only emerged in recent years. Based on the original materials, this material has achieved a hollow structure through exquisite structural design.

The more common core-shell structure materials include hollow cobalt selenide nanocubes, Fe-N co-doped core-shell sodium vanadate nanospheres, porous carbon hollow tin oxide nanospheres and other hollow structures.

Due to its excellent characteristics, coupled with the magical hollow and porous structure, more electrochemical activity is exposed to the electrolyte, and at the same time, it also greatly promotes the ion mobility of the electrolyte to achieve efficient energy storage.

The global renewable energy continues to rise, promoting the development of energy storage technology.

At present, according to different energy storage methods, it can be divided into physical energy storage and electrochemical energy storage.

Electrochemical energy storage meets the development standards of today’s new energy storage technology due to its advantages of high safety, low cost, flexible use, and high efficiency.

According to different electrochemical reaction processes, electrochemical energy storage power sources mainly include supercapacitors, lead-acid batteries, fuel power batteries, nickel-metal hydride batteries, sodium-sulfur batteries, and lithium-ion batteries.

In energy storage technology, flexible electrode materials have attracted many scientists’ research interests due to their design diversity, flexibility, low cost, and environmental protection characteristics.

Carbon materials have special thermochemical stability, good electrical conductivity, high strength, and unusual mechanical properties, making them promising electrodes for lithium-ion batteries and sodium-ion batteries.

Supercapacitors can be quickly charged and discharged under high current conditions, and have a cycle life of more than 100,000 times. They are a new type of special electrochemical energy storage power supply between capacitors and batteries.

Supercapacitors have the characteristics of high power density and high energy conversion rate, but their energy density is low, they are prone to self-discharge, and they are prone to electrolyte leakage when used improperly.

Although the fuel power cell has the characteristics of no charging, large capacity, high specific capacity and wide specific power range, its high operating temperature, high cost price, and low energy conversion efficiency make it only available in the commercialization process. used in certain categories.

Lead-acid batteries have the advantages of low cost, mature technology, and high safety, and have been widely used in signal base stations, electric bicycles, automobiles, and grid energy storage. Short boards such as polluting the environment cannot meet the increasingly higher requirements and standards for energy storage batteries.

Ni-MH batteries have the characteristics of strong versatility, low calorific value, large monomer capacity, and stable discharge characteristics, but their weight is relatively large, and there are many problems in battery series management, which can easily lead to the melting of single battery separators.