Why do lithium batteries produce gas when it is overcharged or discharged?

In the process of charging ordinary lithium ion battery, the internal battery will produce a small amount of gas, and it will typically absorb during discharge.

Charging current is too large, often overcharge will aggravate gases, increase the battery internal pressure leads to bulge phenomenon. Battery produces a slight bulge is allowed, avoid overcharge is the key to reduce bloating.

In addition, the chemical properties of lithium is very lively, very easy to burn, when battery charging and discharging inside the battery is on the rise, activation of gas in the process of inflation, the battery internal pressure increase, pressure reaches a certain extent will burst, causing leakage, fire, explosion, even so to ensure its safety performance is absolutely critical.

The lithium battery it mainly some compounds, toxicity is not very big, but also to have certain polluting, had better not be inhaled.

Of course, lithium ion battery electrolyte ingredient is alkyl carbonate and ethers organic or inorganic lithium salt. But is low toxicity, just pay attention to ventilation and don't eat, small doses may have symptoms of dizziness wants to vomit, immediately to the ventilated place can alleviate a breath of fresh air. Serious will have to go to a doctor.

Lithium battery is the carrier of ion transport in battery electrolyte. Generally consists of lithium salt and organic solvents. Electrolytes in lithium batteries have the effect of conduction ion between positive and negative, is the lithium ion battery can obtain high voltage, high, etc. Electrolyte generally made from high purity of organic solvent and electrolyte of lithium salt, necessary additives such as raw material, under certain conditions, according to certain proportion.

1. The ethylene carbonate: molecular formula: C3H4O3

Colorless transparent liquid (> 35 ℃), for crystalline solid at room temperature. Boiling point: 248 ℃ / 760 MMHG, 243-244 ℃ / 740 MMHG. Flash point: 160 ℃;Density: 1.3218;Refractive index: 50 ℃ (1.4158);Melting point: 35-38 ℃;This product is a good solvent for polyacrylonitrile, polyvinyl chloride (PVC).Can be used as a textile spinning fluid; Can also be used directly as solvent of removing acid gas and concrete additives; In medicine, can be used as a pharmaceutical composition and raw material; Also can be used as a plastic foaming agent and synthetic lubricating oil stabilizer; In the battery industry, can be used as a good solvent of lithium battery electrolyte

2. The propylene carbonate formula: C4H6O3

Colorless, odorless, or light yellow transparent liquid is soluble in water and carbon tetrachloride, and ethyl ether, acetone, benzene and other immiscible. It is a good solvent polarity. This product is mainly used for high polymer, gas separation technology and electrochemistry. Especially used for absorbing carbon dioxide gas, petrochemical plant raw material of synthetic ammonia, also can be used as a plasticizer, spinning solvent, olefins and aromatics extraction agent, etc.

Toxicology data: animal experiment by oral or skin contact has not been found poisoning. The rat oral LD50 = 2900 0 mg/kg.

This product should be stored in a cool, ventilated, dry place, away from the fire, according to provisions of general low toxic chemicals storage and transport.

3. Diethyl carbonate molecular formula: C5H10O3

Colorless liquid, slight odor; The vapor pressure of 1.33 kPa / 1.33 ℃;Flash point 25 ℃ (flammable liquid can evaporate into steam, ran into the air. Temperature has volatile speed. When a mixture of volatile vapor and air in contact with the fire coming to spark, the transient combustion process called flash, called the lowest temperature occur flash point. The lower the flash point, the greater the risk of fire.; Melting point - 43 ℃;Boiling point 125.8 ℃;Solubility: insoluble in water, miscible soluble in most of the organic solvent such as alcohol, ketone, ester; Density, relative density 1.0 (water = 1);Relative density (air = 1) 4.07;Stability: stable. Danger tags 7 (flammable liquid);Main application: used as a solvent, and used in organic synthesis

(1) health hazard

Invasive ways: inhalation, eat, percutaneous absorption.

Health hazard: this product is a mild stimulants and anesthetic. Inhaling causes headache, dizziness, weakness, nausea, difficulty breathing, and so on. Liquid or high concentrations have vapour stimulating. Oral stimulation has gastrointestinal tract. Skin contact for a long time repeatedly stimulating.

(2) the toxicological data and environmental behavior

Toxicity: can estimate through the gastrointestinal tract, skin and respiratory tract into the body of medium degree of toxicity. Stimulus is bigger than dimethyl carbonate.

Acute toxicity: LD501570mg/kg (through the mouth) of rats; Inhaled 20 mg/L (steam) x 10 minutes, tears and nasal mucosa stimulation.

Reproductive toxicity: hamster abdominal 11.4 mg/kg (DAMS), has obvious consultations for action.

Dangerous characteristic: flammable, encounter fire, high fever, has caused the risk of burning. Its vapor is heavier than air, can spread in the low to very far place, meet will leads back to the burning flame.

