WO2018134486A1

WO2018134486A1 - Method for the manufacture of nanostructured solid electrolyte materials for li ion batteries utilising short-term laser pulses

Info

Publication number: WO2018134486A1
Application number: PCT/FI2018/050056
Authority: WO
Inventors: Jari Liimatainen; Ville KEKKONEN
Original assignee: Picodeon Ltd Oy
Priority date: 2017-01-23
Filing date: 2018-01-23
Publication date: 2018-07-26

Abstract

In the present invention there is presented a method for the manufacture of lithium batteries utilising solid electrolytes so that the solid electrolyte material is manufactured by pulsed laser ablation deposition and the other material layers either by pulsed laser ablation deposition or some other method applicable for the material in question. In the method, the so-called roll-to-roll method can be used, in which the base material (15, 22, 42, 65, 75, 85, 95) to be coated is directed from one roll (41 a) to the second roll (41 b), and the coating occurs in the area between the rolls (41 a, 41 b). In addition, turning mirrors (31 ) can be used for directing laser pulses (12, 61, 71 a-b, 81 a-d, 91 ) as a pulse front (33) to the surface of the target material (13, 62, 72a-b, 82a-d, 82A-D, 92).

Description

Method for the manufacture of nanostructured solid electrolyte materials for Li ion batteries utilising short-term laser pulses

Field of the invention The invention relates especially to lithium batteries, their structure and the manufacture of solid electrolytes. The invention further relates to the manufacture of at least one part of said lithium batteries, utilising short-term laser pulses and laser ablation method.

Background of the invention As the need for mobile devices, electrically operated cars and storing of energy grows, the need for the development of battery technology has increased. Li ion batteries have succeeded well in very many applications, especially due to their good energy density and recharging possibilities compared to, among others, traditional Ni-CD (nickel-cadmium) and Ni-Mn (nickel-manganese) batteries. Li ion battery technology is based on a positive cathode, in which active material is, for example, transition metal oxide, and a commonly used carbon-based negative anode. In addition, an electrolyte is needed, which in current solutions has been principally liquid.

Problems are often related to a liquid electrolyte, such as, among others, risks of fires or explosions caused by short circuits, short service life and restrictions in the use of big charge voltages. Solid electrolytes have been presented as an alternative for liquid electrolytes, because their use makes it possible to prevent short circuits and possible fires or explosions, and a longer battery service life and higher charge voltages can be achieved. A problem with batteries using solid electrolytes have been high manufacturing costs, poor functionality in low temperatures, poor ion conductivity and high resistance over interfaces.

Solid electrolytes have been manufactured as thin films e.g. by atomic layer deposition (ALD), physical vapour deposition (PVD) methods and chemical vapour deposition (CVD) methods. Further, solid electrolytes have been utilised mechanically by doping solid electrolytes together with electrode materials by ball milling, after which the layer structures have been sealed by pressing and sintering to produce a finished cell structure. Active electrode materials have also been used by doping with a vitreous electrolyte and by thus forming a composite structure, in which an ion-conductive solid electrolyte surrounding electrode materials is strived for.

Pulsed laser deposition (PLD) technology has been researched e.g. for the coating of cathode material particles with solid electrolytes. In the next step, this method requires the coated powder to be compacted, for example, by pressing and sintering into layer-structured Li ion batteries or parts of these. This causes extra work steps and costs and a need, for example, for the use of binding agents to bind the particles to each other and also to the background material.

Summary of the invention In the present invention, there is introduced a method for the manufacture of Li ion batteries by utilising, instead of liquid electrolytes, the use of solid electrolytes manufactured by ultrashort pulsed laser technology and produced directly as a coating or part of a coating. Solid electrolyte materials, as well as electrode materials, are chosen case-specifically in accordance with the targeted capacity, energy and power density and service life requirements.

In this invention, ultrashort pulsed laser deposition technology is utilised for the manufacture of solid electrolyte material. The same technology can also be used for the manufacture of cathode and anode materials together with the manufacture of solid electrolyte material. On the other hand, the described ultrashort pulsed laser depo- sition technology used for the manufacture of solid electrolytes can also be used together with other thin film coating methods, such as said ALD, PVD and CVD methods; nevertheless so that the ultrashort pulsed laser deposition technology is used for the manufacture of solid electrolyte material.

In the method of the invention, ultrashort laser pulses with a length of less than 10000 ps are directed to at least one target material, the laser pulses detaching material from the target material as atoms, ions, particles or a combination of these. Material detached from the target is directed to the surface of the piece to be coated so that a coating of desired quality and thickness is formed. The quality, structure, quantity, size distribution and energeticity of materials detached from the target are controlled by laser parameters used in laser ablation, such as pulse energy, pulse length, used wavelength, pulse repetition frequency and superposition, used coating temperature and background gas pressure. In addition, the microstructure of target materials (for example, quantity of crystallinity) and doping can be adjusted together with the chosen laser pulse parameters to achieve the desired process, material distribution and coating. The crystallinity of the coating can also be impacted on by optional post-heat treatment. If the objective is to achieve a crystalline structure, but the used parameters provide an amorphic structure, it is possible to change the amorphic structure to a crystalline one by post-heat treatment, for example, in a temperature of over 300 °C.

Depending on the target material used and of the property profile pursued, process parameters for laser ablation can be adjusted to achieve desired microstructure and morphology. One advantage of ultrashort pulsed laser technology is that it can be utilised for very many different materials so that it is possible to produce different material combinations and different microstructure combinations.

