What are the precautions for using lithium-ion polymer batteries?

Abstract: According to the different electrolyte materials used in lithium-ion batteries, lithium-ion batteries can be divided into liquid lithium-ion batteries and polymer lithium-ion batteries. The anode and cathode materials used in polymer lithium ion batteries are the same as liquid lithium ion. The cathode material is divided into lithium cobaltate, lithium manganate, ternary material and lithium ferrous phosphate material, and the cathode is graphite, and the working principle of the battery is basically the same. The following article introduces the matters needing attention in the use of lithium-ion batteries in detail. What are the precautions for using lithium-ion polymer batteries?

According to the different electrolyte materials used in lithium ion batteries, lithium ion batteries can be divided into liquid lithium ion batteries (LIB) and polymer lithium ion batteries (PLB). The anode and cathode materials used in polymer lithium ion batteries are the same as liquid lithium ion. The cathode material is divided into lithium cobaltate, lithium manganate, ternary material and lithium ferrous phosphate material, and the cathode is graphite, and the working principle of the battery is basically the same. Their main difference lies in the difference of electrolytes. Liquid lithium ion batteries use liquid electrolyte, and polymer lithium ion batteries use solid polymer electrolyte, which can be "dry" or "colloidal". At present, polymer colloidal electrolyte is mostly used.

1 classification

solid

Solid polymer electrolyte Lithium ion battery electrolyte is a mixture of polymer and salt. This battery has low ionic conductivity at room temperature and can be used at room temperature.

gel

Gel polymer electrolyte lithium ion battery is a solid polymer electrolyte with additives such as plasticizer to improve ionic conductivity and make the battery available at room temperature.

polymer

Polymer cathode material Lithium-ion battery uses conductive polymer as cathode material, and its specific capacity is relatively increased. Compared with liquid lithium-ion battery, polymer lithium-ion battery has the advantages of thinning, arbitrary area and arbitrary shape, and can be made of aluminum-plastic composite film to improve the specific capacity of the whole battery. Polymer lithium-ion battery can also use polymer as cathode material, and its specific mass energy will be increased by more than 20% compared with the current liquid lithium-ion battery. Polymer lithium-ion battery has the characteristics of miniaturization and thinness. Therefore, the market share of polymer batteries will gradually increase.

2 Note: Pay attention to short circuit.

Polymer lithium-ion batteries are prone to short circuit during charging. Including internal short circuit, external short circuit and so on.

Although most lithium-ion batteries now have short-circuit protection circuits and explosion-proof wires, in many cases, such protection circuits may not work under various circumstances, and the role of explosion-proof wires is limited.

Second, don't overcharge when charging.

If the charging time of polymer lithium-ion battery is too long, the possibility of expansion will increase.

Lithium is very active in chemistry and burns easily. When the battery is charged and discharged, the internal temperature of the battery keeps rising, the gas generated in the activation process expands, the internal pressure of the battery increases, and the pressure reaches a certain level. If the shell is scarred, it will break, causing liquid leakage, fire and even explosion. Polymer lithium-ion batteries will only expand.

Everyone must pay attention to safety when using it.

Principle 3 Lithium-ion batteries currently include liquid lithium-ion batteries (LIB) and polymer lithium-ion batteries (PLB). Among them, the liquid lithium ion battery refers to the secondary battery in which the Li+ intercalation compound is positive and negative. The anode adopts lithium compound LiCoO2, LiNiO2 or LiMn2O4, and the cathode adopts lithium-carbon interlayer compound LixC6. A typical battery system is as follows:

(-) c | lipf6-EC+DEC | LiCoO2 (+) polymer lithium-ion battery

Positive electrode reaction (oxidation reaction) of polymer lithium ion battery (15 sheets): licoo2 = li1-xcoo2+xli++xe-(2.1)

Negative reaction (reduction reaction): 6c+xli++xe-= lixc6-(2.2)

Total battery reaction: licoo2+6c = Li1-xcoo2+lixc6-(2.3)

The principle of polymer lithium-ion battery is the same as that of liquid lithium, but the main difference is that the electrolyte is different from liquid lithium. The main structure of the battery includes three elements: positive electrode, negative electrode and electrolyte. The so-called polymer lithium-ion battery means that at least one or more of these three main structures adopt polymer materials as the main battery system. However, in the currently developed polymer lithium-ion battery system, polymer materials are mainly used as anode and electrolyte. Cathode materials include conductive polymers or inorganic compounds used in common lithium ion batteries, and electrolytes can be solid or colloidal polymer electrolytes or organic electrolytes. The general lithium ion technology uses liquid or colloidal electrolyte, so it needs solid secondary packaging to contain combustible active components, which increases the weight and limits the flexibility of size.

The new generation of polymer lithium-ion batteries can be thin in shape (ATL batteries can be as thin as 0.5 mm, which is equivalent to the thickness of a card), arbitrary in size and shape, which greatly improves the flexibility of battery modeling design, enables them to be made into batteries with arbitrary shapes and capacities to meet product requirements, and provides certain design flexibility and adaptability for equipment developers in power supply solutions, so as to maximize their product performance. At the same time, the unit energy of polymer lithium-ion battery is increased by 20% compared with the current universal lithium-ion battery, and the capacity and environmental protection performance are improved.

