Method for rapidly charging an electric current storage cell

Abstract

The invention relates to a method for rapidly charging an electric current storage cell, in particular a vehicle current storage cell in a vehicle, wherein an actual charging current is set depending on a reversible change in volume of the active electrode material occurring during the charging process.

Description

[0001] Method for fast charging an electrical power storage cell

[0002] The present invention relates to a method for rapidly charging an electrical power storage cell, in particular a vehicle power storage cell of a battery-electric vehicle.

[0003] Fast charging is a key factor in user acceptance of battery-electric vehicles. The goal is to enable particularly short charging times without compromising safety or the battery's service life.

[0004] In a power storage cell designed as a lithium-ion storage cell or a sodium-ion storage cell, ion transport between the anode and the cathode is enabled by an electrolyte solution comprising a lithium conducting salt or a sodium conducting salt and at least one solvent. This electrolyte solution is present in the pores of the anode and cathode, as well as in the pores of the separator located between the anode and the cathode. When filling a power storage cell with an electrolyte solution, the electrolyte solution is added in excess of the available pore volume in the power storage cell to obtain a power storage cell with high capacity and a long service life.A known mechanism for the aging of energy storage cells is the deposition of lithium at the anode, known as "lithium plating" in lithium-ion storage cells, or the deposition of sodium at the anode, known as "sodium plating" in sodium-ion storage cells. This deposition of metal at the anode leads to a rapid loss of the energy storage cell's capacity.

[0005] It is known from the prior art that plating can occur when the anode potential of the storage cell drops below a certain anode potential threshold during the charging process. To counteract plating under real-world conditions, the charging current is typically reduced, which, however, disadvantageously results in an increase in charging time.

[0006] From "Optimum fast charging of lithium-ion pouch cells based on local volume expansion criteria", Spingler et al., Journal of Power Sources, Volume 393, 2018, Pages 152-160, studies of fast-charging processes are known in which a volume change of the active materials is taken into account. Excessive expansion of the dimensions of a storage element is correlated with the occurrence of lithium plating during fast charging. As a result, an adapted fast-charging profile is proposed, which also prevents excessive volume expansion of the storage element by reducing the charging current. A common feature of the state of the art is that the actual cause of the occurrence of plating (hereinafter "primary effect") is not analyzed or recognized.It merely shows possibilities to detect plating (hereinafter "secondary effect") and suggests supposedly optimized charging profiles to limit this secondary effect.

[0007] The object of the present invention is therefore to provide a rapid charging method in which one or more of the aforementioned disadvantages are avoided. The object of the present invention is, in particular, to identify the primary mechanism that results in undesired plating of the electrodes and to offer corresponding options for preventing the primary effect, so that the conditions for the formation of plating cannot occur in the first place. Furthermore, the object of the invention is to propose a rapid charging method in which, on the one hand, efficient charging processes are possible and, at the same time, the probability of premature aging of the storage cell is reduced.

[0008] One or more of these objects is achieved by a rapid charging method according to the present invention. In the method for rapid charging an electrical power storage cell, in particular a vehicle power storage cell of a vehicle, a current charging current is adjusted as a function of a reversible volume change of the active electrode material occurring during the charging process.

[0009] The state of charge of a storage cell (SOC) specifies the capacity available in a storage cell in relation to a fully charged state with a charge level of 100% and an uncharged state with a charge level of 0%. In particular, a charge level of 0% occurs at a defined lower cut-off voltage and a charge level of 100% occurs at a defined upper cut-off voltage. In the case of a lithium-ion storage cell, for example, the lower cut-off voltage can be 2.8 V and the upper cut-off voltage 4.2 V. The lower cut-off voltage and the upper cut-off voltage of a storage cell can be specified in particular by a battery management system.

[0010] The pore volumes in the anode, cathode, and separator can particularly refer to a formed storage cell in which the storage cell has already been charged and discharged after manufacture, so that boundary layers form, particularly on the anode and cathode. On the anode, this boundary layer is referred to as SEI (“solid electrolyte interface”) and on the cathode as CEI (“cathode electrolyte interface”). Due to volume changes of the electrochemically active materials in the anode and cathode, the pore volume of the electrodes can change during the charging and discharging process. Due to the change in pore volume, electrolyte solution is displaced from the electrode or sucked into the electrode. The pore volume of the anode decreases, depending on the state of charge, particularly during charging of the storage cell and increases again during discharging.This can be attributed in particular to an increase in the volume of the electrochemically active anode materials during charging of the storage cell. Furthermore, a conducting salt gradient develops between the cathode and anode during charging and discharging, depending on the charging or discharging current. The higher the charging or discharging current, the stronger the gradient. During the charging phase, the conducting salt concentration in the anode decreases. If, in this state, the electrolyte in the anode is displaced by a change in the volume of the active material, an accumulation of electrolyte with a low conducting salt concentration occurs outside the electrodes. In the subsequent discharging phase, the conducting salt gradient forms in the opposite direction to the charging process, and the conducting salt concentration at the anode increases. Due to the increase in pore volume due to a decrease in the active material volume, electrolyte is now sucked into the anode.This causes electrolyte with a high conducting salt concentration to collect in the center of the anode, while the electrolyte with a low conducting salt concentration that has accumulated outside the anode is drawn back into the anode. This effect creates a conducting salt gradient from the center of the electrode to the edge of the electrode. An excessive conducting salt gradient affects the cell's electrochemical limit potential and can lead to premature aging of the storage cell. In the case of a lithium-ion storage cell, this can lead to the deposition of lithium, and in the case of a sodium-ion storage cell, to increased deposition of sodium on the electrodes.

