Introduction to 3V Button battery manufacturing process and PACK related knowledge

Lithium batteries have unparalleled advantages in the combination of energy density and power density, so they are widely used in various portable electronic products, power tools and electric/hybrid vehicles. The following editor of Xianji.com will give us a detailed introduction to the 3V Button battery manufacturing process and PACK basic knowledge.

3V Button battery structure

The processes of different structural methods and different materials are similar, but the equipment requires new equipment

The lithium-ion battery is mainly composed of four parts: positive electrode, negative electrode, non-aqueous electrolyte and diaphragm. At present, the lithium batteries used more in the market are mainly lithium iron phosphate batteries and ternary lithium batteries. The raw materials of the positive electrodes of the two are quite different. The production process is relatively close, but the process parameters need to be changed greatly. If lithium iron phosphate is completely replaced with ternary materials, the rectification effect of the old production line is not good. For battery manufacturers, it is necessary to replace a large area of equipment on the production line.

3V Button battery manufacturing process: three processes, front, middle and back, accounting for nearly 35%/30%/35%

The production process of lithium batteries is relatively complicated. The main production process mainly covers the stirring and coating stage (front stage) of electrode manufacturing, the winding and liquid injection stage (middle stage) of battery cell formation, and the packaging and testing stage (back stage) of chemical packaging. The value (purchase amount) accounts for about (35~40%): (30~35)%: (30~35)%. The difference mainly comes from different equipment suppliers, different import/domestic ratios, etc. The process is basically the same, and the value ratio has errors but generally conforms to this ratio.

The 3V Button battery equipment corresponding to the front stage of 3V Button battery production mainly includes vacuum mixers, coating machines, roller presses, etc.; the middle stage mainly includes die-cutting machines, winding machines, stacking machines, liquid injection machines, etc.; the back stage includes chemical forming machines, capacity detection equipment, process storage and logistics automation, etc. In addition, the production of battery packs also requires Pack automation equipment.

3V Button battery front-end production process: pole piece manufacturing and battery core function

The result of the 3V Button battery front-end process is to complete the preparation of the positive and negative pole pieces of the 3V Button battery. The first process is stirring, that is, mixing the positive and negative solid-state battery materials evenly, adding solvents, and stirring them into a slurry through a vacuum mixer. The stirring of ingredients is the basis of the subsequent process of lithium batteries, and high-quality stirring is the basis for the high-quality completion of the subsequent coating and rolling processes.

After the coating and rolling processes, there is slitting, that is, the coating is subjected to slitting process. If burrs occur during the slitting process, there will be safety hazards in the subsequent equipment, electrolyte injection and other procedures, and even in the process of battery use. Therefore, the front-end equipment in the 3V Button battery production process, such as mixers, coaters, roller presses, slitting machines, etc., are the core machines of battery manufacturing, which are related to the quality of the entire production line. Therefore, the value (amount) of the front-end equipment accounts for the highest proportion of the entire 3V Button battery automation production line, about 35%.

3V Button battery mid-stage process flow: power first, winding before lamination

In the process of 3V Button battery manufacturing, the mid-stage process is mainly to complete the battery forming. The main process flow includes film making, pole piece winding, die cutting, battery cell winding forming and lamination forming, etc. It is a field where domestic equipment manufacturers are currently competing fiercely, accounting for about 30% of the value of 3V Button battery production lines.

At present, there are two main battery cell manufacturing processes for power lithium batteries: winding and lamination. The corresponding battery structure methods are mainly cylindrical, square and soft pack. Cylindrical and square batteries are mainly produced by winding process, while soft pack batteries are mainly produced by lamination process. The cylinder is mainly represented by 18650 and 26650 (Tesla has independently developed 21700 batteries and is promoting them all over the industry). The difference between square and soft pack is that the outer shell uses two types of hard aluminum shell and aluminum plastic film respectively. Among them, the soft pack is mainly based on lamination process, and the aluminum shell is mainly based on winding process.

The soft pack structure method is mainly aimed at the mid-to-high-end digital market, with a higher profit rate per unit product. Under the same production capacity conditions, the relative profit is higher than that of aluminum shell batteries. Since aluminum shell batteries are easy to form a design effect, and the product qualification rate and cost are easy to control, both of them have considerable profits in their respective market fields. In the foreseeable future, it is difficult for both to be completely replaced.

Since the winding process can achieve high-speed production of battery cells through the rotation speed, and the speed at which the stacking technology can advance is limited, the current domestic power 3V Button battery mainly adopts the winding process, so the shipment volume of the winding machine is now greater than that of the stacking machine.

