Detailed analysis of the current situation of lithium battery technology for electric bicycle

Lithium battery is a kind of lithium metal or lithium alloy anode materials, using water battery electrolyte solution. First the lithium battery is invented by the great inventor Thomas Edison, use the following response: Li + MnO2 = LiMnO2, the reaction of REDOX reaction. Because the lithium chemistry is very active, make lithium metal processing, storage, usage has very high demand on the environment. So, the lithium battery has not been applied for a long time. And now, the lithium battery has become the mainstream.

At present, lithium ion batteries applied in the electric bicycle products is relatively common, lightweight, and solves the electric bicycle MeiGuanHua product demand, but because of its application is not a long time, but power lithium battery technology did not reach the level of perfect, so there are many problems to be solved. The following, we analysis the electric bicycle with lithium batteries in the present situation of the technical level.

A development process, lithium ion batteries

Due to the lithium chemistry is very active, making lithium metal processing, storage, use, the environmental requirements is very high, so the lithium battery production in special environment conditions. Due to the many advantages of lithium-ion batteries, lithium batteries are widely used in electronic instruments, digital products and home appliances. However, most lithium batteries are secondary batteries, there is also a disposable batteries. A few of the secondary battery life and security is bad.

Later, SONY of Japan invented the carbon materials as anode, with lithium compounds as the anode of lithium battery, in the process of charging and discharging, no metal lithium exists, only lithium ion, that is the lithium ion battery. When charging the battery, the battery has lithium ions generated in the anode, the generated lithium ions through the electrolyte to the negative movement. As a cathode carbon layer structure, it has many pores, reach the cathode of lithium ion is embedded into the microporous carbon layer, the embedded lithium ion, the more the higher the charge capacity. Also, when to discharge the battery (i.e., we use the battery process), embedded in the cathode carbon layer of emergence, lithium ions and movement back to the anode.

Back to the anode of lithium ion, the more the higher the discharge capacity. We usually mean by battery capacity is the discharge capacity.In Li - iond of charge and discharge process, the lithium ions in motion from the positive and negative to the positive.Li - ion batteries is like a rocking chair, rocking chair at both ends of the poles for the battery, and lithium ion like athletes running back and forth in a rocking chair. So Li - ion batteries also called rocking-chair batteries.

As digital products such as the widespread use of mobile phones, laptops and other products, lithium-ion battery with excellent performance is widely used in such products, and gradually to other areas of application development products in recent years. In 1998, Tianjin institute of power began commercial production of lithium ion battery. Traditionally, people called the lithium ion battery is lithium batteries, lithium ion battery has now become the mainstream.

Second, the characteristics of lithium ion batteries

Lithium ion batteries and other kind of battery, there is a difference, has its unique features.

(a) high energy density

The weight of the lithium ion battery is the same amount of nickel cadmium or nickel metal hydride batteries, half volume is 20-30% of nickel cadmium, nickel metal hydride 35-50%.

(2) high voltage

A lithium ion battery monomer working voltage of 3.7 V (mean), the equivalent of three series of nickel cadmium or nickel metal hydride batteries.

(3) no pollution

Lithium ion battery does not contain harmful metals such as cadmium, lead, mercury.

(4) do not contain lithium metal

Lithium ion battery does not contain lithium metal, and from the transport plane of bar rules such as jet carrying lithium battery limit.

(5) high cycle life

Under normal conditions, the lithium ion battery charge and discharge cycles can be more than 500 times, lithium iron phosphate (hereinafter referred to as phosphorus iron) can reach 2000 times.

(6) no memory effect

Memory effect refers to the nickel cadmium battery in the process of charging and discharging cycle, the battery capacity to reduce the phenomenon. Lithium-ion batteries, no such effect.

(7) quick charge

Using the rated voltage of 4.2 V constant current constant voltage charger, can make the lithium ion battery charged at 1.5-2.5 hours; And the new development of phosphorus iron lithium electricity, can be recharged in 35 minutes.