[0011] The volume change of the active electrode material is fundamentally reversible. While the active electrode material expands during electrical charging of a storage cell, its volume decreases during discharging. However, the volume change of the active electrode material is not constant throughout the entire charging or discharging process, but is particularly pronounced at the beginning and end of the charging or discharging process. In general, the reversible volume change of the active electrode material depends on the state of charge (SOG) of the energy storage device.

[0012] A metal-ion energy storage cell typically comprises an anode and a cathode. The metal-ion energy storage cell further comprises a porous separator that electrically separates the electrodes and a metal-ion electrolyte that ionically connects the anode and cathode. The energy storage cell is charged by a current source from a power supply.

[0013] The power storage cell can comprise an electrode coil or an electrode stack. The electrode coil or the electrode stack can be housed in a housing, wherein the electrode coil and the electrode stack comprise the above-described anode, cathode, and separator. The electrode coil or the electrode stack can extend in the housing along a longitudinal axis of the power storage cell. In an electrode coil, in particular a strip-shaped anode, a strip-shaped cathode, and a first strip-shaped separator located between the strip-shaped anode and the strip-shaped cathode, together with a second further strip-shaped separator, can be wound in layers around a winding core. In an electrode stack, individual anodes, cathodes, and separators located therebetween can be layered one on top of the other as plate-shaped elements.

[0014] Such power storage cells can achieve particularly high capacities.

[0015] Preferably, the electrode coil or electrode stack has a length of at least 3 cm along the longitudinal axis of the power storage cell. Power storage cells with such lengths along their longitudinal axis exhibit particularly high capacities due to their size. Due to the large length of at least 3 cm along the main axis of the power storage cell, different concentrations of conductive salt along this main axis cannot normally be compensated by diffusion within a very short time during operation of the power storage cell and can therefore lead to premature aging of the power storage cell.

[0016] Examples of energy storage cells with a length of at least 3 cm along the longitudinal axis include round cells of the 18650 type with a length of 6.5 cm along the longitudinal axis. Other examples of energy storage cells with this length are cells of the 4680 type with a length of 8 cm, cells of the 4695 type with a length of 9.5 cm along the longitudinal axis, and cells of the 46120 type with a length of 12 cm along the longitudinal axis. Such energy storage cells can be used particularly in battery-electric vehicles.

[0017] The housing of the energy storage cell can be arranged along the longitudinal axis around the circumference of the electrode coil or electrode stack. The housing can thereby contact the main surface of the anode all the way around. In particular, a separator layer can be present between the housing and the respective electrodes for electrical insulation. Such a housing, in which the electrodes or separators of the electrode coil or electrode stack are contacted by the housing, allows for a particularly compact design of the energy storage cells.

[0018] The housing can, in particular, comprise a metallic outer shell or a plastic outer shell. The housing can, in particular, be cylindrical, with poles for electrically contacting the power storage cell located at the opposite ends of the cylinder. The housing can also comprise a flexible foil, for example, made of aluminum, in which the electrode stack is firmly clamped. Such housings are used, for example, in pouch cells.

[0019] The electrical energy storage device of the present invention can be a metal-ion battery. The electrical energy storage device of the present invention can be a lithium-ion battery. The electrical energy storage device of the present invention can be a sodium-ion battery.

[0020] The pore volume of the anode of the power storage cell can decrease, particularly during the charging process, depending on the state of charge. The anode can, in particular, comprise an electrochemically active anode material. An electrochemically active anode material is understood, in particular, to be a material that is capable of absorbing and releasing lithium ions if the power storage device is a lithium-ion power storage device. The pore volume of the anode of the power storage cell can decrease, particularly during the charging process, depending on the state of charge. This can be attributed, in particular, to the fact that the volume of the electrochemically active anode material increases during the charging process due to the intercalation of lithium into the electrochemically active anode material, for example graphite or silicon oxides, silicon, or mixtures thereof.In particular, the electrochemically active anode material can be selected from a group consisting of: synthetic graphite, natural graphite, graphene, mesocarbon, doped carbon, hard carbon, soft carbon, fullerene, silicon-carbon composites, silicon, surface-coated silicon, silicon suboxide, silicon alloys, aluminum alloys, indium, tin alloys, cobalt alloys, and mixtures thereof. Preferably, the electrochemically active anode material can be selected from a group consisting of: graphite, silicon oxides, and silicon, or mixtures thereof. Such electrochemically active anode materials are particularly suitable for providing lithium-ion storage cells with high capacity.

