The Manufacture and Investigation of 3D Current Collectors in a Lithium Ion Battery Obtained by Laser Powder Bed Fusion

Abstract

The use of additive manufacturing to fabricate current collectors with increased surface area opens new opportunities for controlling electrode morphology, improving conductivity, and thereby boosting the overall performance of batteries. This can be achieved by increasing the contact area between the active mass and the current collector. This paper focuses on the investigation of 3D current collectors with an enhanced surface area for cathodes obtained by laser powder bed fusion. The quality and dimensional accuracy of the 3D current collector structures as well as the electrical characteristics and longevity of batteries were analyzed in this study. It has been demonstrated that the utilization of printing parameters comprising a laser power of 200 W, a scanning speed of 500 mm/s, and a hatch distance of 0.25 mm, with a layer thickness of 0.03 mm, results in a decrease in the number of defects in the 3D current collector. In the first cycle, the capacitance characteristics exhibited discharge capacities of 189.79 mAh/g for Al-f and 192.06 mAh/g for AlSi10Mg. The Coulomb efficiencies for the samples were 86 and 92.5%, respectively. Anisotropy of conductive properties arises during the printing process, which must be considered when designing the 3D current collectors, as it may have an impact on the capacitive and cyclic characteristics of the samples.

1. Introduction

Lithium ion batteries (LIBs) play a crucial role in the advancement of modern technologies, providing power for a wide range of applications, from portable electronics to electric vehicles and stationary energy storage systems [1]. Despite significant progress in improving the energy density, cycle stability, and safety of LIBs, the demand for more efficient and durable batteries continues to grow [2]. One promising approach to enhancing LIB performance is the optimization of the structure and configuration of their electrodes, particularly cathodes [3]. Cathodes are critical in determining LIB characteristics such as capacity, stability, and ionic and electronic conductivity. Traditional cathode manufacturing involves applying active material to a flat current collector, which limits the contact area between the active material and the current collector layer [4]. One promising strategy for enhancing LIB efficiency is to increase the surface area of the current collector, which can improve conductivity and reduce the internal resistance of the battery [5]. Additive manufacturing (AM) represents an innovative technology that enables the creation of structures with an increased surface area, potentially enhancing the performance of cathode materials significantly [6].

In contrast to subtractive manufacturing methods such as machining, casting, and forging, AM enables the creation of a three-dimensional structure through the continuous addition of material in a layer-by-layer process (printing) [7]. In AM, a variety of advanced materials, including polymers, metals, ceramics, and composites, are employed for the fabrication of products. These materials are employed in a variety of AM types: binder jetting (BJT), directed energy deposition (DED), material extrusion (MEX), sheet lamination (SL), material jetting (MJT), vat photopolymerization (VPP), and powder bed fusion (PBF) [8]. In the context of metal product manufacturing, it is possible to identify two distinct production techniques: DED and PBF. PBF can be subdivided into two main categories, depending on the heat source employed: laser powder bed fusion (PBF-LB/M) and electron beam melting (EBM). PBF-LB/M is a manufacturing process that employs layer-by-layer fusion of metal powders according to a digital model, whereby the powders are deposited on a build platform inside the chamber of the machine (printer) [9].