Combustion products (decomposition) : carbon monoxide, carbon dioxide.

(3) leak emergency treatment

Leave quickly leak contaminated area personnel to safe areas, and in isolation, restricted access. Cut off the fire. Recommended emergency personnel wearing positive pressure respirator, wear fire protective clothing. Cut off the leak source as possible. Prevent into the sewer, ditch having restricted space. A small leak: absorption or other inert materials. It can also be made of noncombustible dispersant emulsion scrub, lotion diluted into waste water system. A large number of leak: constructing dike to dig a hole or asylum. In foam cover, reduce the steam disasters. Use explosion-proof pump to tank lorry or dedicated collector, recycling or shipped to the disposal of waste places.

(4) protective measures

Respiratory protection: when the concentration is higher in the air, recommends wearing self-priming filter type gas mask (half mask).

Eye protection: sending protective glasses.

Body protection: wear anti-static overalls.

Hand protection: wear rubber gloves.

Other: no smoking on site. Work and shower change clothes. Pay attention to personal hygiene.

(5) emergency measures

Skin contact: remove contaminated clothing and water with soap and water to thoroughly flushed the skin.

Eye contact: mention eyelid, irrigate with flowing water or normal saline. Go to a doctor.

Inhalation: quickly from the scene to fresh air. Keep respiratory tract unobstructed. Such as difficulty in breathing, give oxygen. If breathing stops, artificial respiration immediately. Go to a doctor.

Eating: drink enough water, vomiting, seek medical attention.

Fire extinguishing methods: spray cooling container, remove from the fire to empty the container if possible. Fire extinguishing agent, foam, dry powder, carbon dioxide, sandy soil.

4. Dimethyl carbonate: C3H6O3

(DMC), dimethylcarbonate, is a non-toxic, environmental performance, USES a wide range of chemical raw materials, it is a kind of important intermediates in organic synthesis and molecular structure containing carbonyl, methyl and methoxyl functional groups, with multiple reaction performance, in the production with the use of safe, convenient, less pollution and easy transportation, etc. Due to the toxicity of dimethyl carbonate is small, is a development prospect of the "green" chemical products,

DMC has excellent solubility property, its melting, boiling point range narrow, surface tension, low viscosity, medium small electric constant, at the same time has high evaporation temperature and faster evaporation rates, thus can be used as a low toxicity solvents used in the coatings industry and pharmaceutical industry. Can be seen from table 1, DMC not only small toxicity, but also has high flash point and lower explosive limit is high in the air, steam down, so is the collection green solvent in a clean and safety.

5. Methyl ethyl carbonate

Molecular weight: 104.1, 1.00 g/cm3 density, colorless transparent liquid, the boiling point 107 ℃, melting point - 14 ℃, is in recent years the rise of high-tech, high value-added chemical products, a good lithium ion battery electrolyte solvent, is with dimethyl carbonate and lithium ion battery production increasing and extending the latest product, because it also has the methyl and ethyl, dimethyl carbonate, diethyl carbonate features, and special spices intermediates and solvents. Because of the imbalance in methyl ethyl, this product is not stable, not suitable for long-term storage.

This product should be stored in a cool, ventilated, dry place, according to provisions of flammable chemicals storage and transport

6. Six fluorine lithium phosphate

White crystal or powder, relative density 1.50.Deliquescence is strong; Soluble in water and soluble in low concentration of methanol, ethanol, acetone, carbonate and organic solvents. When exposed in the air or heat decomposition. When exposed in the air or heat six lithium fluoride phosphate due to the effect of water vapor in the air and fast decomposition, release PF5 and produce white smoke.

7. Phosphorus pentafluoride

Phosphorus pentafluoride (chemical formula: PF5), is phosphorus halide compound, the oxidation of phosphorus atoms number is + 5, contains a three center four electronic key. Phosphorus pentafluoride colorless stench gas under atmospheric pressure, the skin, eyes, mucous membrane has a strong irritating. Is the great reactive compounds, in the moist air will produce toxic and corrosive hf white smoke. Phosphorus pentafluoride was used as a polymerization catalyst.

National standard no. 23022

CAS number 19-7647-0

Chinese name of phosphorus pentafluoride

English name phosphoruspentafluoride

The alias fluoride phosphate

Molecular formula PF5 appearance and properties colorless, stimulating the stench gas, intense smoke in the moist air

Molecular weight 126.0 boiling point 84.6 ℃

Melting point - 93.8 ℃ solubility

The density of the relative density (water = 1) 5.81 (gas);Relative density (air = 1) 4.3 stability and stability

Danger tag 6 (poisonous gas, inorganic drama) main use for gas, and used as a polymerization catalyst

(1) the impact on the environment

A health hazard

Invasive ways: suction.

Health hazard: in damp produce toxic and corrosive hydrogen fluoride in the air. This product has strong stimulation to the skin, eyes, mucous membrane, when inhaled can cause respiratory inflammation and pulmonary edema.