[0021] In a sodium-ion storage cell, the anode can comprise an electrochemically active anode material. The electrochemically active anode material in a sodium-ion storage cell can be designed to absorb and release sodium ions during charging and discharging. The electrochemically active anode material in a sodium-ion storage cell can, in particular, comprise hard carbon, carbon, for example in the form of graphite, which, similar to a lithium-ion storage cell, can absorb and release sodium ions through intercalation. Similar to the lithium-ion storage cell, this can lead to a change in the pore volume of the anode in the sodium-ion storage cell.

[0022] In the power storage cell, the pore volume of the cathode can increase during the charging process depending on the state of charge. The cathode can in particular comprise an electrochemically active cathode material. In a lithium-ion power storage cell, an electrochemically active cathode material is understood to mean in particular a cathode material that is capable of releasing and reabsorbing lithium ions during charging and discharging. In a lithium-ion power storage cell, the electrochemically active cathode material can be selected from a group consisting of: lithium transition metal oxides such as lithium cobalt oxide (UCOO2), lithium nickel cobalt manganese compounds (abbreviated to NCM orNMC), for example UCOO2, LiNio,33Coo,33Mno,33O2, lithium nickel cobalt aluminum oxides (NCA), lithium olivines such as lithium iron phosphate (LFP), lithium spinels such as lithium manganese oxide spinel (LMO) or combinations thereof, further preferably wherein the electrochemically active cathode material is selected from a group consisting of: lithium nickel cobalt manganese compounds.

[0023] As cathode material, for example, materials containing sodium ions such as phosphates and diphosphates, for example sodium iron phosphates or compounds such as Na2 / 3Fei / 2Mni / 2O2 can be used in a sodium ion power storage cell.

[0024] The electrolyte solution for a power storage cell may comprise a lithium salt as a conductive salt and at least one organic solvent.

[0025] The electrolyte solution for a power storage cell may comprise a sodium salt as a conductive salt and at least one organic solvent.

[0026] In a lithium-ion power storage cell, the lithium salt can preferably be selected from a group consisting of: LiPFe, LiAsFe, UCIO4, ÜCF3SO3, lithium bis(trifluoromethylsulfonyl)amide or combinations thereof.

[0027] In a sodium ion power storage cell, the sodium salt may preferably be selected from a group consisting of: NaPFe, NaCIO4, Na-bis(trifluoromethane)sulfonimide, Na-bis(fluorosulfonyl)imide, Na-difluoro(oxalato)borate, Na-bis(oxalato)borate or combinations thereof.

[0028] The organic solvent may, in particular, comprise an organic polar solvent. The organic solvent may, in particular, be selected from a group consisting of: C2 to C4 cyclic esters of carbonic acid, for example propylene carbonate, ethylene carbonate, lactones, for example γ-, δ-, and ε-lactone, or combinations thereof.

[0029] According to one aspect of the invention, the metal-ion current storage cell is charged with a reduced charging current in a first state-of-charge range, a state-of-charge range with a low state of charge. This adapts the charging current to a reduced conducting salt concentration of the electrolyte in the vicinity of the anode due to the volumetric work of the active material of the electrodes.

[0030] During the charging of a metal-ion energy storage cell, a conducting salt gradient forms in the electrolyte. The extent of the conducting salt gradient depends primarily on the charging current. Furthermore, it has been determined that the conducting salt gradient can be amplified by the volumetric work of the active material of the electrodes. More specifically, it has been determined that, particularly during rapid charging, increased volumetric work of the active material of the electrodes occurs in a first state of charge range, and that this results in an additional reduction in the conducting salt concentration in the electrolyte in the vicinity of the anode in this first state of charge range. It has also been determined that, due to the reduced conducting salt concentration, the electrochemical limit potential also decreases. This, in turn, increases the likelihood of plating, which leads to avoidable and premature aging of the energy storage cell.In order to counteract this effect, it is proposed according to the present invention to use a lower charging current, particularly in this first state of charge range.

[0031] The exact boundaries of the first state of charge range depend on the design and materials used in the energy storage cell. In general, the first state of charge range, where increased volume work of the active electrode material occurs, can extend between SOG = 0% and SOG = 30%. The first state of charge range can also extend between SOG = 0% and SOG = 20%. The first state of charge range can also extend between SOG = 0% and SOG = 15%.