Pulsed laser technology can be used to adjust the porosity of the coating layer to be manufactured, particle size and free area of the material, which have several meanings significant for the Li ion battery. For example, for conductivity it is advantageous to reduce the size of cathode and anode particles by shortening diffusion ranges and increasing the contact surface of solid electrolyte and electrode particles.

By manufacturing a composite structure either layer by layer or in a combinatory manner by means of two simultaneous material flows produced by ablation, it is possible to adjust the distribution of the solid electrolyte material e.g. together with the particles in the cathode material. This is especially important in case of solid electrolytes, in which the conductivity of ions cannot be contributed to by the penetration of a liquid electrolyte through the porous structure, thus forming a continuous conductivity channel. To improve electron conductivity, it may also be necessary to add materials increasing conductivity either in layers or using a combinatory method in connection with the coating of the electrolyte material or the coating of electrode materials.

In certain cases, when the ablation behaviour of different materials is appropriate, the different materials or part of them, such as the solid electrolyte, electrode materials and/or materials enhancing electron conductivity can be added into the same target material of which the ablation process and material flow of a desired type are produced by ultrashort pulsed laser technology.

In a combinatory manufacturing method, a combination of several different materials can be simultaneously directed from different targets towards the piece to be coated, adjusting separately the ablation process of different materials to achieve the desired structure and material distribution. For example, in a roll-to-roll method, the combination of a cathode material and solid electrolyte is first coated so that the solid electrolyte forms a layer around the target material particles, which is as uniform as possible and which ensures sufficient conductivity. As the coating progresses to the solid electrolyte layer, the share of cathode material particles is re- duced. The cathode material can be delivered to the solid electrolyte material flow to be produced by ultrashort pulsed laser technology also by other methods, nevertheless so that the desired quantity and distribution of solid electrolyte is achieved. Likewise, the method can be used when manufacturing the anode side of a Li ion battery either in the same coating step with the cathode and solid electrolyte layer or as a work step of its own.

A challenge with the combinatory process is to control the material flow in a situation, in which the gas atmosphere must be applicable to the processing of all separately ablatable materials. For example, the background gas pressure must be suitable in proportion to the desired material morphology with all ablatable materials. If the objective with one material is to generate particles of a certain size and with another material, for example, particles of different sizes or an atomized material flow is pursued, the background gas must be appropriate for this purpose. In addition, undesired reactions between the materials leaving from different targets must be prevented in the material flow or in the generation of the coating. On the other hand, it is also possible that the material flows from different target materials are desired to react with each other, forming the desired coating material layer. The reaction of the material flows with the background gas used in the coating chamber can also be used for doping the material flow. These methods can be described as reactive PLD methods. The crystalline structure of the solid electrolyte material manufactured by laser ablation can be adjusted, for example, by changing the coating temperature. Without an increase in the coating temperature, a principally amorphic structure is very easily produced in laser ablation. Raising the coating temperature, for example, by heating the substrate and by editing the process parameters of laser ablation, can pro- mote the crystallinity of the structure. The crystallinity of the structure can also be impacted on by executing a thermal processing after the coating, if it is desired to change the structure from amorphic to a more crystalline one.

Ultrashort pulsed laser ablation can be utilised to generate many above-described advantages on the basis of one process technology, with certain preconditions even in one coating process step. The laser ablation process can also be executed alternatively in several steps, for example, by using a coating line, in which the coating of desired material layers is carried out in several different steps.

In principle, it is possible to combine one or some of the above-mentioned methods with some other coating method, for example, in successive process steps so that ultrashort pulsed laser technology is used for the coating process step best suited for it, and another coating technology is used to complement it. This can be done either as immediate successive process steps or as separate independent processes. The coating process can be carried out as a roll-to-roll method or, for example, on sheets which are entered into the coating line as successive sheets.

For productivity, it is advantageous in one example to carry out the coating by using a wide laser beam distribution, which can be generated by means of turning mirrors. The laser pulse front detaches material from the target material in a desired manner, and the material flow is directed from the target to the surface of the piece to be coated.

The inventional idea of the invention further comprises the final product manufactured by the method, i.e. the different material layers of the Li ion battery, in which the solid electrolyte of the Li ion battery has been manufactured by pulsed laser ablation coating utilising ultrashort laser pulses.

Brief description of the drawings

Figure 1 illustrates the principle of the coating transaction with different physical components in an example of the invention;

Figure 2 illustrates the principle of forming a fan-shaped rectilinear laser pulse front with an apparatus arrangement of the invention;

Figure 3 illustrates an example of the so-called roll-to-roll method relating to the coating process;

Figure 4 illustrates the typical structure of a lithium ion battery as a cross-sectional view, when a solid electrolyte is used;

Figure 5 illustrates an example for the production of a solid electrolyte material by PLD technology;

Figure 6a illustrates the possible porous structure produced with the principle in Figure 5, in which one material is used; Figure 6b illustrates the possible porous structure produced with the principle in Figure 5, in which two materials are used to produce a composite material;

Figure 6c illustrates the possible porous structure produced with the principle in Figure 5, in which doped material is used in addition to the principal material;

Figure 7 illustrates the combinatory coating method using two simultaneous material flows;

Figure 8a illustrates the use of successive coating stations to improve productivity when manufacturing sandwich structures;

Figure 8b illustrates the use of successive coating stations to improve productivity when manufacturing composite structures;

Figure 8c illustrates the use of successive coating stations to improve productivity when manufacturing a doped material;

Figure 8d illustrates a closer detail of the basic material, which includes doped particles; and

Figure 9 illustrates an example of the use of a composite target material in the manufacture of a composite coating.