Lattice structures are an example of products with complex geometry and increased surface area. The most efficient method for obtaining lattice structures from metals is PBF-LB/M. This method is based on the melting of powder material, which ensures the creation of products with higher properties compared to other AM technologies. This is important because the mechanical properties of the lattice structures that can be used in current collectors require a high level of strength to avoid damage to the structures during LIB assembly and operation. Two main metals can be used for the production of lattice structures for electrodes in LIBs—aluminum (cathode) and copper (anode) [10]. The aim of our research is to focus on the current collectors for the cathode. Aluminum is a more technologically advanced material for fabrication by PBF-LB/M, and the specific characteristics per unit area of the anode are superior to those of the cathode. It can be reasonably assumed that improvements to the cathode will have a greater overall effect. In this regard, further studies on the fabrication of cellular structures made of aluminum and its alloys via the PBF-LB/M method will be presented. The most common aluminum-based alloy used in PBF-LB/M is the AlSi10Mg alloy. In their work, Li Z. et al. investigated lattice structures made of the AlSi10Mg alloy obtained by PBF-LB/M [11]. The fabrication of lattice structures was successfully completed, and they were found to be free of large pores and cracks. Localized plastic stresses were identified in the region of the rod nodes, leading to the formation of zones with plastic deformation. However, the majority volume of the rods exhibited elastic behavior during deformation. Vrana et al. investigated the fabrication accuracy of the AlSi10Mg lattice structures using PBF-LB/M [12]. It was found that the dimensions of the samples exhibited discrepancies from the 3D model. It was observed that the magnitude of the deviations decreased as the diameter of the rods increased. In the range of rod diameters from 1.5 to 3.0 mm, the shape of the cellular structures can be described as a circle. For smaller diameters, it is reasonable to represent the actual cross-section of the rod as an ellipse. In another study, the authors also considered the PBF-LB/M process and fabrication of lattice structures, but utilizing an AlMgScZr alloy [13]. It was found that the formation of printing defects was significantly enhanced when the power was high and the scanning speed was high. Conversely, the cellular structures fabricated at a low power and slow scanning speed (100 W and 250 mm/s) exhibited superior geometric accuracy at equivalent energy density.

PBF-LB/M is a suitable method for the fabrication of LIBs and their components [14,15,16]. Ma Y. et al. proposed the fabrication of an anode composed of the 6061 aluminum alloy by PBF-LB/M [17]. The findings indicated that the corrosion resistance of the aluminum alloy 6061 produced by the PBF-LB/M declined rapidly with time. However, it exhibited enhanced corrosion resistance compared to the cast aluminum alloy 6061 at the initial stage of corrosion, which could potentially enhance the discharge performance. The surface analysis of the samples, obtained by PBF-LB/M from the 6061 alloy, were in accordance with the findings of the self-corrosion and electrochemical performance tests. In their study, Ambrosi A. et al. employed combination PBF-LB/M and fused deposition modeling (FDM), to fabricate a water electrolysis device [18]. This approach enabled the fabrication of the metal electrodes via PBF-LB/M and the plastic components of the liquid/gas cells by FDM. Both of the components were designed to ensure optimal integration and assembly into the final device. Acord et al. employed a comparable technology to PBF-LB/M for the fabrication of the 3D nickel–cobalt–aluminum oxide (NCA) cathodes [19]. It has been demonstrated that the utilization of substrate heating can effectively mitigate the effects of thermal stress. A comprehensive study of single-track formation revealed that the samples exhibited discontinuous characteristics at energy densities below 75 J/mm³, while exhibiting continuous behavior at higher energy densities. The development of 3D LIB cathodes represents a promising direction for future research.

To date, a few studies have been conducted on the fabrication of current collectors with an increased surface area obtained by PBF-LB/MAM. In their work, Chen C. et al. developed a 3D-printing method for a 3D-structured copper current collector for an anode [20]. The material extrusion method was taken as a basic framework. Using polyvinylidene fluoride and copper powder, a paste for printing was obtained. Based on the results of the current collectors obtained, it was found that the 3D Cu mesh anode exhibited excellent deposition and stripping capability, high-rate capability, and a long-term stable cycle. A full lithium battery based on this anode exhibited a good cycle life. In their study, Callegari D. et al. also considered a Cu current collector obtained by material extrusion [21]. The results also confirmed the high-rate capability and stable cycle of the 3D current collector, as well as demonstrating its stability and low-voltage hysteresis at varying current densities. Furthermore, the 3D current collector demonstrated specific capacity values exceeding 100 mAh g at 1 C, along with a Coulombic efficiency exceeding 99%. Martinez et al. employed a combination of methods to develop a 3D current collector [22]. The utilization of a triply periodic minimal surface generation program in conjunction with digital light processing (DLP) enabled the fabrication of structures with an increased surface area. Furthermore, the electrophoretic deposition of the electrode materials enabled the fabrication of a copper 3D current collector. The findings of this study indicate that the combination of 3D printing with electrophoretic deposition has the potential to facilitate the structural manufacturing of batteries, exhibiting dual functionality in terms of load bearing and energy storage capabilities. It is evident that the aforementioned studies were focused on the fabrication of current collectors for anodes. Conversely, there is a lack of similar studies of current collectors for cathodes obtained by PBF-LB/M, which makes it important to carry out further studies in this area.

