How to calculate the energy density of lithium ion battery cells with different anode materials?

First, Energy density calculation of lithium ion battery cells with different anode materials

The positive and negative materials determine the energy density of the battery, but most of the literature calculates the energy density based on the quality of a single active cathode material. Some literatures consider the sum of the active materials of the positive and negative materials. The quality of the non-active battery material is neglected, which makes the calculated results deviate greatly from the actual ones.

According to the calculation method of the literature, the energy density of common positive and negative lithium battery materials is calculated. The capacity and voltage are shown in Table 1 and Table 2. Recently, the capacity of cathode materials is increasing, but there is still a large gap with the theoretical value. The selection of the highest capacity does not use the highest value reported, but the feasibility of selecting the technical indicators to select the values of Tables 1 and 2. There are still many problems in achieving this value, such as controlling volume expansion, rate characteristics, and cycle characteristics. Table 3 gives typical parameters for the removal of encapsulating materials and leads, inactive materials inside the encapsulating material [4].

However, the shape of the battery varies, and the cell in this work refers to all other materials that do not contain the encapsulating material and leads, and most of the calculations are based on the results of the cell. Moreover, since the allowable thickness of the electrode coating, the battery of different shapes, and the characteristic parameters of the inactive material have a certain influence on the calculation result, the calculation result of the table may have a certain deviation from the actual battery, which is closely related to the battery manufacturing process.

Figures 29(a)-(j) show the calculation results of the energy density of the cells formed by the combination of 10 different negative electrodes and 16 positive electrode materials. Figure 2(i) shows that the Li-rich-300 vs. Si-C-2000 cell system has the highest mass energy density of 584Whkg-2 in all battery systems, and the highest volumetric energy density of 1645WhL-1 (excluding package) Materials and tabs).

Table 1 calculates the positive active material used and its specific capacity and voltage

Table 2 calculates the mass of the negative active material used and its specific capacity and voltage

Figure 2 Calculation of cell energy density of different anode materials and different cathode materials (a) graphite; (b) soft carbon SC-400; (d) hard carbon-250; (e) SiOx-420; (f) SiOx- 1000; (g) Si-C-450; (h) Si-C-1000; (j) lithium titanate

Second, metal lithium ion battery cell energy density calculation

The above calculation results are all negative electrode materials, the theoretical theoretical capacity of graphite is 372mAhg-1 [5], the current reversible capacity can reach 365mAhg-1, and the reversible capacity of high-capacity track negative electrode materials can reach 1000-1500mAhg-1. However, there is a large volume expansion and contraction in the process of deintercalating lithium. And it is difficult to fully exert the actual capacity, which is only 380-450 mAhg-1. In contrast, the theoretical specific capacity of metallic lithium is as high as 3,860mAhg-1, and even if the utilization rate is 33%, there is 1287 mAhg-1, and it can serve as a lithium source. However, metallic lithium has many safety problems such as lithium dendrite, uneven growth of pores, and continuous side reaction with electrolyte, volume expansion problems, and interface stability during circulation.

Considering the different possibilities of metal lithium capacity in different batteries, this work calculates the energy density of lithium metal batteries with different lithium metal utilization rates of 100%, 80%, 50%, and 33%, respectively. Comparing Fig. 3 with Fig. 2, it can be seen that when the metal lithium capacity is exerted, the same positive electrode system, the metal lithium ion battery has a more significant energy density than the lithium battery. For example, when Li-rich-300 cathode material is used as a negative electrode in metallic lithium, the energy density is 649 Whkg-1, and the energy density is 521 Whkg-1 even when only 33% is exerted.

(a) Li capacity is fully utilized;

(b) Li capacity is 80%;

(c) Li capacity is 50%;

(d) Li capacity is 33%.

The page contains the contents of the machine translation.