Detailed description of the invention

In a method of the invention there is manufactured a solid electrolyte for a Li ion battery as a layer of its own or together with electrode materials and doping sub- stances enhancing electron conductivity, utilising pulsed laser ablation deposition for the manufacture of material layers that are applicable to it or that gain relative productivity or quality advantages from it. Pulsed laser ablation deposition is based on the use of ultrashort pulsed lasers, in which the pulse length is at most 10000 ps.

Pulsed laser ablation deposition is utilised to control the micro and nanostructure in a Li ion battery and to obtain and optimise the above-described functional advantages of the Li ion battery.

In the invention, a solid electrolyte material can be chosen as one part of the entire electrochemical design of the Li ion battery. The material must fulfil certain basic characteristics, such as ion conductivity, sufficient contact and compatibility with ac- tive electrode materials, and coatability. If the coating is performed by a combinatory method, the compatibility of the coating environment, such as gas atmosphere, together with the solid electrolyte material and electrode materials and/or other doping substances must be taken into account. Solid electrolyte material can also be doped during the coating by means of gas atmosphere or by supporting the reaction of material flows generating of different target materials with each other. The solid electrolyte material can be, for example, a lithium-bearing oxide (e.g. LiPON) or lithium-bearing sulphide (e.g. U2S-P2S5). Also other materials or composites or sandwich structures formed of these can be used. The objective of the use of composite materials or doping (e.g. use of additives) is, for example, to eliminate certain weaknesses of cathode materials, such as poor conductivity or microscopic damages caused by a large volume change. Doping is possible by adding to the structure materials enhancing electron conductivity and by transferring these materials to a desired coating layer either from a separate target material by ultrashort pulsed laser technology or by adding additive material to the same target material, from which solid electrolyte and/or electrode material (anode or cathode) is detached.

Detaching materials and producing a material flow from the target or targets to the surface of the piece to be coated occurs by adjusting the parameters of short laser pulses. It is characteristic for each material that there are parameters specifically suitable for it, for adjusting the ablation process and the structure of the coating to be generated. To detach material from the target material, the energy import (J/cm²) generated by the laser pulses must be sufficient. Threshold energy, with which the detachment of material starts from the target, is called the ablation threshold, and it is a material-specific parameter, but it is also dependent on e.g. the wavelength of the laser beams. Material can detach from the target as atoms, ions, molten particles, broken particles, particles condensed from the atoms and ions after the detachment from the target or as a combination of these. Depending on the solid electrolyte material and the requirements set on its structure and the morphology of the coating, the laser ablation parameters can be changed. It is essential to note that after the detachment from the target, changes can occur in the material structure and size distribution of the material flow before the material adheres to the base material. This change process can be controlled by process-technical means, for example, by adjusting the atmosphere of the coating chamber and the flight range of the material (from the target to the base) in addition to the laser pulse parameters. The choice of parameters for the laser ablation process is impacted by the desired porosity of the coating, particle size and thus open area, thickness of the coating (particle sizes produced by different ablation mechanisms vary), quantity of crystal- linity, productivity requirement and stoichiometric control requirements.

Ultrashort pulsed laser ablation process differs from the other methods in that it makes possible the relatively precise control of the size and size distribution of the material and particles. If it is attempted to generate a desired coating by first producing an essentially atomized or ionized material, the tendency of the material to form clusters depends especially on the density and energeticity of the detached material and background gas. As the density of the material increases in the ablated material, the tendency to form particles and particle clusters grows; in other words, for example, increasing the pulse energy, increasing the pulse repetition frequency or reducing the ablation threshold of the target material enhance the tendency to form particles, because the density of the material flow grows. The use of background gas is a good way to increase the tendency of the material flow to form particles. In addition, it can be used to adjust the energeticity of the material flow and, further, to impact the composition of the solid electrolyte material and doping substances through a reactive process when executing laser ablation in a desired gas atmosphere.

For the production of solid electrolyte material and other coatings to be produced simultaneously with it by ultrashort pulsed laser technology it is also possible to carry out the ablation process so that particles are detached from the target material, for example, by breaking along the powder particle interfaces of the target material made of powdery material. Alternatively, the laser ablation process can be controlled so that molten particles detach from the target material, which are then directed to the surface of the base material. The above-described alternative methods can be chosen according to what type of microstructure is pursued and which material is concerned.