The use of AM to fabricate current collectors with increased surface area opens new opportunities for controlling electrode morphology, improving conductivity, and thereby boosting the overall performance of batteries. This can be achieved by increasing the contact area between the active mass and the current collectors. Furthermore, the utilization of AM facilitates the achievement of a balance between the mechanical strength and the electrochemical performance of the 3D current collectors. The aim of this work is to analyze the impact of 3D current collectors with enhanced surface areas for the cathode obtained by PBF-LB/M on the electrical characteristics and longevity of LIB, as well as to evaluate the potential benefits and challenges associated with the use of AM technologies in this field.

2. Materials and Methods

2.1. Starting Materials and the PBF-LB/M Process Parameters

Metal powders from pure aluminum and aluminum alloy AlSi10Mg were used for the fabrication of 3D current collectors by PBF-LB/M. The particle size distribution of the powders was analyzed using a laser diffraction particle size analyzer—Analysette 22 NanoTec plus (Fritsch GmbH, Amberg, Germany). The chemical compositions of the powders were determined using energy dispersive spectroscopy on a Mira 3 scanning electron microscope (TESCAN, Brno, Czech Republic), which was equipped with an energy dispersive X-ray spectroscopy module. The oxygen content was determined by atomic emission spectroscopy using the SHIMADZU ICPE-9000 spectrometer (Shimadzu Corporation, Kyoto, Japan).

The fabrication of the 3D current collectors by PBF-LB/M was carried out on the 3DLam Mini machine (3DLAM LLC, Saint-Petersburg, Russia). The equipment had the following characteristics: build platform—ø90 × 100 mm; laser type—Yb-fiber laser, 1070 nm; laser power—300 W; layer thickness—20–100 µm. Different process parameters were considered to improve the geometric accuracy of the 3D current collectors, which are presented in

Table 1. Process parameters for the manufacturing samples by PBF-LB/M.

№ of Sets	P, W	v, mm/s	H, mm	h, mm	VED, J/mm3
0	175	500	0.3	0.03	38.9
1	175	500	0.35	0.03	33.3
2	175	500	0.25	0.03	46.7
3	225	500	0.35	0.03	42.9
00	175	450	0.3	0.03	43.2
11	175	450	0.35	0.03	37.0
22	175	450	0.25	0.03	51.9
33	250	500	0.35	0.03	47.6
000	200	500	0.3	0.03	44.4
111	200	500	0.35	0.03	38.1
222	200	500	0.25	0.03	53.3
333	275	450	0.35	0.03	58.2

. The selection of parameters is based on two fundamental principles. Primarily, the chosen parameters must guarantee the defect-free fusion of the metal powder. This should prevent the formation of defects resulting from a lack of volume energy density (irregular texture). Additionally, the parameters must avoid the creation of defects caused by high energy density (discontinuities and irregularities). Secondly, the selected parameters must ensure the structural integrity of the substrate (foil) on which the 3D current collectors are fabricated.

2.2. Geometry of the 3D Current Collector

Structurally, the 3D current collector is a base made of a thin sheet of metal, on which metal elements with a developed surface are grown using a 3D printer to increase the surface areas (Figure 1). The manufacturing process was as follows: a foil of 0.06 mm in thickness was attached to the build platform of the 3D printer. Lattice structures were then built on the fixed foil. After the printing process was complete, the foil was separated from the build platform, and the 3D current collectors were cut out.

LIB consists of four main components: electrodes (cathode and anode), an electrolyte, current collectors, and a separator. The principle of operation of LIB is that the positive and negative electrodes are separated by an electrolyte through which the transition of Li⁺ ions from one electrode to another takes place. The battery has 2 modes of operation: charge and discharge. Figure 2 shows the principal scheme of LIB. During the charge, lithium ions passed from the cathode to the anode through the electrolyte, and free electrons were formed, which passed through an external circuit to a negative current collector at the anode. During the discharge process, the lithium ions moved in the opposite direction.

