Cylindrical lithium batteries come in many models, such as 14650, 17490, 18650, 21700, and 26500. Cylindrical lithium battery manufacturing processes are mature, resulting in lower PACK costs, higher battery product yields, and higher battery pack consistency. Due to their larger heat dissipation area, their heat dissipation performance is superior to prismatic batteries. Cylindrical batteries are easy to combine in various forms, making them suitable for efficient layout in electric vehicle designs. However, cylindrical batteries are generally encapsulated in steel or aluminum shells, making them relatively heavy and resulting in a relatively lower energy density. Currently, there are established manufacturers in China, Japan, South Korea, and the United States, such as SANYO, SONY, LG, and Wanxiang A123.
As the electric vehicle market expands and demands for longer driving ranges increase, automakers are placing higher demands on power batteries in terms of energy density, manufacturing costs, cycle life, and added product attributes. Without significant breakthroughs in raw materials, increasing the volume of cylindrical batteries to achieve greater capacity has become a viable option. Tesla has already begun mass production of its 21700 batteries, planning to use them in its Model 3. If successful in testing on other Tesla models, they will replace the previously used 18650 batteries. Tesla's approach may lead to a global "21700 trend."
Square hard-shell batteries: Too many models, difficult to standardize manufacturing process
Square hard-shell batteries are mostly made of materials such as aluminum alloy and stainless steel. They use a winding or stacking process inside, which provides better protection for the battery cells than aluminum-plastic film batteries (i.e., soft-pack batteries). The safety of the battery cells is also significantly improved compared to cylindrical batteries.
Lithium-ion battery aluminum casings evolved from steel casings. Compared to steel casings, aluminum casings offer advantages in weight reduction, safety, and resulting performance, making them the mainstream choice for lithium-ion battery housings. The development of aluminum casings for lithium-ion batteries is currently progressing towards higher hardness and lighter weight, which will provide the market with technologically superior lithium-ion battery products. Currently, companies producing square hard-shell batteries include Guoxuan High-Tech, Samsung SDI, Lishen, and CATL.
Because prismatic lithium batteries can be customized to fit specific product dimensions, there are thousands of different models on the market. This sheer number of models makes it difficult to standardize the manufacturing process. While prismatic batteries work fine in ordinary electronic products, for industrial equipment requiring multiple batteries connected in series or parallel, it's best to use standardized cylindrical lithium batteries. This ensures a reliable manufacturing process and makes it easier to find replacement batteries later.
Pouch batteries: Market share expected to exceed 50% in the future.
The key materials used in pouch lithium batteries—positive electrode materials, negative electrode materials, and separators—are not significantly different from those in traditional steel-cased and aluminum-cased lithium batteries. The biggest difference lies in the soft packaging material (aluminum-plastic composite film), which is the most critical and technically challenging material in pouch lithium batteries. Soft packaging materials typically consist of three layers: an outer barrier layer (usually an outer protective layer made of nylon BOPA or PET), a permeation barrier layer (the middle layer of aluminum foil), and an inner layer (a multifunctional high-barrier layer).
The packaging materials and structure of pouch batteries give them a series of advantages, such as: good safety performance; pouch batteries use aluminum-plastic film packaging, so in the event of a safety issue, they will generally bulge and crack, unlike steel-cased or aluminum-cased cells which may explode; light weight; pouch batteries are 40% lighter than steel-cased lithium batteries of the same capacity and 20% lighter than aluminum-cased lithium batteries; low internal resistance; pouch batteries have lower internal resistance than lithium batteries, which can greatly reduce self-discharge; good cycle performance; pouch batteries have a longer cycle life, with 4% to 7% less cycle decay than aluminum-cased batteries after 100 cycles; and flexible design; they can be made into any shape, can be thinner, and can be customized according to customer needs, allowing for the development of new cell models.
The disadvantages of pouch batteries include poor consistency, higher cost, and a tendency to leak. High cost can be addressed through large-scale production, while leakage can be reduced by improving the quality of the aluminum-plastic film. Companies producing pouch batteries include Do-Fluoride Chemicals, CALB, Wanxiang, CITIC Guoan, and Microvast.
In the digital field, the requirements for batteries in consumer electronics products are trending towards smaller size and thinner design. The replacement of square aluminum-cased batteries with pouch batteries is accelerating. Pouch polymer lithium batteries, with their excellent overall performance, are widely used in consumer electronics products such as smartphones, tablets, and wearable devices, and their growth rate far exceeds the average level of the lithium battery industry.
Furthermore, the application of power batteries is accelerating. Research shows that domestic mid-to-high-end new energy passenger vehicles from manufacturers such as BAIC, Changan, and Dongfeng are beginning to use pouch batteries. Statistics show that in 2015, the domestic production of square, cylindrical, and pouch lithium batteries was 17 GWh, 10.1 GWh, and 19.8 GWh respectively, accounting for 36.4%, 21.5%, and 42.3% of the total. The proportion of pouch batteries has already surpassed that of square and cylindrical batteries.