The method makes possible the production of different material and coating concepts with even just one method and apparatus, due to the flexibility of the method and its applicability to very different materials by means of the choice of parameters. This reduces significantly the quantity of required apparatus investments in different coating solutions of solid electrolytes in Li ion battery applications, accelerates the manufacture and delivery time and minimizes the quantity of manufacturing and processing errors. The method is especially suited for roll-to-roll manufacture, in which the base material (for example, copper strip) is directed from a roll to coating stations as a continuous strip, after which the strip is coated with a solid electrolyte material, necessary materials containing electron conductivity and electrode materials in a desired proportion and distribution in the coating stations (of which there can be one or several). Coating stations can also be placed sequentially so that either the same materials are coated in several coating stations successively so that the coating efficiency increases, or different materials can be coated in different coating stations to manufacture composite or multilayer structures or by, for example, doping materials con- taining conductivity to desired layers. On the coating stations it is also possible to manufacture different types of protective layers to different layers on the surface of different materials. As an alternative for successive stations, the coating is manufactured in the roll-to-roll method so that the strip to be coated moves first through the coating station so that one layer of material is provided of a desired material to its surface. After this the direction of motion of the roll is changed and the target material is automatically changed in the coating station and the coating of another material, for example, additive material, a second party of the composite material or, in a layered material, the coating of a second layer material is performed, and this process is repeated as long as the desired total structure is complete. It is not necessarily required to use laser ablation for the coating of all material layers, and in an embodiment of the invention also other coating and manufacturing methods of material layers can be linked to the manufacturing chain, if this is optimal for the total solution. Such supporting methods are, among others, the technologies of chemical vapour deposition (CVD), atomic layer deposition (ALD) and physical vapour deposition (PVD).

The composition of material detached by laser ablation must remain on the appropriate area for the functionality of the coating. In principle, the pulsed laser technology, especially ultrashort pulsed laser technology, is a suitable method to minimize disadvantageous composition changes, for example, due to the evaporation of dop- ing materials. Ultrashort pulsed laser technology can be used for minimizing the melting of materials and formation of wide molten areas, which otherwise would contribute to material losses and complicate the control of correct stoichiometry. With several target materials, restricting the laser pulse length to under 5 - 10 ps is sufficient to minimize the melting of the target and the excessive loss of doping ma- terials in laser ablation, if the superposition of laser pulses is slight. On large repetition frequencies, the superposition of laser pulses may cause material melting even with short pulse lengths. A change in stoichiometry may cause a loss of structure and correct functionality.

When manufacturing composite materials, sandwich structures or when doping a material layer with another material, the optimal process parameters and circumstances for different materials are not necessarily identical. This must be taken into consideration in the design and combining of different steps in the production process. If it is desired to manufacture a composite material by a combinatory solution, laser parameters can be tailored optimally in relation to different materials by using two different laser sources, but in this case the materials must be ablatable suffi- ciently well in the same coating atmosphere, because it can be difficult to control them separately. If it is necessary to adjust the coating atmosphere separately for all materials, this can be most easily executed in successive coating steps, in which it is possible to control separately the coating atmosphere advantageous for different materials. In certain situations, it is also possible to make the desired doping among target materials, and if the ablations thresholds of materials in relation to each other and the condensation tendency in a selected gas atmosphere are suitable, the composite structures can be manufactured by blending the desired materials into one target material piece in a desired proportion, and by ablating the target material piece in question. The basic principle of the method is illustrated in the view of principle of Figure 1 , in which the structural parts and directions of travel of the material included in the coating transaction are shown on a principled level. In Figure 1 , the energy source for the ablation process is the laser light source 1 1 , from which laser light is directed as short pulses 12 towards the target material 13. The laser pulses 12 cause local de- tachment of the material from the target as particles or other respective parts mentioned above on the surface of the target material 13. This generates a material flow 14, which extends towards the piece 15 to be coated. The piece 15 to be coated can also be called the coating base or substrate. The correct orientation can be executed by placing the direction of the plane of the target material surface 13 in suitable proportion to the piece 15 to be coated so that the direction of motion energy releasing in the form of plasma is towards the piece 15 to be coated. The laser source 1 1 can naturally be transferred in relation to the target 13, or the angle of orientation can be varied in relation to the surface of the target 13. Further, a separate arrangement can be placed between the laser source 1 1 and the target 13, with which it is possible to parallelize the laser pulse front hitting the target 13. Of this arrangement there is the separate figure 2. It is also possible to place other types of optics and, for example, mirrors between the laser source 1 1 and the target 13.

The plasma and particle material flow 14 in figure 1 can be fan-shaped so that a wider area can be coated to the area of the piece 15 to be coated with one angle of orientation of the laser pulses; assuming that the material to be coated is not transferred in the lateral direction (seen from the figure). In a second embodiment, the material to be coated is movable, and of this embodiment there is the separate figure 3.

Generally speaking in an example of ablation used in the invention the detachment of surface material, formation of particles and transfer of material from the target to the base and to the previously formed material layer is achieved by laser pulses directed to the target, in which the timely duration of an individual laser pulse can be between 0.1 - 10000 ps.

In an example of the invention laser pulses can be generated on a repetition frequency, which is between 10 kHz - 100 MHz. A film produced by laser ablation and formed of a material transferring as particles from the target material to the base material must form a reliable bond to the base material or a previously manufactured material layer. This can be achieved by a sufficient kinetic energy of particles, which makes possible sufficient energy to generation a joint between different materials. A very essential process parameter in laser ablation when manufacturing coatings of particles condensing from a material flow is the gas pressure used in the process chamber. An increase in gas pressure promotes the formation and growth of particles during the flight of material from the target to the surface of the material to be coated. The optimal gas pressure may vary according to what material is coated and what is the desired particle size distribution, porosity and adhesion between particles, and the bond of particles with the rest of the battery material.

