The “size code” of power batteries: From 18650 to 4680, the cylindrical cell’s journey of “growing up”
time：2026-08-06
In the world of power batteries, a string of numbers often defines the fate of a product. 18650, 21700, 4680 -- these seemingly boring model codes are actually the "figure codes" of cylindrical cell, recording the technological transition of the power battery industry for more than 20 years. From the standard configuration cell of notebook computers to the "heart" of electric vehicles, every "growth" of cylindrical cell is a precise game of energy density, manufacturing technology and cost control.
I. 18650: "Childhood" of power battery"
18650 is the "ancestor" model of cylinder cell-diameter 18mm, height 65mm, cylindrical (0 represents cylinder). It was born in the notebook computer market in 1990 s and became the "general currency" in the era of consumer electronics by virtue of its standardized, highly consistent and mature automatic production line ".
In the 1980 S, Tesla connected thousands of 18650 cell series in parallel to create Roadster of the first generation of battery pack and Model S. This choice was questioned at that time: Can consumer electronics cell withstand the vibration, temperature difference and cyclic load of automobile working conditions? But Tesla's bet is that the extreme consistency of 18650 (capacity deviation <1%) and mature supply chain are enough to make up for the shortage of monomer energy density.
II. 21700: "Youth" in balanced era"
in 2017, Tesla and Panasonic jointly launched 21700 cell (21mm in diameter and 70mm in height), and cylindrical cell ushered in the first "growing up".
The benefits brought by the size increase are intuitive: the monomer capacity jumps from 3Ah to 4.8Ah, the energy density increases by about 15%; The number of battery pack decreases by about 30% within cell, the synchronization of connection points and BMS sampling points is reduced, and the system cost is reduced. More importantly, the volume increase of 21700 does not sacrifice power performance-by optimizing the positive and negative electrode materials and electrolyte formula, its rate performance is the same as 18650 or even slightly better.
"21700 is the product of" equilibrium. "Analysis by new energy technology engineers," it finds the best balance between energy density, power performance, manufacturing process and supply chain maturity, thus becoming the most mainstream cylindrical cell specification from 2017 to 2023. "
III. 4680: the "big" revolution of adulthood celebration
in 2020, Tesla battery released 4680 cell (diameter 46mm, height 80mm), and cylindrical cell ushered in a "adulthood celebration" leap.
The "Big" of 4680 is subversive: the monomer capacity reaches 25Ah, which is more than 5 times of 21700; The energy density increases to 380Wh/kg (with high nickel positive electrode and silicon carbon negative electrode); what is more revolutionary is the design of "Electrodeless ear"(Tabless) -- The traditional cell polar ear (current export end) is concentrated on the top, and the heat is concentrated under high current; 4680 distribute the polar ear on the edge of the entire electrode, the current path is shortened by 90%, the internal resistance is reduced by 50%, and the fast charging capability jumps to over 4C.
The 'big' of "4680" is not a simple size enlargement, but a reconstruction of the manufacturing paradigm. "The head of research and development of energy gathering new energy cell pointed out," it requires brand-new winding technology, laser cutting precision and dry electrode technology, and the production line of traditional liquid batteries is almost incompatible. "
but the challenge of 4680 is also "big". The failure energy of monomer cell is 5 times that of 21700, and the difficulty of thermal runaway suppression increases exponentially; The manufacturing yield is slow to climb, and the yield of Tesla at the initial stage of mass production is less than 80%, far less than 95% of 21700; The investment in production line is huge, and the investment in single GWh capacity is 2-3 times that of 21700.
Fourth, the underlying logic of size game: why not the bigger the better?
The "growth" of cylindrical cell is not unlimited. The simulation analysis of new energy sources reveals the boundary conditions of size optimization.
Heat dissipation efficiency is the primary constraint. After the diameter of cell increases, the heat dissipation path in the central area is extended, and the temperature rise during fast charging increases. The diameter of 4680 (46mm) is considered as the heat dissipation limit of the liquid electrolyte system-if it is larger, the center temperature will break through the safety threshold.
Mechanical stress it is another hidden worry. The expansion displacement of large size cell is more obvious, which requires higher clamping force and structural strength of the module. The volume expansion rate (about 300%) of silicon-carbon anode is especially difficult in large-size cell.
"Size Selection is system engineering. "Summary of the vice president of energy gathering new energy technology," it needs to find the optimal solution between electrochemical limit, thermometrical constraint, manufacturing capacity and cost target. 4680 is the optimal solution of the current liquid system, but in the era of solid-state batteries, the size logic may be completely different. "
v. Future Picture: from "standardization" to "scenario"
the size evolution of cylinder cell is moving from "single standard leading" to "multi-specification scenario adaptation".
In the product matrix of energy gathering, 21700 still occupies the mainstream of high-end passenger cars and unmanned aerial vehicles; 4680 gradually penetrates into high-end long-life models and energy storage systems; Smaller 1650 (diameter 16mm) the niche market was found in miniature scooters and wearable devices.
"The size selection in the future will be more and more 'scenic '. "Cell Technical Experts look forward," different models, different working conditions, and different cost sensitivity correspond to different optimal sizes. LabelAccuracy is the pursuit of the industrial era, and scenario is the trend of the intelligent era. "
conclusion
from 18650 to 4680, the "growing" road of cylinder cell is power Battery Industry the epitome from immature to mature. Every Size transition is accompanied by the breakthrough of energy density, the innovation of manufacturing technology and the reconstruction of supply chain. However, "Growing Up" is not the purpose, and "adaptation" is the essence-adapting to the limit of electrochemical system, adapting to the boundary of manufacturing capacity, and adapting to the requirements of application scenarios.
CUSTOMER SERVICE
Yue Gong Wang An Bei No. 4419002007491