2.3. Equipment for Electrochemical Characterization

To determine the electrochemical characteristics of the cathode material on the 3D-printed current collectors it was smeared and assembled into CR2032 layouts made of stainless steel. The cathode material NCM811 was used in this study; it was smeared on the printed aluminum 3D current collectors together with a binder and a conductive additive in a ratio of 8:1:1, respectively.

N-methylpyrrolidone was used to create a homogeneous suspension with NCM 811 powder. The coated 3D-collectors were dried at 80 °C for 12 h. The dried electrodes were weighed with an accuracy of up to the fifth decimal place. The layouts were assembled in a glovebox with a water content of ≤1 ppm and an oxygen content of ≤100 ppm. CR2032 housings with 1 mm-thick stainless steel pressure plates were used for assembly. During the assembly process, a three-layer (polypropylene/polyethylene/polypropylene) separator with a thickness of 38 microns and a diameter of 19 mm was used, which ensured good overlap of the electrodes. Lithium with a diameter of 15.9 mm and a thickness of 0.6 mm was used as an antielectrode. The electrolyte used consisted of a mixture of three carbonates: ethylene carbonate, ethylmethyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1 with 1.1 M of dissolved lithium hexafluorophosphate. The schematic picture of the testing layouts is demonstrated in Figure 3.

To determine the electrochemical characteristics of the NCM811 material with the 3D-printed current collectors, the cathodes were assembled into the CR2032 layouts and tested using a Neware 5V10mA Coin Cell Battery Testing System (Neware, Shenzhen, China) during the charging–discharging processes. The resistance of the samples was measured using a Corrtest CS310 Potentiostat (Wuhan Corrtest Instruments Corp., Wuhan, China). The measurement was conducted using a two-electrode circuit. The resistance was determined from the current–voltage characteristics obtained by the linear potential sweep according to Ohm’s law using Equation (1):

$$\rho ={\displaystyle \frac{S}{l}}\ast {{\displaystyle \frac{dI}{dU}}}^{-1},$$

(1)

where U is the voltage, V; I is the current strength; S is the cross–sectional area of the sample; l is the length of the sample.

3. Results and Discussion

3.1. Analysis of the Powders for the 3D Current Collectors Obtained by PBF-LB/M

Two types of powder for pure aluminum were considered: one comprising larger particles (Al-c) and the other comprising smaller particles (Al-f). The results of the particle size distribution study are presented in

Table 2. The particle-size distribution of the powders.

Vol. %	Powders
	Al-f	Al-c	AlSi10Mg
	<μm	<μm	<μm
10	22.4	75.4	17.1
50	61.1	169.8	39.6
90	107.7	272.9	65.7

. The larger particles exhibited superior processing characteristics, including flowability and bulk density, which enhanced their suitability for use in AM. Furthermore, the larger particles exhibited a reduced specific surface area, which was expected to result in a lower oxygen content [23]. The results of the chemical composition analysis are presented in

Table 3. The chemical composition of the powders.

Powders	Al, %	Si, %	Mg, %	Fe, %	O, %
Al-f	99.92	-	-	0.08	0.046
Al-c	99.35	0.18	-	0.47	0.041
AlSi10Mg	87.88	11.28	0.53	0.31	0.057

. The aluminum powder, in both coarse and fine fractions, was characterized by the presence of non-spherical particles (see Figure 4a,b). The number of such particles in the powder with coarse granules was greater. It is important to note that for the selected process (PBF-LB/M), the presence of non-spherical particles was undesirable as it could lead to a reduction in the manufacturability of the samples. Furthermore, a higher energy density may be necessary for the effective melting of the coarse powder. The AlSi10Mg alloy powder exhibited spherical particles of the fine fraction, with the presence of satellites observed on the particles (Figure 4c). The PBF-LB/M process involved the complete remelting of the particles, which means that the shape and size of the particles after a successful melting iteration would not affect the functionality or performance of the final product.