In an embodiment, laser ablation and coating occur in a vacuum chamber, i.e. either in a vacuum or background gas, to which a desired pressure can be set. An option is to set the pressure between 10^"8 - 1000 mbar. When striving for coatings, which are partly or entirely generated of particles of different sizes, a background pressure of 10^"3 - 1 mbar is typically used, but a desired quantity and size distribution of particles can be also generated with pressures of less than 10^"3 mbar by adjusting the laser beam parameters.

In an embodiment, during the coating of at least one material layer the surface of the base material has been preheated to a temperature, which is chosen to be at least 300 °C. In an example, the said elevated preheating temperature is chosen to be at least 600 °C. In an embodiment, heat treatment is performed for the coated film after pulsed laser ablation deposition in a temperature, which is at least 300 °C, to increase the crys- tallinity of the microstructure. In this connection, the temperature can also be chosen to be at least 750 °C. To improve conformity and productivity, it would be preferable to provide as wide a material flow as possible from the target to the base material. In an example of the invention, this can be performed by disintegrating the laser pulses by turning mirrors to form a laser pulse front in the same plane. This arrangement has been illustrated in figure 2. The laser pulses 12 of the laser source 1 1 are thus directed, instead of the target, to the turning mirrors 31 , which can be, for example, a hexagonal and rotatable mirror surface as illustrated in the figure. The laser pulses 12 reflect from the turning mirrors 31 to form a fan-shaped laser pulse front (or laser beam distribution), and the said reflected pulses are directed to the telecentric lens 32. The laser pulse front can be directed to form an essentially parallel laser pulse front 33 by means of the telecentric lens 32 so that the laser pulses hit the target material 13 at the same angle. In this example in figure 2, the extent of the said angle is 90° The laser pulse front can be executed also in other ways; among others, by a rotatable monohedron mirror, which targets the laser pulses, for example, to an annular target material, which forms an annular material front. In an application example, a part of the Li ion battery is well suited to be coated so that material is discharged from a roll to be coated to a desired width in the coating chamber. A view of principle of this application alternative is illustrated in figure 3. Material is targeted to a desired coating width from one or several coating sources so that material is continuously discharged from a roll to coating and, after it has passed the coating zone, material is reassembled to the roll. The method can be called a roll-to-roll method, as has already been mentioned above. In other words, the part 42 to be coated of the Li ion battery is originally found around the roll 41 a. The ablation apparatus with the laser source 1 1 and target material 13 is included in the same way as has been described above. The laser pulses 12 make the ma- terial to detach as the particle flow 14 (in other words, in the form of a material flux) towards the material 42 to be coated, and the coated Li ion battery part 43 is formed as the result of adhesion. The coated film 43 is let to rotate around the second roll 41 b as the direction of travel of the film is from left to right in the case of Figure 3. The roll structures 41 a, 41 b can be motor-driven. The Li ion battery film to be coated can be the entire surface area, or only part of the surface, seen in the direction of depth in the figure. Likewise, in the direction of travel of the film, a desired part (length) of the film can be chosen for coating or, alternatively, the entire roll can be gone through from the beginning to the finish so that the entire roll becomes coated.

Figure 4 illustrates a typical structure of the lithium ion battery as a cross-sectional view. Of the parts, the first one from the top is the aluminium film 51 , which functions as the current collector. Moving downwards from this, the next part is the cathode material 52. The third film is the anode material 54. The lowermost, fourth film is the copper film 55, which functions as a current collector in the respective manner as the uppermost aluminium film 51 .

Figure 5 illustrates an arrangement of the structural view, in which anode material is coated to the base using the PLD technology. Here the laser beam pulses 61 are marked with thick dashed lines in the lower part, and the laser pulses enter the figure area from the bottom right. The laser pulses are directed to the surface of the target material piece 62, and preferably, the direction of the target surface met by the pulses is set to an inclined direction in relation to the direction of arrival of the pulses. Of this interaction there is generated the material flow 63, which consists of particles, atoms and/or ions. This material flow is shown as a droplet-shaped material cloud in the figure. The base material 65 to be coated is uppermost, and the actual coating 64 is formed to its lower surface, which in this figure is shown as five circles with equal diameters. In other words, the material flow hits the lower surface of the base and adheres to it.

Figure 6a illustrates a possible coating structure to be produced using the principle in Figure 5, in which the coating adheres to the lower surface of the base 65. As can be seen in the figure, the coating forming of the material flow is porous, and it consists of only one material, which can here be called the principal material 66. In other words, also the target used in this example consists of one material, and there is one target to be used.

Figure 6b illustrates a possible coating structure 65 of a second type to be produced onto the surface of the base 65 using the principle in Figure 5. In this situation, a composite material is generated, which consists of two different materials. The prin- cipal material 66 is marked with circles, and among the principle material there is found the second material 67. The structure is still porous.

Figure 6c illustrates a possible porous structure to be produced by using the principle in Figure 5, in which so-called doped material is used in addition to the principal material. Here the bigger circles seen on the lower surface of the base 65 illustrate the principal material 66, and the smaller circles the so-called doping material, i.e. the additive 68. In this situation it can be determined, for example, that the quantity of the additive 68 is at most 10 percent by volume of the volume of the entire coating. Also this structure is porous. As can be seen in the figure, the additive 68 settles among the principal material 66, and in an advantageous embodiment this distribution of the doping material into the principal material is made homogeneous so that the entire porous coating is identical, i.e. of uniform quality.