Second, the toxicology material and environmental behavior

Toxicity: irritating.

Dangerous characteristic: white in moist air corrosive and stimulating hf fumes. In the water decomposition emits poisonous corrosive gas. Encounter alkali decomposition.

Combustion products (decomposition) : oxidation of phosphorus, phosphorus alkanes, hydrogen fluoride.

(2). The emergency disposal method

A, leakage emergency handling

Rapid evacuation leakage pollution area personnel to windward, and immediately in isolation, small leakage isolation of 300 meters, 450 meters of large leakage isolation, restricted access. Recommended emergency personnel wearing positive pressure respirator, wear protective clothing. Cut off the leak source as possible. Reasonable ventilation, accelerate the diffusion. Flat container to properly handle, reoccupy after repairing, inspection.

Second, the protective measures

Respiratory protection: may contact the steam, must wear self-priming filter type gas mask (comprehensive cover).When necessary, wear air breathing apparatus.

Eye protection: respiratory protection has been made in protection.

The body protection: wear tape gas-protection clothing.

Hand protection: wear rubber gloves.

Other: no smoking on site. Pay attention to personal hygiene.

Three, first aid measures

Skin contact: remove contaminated clothing and flush with plenty of liquid water. Go to a doctor.

Eye contact: mention eyelid, irrigate with flowing water or normal saline. Go to a doctor.

Inhalation: quickly from the scene to fresh air. Keep respiratory tract unobstructed. Such as difficulty in breathing, give oxygen. If breathing stops, artificial respiration happens immediately. Go to a doctor.

Fire extinguishing methods: firefighters whole body fire protective clothing must be worn. Cut off the gas source. Water spray cooling container, possible remove the container from fire to open. Agent: dry chemical, carbon dioxide.

8. Hydrofluoric acid

This article accords to the hazardous chemical materials safety management regulations by the public security department control.

Colorless transparent liquid smoke is as the aqueous solution of hydrogen fluoride gas. A weak acid. Stimulating odour. React with silicon and silicon compounds to generate gaseous silicon tetrafluoride, but for plastic, paraffin corrode, lead, gold, platinum. Can miscibility with water and ethanol. Relative density 1.298.38.2% of hydrofluoric acid for azeotrope, azeotropic temperature 112.2 ℃.Toxic, minimal lethal dose (rats, the abdominal cavity) 25 mg/kG. Corrosive, and can strongly corrosive action on metals, glass and object containing silicon. Such as inhalation of vapor or contact with the skin can become more difficult to healing of ulcer.

(1) the safety measures

Leak: leave quickly leak contaminated area personnel to safe areas, and in isolation, restricted access. Recommended emergency personnel wear positive pressure respirator, wear resistant acid and alkali overalls. Don't direct contact with the leakage. As far as possible to cut off the leak source, prevent into the sewer, ditch having restricted space.

A small leak: lime or soda ash mixed with sand, dry. Also can use a lot of water washing, wash water diluted into the wastewater system.

A large number of leaks: constructing dike or dig a pit asylum; Pump to tank lorry or dedicated collector, recycling or shipped to the disposal of waste places.

(2) extinguishing method

Combustibility: non-combustible

Agent: water fog, foam.

Fire precautions: fire personnel must wear oxygen respirator, wear full protective clothing.

(3) emergency treatment

Inhalation: quickly from the scene to fresh air. Keep respiratory tract unobstructed. Such as difficulty in breathing, give oxygen. If breathing stops, artificial respiration happens immediately. Go to a doctor.

One person eat: water gargle, to drink milk or egg white. Go to a doctor.

Skin contact: remove contaminated clothing and immediately flush with plenty of liquid water, at least 15 minutes. Go to a doctor. Or, immediately remove contaminated clothing and flush with enemy rotten trane, if it is acid containing fluorine, flush with six fluorine spirit. Go to a doctor.

Eye contact: immediately filed a eyelid, with plenty of liquid water or saline thoroughly flushed at least 15 minutes. Decay or use the enemy trane eye bath (if it is acid containing fluorine, flush with six fluorine spirit).

(4) the physical and chemical properties

Hydrofluoric acid aqueous solution has hydrogen fluoride gas, colorless transparent liquid to pale yellow smoke. Stimulating odour.

Has weak acidity, but strong when the degree of ionization of large, and generally weak than when dilute electrolyte are different. A strong corrosive, tooth, bone damage more serious. For silicon compounds have strong corrosion resistance. Should be kept in airtight plastic bottles.

HF is soluble in water. It is used for engraving on the glass, cleaning casting sand, controlling of fermentation residue, electrolytic polishing and cleaning corrosion semiconductor wafers (with mixed acid of HNO3). Because hydrogen atoms and fluorine atoms have relatively strong capability, make the hydrofluoric acid can't completely ionization in the water.

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