3.2. Selecting of the Printing Parameters for Improved Geometric Accuracy

In selecting the process parameters, we considered parameters with a hatch distance of 0.35 mm (the sets № 1, 3, 11, 33, 111, 333, Table 3). It was determined that the set of parameters № 1 had a low energy density, which resulted in the formation of droplets. The sets № 11 and 111 for Al-f and AlSi10Mg were optimal and facilitated the satisfactory formation of the lattice structures (Figure 5a,b). These process parameters guaranteed a minimal number of defects, such as the detachment of the lattice structures from the foil, the destruction of the lattice structures, etc. However, for Al-c, the energy density of these sets was insufficient, and there was no effective remelting of the powder (Figure 5c). This phenomenon can be attributed to the incomplete melting of the large particles and their insufficient adhesion to the substrate. Consequently, separate particles were formed on the aluminum substrate, resulting in an irregular texture. Conversely, the utilization of powder comprising particles of a smaller size provided higher accuracy of manufacturing. This can be attributed to the fact that particles of a smaller size had sufficient time to fully melt and bond with the substrate.

An increase in energy density (the sets № 3, 33 and 333) results in the emergence of several defects. In the set № 3, discontinuities and irregularities in the tracks were observed for Al-f and AlSi10Mg. For Al-c, however, there was still no full remelting of the powder. The use of the sets № 33 and 333 resulted in the damage and burning of the aluminum foil; therefore, their use is undesirable. From the aforementioned analysis, it is evident that for Al-c, there were no optimal process parameters that could be selected that would simultaneously achieve the quality remelting of the powder and prevent damage to the foil. Considering the aforementioned considerations, Al-c will not be subjected to further analysis in this study. It is recommended that the set № 111 be selected for Al-f and AlSi10Mg, as it provides a satisfactory formation of the lattice structure.

3.3. Analysis of the 3D Current Collectors Obtained by PBF-LB/M

In this phase of the work, the lattice structures were studied for the Al-f and AlSi10Mg produced, using the sets № 000 and 222. These process parameters had different hatch distances: 0.3 mm and 0.25 mm. The height of the samples during the study was 270 µm. Using the selected printing parameters, the shape of the lattice structure was relatively distinct with a well-defined geometry (Figure 6). The two sets were distinguished by the presence of a small number of defects—the incomplete fusion of the parts of the lattice structures. It can be assumed that changing the hatch distance will probably lead to the fusion of lattice structures between each other (Figure 6a). However, further research is required to gain a deeper insight into this behavior. This can be attributed to an undesirable phenomenon, as it can lead to a decrease in the impregnation ability of the 3D current collector. Therefore, the set № 222 was chosen for further studies: laser power—200 W, scanning speed—500 mm/s, hatch distance—250 μm, layer thickness—30 μm.

To gain further insight into the geometry of the 3D current collectors produced by PBF-LB/M, the impact of the lattice structure height on the print quality was examined (Figure 7). Four variants of the samples were considered, comprising 3, 6, 9 and 12 layers of lattice structures, respectively. It can be observed that when three layers were built, the incomplete fusion of the structure occurred, resulting in the formation of elements of varying heights. As the number of layers increased, the lattice structure began to acquire a specified geometry, although the resulting structure differed from the intended design. Areas of inhomogeneous fusion were also observed, which disturbed the overall geometry. Additionally, a small quantity of unmelted powder particles was observed. The specimen with nine layers showed the presence of lattice structures with the specified geometry; however, the defects present in the previous specimen were also evident in this one. The heterogeneous fusion resulted in the partial contact between the lattice structures and the substrate. Furthermore, the number of unmelted particles also increased. The aforementioned defects have the potential to impact the functionality of LIB. Unmelted particles may be separated during assembly and operation, which is undesirable. Furthermore, insufficient fusion may result in the separation of structural elements from the substrate, which is also an unfavorable outcome. It is important to highlight that a correlation between the number of layers in the 3D model and the height of the lattice structures was not evident. A shift towards increasing the height of the lattice structure was observed. The structure, which should have had a height of 270 µm (9 layers of 30 µm), had a real height of approximately 400 µm. It is recommended that this phenomenon be considered when designing the geometry of the 3D current collectors. The addition of further layers, up to 12, led to a decrease in geometry accuracy and an increase in the prevalence of defects observed in the previous samples. It is therefore recommended that the height of lattice structures should not exceed nine layers.