Figure 7 illustrates an example of the combinatory coating method using two simultaneous material flows. Here two separate laser beams, i.e. the first pulse string 71 a and the second pulse string 71 b enter the arrangement, and these pulse strings are directed to hit the target material pieces, i.e. the first target 72a and the second target 72b. The material of the first target is different from the material of the second target. Of these interactions, the material flows 73a and 73b are generated as the result of laser ablation. These both material flows comprise particles, atoms and ions, but concerning different materials. The material flows hit the lower surface of the base 75 simultaneously, thus forming the composite coating 74. The compositions of the different substances in the composite coating 74 can be varied, for example, by independently adjusting either one or both laser sources, which produce the laser beams 71 a and 71 b. The composite coating 74 is thus composed of the material flows 73a and 73b to the lower surface of the base 75 at the same time, forming immediately the finished coating.

Figure 8a illustrates the use of successive coating stations to improve productivity when manufacturing sandwich structures. In this example there are shown four coating stations, and each of the incoming laser beams (or pulse strings) 82a-d is tar- geted at the appropriate target 82a-d through a mirror (P, each beam having its own). In this situation, the roll-to-roll method can be used, and the lower surface of the base 85 contacts first the first material flow 83a, which forms the first coating layer 84a. This first coating layer 84a again contacts the second material flow 83b as the base moves, and this way the second coating layer 84b is formed onto the first coating layer 84a. This process still continues in two coating stations, and the final result is the base material 85, which contacted four material flows, and the generated coating has a sandwich-type structure 84a, 84b, 84c, 84d. The targets 82a-d can be of the same material, as has been shown in this figure.

Figure 8b illustrates the use of successive coating stations to improve productivity when manufacturing composite structures. This is in other ways similar to the case in Figure 8a, but two different types of materials are now chosen as the target material pieces 82A, 82B, and these are positioned alternately, one target to one coating stations, the next target then being of the second material. In other words, from the left, the first and third target are of the same first material "A" and, respectively, the second and fourth target are of the same second material "B". The laser pulse strings 81 a-d can still be controlled independently and they can be directed to the targets through the mirrors P. This arrangement produces two material flows 83A, 83B of different types, which alternate. When the material flows hit the moving base 85, a new different layer is formed onto the old layers, and the final result the 4- layered composite structure 84A, 84B, 84A, 84B shown in the right edge. In this coating, the material layers thus alternate with each other.

Figure 8c illustrates the use of successive coating stations to improve productivity when manufacturing a doped material. This arrangement is in other ways similar to the one in Figure 8b, but now the first and third target 82C are made of the basic material and, respectively, the second and fourth target 82D are made of the additive, i.e. the doping material. The laser pulse strings 81 a-d can still be controlled independently and directed to the targets through the mirrors P. Two different types of material flows 83C, 83D are produced of this arrangement, which alternate. With a respective principle as above, a doped base material is now formed as a coating to the base 85, and the relative proportion of the doped material of the whole coating can be selected by independently adjusting the laser parameters. In the coating layers, 84C represents the basic material layer and 84D the additive layer.

Figure 8d illustrates a more specific detail of the basic material, including doped particles. Thus, this illustrates a more detailed structure of the coating generated by the arrangement in Figure 8c. The basic material 86 is shown as bigger parts in the figure, and the doped material, i.e. additive 87 is shown as smaller parts among the basic material in the figure. In practice, the additive is found as particles among the basic material.

Figure 9 illustrates an example of the use of a composite target material in the man- ufacture of a composite coating. Now there only is one physical element as the target material piece, but this element in itself has a composite structure, i.e. the target 92 consists in this example of two different materials. When laser beam pulses 91 are targeted at such a target 92, the material flow 93 is generated, consisting of the atoms, ions and particles of two different materials. This material flow 93 hits the lower surface of the base material 95, and the final result is the composite coating 94 containing two materials, which has adhered to the lower surface of the base material 95.

The combinatory coating arrangements and successive coating stations according to Figures 7 and 8a can be combined so that, for example, at the place of one or some of the coating stations in Figure 8a there is taken one coating arrangement of another type, such as a combinatory coating station comprising two or more targets according to the principle of the example in Figure 7.

As has been disclosed in many connections above, the inventional idea comprises, in addition to the manufacturing method, also the manufactured partial product, i.e. solid electrolyte manufactured by pulsed laser ablation deposition; further, the inventional idea comprises the finished Li ion battery including the solid electrolyte manufactured in the above-mentioned manner.

In short, in the invention there is produced a solid electrolyte material by pulsed laser ablation deposition as a layer of its own or together with electrode materials and/or desired additives.

In the following, the characteristics of the invention are still assembled in a list-type form in way of a summary.

The invention relates to a method for manufacturing material layers of Li ion batteries comprising solid electrolyte material, the method comprising the steps of - directing short-term laser pulses (12, 61 , 71 a-b, 81 a-d, 91 ) to least at one target (13, 62, 72a-b, 82a-d, 82A-D, 92);

detaching at least one material (14, 63, 73a-b, 83a-d, 83A-D, 93) from at least one target (13, 62, 72a-b, 82a-d, 82A-D, 92) by laser ablation;

directing at least one detached material (14, 63, 73a-b, 83a-d, 83A-D, 93) to the base material (15, 22, 42, 65, 75, 85, 95) of the coating at least at one surface or part of surface.