The front-end process corresponding to the winding and stacking production is the production and die-cutting of the pole piece. The production includes welding of the pole piece/ear after slitting, dust removal of the pole piece, sticking of protective tape, rubber coating of the ear, and winding or fixed-length cutting. Among them, the winding pole piece is used for subsequent fully automatic winding, and the fixed-length cutting pole piece is used for subsequent semi-automatic winding; the punching pole piece is to wind and punch the slit pole piece for subsequent stacking process.

In terms of 3V Button battery packaging welding, the mainstream laser technology integration application manufacturers of Lianying, Daju, and Guangda are all involved, which can meet the needs and do not need to be imported.

3V Button battery back-end process flow: Capacity separation and formation are the core links

The 3V Button battery back-end production process mainly consists of four processes: capacity separation, formation, testing and packaging and warehousing, accounting for about 35% of the production line value. Formation and capacity separation are the most important links in the back-end process. The formed batteries are activated and tested. Since the battery charge and discharge test cycle is long, the equipment has the highest value. The main function of the formation process is to charge and activate the battery cells after liquid injection and packaging, and the capacity separation process is to test the battery capacity and other electrical function parameters after the battery is activated and graded. Formation and capacity separation are respectively completed by the formation machine and the capacity separation machine, which are generally completed by the automatic capacity separation and formation system.

3V Button battery pack process: It seems simple but needs to be combined with systematic planning

The power battery pack system is a battery pack that connects many individual batteries in series and parallel, and summarizes the battery hardware systems such as power and thermal management. Pack is the key to the production, design and application of power battery systems. It is the core link connecting upstream battery cell production and downstream vehicle application. Generally, the design requirements are proposed by battery cell factories or car factories, and are generally completed by battery factories, car factories or third-party Pack factories.

The 3V Button battery Pack production line is relatively simple. The core processes include feeding, bracket pasting, electric welding, testing and other processes. The core equipment is laser welding machine and various pasting and testing equipment. At present, major 3V Button battery equipment manufacturers have few automated integrated layouts in this field, while laser equipment manufacturers such as Han's Laser and Lianying Laser have a high market share in the Pack equipment field due to their absolute advantages in the laser field.

The current automation ratio of Pack production is relatively low because the sales volume of a single new energy vehicle is not large enough, and the cost of installing an automated production line is high.

Lithium iron phosphate and ternary: energy density is an unavoidable topic, and different materials require a full set of equipment investment

At present, the positive electrode materials of mainstream domestic power lithium batteries are divided into two categories: lithium iron phosphate and ternary. Among them, lithium iron phosphate is the safest positive electrode material for lithium-ion batteries. Its cycle life is generally more than 2,000 times. In addition, due to the maturity of the industry, the price and technical threshold have dropped, so many manufacturers will choose lithium iron phosphate batteries for various reasons. However, lithium iron phosphate batteries have obvious defects in energy density. At present, the energy density of lithium iron phosphate monomer cells of BYD, the leader of lithium iron phosphate batteries, is 150Wh. BYD is expected to increase the energy density to 160Wh by the end of 2017. In theory, the energy density of lithium iron phosphate is difficult to exceed 200Gwh.

Ternary polymer 3V Button battery refers to a 3V Button battery whose positive electrode material uses lithium nickel cobalt manganese oxide. The actual ratio of nickel, cobalt and manganese can be adjusted according to specific needs. Since ternary lithium batteries have higher energy density (currently, the energy density of ternary lithium batteries of first-class power battery manufacturers such as CATL can generally reach 200Wh/kg-220Wh/kg, and the industry estimates that by 2020, the energy density of ternary battery cells will reach 300Wh/kg), the passenger car market has begun to turn to ternary lithium batteries, while lithium iron phosphate is more popular in buses with higher safety requirements. With the development of all-electric passenger cars, ternary lithium batteries are occupying an increasingly important position.

The energy density and cost of the two materials are different, and different cars and different car companies have different choices. The two are roughly the same in production process flow. The difference is mainly reflected in the different use and ratio of materials, the specific process parameters are quite different, the equipment cannot be produced on the same line, and the cost of simply changing and switching production capacity is high (ternary materials have strict requirements for vacuum dehumidification, etc., and the previous lithium iron phosphate production line has no dehumidification requirements at all), so many battery cell factories will jointly plan and purchase equipment separately in capacity planning.

5 minutes to help you understand the basic knowledge of 3V Button battery PACK

The process of assembling 3V Button battery cells into groups is called PACK, which can be a single battery or a battery module connected in series and parallel. Under the background of the new national standard, the demand for lithium batteries is increasing, and many lead-acid battery companies are also launching 3V Button battery products; in fact, the 3V Button battery PACK process is not difficult. Mastering this technology can assemble batteries by yourself, instead of just acting as a "battery porter" for manufacturers, and profits and after-sales are no longer subject to others; mastering a technology, you can travel all over the country with "lithium".

