How to calculate the cost of lithium batteries for new energy vehicles?

With the promotion of policies and markets, my country produced about 1.22 million new energy vehicles in 2018, a year-on-year increase of 50%, and the total installed power of power batteries was about 56.98GWh, a year-on-year increase of 56%. The author predicts that new energy vehicles will continue to compete with internal combustion engine-driven vehicles in the market in the next 5 to 10 years. Doing a good job in the cost planning of new energy vehicles and optimizing the cost of power batteries will be one of the core tasks of automakers and parts suppliers in the coming years.

Power batteries and cells

Currently, new energy vehicles mostly use lithium batteries , and their basic working principle is shown in Figure 1:

Figure 1 Working principle of lithium battery

There are two main types of active materials for the positive electrode, one is nickel-cobalt-manganese lithium compound (NCM), and the other is lithium iron phosphate (LFP); the negative electrode is mostly graphite (95%), plus some additives. Lithium ions are deintercalated during discharge and intercalated during charging, forming a discharge or charging current. Usually, the lithium batteries on new energy vehicles are mostly composed of cells, modules, and battery packs; the cell is the smallest unit of the battery pack, the module is composed of multiple cells connected, and the battery pack is composed of multiple modules, plus a battery management control module, connection terminals, etc. If the on-board lithium battery pack is regarded as a subsystem, then the proportion of the cell cost is about 85%. Therefore, making an accurate calculation of the cell cost, finding the main cost driving points, and then optimizing the technology are important ways to optimize the battery pack cost and do a good job in the cost planning of the whole new energy vehicle.

Lithium battery cell disassembly

This article only describes some of the disassembly steps and is not comprehensive. Lithium battery cell disassembly must be done in a professional laboratory to ensure safe operation!

First, fully discharge the lithium battery cell for a long time.

The lithium battery cell used by the author to disassemble is a square cell with a voltage of 3.65V, a capacity of 255Wh, and a gross weight of 1.4 kg (see Figure 2).

Figure 2 Lithium battery cell sample (NCM111, 255Wh, 3.65V)

Then, low-temperature operation was carried out in a dry laboratory, the battery cell casing was opened, and the thickness and external dimensions of the positive electrode membrane, negative electrode membrane, and separator were measured respectively. The positive electrode membrane contained an active compound (NCM) and an aluminum substrate, and the negative electrode membrane contained an active compound (Graphit) and a copper substrate, so as to obtain the main material input parameters for the cost calculation of lithium battery cells.

Figure 3 Lithium battery cell positive electrode membrane

Figure 4 Lithium battery cell negative electrode membrane

Figure 5: Lithium battery cells are disassembled and measured in a professional laboratory

The reference cost calculation model of Guanyu Electromechanical Technology (Shanghai) Co., Ltd. is used to calculate the material cost and distribution of this lithium battery cell (see Figure 6).

Figure 6: Material cost breakdown and distribution of lithium battery cells

The main material cost drivers are ternary materials, electrolytes, copper films, etc. Optimizing material costs starts with these material cost drivers. For example, ternary materials (NCM), where C refers to expensive cobalt materials, how to reduce the proportion of cobalt materials is the priority option for optimizing material costs. From the original NCM111 to NCM523, or even NCM811, the nickel content is increased to reduce the cobalt content. Of course, the increase in nickel content also affects the stability of the battery cell, so it is necessary to balance the optimization in terms of stability and material costs. In addition, copper films, electrolytes, etc. also have room for optimization.

Lithium battery cell manufacturing process

The manufacturing of lithium battery cells, like the production of noodles, can be divided into about 18 steps, as shown in Figure 7.

Figure 7 Lithium battery cell manufacturing process steps

Among them, processes such as mixing, coating, drying, compacting, rolling, vacuum drying, and aging are batch processing processes, while processes such as slicing, stacking, electrolyte filling, and packaging are beat manufacturing processes.

The reference cost calculation model of Guanyu Electromechanical Technology (Shanghai) Co., Ltd. can be used to calculate the manufacturing cost and distribution of this lithium battery cell (see Figure 8).

Figure 8 Lithium battery cell manufacturing cost breakdown and distribution

Judging from the results of reference cost calculation, the driving point of manufacturing cost is mainly in the rhythm manufacturing process, such as slicing, stacking, electrolyte injection, packaging and other process steps. To optimize the manufacturing cost of battery cells, we must start from these processes.

Figure 9 Reference cost and distribution of lithium battery cells

Summarize

How to improve the future development and market competitiveness of new energy vehicles? One of the important paths is to optimize the material and manufacturing costs of lithium battery cells through technology. Through accurate reference cost calculation and cost driving point analysis of lithium battery cells, we can systematically find out the ideas and even technical solutions for reducing costs. How to do a good job in the cost planning of new energy vehicles and develop safe and reliable models that customers can afford and use, one of the core tasks is to do a good job in the technical cost optimization of lithium battery cells!