The invention is characterised in that the method further comprises the step of producing a solid electrolyte material by pulsed laser ablation deposition as a layer of its own or together with electrode materials and/or desired additives. In an embodiment of the invention, it is still assembled in the method a Li ion battery using manufactured material layers, which comprise an anode, cathode and solid electrolyte material so that at least the solid electrolyte material is manufactured by using pulsed laser ablation deposition.

In an embodiment of the invention, when using pulsed laser ablation deposition, the detachment of the material, formation of particles and transfer of the material from the target (13, 62, 72a-b, 82a-d, 82A-D, 92) to the base material (15, 22, 42, 65, 75, 85, 95) is achieved by laser pulses (12, 61 , 71 a-b, 81 a-d, 91 ) targeted at the target (13, 62, 72a-b, 82a-d, 82A-D, 92), in which the timely duration of an individual laser pulse is between 0.1 - 10000 ps.

In an embodiment of the invention, laser pulses (12, 61 , 71 a-b, 81 a-d, 91 ) are gen- erated on a repetition frequency, which can be chosen between the range of 10 kHz - 100 MHz.

In an embodiment of the invention, the average particle size of the solid electrolyte material is at most 3000 nm.

In an embodiment of the invention, the solid electrolyte material comprises at least 15 atom percent of lithium.

In an embodiment of the invention, the solid electrolyte material comprises at least 50 percent by volume of lithium-bearing oxide or oxi-nitride.

In an embodiment of the invention, the solid electrolyte material comprises at least 50 percent by volume of sulphide. In an embodiment of the invention, the solid electrolyte material is coated in at least part of the material layers so that the solid electrolyte material forms a composite material together with a cathode and/or anode material.

In an embodiment of the invention, the said desired additives are added materials enhancing electron conductivity in at least one material layer. In an embodiment of the invention, at least two laser sources are set to transmit laser pulses simultaneously to at least two different targets (72a-b, 82a-d, 82A-D), forming a continuous material flow from at least two different targets (72a-b, 82a-d, 82A-D) to the surface of the base material (75, 85, 95), and forming a composite structure consisting of at least two different materials, in which an electrode material and/or additives enhancing electron conductivity are coated together with the solid electrolyte material so that the solid electrolyte material is found in at least one material layer. In an embodiment of the invention, the coating is performed in at least two successive coating stations so that at least one of the coating stations functions so that the material flow produced by it does not contact the material flow produced by the adjacent coating station before the coating has been generated, and that the material flows from the targets form a composite structure consisting of at least two different materials, in which an electrode material and/or additives enhancing electron conductivity are coated together with the solid electrolyte material so that the solid electrolyte material is found in at least one material layer.

In an embodiment of the invention, the coating of at least one material layer is per- formed by pulsed laser ablation deposition in a partial background gas pressure, which is at least 10^"6 mbar.

In an embodiment of the invention, at least 50 percent by volume of the total quantity of the material to be coated is executed in an atmosphere containing oxygen, nitrogen or argon, in which the total gas pressure is at least 10^"4 mbar. In an embodiment of the invention, the anode and/or cathode material particles in contact with the solid electrolyte material are of the average sizes of at most 5 pm.

In an embodiment of the invention, the size of additive particles enhancing electron conductivity is at most 2 pm, on average.

In an embodiment of the invention, the thickness of one material layer manufactured by pulsed laser ablation deposition is at most 200 pm.

In an embodiment of the invention, during the coating of at least one material layer, the surface of the base material (15, 22, 42, 65, 75, 85, 95) has been preheated to a temperature, which is at least 300 °C.

In an embodiment of the invention, after the coating of at least one material layer, the coated product is subjected to a heat treatment in a temperature, which is at least 300 °C.

The inventional idea further comprises the Li ion battery, which comprises the cathode material (52) and anode material (54). A characteristic feature is that the Li ion battery further comprises a solid electrolyte material, in which at least one embodi- ment option of the above-described method has been utilised in the manufacture of at least the solid electrolyte material.

The method of the invention has the following advantages: i. It is possible to manufacture different quantities of material layers containing solid electrolytes for Li ion batteries using a simple arrangement;

ii. Good adhesion is achieved between the different material layers without special adhesion layers or binding agents.

iii. Solid electrolyte, electrode material particles and desired additives, such as materials containing electron conductivity can be manufactured in a controlled manner using one or several methods to generate a desired material layer distribution to the Li ion battery.

iv. During the processing and installation of different material layers there is no risk of material damage or contamination, if the method is executed using one apparatus.

v. It is possible to manufacture composite structures to combine different materials in an optimal manner and to produce the desired solid electrolyte distribution with cathode and anode material particles and blending agents enhanc- ing conductivity.

vi. It is possible to retain the correct coating composition from the target to the coating especially where materials with a complex composition are concerned. vii. It is possible to avoid the use of binding agents, which reduces the contamination risk of battery chemistry in long-term use.

viii. Several material layers important for different functionalities can be manufactured with one manufacturing method (and partly even in one manufacturing step).

ix. The quantity of productional investments can be reduced.

x. The particle size of different materials in material layers used can be adjusted and thus impact the electrochemical and mechanical behaviour

xi. The crystallinity of materials used can be controlled by adjusting process parameters, work temperature and post-heat treatment

In the invention it is possible to combine individual features of the invention mentioned above and in the dependent claims into new combinations, in which two or several individual features can have been included in the same embodiment.