Three, lithium ion battery in the application in the field of electric bicycle

At present in the application of high-power electric bicycle lithium ion power battery basically all is by more than single cells in series and in parallel. In the process of its application, the problems existing in the lithium power battery is mainly between each monomer battery large discreteness, thus affect the entire safety and service life of the battery pack.

Therefore, we should think the ideal lithium power battery management for safety and service life of the battery pack. The control requirement is: not only to manage and protect each of monomer battery, the battery pack and at the time of discharge also keep each battery voltage balance is consistent, like many glasses of water in the same horizontal line balance out consistently. In charge to ensure that all the batteries in the battery pack in the same voltage line balancing consistently recharged, until all the battery, as many a cup, although is not the same as the capacity, but at the same flow injection, to ensure that each cup water.

To sum up, the electric bicycle with lithium batteries in use process, to keep the battery but admit, however, no fever, long service life, especially the use of security. This requires the battery pack must have a battery charge and discharge of each monomer equilibrium and protection function.

Four, the classification of the electric bicycle with lithium batteries

Electric bicycle with lithium batteries can be roughly divided into three broad categories: manganese acid lithium battery, batteries ternary materialand lithium iron phosphate batteries。

Manganese acid lithium battery: solve the high temperature performance of manganese acid lithium battery, battery cathode material, the battery must be modified structure design and the electrolyte formula. In Japan and South Korea USES the modified lithium manganese acid, modified manganese acid lithium battery, one week after the 65 ℃ storage capacity only dropped to 99%.

Ternary material battery: cobalt, nickel and manganese ternary material as the anode material of lithium battery, it overcomes the defects about the worse performance of high temperature of manganese acid lithium, and improves the specific energy of the battery.

Lithium iron phosphate battery: since 2002, the United States and Canada started developing lithium iron phosphate batteries, it become a new kind of great development prospect of power type lithium ion batteries. Long life, charge and discharge cycle 1 c at room temperature up to 2000 times.

Lithium iron phosphate batteries advantages: high safety. Stronger binding force, structure of phosphoric acid root chemical stability is good; Environmental protection and does not contain any heavy metals; Non-toxic (through the SGS certification), no pollution; Fast charging, lithium iron phosphate batteries can be large current 5 ~ 10 c fast charge and discharge; Large current discharge performance is good; Can be 10 ~ 50 c large current high power discharge.

Lithium iron phosphate battery disadvantages: low temperature performance is inferior to manganese acid lithium and other positive electrode material. Lithium iron phosphate monomer battery voltage is 3.2 V.36 v battery pack need 12 single cells in series. Monomer lithium iron phosphate battery life is more than 2000 times, but the life of the battery pack may only 500 times.

Fifth, the advantages and disadvantages of lithium battery electric bicycle

(a) the advantages of electric bicycle with lithium batteries

Lithium battery power than lead-acid batteries twice more, currently use lead-acid battery electric bicycle charging a range of 50 ~ 70 km, use the same weight of lithium battery can drive 100 ~ 100 km, it also has a high number of charging and discharging, existing problems are: the price is higher, 6 times for lead-acid batteries, each car is $1800 ~ 2000.Moreover, existing specifications are applicable to the small type of the mobile phones, laptops, larger models need to be developed more than 10 ah, this kind of battery is currently only used for luxury bicycle or electric motorcycle, but its price reduction potential is bigger, foreground is very good.

