Discussion on the relationship between batteries and the environment

The development of information technology, especially the rapid development of mobile communications and laptop computers, urgently requires batteries to be small, lightweight, have long service time, long working life and maintenance-free; the call for environmental protection is getting louder and louder, which requires the battery itself to be non-toxic and pollution-free. Therefore, new green and environmentally friendly batteries will play a pivotal role in the development of major technological fields such as electronic information, new energy and environmental protection in the 21st century.

However, in recent years, the environmental management of waste batteries has increasingly attracted the attention of the public, the media, and environmental management departments. Waste batteries contain a large amount of heavy metals, acids, alkalis and other substances, which may leak into the environment and cause great harm to the environment. Therefore, it is very necessary and urgent to strengthen the environmentally sound management of waste batteries.

1. Recycling and reproduction of several types of waste batteries

The main pollutants contained in batteries include a large amount of heavy metals and electrolyte solutions such as acids and alkalis. The main heavy metals are: cadmium, lead, mercury, nickel, zinc, manganese, etc. Among them, cadmium, mercury and lead are more harmful to the environment and human health. The types of waste batteries that are more harmful to the environment and human health are mainly: (1) mercury-containing batteries, mainly mercury oxide batteries, and some zinc-manganese and alkaline-manganese dry batteries with high mercury content; (2) lead-acid batteries; (3) cadmium-containing batteries, mainly Cd-Ni batteries.

The following will analyze the recycling and reproduction of lead-acid batteries and cadmium-nickel waste batteries in detail.

1.1 Recycling and Reproduction of Lead-acid Batteries

Lead-acid batteries are the most widely used and produced batteries in the world. The lead they consume accounts for 82% of the world's total lead consumption. my country's lead-acid battery industry entered a period of vigorous development in the 1980s. With the development of the national economy, its market will continue to expand, with automobiles, motorcycles, electricity and communications as the main targets. By the 1990s, my country's annual output of lead-acid batteries was more than 30 million kWh. In recent years, the development of smoke-free transportation vehicles such as electric vehicles will lead to greater development of lead-acid batteries. The greater the output of lead-acid batteries, the more lead-acid batteries will be scrapped and updated. From an environmental protection perspective, lead-acid batteries are also the most harmful to the environment and human health. If a more complete recycling system is not adopted, the heavy metals and toxic waste liquids decomposed by the randomly discarded waste lead-acid batteries will pose a serious threat to ecological balance and human health. Acute or chronic intake of lead into the human body can cause neuro-metabolism, reproductive and mental diseases, and in severe cases can lead to death.

Waste lead-acid batteries are hazardous wastes among solid wastes. They should be classified and managed, and must be disposed of in a mandatory manner. Strict requirements and key controls should be imposed on key links such as their collection, transportation, storage, and treatment, and they should be managed in accordance with the principle of centralized disposal. The recycled lead industry is an emerging industry that has gradually developed in my country while paying attention to environmental protection and making full use of recycled metal resources. With the rapid development of my country's automobile, communications, and chemical industries, the demand for lead has continued to increase. This has not only expanded the consumer market for recycled lead, but also increased the amount of waste batteries due to the increase in battery consumption, giving the recycled lead industry more sources of raw materials. my country's recycled lead industry is in a very favorable period of development.

Foreign countries also have corresponding technologies for the treatment of waste lead-acid batteries. Developed countries mainly use pre-treatment technologies such as mechanical crushing and sorting and desulfurization of sulfur-containing lead paste, and then use pyrolysis, wet processing, and dry-wet combined processes to recover lead and other valuable substances. The lead of waste batteries is recycled after pre-treatment, which not only reduces the labor intensity of workers, but also reduces the amount of materials entering the furnace and improves the lead grade of the charge, thereby reducing the amount of flue gas, waste slag, smoke, energy consumption, sulfur dioxide emissions, and improving metal recovery rate, work efficiency, and production capacity.

1.2 Recycling process of waste nickel-cadmium batteries

Since the 1980s, portable electronic devices such as mobile phones and laptops have developed rapidly. The number of cadmium-nickel batteries used in such electronic devices has also increased rapidly. Although metal hydride-nickel batteries have incomparable advantages over cadmium-nickel batteries, their price has hindered their pace of replacing cadmium-nickel batteries . Cadmium-nickel batteries still occupy nearly half of the market share. The cadmium in cadmium-nickel batteries is an element that has serious toxic effects on humans, animals and plants, and nickel and cobalt are also heavy metal elements that pollute the environment. At the same time, since cadmium is mainly produced as a by-product of zinc smelting, the source is very limited. Nickel and cobalt are also non-ferrous metals with very high value. Therefore, if waste cadmium-nickel batteries are not recycled, it will not only pose a serious threat to the environment, but also be a major waste of resources.