In the first three quarters of 2016, affected by factors such as fluctuations in the new energy vehicle market, the production of square and cylindrical batteries both declined to varying degrees compared to the previous quarter. Only the production of pouch batteries increased compared to the previous quarter, with domestic pouch battery production reaching 13 GWh in the first three quarters, including a 20% increase in the third quarter. In recent years, major domestic electric vehicle manufacturers such as Dongfeng, Zotye, and BAIC New Energy have also begun to experiment with pouch power batteries, and companies such as Shanghai Canai New Energy and Shandong Hengyu have also begun to invest heavily in pouch power battery production lines.
In general, cylindrical, prismatic, and pouch batteries each have their advantages and disadvantages, and each type has its dominant market. For example, prismatic batteries are predominantly lithium iron phosphate batteries, while pouch batteries are more predominantly ternary lithium batteries. With the introduction of new subsidy policies for new energy vehicles, battery system energy density has become an important performance indicator. For instance, the new subsidy policy requires pure electric buses to have a range of no less than 200 kilometers, a battery system energy density higher than 85Wh/kg, and a battery system weight accounting for no more than 20% of the vehicle's curb weight. These requirements indicate a shift in subsidies towards lighter and longer-range ternary lithium batteries. Ternary pouch batteries have a capacity 10-15% higher than steel-cased lithium batteries of the same size and 5-10% higher than aluminum-cased batteries, while being lighter than steel-cased and aluminum-cased batteries of the same capacity. Therefore, the new subsidy policy is more favorable to ternary pouch batteries. Given the advantages of pouch batteries, industry experts predict that with the development of battery technology, the penetration rate of pouch batteries in the new energy vehicle market will continue to increase, and in the future, the proportion of pouch batteries in all types of batteries is expected to exceed 50%.
Cylindrical lithium batteries come in many models, such as 14650, 17490, 18650, 21700, and 26500. Cylindrical lithium battery manufacturing processes are mature, resulting in lower PACK costs, higher battery product yields, and higher battery pack consistency. Due to their larger heat dissipation area, their heat dissipation performance is superior to prismatic batteries. Cylindrical batteries are easy to combine in various forms, making them suitable for efficient layout in electric vehicle designs. However, cylindrical batteries are generally encapsulated in steel or aluminum shells, making them relatively heavy and resulting in a relatively lower energy density. Currently, there are established manufacturers in China, Japan, South Korea, and the United States, such as SANYO, SONY, LG, and Wanxiang A123.
As the electric vehicle market expands and demands for longer driving ranges increase, automakers are placing higher demands on power batteries in terms of energy density, manufacturing costs, cycle life, and added product attributes. Without significant breakthroughs in raw materials, increasing the volume of cylindrical batteries to achieve greater capacity has become a viable option. Tesla has already begun mass production of its 21700 batteries, planning to use them in its Model 3. If successful in testing on other Tesla models, they will replace the previously used 18650 batteries. Tesla's approach may lead to a global "21700 trend."
Analysis of the advantages and disadvantages of square, soft-pack, and cylindrical power batteries, and their differences.
Lithium-ion battery aluminum casings evolved from steel casings. Compared to steel casings, aluminum casings offer advantages in weight reduction, safety, and resulting performance, making them the mainstream choice for lithium-ion battery housings. The development of aluminum casings for lithium-ion batteries is currently progressing towards higher hardness and lighter weight, which will provide the market with technologically superior lithium-ion battery products. Currently, companies producing square hard-shell batteries include Guoxuan High-Tech, Samsung SDI, Lishen, and CATL.
Because square lithium batteries can be customized to fit the product's dimensions, there are thousands of models on the market. However, this sheer number of models makes it difficult to standardize the manufacturing process. While square batteries work fine in ordinary electronic products, for industrial equipment requiring multiple batteries connected in series or parallel, it's best to use standardized cylindrical lithium batteries. This ensures a reliable manufacturing process and makes it easier to find replacement batteries later.
Pouch batteries: Market share expected to exceed 50% in the future.
The key materials used in pouch lithium batteries—positive electrode materials, negative electrode materials, and separators—are not significantly different from those in traditional steel-cased and aluminum-cased lithium batteries. The biggest difference lies in the soft packaging material (aluminum-plastic composite film), which is the most critical and technically challenging material in pouch lithium batteries. Soft packaging materials typically consist of three layers: an outer barrier layer (usually an outer protective layer made of nylon BOPA or PET), a permeation barrier layer (the middle layer of aluminum foil), and an inner layer (a multifunctional high-barrier layer).
The packaging materials and structure of pouch batteries give them a series of advantages, such as: good safety performance; pouch batteries use aluminum-plastic film packaging, so in the event of a safety issue, they will generally bulge and crack, unlike steel-cased or aluminum-cased cells which may explode; light weight; pouch batteries are 40% lighter than steel-cased lithium batteries of the same capacity and 20% lighter than aluminum-cased lithium batteries; low internal resistance; pouch batteries have lower internal resistance than lithium batteries, which can greatly reduce self-discharge; good cycle performance; pouch batteries have a longer cycle life, with 4% to 7% less cycle decay than aluminum-cased batteries after 100 cycles; and flexible design; they can be made into any shape, can be thinner, and can be customized according to customer needs, allowing for the development of new cell models.