PACK composition

PACK includes battery packs, bus bars, soft connections, protection boards, outer packaging, outputs (including connectors), barley paper, plastic brackets and other auxiliary materials. These items together constitute PACK.

3V Button battery PACK example

Characteristics of PACK

① Battery pack PACK requires that the battery has a high degree of uniformity (capacity, internal resistance, voltage, discharge curve, life).

② The cycle life of the battery pack PACK is lower than that of a single battery.

③ Use under limited conditions (including charging and discharging current, charging method, temperature, etc.).

④ After the 3V Button battery pack PACK is formed, the battery voltage and capacity have greatly improved, and it is necessary to protect it, and monitor the charging balance, temperature, voltage and overcurrent.

⑤ The battery pack PACK must meet the voltage and capacity requirements of the design.

PACK method

① Series-parallel composition: The battery is composed of single cells in parallel and series. Parallel connection increases capacity and the voltage remains unchanged. After series connection, the voltage doubles and the capacity remains unchanged. For example, a 3.6V/10Ah battery is composed of a single N18650/2Ah through 5 parallel connections. Parallel first and then series: Parallel connection will affect the battery cycle life after parallel connection due to differences in internal resistance and unequal heat dissipation. However, a single battery fails and automatically exits. In addition to the decrease in capacity, it does not affect the use after parallel connection. The parallel process is more stringent. When a unit battery in parallel is short-circuited, the current of the parallel circuit is very large, which is generally prevented by adding fuse protection technology. First connect in series and then in parallel: connect in series according to the capacity of the whole battery pack, such as 1/3 of the whole capacity, and finally connect in parallel, which reduces the probability of failure of large-capacity battery packs.

② Requirements for battery cells: Select the corresponding battery cells according to your own design requirements. The batteries in parallel and series require the same type and type, and the difference in capacity, internal resistance and voltage value is no more than 2%. Under normal circumstances, the capacity of the battery is lost by 2%-5% after the battery is combined in parallel and series. The more batteries there are, the more capacity is lost. Whether it is a soft-pack battery or a cylindrical battery, multiple strings are required. If the consistency is poor, the battery capacity is affected. The battery with the lowest capacity in a group determines the capacity of the whole battery pack. Requires high current discharge function. The starting current of the motor is 3 times the normal operating current. Only high current discharge can improve the power function of the motor. Requires good heat dissipation of the battery. There are a large number of batteries, and the temperature rise of the batteries inside the battery box is not easy to dissipate, resulting in uneven temperature between the batteries, different discharge characteristics, and long-term battery performance decline. High production process level. The battery must be able to withstand the shock of the oscillation of the undulating road surface. High requirements for production process, especially spot welding process. After welding, test to prevent cold solder joints and desoldering.

③PACK process: Battery PACK is completed in two ways. One is laser welding, ultrasonic welding or pulse welding. This is a commonly used welding method. The advantage is good reliability, but it is not easy to replace. The second is through elastic metal sheet contact. The advantage is that no welding is required, and the battery replacement is simple. The disadvantage is that it may cause poor contact.

Pack example

Charge and discharge time

Charge time (hours) = (battery capacity Ahx charging factor) / charging current A

Discharge rate: The discharge rate of the battery is indicated by the discharge time or the hour factor required to discharge the additional capacity with a certain discharge current. Among them, discharge rate = additional capacity / discharge current

Assembly of bus soft connection

In the PACK process, nickel sheets, copper-aluminum composite buses, copper buses, total positive and total negative buses, aluminum buses, copper soft connections, aluminum soft connections, copper foil soft connections, etc. will also be used. The processing quality of buses and soft connections needs to be evaluated from these aspects.

①Whether the material quality meets the requirements. If the bus material does not meet the standards, the resistivity will increase. In particular, it is necessary to confirm whether it meets the relevant requirements of ROHS.

②Whether the key standard processing is in place. The deviation of key standards may lead to insufficient safety distance between high-voltage equipment during the equipment process and pose a serious safety hazard.

③The bonding force of the hard area of the soft connection and the stress absorption of the soft area.

④Whether the actual processing of the soft connection and the current capacity of the bus meet the design standards, and whether there is damage to the insulating thermoplastic sleeve.

The above is an introduction to the manufacturing process of lithium batteries and basic knowledge of PACK. Looking forward to the future, can lithium batteries meet people's requirements for portable energy storage devices? If it can be improved in terms of cost and function, the application of lithium batteries will be greatly expanded, enabling many new technologies to break through the bottleneck of energy storage. A considerable part of the research on lithium batteries is about electrode materials. Electrodes with higher discharge rates, larger capacities and sufficiently high voltages (only for the positive electrode) can significantly improve the energy and power density of lithium batteries, reduce volume and reduce costs.

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