The main production technology and process of lithium ion battery

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

Lithium battery manufacturing process: the first three processes, the proportion of nearly 35% / 30% / 35%

lithium battery production process is more complex, the main production process mainly covers the electrode coating agitation coating stage (front), battery The synthetic winding injection stage (middle section) and the packaging inspection stage (back stage) of the chemical package, the value (purchasing amount) is about (35~40%): (30~35)%: (30~35) )%. The difference mainly comes from the difference of equipment suppliers and the difference of import/domestic ratio. The process flow is basically the same, and the proportion of value is deviated but the ratio is generally consistent.

The lithium battery equipment corresponding to the previous stage of lithium battery production mainly includes a vacuum mixer, a coating machine, a roller press, etc.; the middle stage process mainly includes a die cutting machine, a winder, a laminating machine, a liquid filling machine, etc.; the latter process includes a forming machine, sub-capacity testing equipment, process warehousing logistics automation. In addition, the production of battery packs requires Pack automation equipment.

Lithium-ion front production process: pole piece manufacturing relationship Battery core performance The result of the lithium battery front-end process is to complete the preparation of the positive and negative electrodes of the lithium battery. The first process is stirring, that is, the positive and negative solid battery materials are uniformly mixed and added to the solvent. Stirred in a slurry by a vacuum mixer. Stirring of ingredients is the basis of the subsequent process of lithium battery, and high-quality stirring is the basis for the high-quality completion of subsequent coating and rolling processes.

The coating and rolling process is followed by slitting, that is, the coating is subjected to a slitting process. If burrs are generated during the cutting process, subsequent procedures such as assembly and electrolyte injection, and even battery safety may occur during use. Therefore, the front-end equipment in the lithium battery production process, such as mixers, coating machines, roller presses, slitting machines, etc., is the core machine for battery manufacturing, which is related to the quality of the entire production line. Therefore, the value (amount) of the front-end equipment accounts for the entire lithium battery. The proportion of automated production lines is the highest, about 35%.

Lithium-ion middle-stage process: efficiency first, winding in the lithium battery manufacturing process before the lamination, the middle process is mainly to complete the battery molding, the main process includes sheet production, pole piece winding, die cutting, cell winding forming And lamination molding, etc., is a field where the competition of domestic equipment manufacturers is fierce, accounting for about 30% of the value of lithium battery production lines.

At present, the manufacturing process of the core of the power lithium battery mainly includes winding and lamination. The corresponding battery structure forms mainly three kinds of cylinders, squares and soft packs. The cylindrical and square batteries are mainly produced by the winding process, and the soft pack battery is used. The lamination process is mainly used. The cylinder is mainly represented by 18650 and 26650 (Tesla has developed 21700 batteries separately and is being promoted in the whole industry). The difference between the square and the soft package is that the outer casing is made of hard aluminum shell and aluminum plastic film respectively, and the soft bag is mainly laminated. Mainly, the aluminum shell is mainly based on the winding process.

The soft package structure is mainly for the mid-to-high-end digital market, and the profit rate per unit product is higher. Under the same production capacity, the relative profit is higher than that of the aluminum shell battery. Since the aluminum shell battery is easy to form a scale effect, the product qualification rate and cost are easy to control, and both of them have considerable profits in their respective market fields, and it is difficult to completely replace both in the foreseeable future.

Since the winding process can achieve high-speed production of the battery core through the rotation speed, and the speed of the lamination technology can be limited, the current domestic power lithium battery mainly adopts the winding process, so the winding machine shipment is currently larger than the stack of tablet machine.

The previous process corresponding to winding and lamination production is the production and die cutting of the pole piece. The production includes the pole piece/polar welding after the slitting, the dust removal of the pole piece, the protective tape, the polar ear wrapping and the winding or the fixed length cutting, wherein the winding pole piece is used for the subsequent fully automatic winding. The fixed length cutting pole piece is used for subsequent semi-automatic winding; the punching pole piece is formed by punching and cutting the divided piece piece for subsequent lamination process.

In the aspect of lithium battery package soldering, the mainstream laser technology integrated application manufacturers of Lianhe, Dazu and Everbright are involved, which can meet the demand and do not need to import.

The process of lithium battery back-end process: the division into the core is the core process of

lithium battery production process is mainly divided into four processes of capacity, formation, testing and packaging, accounting for about 35% of the production line value. As the main link in the latter stage of the process, the formation and activation of the formed battery, because the battery charge and discharge test cycle is long, so the value of the device is the highest. The main function of the chemical conversion process is to activate the charging and charging of the battery core, and the volumetric process is to test and classify the battery capacity and other electrical performance parameters after the battery is activated. The formation and separation of the formation and separation of the machine are usually completed by automated sub-combination into a system.

Lithium Pack Technology: It seems simple but needs to be combined with system design. The

power battery system is a battery pack that connects many individual batteries through series and parallel, and 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 part of the application of connecting upstream battery production and downstream vehicle. Usually the design requirements are raised by the battery factory or the automobile factory, usually by battery factory, automobile factory or third party Pack. The factory is completed.

The production line of lithium battery Pack is relatively simple. The core processes include feeding, bracket bonding, electric welding, testing and other processes. The core equipment is laser welding machine and various types of adhesive testing equipment. At present, the major lithium-ion equipment manufacturers have less automation integration in this field, and the laser equipment manufacturers such as Dazu Laser and Liansheng Laser have higher market share in the Pack equipment field due to their absolute advantages in the laser field.

At present, the automation ratio of Pack production is relatively low, because the current sales of new energy vehicles are not large enough, and the cost of automated production lines is relatively high.

Lithium iron phosphate and ternary: the topic of energy density cannot be avoided, different materials need a full set of equipment investment

At present, the cathode material of domestic mainstream power lithium battery is divided into two types: lithium iron phosphate and ternary. Among them, lithium iron phosphate is the most safe cathode material for lithium-ion batteries, and its cycle life is usually more than 2,000 times. Coupled with the decline in price and technology threshold due to industrial maturity, many manufacturers consider various factors. Lithium iron phosphate batteries will be used. However, lithium iron phosphate battery has obvious defects in energy density. At present, the energy density of BYD lithium iron phosphate battery core is 150Wh. At the end of 2017, BYD is expected to increase the energy density to 160Wh. Theoretically, the energy density of lithium iron phosphate is hard to exceed 200 Gwh.

The ternary polymer lithium battery refers to a lithium battery using lithium nickel cobalt manganese oxide as a positive electrode material, and the actual ratio of nickel cobalt manganese can be adjusted according to specific needs. Because the ternary lithium battery has higher energy density (currently the energy density of the ternary lithium battery of the first-class power battery such as Ningde era can reach 200Wh/kg-220Wh/kg, the industry expects ternary battery cell by 2020 The energy density will reach 300Wh/kg), the passenger car market will start to turn to the ternary lithium battery, and in the passenger car with higher safety requirements, lithium iron phosphate is more popular. 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 basically the same in the production process. The difference is mainly reflected in the different use and proportion of materials, the difference in specific process parameters, the equipment cannot be produced in line, and the cost of simply changing the production capacity is high (the ternary material pair Vacuum dehumidification and other requirements are strict. The previous lithium iron phosphate production line basically has no dehumidification requirements. Therefore, multi-home appliance core factories will arrange and separately purchase equipment in the capacity planning.