4 Looking forward to the following development trends of mobile phones:

(1) The mobile phone itself is developing in the direction of miniaturization and thinness, which is convenient for consumers to carry;

(2) The individuation of mobile phone design lies in that the design concept is no longer square, and the design of irregular shape, curve and cambered surface has become the mainstream of mobile phone design aesthetics;

(3) Color screen and mobile phone functions are used more and more. In order to miniaturize the mobile phone, reducing and thinning the battery is the most effective method. Batteries with a thickness of less than 4mm have become the mainstream trend of thin and light mobile phone configuration, which is the specialty of polymers in cost performance. The effective space left by the mobile phone with irregular shape, curve and cambered surface design has become irregular shape. Liquid rectangle can't make effective use of space, and its capacity is low, while laminated polymer can make the most effective use of this irregular space and enlarge its capacity. Recently, the arc battery, trapezoidal battery and backpack battery introduced by TCL Jinneng Company can increase the capacity of mobile phones by more than 20% compared with the corresponding liquid batteries. There are more and more functions of mobile phones, which leads to more and more power consumption. It is necessary to increase the battery capacity accordingly. Polymer battery has obvious advantages without increasing the battery thickness. Similarly, notebook computers, Bluetooth headsets, PHS mobile phones, mobile DVD and other electrical appliances are all developing in the direction of mobility and portability, all of which are equipped with LCD screens, and there are more and more functions and LCD screens. All these provide some opportunities for polymer lithium-ion batteries.

It has been more than two years since polymer lithium-ion battery technology was matured and commercialized in the world. Although the sales volume is growing rapidly, the market share is still around 10%, which is incomparable with the 90% market share of liquid lithium batteries and far below people's expectations. For various reasons, the price of polymers in the market is generally higher than that of liquid lithium batteries. However, because the competition mode of mobile appliances is changing quietly, especially the innovation of design value brought by polymer batteries (such as superior performance below 4mm thickness and large-size batteries), polymer batteries are being recognized by more and more designers such as mobile phones and mobile DVDs, so polymer manufacturers are still full of confidence and firmly believe that the era of polymers will surely come.

5 Advantages and Disadvantages Advantages

The working voltage of 1. single battery is as high as 3.6v~3.8v, which is much higher than the voltage of 1.2V of Ni-MH and Ni-Cd batteries.

2. The capacity density is high, which is 1.5~2.5 times or higher than that of Ni-MH battery or Ni-Cd battery.

3. The self-discharge is small, and the capacity loss is also small after long-term storage.

4. Long service life, and the cycle life can reach more than 500 times during normal use.

5. No memory effect, no need to empty the remaining power before charging, and easy to use.

6. Good safety performance

Lithium polymer adopts aluminum-plastic soft packaging in structure, which is different from the metal shell of liquid battery. In the case of potential safety hazards, liquid batteries are easy to explode, while polymer batteries will only inflate at most.

7. The thickness is small and can be made thinner.

Ultra-thin, the battery can be assembled into a credit card. The common liquid lithium battery adopts the method of customizing the shell first and then plugging the anode and cathode materials. There is a technical bottleneck when the thickness is less than 3.6mm, but the polymer battery does not have this problem. The thickness can be less than 1mm, which is in line with the current demand direction of mobile phones.

8. Lightweight

The battery using polymer electrolyte does not need a metal shell as a protective outer package. The weight of polymer battery is 40% lighter than that of steel-shell lithium battery with the same capacity specification and 20% lighter than that of aluminum-shell battery.

9. Large capacity

Polymer battery is higher 10 ~ 15% than steel battery of the same size and specification, and 5 ~ 10% higher than aluminum battery, so it is the first choice for color screen mobile phones and MMS mobile phones. At present, most new color screen and MMS mobile phones on the market also use polymer batteries.

10. Small internal resistance

The internal resistance of polymer battery is smaller than that of ordinary liquid battery. At present, the internal resistance of domestic polymer batteries can even reach below 35mΩ, which greatly reduces the self-consumption of batteries and prolongs the standby time of mobile phones, and can completely reach the level of international standards. This li-polymer, which supports large discharge current, is an ideal choice for remote control models and the most promising product to replace Ni-MH batteries.

1 1. The shape can be customized.

Manufacturers don't need to be limited to standard shapes, and can make them into suitable sizes economically. Polymer batteries can increase or decrease the battery cell thickness according to customers' needs, and develop new battery cell models, which are cheap, short in mold opening cycle, and some can even be tailored according to the shape of mobile phones, making full use of battery shell space and enhancing battery capacity.

12. Good discharge characteristics

Colloidal electrolyte used in polymer batteries. Compared with liquid electrolyte, colloidal electrolyte has stable discharge characteristics and higher discharge platform.

13. The protection board is simple in design.

Due to the use of polymer materials, the battery cell will not catch fire or explode, and the battery cell itself has sufficient safety. Therefore, PTC and fuse can be omitted in the protection circuit design of polymer battery, thus saving battery cost.

disadvantaged

1. The battery cost is high, and it is difficult to purify the electrolyte system.

2. It is necessary to protect the circuit control. Overcharge or overdischarge will destroy the reversibility of chemicals in the battery, thus seriously affecting the life of the battery.

6 Performance study The performance of homopolymer vinylidene fluoride (PVdF), vinylidene fluoride and hexafluoropropylene (PVdF-HFP) as skeleton materials of polymer lithium ion batteries was compared. The results show that PVdF as the skeleton material of polymer lithium-ion battery can obtain better performance than PVdF-HFP*** polymer by appropriate technical means.