The production and manufacture of lithium-ion batteries is a process closely linked by process steps. The production process of lithium battery is relatively complex. The main production process mainly covers the stirring and coating stage of electrode production (front section), the winding and liquid injection stage of cell synthesis (middle section), and the packaging and testing stage of packaging (rear section). The value (purchase amount) accounts for about (35 ~ 40%): (30 ~ 35)%: (30 ~ 35)%. The difference mainly comes from the difference of equipment suppliers and the difference of import / domestic proportion. The process flow is basically the same. There is a deviation in the proportion of value, but it is generally in line with this proportion.
Lithium battery equipment corresponding to the previous process of lithium battery production mainly includes vacuum mixer, coater, roller press, etc; The middle process mainly includes die cutting machine, winding machine, laminating machine, liquid injection machine, etc; The latter process includes chemical forming machine, split volume detection equipment, process warehousing and logistics automation, etc. In addition to this pack of production equipment, it also needs to be automated.
Production process of lithium battery in the front stage: electrode manufacturing is related to the core performance of the battery
The result of the front-end process of lithium battery is that the positive and negative electrode sheets of lithium battery are prepared. The first process is stirring, that is, after the positive and negative solid battery materials are mixed evenly, the solvent is added and stirred into a slurry through a vacuum mixer. The mixing of ingredients is the basis of the subsequent process of lithium battery, and high-quality mixing is the basis for the high-quality completion of the subsequent coating and rolling process.
The coating and rolling process is followed by slitting, that is, the coating is treated by slitting process. If burr occurs during slitting, there will be potential safety hazards in subsequent assembly, electrolyte injection and other procedures, and even in the process of battery use. Therefore, the front-end equipment in the production process of lithium battery, such as mixer, coater, roller press and Slitter, is the core machine of battery manufacturing, which is related to the quality of the whole production line. Therefore, the value (amount) of front-end equipment accounts for the highest proportion of the whole lithium battery automatic production line, about 35%.
Middle process flow of lithium battery: efficiency first, winding before lamination
In the manufacturing process of lithium battery, the middle process is mainly to complete the molding of the battery. The main process flow includes production, pole winding, die cutting, cell winding and lamination molding. It is an area with fierce competition among domestic equipment manufacturers, accounting for about 30% of the price of lithium battery production line.
At present, there are two main cell manufacturing processes of power lithium battery: winding and lamination. The corresponding battery structure forms are mainly cylindrical, square and soft package. Cylindrical and square batteries are mainly produced by winding process, while soft package batteries are mainly produced by lamination process. The columns are mainly represented by 18650 and 26650 (Tesla has independently developed 21700 batteries and is promoting them in the whole industry). The difference between square and soft package is that the shell adopts hard aluminum shell and aluminum plastic film respectively. The soft package mainly adopts lamination process, and the aluminum shell mainly adopts winding process.
The soft package structure is mainly for the medium and high-end digital market. The profit margin per unit product is high. Under the same production capacity, the relative profit is higher than that of aluminum shell battery. Due to the easy scale effect of aluminum shell battery and the easy control of product qualification rate and cost, both of them have considerable profits in their respective market fields. In the foreseeable future, both of them are difficult to be completely replaced.
Because the winding process can realize the high-speed production of electric cells through speed, and the speed that lamination technology can improve is limited, at present, the domestic power lithium battery mainly adopts the winding process, so the shipment volume of winding machine is larger than that of lamination machine.
The previous process corresponding to winding and lamination production is the production and die cutting of polar film. The production includes the welding of the pole piece / pole lug after slitting, the dust removal of the pole piece, the pasting of protective tape, the glue wrapping of the pole lug and the winding or fixed length cutting, in which the winding pole piece is used for the subsequent full-automatic winding and the fixed length cutting pole piece is used for the subsequent semi-automatic winding; Punching and cutting pole piece is to wind and punching the slitted pole piece for subsequent lamination process.
In terms of lithium battery packaging and welding, the mainstream laser technology integration application manufacturers of Lianying, Han Zu and Everbright are involved, which can meet the demand without import.
Process flow of the later stage of lithium battery: Volume separation is the core link
The production process of the rear section of lithium battery mainly includes four processes: Volume separation, chemical formation, detection and packaging and warehousing, accounting for about 35% of the value of the production line. As the most important link in the later stage of the process, formation and volume division detect the activation of the formed battery. Due to the long charge and discharge test cycle of the battery, the value of the equipment is the highest. The main function of the formation process is to charge and activate the battery cell after liquid injection packaging, and the capacity separation process is to test the battery capacity and other electrical performance parameters and grade them after battery activation. The chemical forming and volume dividing are completed by the chemical forming machine and the volume dividing machine respectively, which are usually completed by the automatic volume dividing system.
Lithium battery technology: it seems simple but needs to be combined with systematic design
Power battery pack system is a battery pack that connects many single cells in series and parallel. It integrates battery hardware systems such as power and thermal management. Pack is the key to the production, design and application of power battery system. It is the core link connecting the production of upstream cells and the application of downstream vehicles. Usually, the design requirements are put forward by cell factory or automobile factory, and usually completed by battery factory, automobile factory or third-party pack factory.
The lithium 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, the major lithium battery equipment manufacturers have less automation integration layout in this field, while Han's laser, Lianying laser and other laser equipment manufacturers have a high share in the field of pack equipment due to their absolute advantages in the field of laser.
At present, the automation proportion of pack production is relatively low, because the current sales volume of single new energy vehicles is not large enough, and the cost of automatic production line is high.
Lithium iron phosphate and ternary: energy density is an inseparable topic. Different materials need a full set of equipment investment
At present, the cathode materials of domestic mainstream power lithium batteries are divided into lithium iron phosphate and ternary. Among them, lithium iron phosphate is the safest cathode material for lithium-ion batteries at present, and its cycle life is usually more than 2000 times. Coupled with the decline of price and technical threshold due to the maturity of the industry, many manufacturers will adopt lithium iron phosphate batteries for various factors. However, lithium iron phosphate battery has obvious defects in energy density. At present, the energy density of BYD lithium iron phosphate monomer cell, the leader of lithium iron phosphate battery, is 150wh. BYD is expected to increase the energy density to 160wh by the end of 2017. Theoretically, the energy density of lithium iron phosphate is difficult to exceed 200gwh.
Ternary polymer lithium battery refers to lithium battery with nickel cobalt manganate as cathode material. The actual proportion of nickel cobalt manganese can be adjusted according to specific needs. Due to the higher energy density of ternary lithium batteries (at present, the energy density of ternary lithium batteries in first-class power battery manufacturers such as Ningde times can generally reach 200wh / kg-220wh / kg, and the industry expects that the energy density of single cells of ternary batteries will reach the level of 300wh / kg by 2020), the passenger car market began to turn to ternary lithium batteries, and on buses with higher safety requirements, Lithium iron phosphate is more popular. With the development of all electric passenger vehicles, ternary lithium battery is occupying a more and more important position.
The energy density and cost of the two materials are different, and different cars and car companies have different choices. The two are roughly the same in terms of production process flow. The differences are mainly reflected in the use and proportion of materials, large differences in specific process parameters, equipment can not be produced in the same line, and the cost of simply transforming and switching production capacity is high (ternary materials have strict requirements for vacuum dehumidification, while the previous lithium iron phosphate production line basically has no dehumidification requirements), Therefore, multi-core appliance factories will layout and purchase equipment at the same time in capacity planning.