The present invention is not limited to the presented examples, but many variations are possible within the scope of protection defined in the attached claims.

Claims

1 . Method for the manufacture of material layers comprising solid electrolyte material for Li ion batteries, the method comprising the following steps:

short-term laser pulses (12, 61 , 71 a-b, 81 a-d, 91 ) are directed to at least one target (13, 62, 72a-b, 82a-d, 82A-D, 92);

at least one material (14, 63, 73a-b, 83a-d, 83A-D, 93) is detached from at least one target (13, 62, 72a-b, 82a-d, 82A-D, 92) by laser ablation;

at least one detached material (14, 63, 73a-b, 83a-d, 83A-D, 93) is directed to the coating base material (15, 22, 42, 65, 75, 85, 95) to at least one surface or part of surface, characterised in that the method further comprises the step, in which

a solid electrolyte material is produced by pulsed laser ablation deposition as a layer of its own or together with electrode materials and/or desired additives.

2. Method according to claim 1 , characterised in that in the method there is fur- ther assembled a Li ion battery using manufactured material layers, the material layers comprising an anode, cathode and solid electrolyte material so that at least the solid electrolyte material has been manufactured using pulsed laser ablation deposition.

3. Method according to any of the preceding claims 1 - 2, characterised in that when using pulsed laser ablation deposition, the detachment of the material, formation of particles and transfer of the material from the target (13, 62, 72a-b, 82a- d, 82A-D, 92) to the base material (15, 22, 42, 65, 75, 85, 95) is achieved by laser pulses (12, 61 , 71 a-b, 81 a-d, 91 ) targeted at the target (13, 62, 72a-b, 82a-d, 82A- D, 92), in which the timely duration of an individual laser pulse is between 0.1 - 10000 ps.

4. Method according to any of the preceding claims 1 - 3, characterised in that laser pulses (12, 61 , 71 a-b, 81 a-d, 91 ) are generated on a repetition frequency, which can be chosen between 10 kHz - 100 MHz.

5. Method according to any of the preceding claims 1 - 4, characterised in that the average particle size of the solid electrolyte material is at most 3000 nm.

6. Method according to any of the preceding claims 1 - 5, characterised in that the solid electrolyte material contains at least 15 atom percent of lithium.

7. Method according to any of the preceding claims 1 - 6, characterised in that the solid electrolyte material contains at least 50 percent by volume of lithium-bearing oxide or oxi-nitride.

8. Method according to any of the preceding claims 1 - 6, characterised in that the solid electrolyte material contains at least 50 percent by volume of lithium-bearing sulphide.

9. Method according to any of the preceding claims 1 - 8, characterised in that the solid electrolyte material is coated in at least part of the material layers so that the solid electrolyte material forms a composite material together with the cathode and/or anode material.

10. Method according to any of the preceding claims 1 - 9, characterised in that the said desired additives are material additives enhancing electron conductivity in at least one material layer.

1 1 . Method according to any of the preceding claims 1 - 10, characterised in that at least two laser sources are set to transmit laser pulses simultaneously to at least two different targets (72a-b, 82a-d, 82A-D), forming a continuous material flow from at least two different targets (72a-b, 82a-d, 82A-D) to the surface of the base material (75, 85, 95), and forming a composite structure consisting of at least two different materials, in which the electrode material and/or additives enhancing electron con- ductivity are coated together with the solid electrolyte material so that the solid electrolyte material is found in at least one material layer.

12. Method according to any of the preceding claims 1 - 1 1 , characterised in that the coating is executed in at least two successive coating stations so that at least one of the coating stations functions so that the material flow produced by it does not meet the material flow produced by the adjacent coating station before the generation of the coating and that the material flows from the targets form a composite structure consisting of at least two different materials, in which the electrode material and/or additives enhancing electron conductivity are coated together with the solid electrolyte material so that the solid electrolyte material is found in at least one ma- terial layer.

13. Method according to any of the preceding claims 1 - 12, characterised in that the coating of at least one material layer is executed by pulsed laser ablation deposition in a partial background gas pressure, which is at least 10^"6 mbar.

14. Method according to any of the preceding claims 1 - 13, characterised in that at least 50 percent by volume of the total quantity of the material to be coated is executed in an atmosphere, which contains oxygen, nitrogen or argon, in which the total gas pressure is at least 10^"4 mbar.

15. Method according to any of the preceding claims 1 - 14, characterised in that the anode and/or cathode particles in contact with the solid electrolyte material have the average sizes of at most 5 pm.

16. Method according to any of the preceding claims 1 - 15, characterised in that the size of additives enhancing electron conductivity is at most 2 pm, on average.

17. Method according to any of the preceding claims 1 - 16, characterised in that the thickness of one material layer manufactured by pulsed laser ablation deposition is at most 200 pm.

18. Method according to any of the preceding claims 1 - 17, characterised in that during the coating of at least one material layer the surface of the base material (15, 22, 42, 65, 75, 85, 95) has been preheated to a temperature, which is at least 300 °C.

19. Method according to any of the preceding claims 1 - 18, characterised in that after the coating of at least one material layer the coated product is heat-treated in a temperature, which is at least 300 °C.

20. Li ion battery, which comprises

a. a cathode material (52), and

b. an anode material (54), characterised in that the Li ion battery further comprises

c. a solid electrolyte material, in which a method according to any of the claims 1 - 19 has been utilised in the manufacture of at least the solid electrolyte material.