3.4. The Electrochemical Properties Analysis

The electrochemical properties were analyzed for LIB with the 3D current collectors made of Al-f and AlSi10Mg, obtained by PBF-LB/M according to the set № 222 and having heights of 270 μm. The results of the analysis of the charge–discharge characteristics at cycles 1 and 10 are shown in Figure 8. The shape of the charge–discharge curves was typical for layered cathode materials; there was no clearly defined discharge area. It can be seen from the figure that during the first cycle, the samples made of Al-f had an initial discharge capacity of 220.42 mAh/g, and a discharge capacity of 189.79 mAh/g. In turn, the sample made of AlSi10Mg demonstrated a charging and discharge capacity of 207.90 mAh/g and 192.06 mAh/g, respectively. A comparative sample with foil as a current collector showed values of 179.60 mAh/g and 179.69 mAh/g when charged and discharged, respectively. With further cycling, by cycle 10, the values of the charging and discharge capacities for the Al-f and AlSi10Mg samples increased to 204.03/203.10 mAh/g and 193.84/193.21 mAh/g, respectively. For a comparative sample with foil, the values on cycle 10 were 176.45 mAh/g on charge, and 175.49 mAh/g on discharge. In the first cycle, we can observe a large irreversible loss of capacitance in the samples with the 3D current collectors, associated with an increase in the surface area of the sample, which led to a greater number of irreversible reactions at the interface of the phases of the 1–2 types. During the cycling process, the capacitive characteristics of the samples become more stable and the value of the discharge capacitances increased, which was explained by the effect of working out the active mass on 3D current collectors. The 3D structure of the printed samples did not allow the entire mass of the active material to participate in the exchange of lithium ions in the first cycle, but during further work, the entire mass was impregnated with an electrolyte and began to participate in the process of lithium intercalation/deintercalation.

Figure 9 shows the Coulombic efficiency values at the 1st and 10th cycles for three layouts. The largest loss of capacity during the first cycle was observed in the Al-f sample; the Coulomb efficiency was 86%. This phenomenon may be attributed to the increased specific surface area of the sample. Due to the larger specific surface area, the amount of electrolytes increased, which entered an irreversible reaction to form a cathode–solid electrolyte interface (CSEI); as a result, the Coulomb efficiency in the first cycle became lower. In turn, the Coulomb efficiency of the alloy sample in the first cycle was 92%, which was also lower than the comparative sample. In this case, the loss of capacitance was also explained by the increased specific surface area; however, the presence of Si and Mg in the original powder could lead to quasi-reversible side reactions at the electrode, which would cause a Coulomb efficiency greater than that of the 3D-electrode made of pure aluminum by cycle 10; the values for all the samples approached almost 100%, which indicates the fact that the 3D current collectors, like foil, did not exhibit electrochemical activity after the first cycle.

The cyclic life of the test layouts has also been investigated. The graph is shown in Figure 10. On cycle 20, the discharge capacity for the Al-f layout was 199.93 mAh/g; it was 188.11 mAh/g for the AlSi10Mg layout and 159.41 mAh/g for the NCM811_foil layout. During cycling, as mentioned earlier, the samples with the 3D current collectors demonstrated an increase in capacitive characteristics because of working out the active mass in the 3D structure of the current collectors. In turn, during cycling of the comparative sample with aluminum foil, it showed a slight decrease in capacity during 20 cycles. Thus, during 20 cycles, the Al-f layout showed an increase in discharge capacity by 5.1%, the AlSi10Mg layout showed a decrease in capacity by 2.1%, and a comparative layout with foil showed a decrease in discharge capacity by 6.3%. All the obtained metric results of electrochemical behavior are summarized in

Table 4. The metrics of electrochemical behavior.