Lithium battery electric bicycle has the advantage of its long life, light weight, small volume. There is a small of lithium battery electric bicycle, weighs only about 16 kilograms, the battery is the size of a book, only 2.5 kg, can carry on bag, can also be used to recharge my computer, and the horsepower of lead-acid battery weight is around 15 kg. The electric price is more expensive, however, to more than 2800 yuan." This car on the market only a week, the price is higher, but the sales is better than expected, a week will sell several cars."Luyuan ev zhang, director of introduction, this kind of car USES lithium battery, a charge can run 30 km.Giant, bridge stone brand store also has a lithium battery electric vehicles." The dynamic properties of lithium battery electric bicycle and lead-acid battery, charging 6 ~ 8 hours, depending on the battery capacity can run 30 ~ 45 kilometers, the weight is only about 1/5 of the lead-acid battery." Giant of the sales staff said that the biggest advantages of lithium battery electric bicycle long life, a group of cells available 4 ~ 5 years, while lead-acid battery life only 2 years.

(2) the shortcoming of electric bicycle with lithium batteries

The disadvantages of lithium battery is the price on the high side, the market share of only 4%.Now the price of lithium battery electric bicycle is generally higher than that of lead-acid battery electric vehicle several hundred yuan to one thousand yuan, so the sales is not big. "Both differ 800 yuan, if only hundred yuan I might consider." Is the choose and buy electric bike ms zhang finally bought the traditional lead-acid battery electric vehicles.

Six, electric bicycle with li-ion battery problems and solutions

Lithium-ion batteries used in electric bicycle products is not a long time, its technology did not achieve a high level, therefore, there are many technical problems, to a certain extent restricts the development of electric bicycle lithium battery industry.

At present, the electric bicycle with lithium ion batteries need to solve the problem is mainly used in the process of security problems, how to solve security problems become one of the electric bicycle with li-ion battery development in the future trend, here we make a brief introduction of how to solve this problem.

(a) the overcharge

Normal li-ion battery should be charged the highest 4.2 v, lithium iron batteries on the basis of the upper and lower bounds minus 0.5 volts do, charge is higher than 4.3 v for filling. To solve this problem, need to accurately measure the voltage value: the scientific way of charging, full of, but charge;Reasonable setting: single section as the overcharge protection voltage, such as: 4.2 V + / - 0.05 V, make sure that there is no overcharge and explosion.

(2) the discharge

Minimum 3.2 v lithium battery discharge, discharge under 3 v for put, accurate measurement power true value: use scientific and safe way of discharge, but put it finished; Reasonable setting: single section put protection voltage, such as: 3.20 V + / - 0.05 V, make sure that there is no discharge and explosion.

(3) the battery temperature detection

Lithium battery temperature is too high will produce explosion may, therefore, need to monitor the temperature of the battery for each session, ensure that won't produce explosion because of the battery temperature is too high.

(4) the over-current protection

Lithium-ion batteries have a rated current, does not allow more than rated current, otherwise it will burn out the battery. Therefore, we need to accurate measurement and control charge and discharge current, and efficient rapid over-current protection measures are taken, when the current exceeds set current time, avoid the accident of the short circuit, reverse connection, etc.

(5) equilibrium

Lithium ion battery monomer voltage deviation, if not balanced control, with the increase of charge and discharge cycle, each monomer battery voltage gradually differentiation, will greatly reduce the service life. When on a group of lithium-ion battery charge and discharge, considering the inconsistencies, each monomer battery can be balanced measures to ensure security and stability.

Examples of lithium battery is widely used energy storage power system, post and telecommunications communication uninterruptible power supply, and power tools, electric bicycles, electric motorcycles, electric cars, military equipment,special and other fields.

Application in the field of lithium-ion batteries in electric bicycle, although has not yet reached a mature degree, but the good development prospects, as well as the lithium-ion batteries in electric bicycle products exhibit excellent characteristics, make lithium electric bicycle gets relatively rapid development.

In addition, at present, the development of large capacity lithium ion battery has started trial in electric cars, is expected to become one of the main power source in the 21st century, the electric car, and will be in the aspect ofspecial,special and energy storage applications.

As energy shortage and the environmental pressure of the world, lithium electricity now is widely used in electric car industry, particularly the emergence of lithium iron phosphate batteries, has promoted the lithium battery industry technology progress and breakthrough.

The page contains the contents of the machine translation.