Development trend of cylindrical lithium-ion batteries in electric vehicles

No matter how many disputes for small cylindrical batteries used for EV, 18650 because of high energy density and high cost performance, become more and more important option for the passenger car and car logistics.18650 is the advantage of high maturity, high consistency, high energy density, cost, flexible configuration; The disadvantage is that number, pack the difficulty is high, the quality control points. And more monomer batteries can by changing the internal design, greatly enhance life, ratio, etc., also make Pack look easy, but also can greatly reduce the energy density (volume and weight), reduces the assembly flexibility, the use of space when large size of high energy density battery, most of the low degree of automation, as well as the process of the cost is very high, poor consistency, and once the failure, terrible consequences.

At present, the advantage of the cylindrical batteries owes its size standardization, product maturity and cost competitiveness, with the standardization must be strong;26/32 bigger cylinder and so on have not been able to become the mainstream; Be vividly portrayed the new size of 20/21, is itself a variety of market factors to measure balance and based on the 18650 existing advantages of both choice!

What kind ofLithium electricityThe core is more suitable for?

Unit volume capacity and cycle life, ratio, strong security is related factors: every 10% increased capacity, cycle life reduces about 20%;Every 10% increase capacity, charge and discharge rate reduce 30-40%;Every 10% increase capacity, temperature rise will increase about 20%, and the geometric level rise;The higher energy density, the bigger the security risk.

18650 with 523 + graphite system, according to the new national standard, 1 c to the limit of 2.4 AH has reached design, higher energy density materials (NCA, 811, etc.) itself stability and process control, is not imagination of so easy.So, it wasn't too good, but expensive...

Cylindrical 18650Lithium ion batteries development faces many challenges

Battery energy density requirement enhances unceasingly, improves the cost of materials: a. new materials such as NCA, silicon carbon material supply chain is not yet mature, the cost is high, supply stability;B. new material process on the environment demand is high, investment in fixed assets is high, the energy consumption;Monomer battery capacity is low, PACK group technology requirements and higher cost;Monomer batteries up to adapt to the list of positive and negative bipolar structure, and the impact on the energy density is significant;Part high curvature ratio is bigger, cycle life affected by the larger;High energy density and high rate of charging requirements at the same time, the design space has to the limit.

A larger diameter cylindrical lithium-ion battery will become the inevitable trend: 20/21 relatively 18 is a better choice

With volume, the energy density advantages: increasing diameter and height can be more effective volume.

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The benefits of: a. appropriate cases, improve the energy density can choose regular material, stability, cost-effective;B. can be appropriate for a multipolar ear mechanism design to reduce internal resistance;C. under the same energy density, can choose quick charge properties of graphite, to improve the quick charge performance;D. part high curvature ratio is reduced, extend the life of the cell cycle.E. monomer batteries capacity increase, decrease the cost of Pack.

Multipolar ear structure design: can achieve low internal resistance or DCIR on intergovernmental relations (ACIR).

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A low rate of curve area ratio increases, cycle life extension.

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1. Can be got from the above, 21700 in different proportion model high curvature points is the smallest, medium 20650, and 18650 is the highest.

2. When the battery in the process of circulation, such as deteriorated, the maximum curvature point, in 21700 due to its minimum proportion, so the effect the performance of the cycle is smallest.

The same capacity of PACK bag under a safe distance from the same design, 20 series energy density than the optimal size, weight 21 best energy density.

The new standard, day peng's choice

New factory invested heavily in Japan and South Korea's most advanced production equipment, choose from feeding to fully automated, four automation production line of 200 PPM.Compatibility production line, Nissan 1 million only 20650/21700201 April 7 years to realize mass production supply, while 20/21 of the diameter of mature material system to extend the period for use, is still the most stringent environmental control, to ensure that we reserve the high volume of product technology for many years, in a safe and reliable environment to realize mass production, more of the supply chain is matured given a certain time.

Why 20650/21700, instead of 20700?

18650 to the transition of the new size, most of the existing battery pack can easily switch on the diameter, the cost is low speed, and the height of the 65-70 change, will lead to the existing battery pack mold abandoned trouble;Use their market advantages, 20650 cuhk ratio battery production has more than a year and a half, produced 20650 subprime market and has begun to take shape, can be faster to achieve the cost advantage of vertical industry chain level.To provide customers more monomer (21700) and less size change but at the same time, high space utilization (20650), two options.

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