Sample	Chg Capacity 1st Cycle, mAh/g	Dchg Capacity 1st Cycle, mAh/g	Chg Capacity 10th Cycle, mAh/g	Dchg Capacity 10th Cycle, mAh/g	Dchg Capacity 20th Cycle, mAh/g	Loss of Capacity, %
Al-f	220.42	189.79	204.03	203.10	199.93	1.6
AlSi10Mg	207.90	192.06	193.84	193.21	188.11	2.7
NCM811_foil	179.60	179.69	176.45	175.49	159.41	9.2

.

To confirm the repeatability of the results, a new batch of samples was produced and further studies were conducted on the charge–discharge characteristics of the Al-f samples, which demonstrated improved values compared to the other samples. The findings of these studies are presented in Supplementary Materials (Figure S1—charge–discharge curves of the Al-f sample). To analyze the impact of the printing direction of the samples on their electric conductivity properties, the resistivity of the Al-f sample built in the vertical direction and in the horizontal direction was measured. To compare the obtained results and their effect on the electrochemical characteristics of the printed electrodes, the resistance of the foil was also studied. The dimensions of Al-f (ver) were an ø of 1 mm and a length of 51.5 mm; Al-f (hor) had a cross-section of 1.2 × 2.8 mm and a length of 53 mm; and the foil sample’s dimensions were 14 × 55 mm. The investigation was conducted on three samples of each type, including three foil samples. The results are shown in Figure 11. Apparently, the printing direction can also significantly affect the Ohmic resistance of the current collector and, as a result, the resistance of the entire electrode. This was observed on the 10th cycle in Figure 8b. The discharge curve of the 3D current collector lay above the discharge curve of the foil sample, and the charging curve of the current collector was below the charging curve of the foil, which indicated a lower resistance. This is probably due to the lower resistance of the aluminum sample with vertical building orientation relative to the foil current collector. Consequently, anisotropy of the conductive properties arose during the printing process, which must be considered when designing 3D current collectors.

4. Conclusions

The study of the impact of the 3D current collectors obtained by PBF-LB/M with enhanced surface area on the electrical characteristics and longevity of the LIB yielded the following conclusions:

• To obtain the high-quality geometry of a 3D current collector, it is not reasonable to use the metal powder of a coarse fraction, as this will not provide the desirable level of accuracy. It has been demonstrated that the utilization of printing parameters comprising a laser power of 200 W, a scanning speed of 500 mm/s and a hatch distance of 0.25 mm, with a layer thickness of 0.03 mm, results in the lowest number of defects in the production of a 3D current collector. The optimal height of the 3D current collector structure for achieving high-quality geometry is 270 μm, which corresponds to nine layers of 30 μm each;
• In the first cycle, the capacitance characteristics of three-dimensional samples demonstrated discharge capacities of 189.79 mAh/g for Al-f and 192.06 mAh/g for AlSi10Mg. The Coulomb efficiencies for the samples were 86 and 92.5%, respectively. During cycling, due to the effect of working out the active masses, the values of the capacitances and Coulomb efficiency approached typical values and even exceeded them, in comparison to a sample with a foil current collector. Anisotropy of the conductive properties arose during the printing process, which must be considered when designing 3D current collectors, as it may have an impact on the capacitive and cyclic characteristics of the samples.
• Future Research Directions

This study opens several pathways for future research. One promising area is the use of alternative metal alloys, specifically copper alloys, in the fabrication of anode current collectors. Copper alloys present unique advantages in terms of conductivity, durability, and thermal stability, which could potentially improve the performance of current collectors. Future studies might investigate a range of copper alloys with different compositional properties to assess their impact on the overall efficiency and longevity in energy storage applications.

Another important direction is the in-depth analysis of conductivity as influenced by printing orientation. Initial observations suggest that conductivity could vary depending on the direction of the printing layers, which may impact the structural integrity and functional efficiency of the collectors. A systematic investigation into the effects of printing orientation on conductivity would help refine the manufacturing parameters and potentially lead to optimizations in both performance and cost. Such research would contribute valuable insights to the AM field, particularly for applications requiring precise control over electrical conductivity.

By pursuing these research avenues, future studies can further optimize the materials and methods used in manufacturing current collectors, thus enhancing their relevance and applicability in modern energy storage solutions.