A number of patent technologies have been published on the recovery and separation of cadmium-nickel waste batteries. The typical method is to first completely immerse the battery in a solution with H ₂ SO ₄ , and then use the following methods to separate cadmium and nickel: (1) Electrodeposit cadmium at the cathode by electrolysis. This method requires a low current density and must be strictly controlled to prevent nickel electrodeposition. Therefore, this method is inefficient and costly. (2) Use aluminum powder to displace and precipitate cadmium and nickel in stages. The purity of the recovered cadmium and nickel is low. (3) Use NH ₄ HCO ₃ to selectively precipitate CdCO _3. This method requires the addition of a large amount of (NH ₄ ) ₂ SO _{4 at the same time as NH 4} HCO ₃ , so that the nickel ions form nickel ammine complex ions to reduce the amount of nickel precipitation. In addition, the process must be strictly controlled to prevent the decomposition of NH ₄ HCO _{3 .}

2New green and environmentally friendly batteries

New green and environmentally friendly batteries refer to a type of high-performance, pollution-free batteries that have been put into use or are being developed in recent years. Currently, nickel-metal hydride batteries and lithium-ion batteries that are already in large quantities, mercury-free alkaline zinc-manganese primary batteries and rechargeable batteries that are being promoted, polymer lithium or lithium-ion batteries that are being developed, fuel cells, electrochemical energy storage supercapacitors, and solar cells that use solar energy for photoelectric conversion (also known as photovoltaic power generation) that are currently widely used all fall into this category.

Metal hydride nickel storage battery (MH-Ni) has the same working voltage (1.2V) as cadmium nickel storage battery (Cd-Ni), but because rare earth alloy or TiNi alloy hydrogen storage material is used as the negative electrode active material, replacing the carcinogenic cadmium, this new type of battery not only becomes a green battery , but also increases the specific energy of the battery by nearly 40%, reaching 60-80 Wh/kg and 210-240 Wh/L.

Lithium-ion batteries are composed of a carbon negative electrode that can embed and de-embed lithium ions, a metal oxide positive electrode (LiCoO ₂ , LiNiO ₂ or LiMn ₂ O ₄ ) that can reversibly embed lithium, and an organic electrolyte. Its operating voltage is 3.6V, so one lithium-ion battery is equivalent to three nickel-cadmium or nickel-metal hydride batteries. The specific energy of this battery can exceed 100Wh/kg and 280Wh/L, which greatly exceeds the specific energy of nickel-metal hydride batteries.

Alkaline zinc-manganese dry batteries have higher capacity than ordinary dry batteries of the same size and have large current discharge capabilities. In recent years, mercury-free zinc powder has been used, making this battery a green battery and a mainstream product among primary batteries. This battery maintains the discharge characteristics of the primary battery and can be recharged and used dozens to hundreds of times.

Polymer lithium battery (also known as plastic lithium battery) is a new type of battery with metal lithium as negative electrode and conductive polymer as electrolyte, and its specific energy has reached 170Wh/kg and 350Wh/L. Polymer lithium-ion battery (also known as plastic lithium-ion battery) stores the organic electrolyte in the current lithium-ion battery in a polymer film, or uses conductive polymer as electrolyte, so that there is no free electrolyte in the battery. This kind of battery can be hot-pressed with aluminum-plastic composite film, and has the characteristics of light weight, arbitrary shape change and better safety.

A fuel cell is a device that uses fuel (such as hydrogen or hydrogen-containing fuel) and an oxidant (such as pure oxygen or oxygen in the air) to directly and continuously generate electricity. Since it avoids the limitations of the Carnot cycle, this power generation device is not only highly efficient (the electrochemical reaction conversion efficiency can be as high as 40% or more), but also does not emit any polluting gases. Therefore, it is an efficient and clean way of generating electricity in the future, and is also an ideal power source for electric vehicles.

Solar cells are devices that use solar energy to generate electricity based on the principle of the photoelectric effect of semiconductor pn junctions. According to the user's power requirements, this type of device is used to form a component or array to become a power generation device. Obviously, this power generation method has incomparable advantages over other power generation methods: no need for fuel, no pollution, no noise, simple and reliable operation, less maintenance, and a short construction period. Therefore, photovoltaic power generation is the most promising new energy source in the future world.

New green and environmentally friendly batteries also play a very important role in meeting the needs of modern military equipment and weapons, transportation, office automation, mineral exploration, oil drilling, medical equipment and even household appliances, which are closely related to the national economy and people's lives.

3 Conclusion

From the above analysis, it can be seen that comprehensive resource utilization is an effective way to solve resource shortages and manage the environment, and it is also a major issue related to the sustainable utilization of effective resources. New green and environmentally friendly battery technology has been recognized internationally as a technology that should be given priority development. Therefore, in light of China's national conditions, accelerating the development of new green and environmentally friendly battery technology and corresponding industries is an urgent task.