[0032] The extent to which the charging current should be reduced in this first state of charge range in order to reduce the likelihood of plating occurring can also depend on the design and the materials used in the power storage cell. According to the invention, it is proposed to charge a metal-ion power storage cell in the first state of charge range with a reduced charging current of a maximum of 70% of the maximum charging current applicable for a given power storage cell. Furthermore, it is proposed to charge a metal-ion power storage cell in the first state of charge range with a reduced charging current of a maximum of 80% of the maximum charging current applicable for a given power storage cell. Finally, it is proposed to charge a metal-ion battery in the first state of charge range with a reduced charging current of a maximum of 90% of the maximum charging current applicable for a given power storage cell.

[0033] When designing a conventional fast charging profile, the initial state of charge (SOCini) and the charging stroke (ASOC) are taken into account in addition to the dimensions and materials of the power storage cell. Furthermore, the temperature and the

[0034] Temperature spread in the power storage cell, i.e. the coldest temperature Tmin and the hottest temperature Tmax as well as their temperature difference AT.

[0035] A fast-charging profile is conventionally determined based on these parameters, where the charging current is maximized "along the electrochemical boundary potential." Electrochemical-thermal cell models are typically used to design the fast-charging process, which can be used to describe a boundary potential—the so-called anode potential E [\|—].

[0036] By reducing the charging current to values ​​below the maximum possible charging current with such conventional electrochemical-thermal cell models, the additional effect of the change in the conducting salt concentration due to the volume work of the active electrode material in the first state of charge range is taken into account. By reducing the charging current, the probability of plating occurring is therefore significantly reduced. While the selective reduction of the charging current in the first state of charge range temporarily extends the charging time of a power storage cell, over the service life of the power storage cell, it can significantly delay premature aging of the cell. Overall, the rapid charging method according to the invention can thus achieve a considerable increase in the performance of the power storage cell over its entire service life.

[0037] According to a further aspect of the present invention, the power storage cell can be charged with maximum charging current in a second, intermediate state of charge. The second state of charge range is the state of charge range in which little or no volume work of the active electrode material occurs.

[0038] The second state of charge range can extend above a state of charge of 30% SOG. The second state of charge range can extend above a state of charge of 20% SOC. The second state of charge range can extend above a state of charge of 15% SOC. Since the second state of charge range usually extends over more than 50% of the total state of charge range of a power storage cell, the total charging time depends in particular on the level of the charging current in this second state of charge range. In conventional charging profiles, a charging current buffer is often provided. This means that a charging current that is only approximately 90-95% of the maximum charging current is used over the entire charging process. With the present invention, it has been found that such a buffer is not absolutely necessary in the second state of charge range.Thanks to the present invention, not only can a reduction in the charging current be dispensed with in the second state of charge range, but the present invention also enables a more in-depth understanding of the rapid charging process and now even makes it possible to dispense with unnecessary charging current buffers in the second state of charge range.

[0039] According to a further aspect of the invention, the metal-ion current storage cell is charged with a reduced charging current in a third state-of-charge range, a high state-of-charge range. This also adapts the charging current to a reduced conducting salt concentration of the electrolyte in the vicinity of the anode, due to the volumetric work of the active material of the electrodes.

[0040] The third state of charge range can extend above a state of charge of 70% SOC. The second state of charge range can extend above a state of charge of 80% SOC. The second state of charge range can extend above a state of charge of 90% SOC. The same applies to the charging current that can be used in the third state of charge range as has already been described above in connection with the reduction of the charging current in the first state of charge range. In particular, in the third state of charge range, a metal-ion battery can also be charged with a reduced charging current of a maximum of 70% of the maximum charging current that can be used for a given power storage cell in this state of charge range. Alternatively, a reduced charging current of a maximum of 80% or a maximum of 90% of the maximum charging current that can be used for a given power storage cell in this state of charge range can also be charged.

[0041] The present invention provides new insights into primary effects that promote the occurrence of undesirable plating in energy storage cells. In particular, it was discovered that during the charging process, the volumetric work of the active electrode materials occurring in certain charge state ranges leads to an additional change in the conducting salt gradient. It was further discovered that this leads to a shift in the electrochemical limit potential. Precise knowledge of the electrochemical limit potential of an energy storage cell is crucial for the design of optimal fast-charging profiles, which then offer the possibility of utilizing the electrochemical limit potential of an energy storage cell during fast charging while simultaneously avoiding secondary effects such as aging due to plating.

[0042] In a further aspect, the present invention relates to a method for designing a fast-charging characteristic map for fast-charging an electrical energy storage cell, in particular a vehicle power storage cell of a vehicle. When designing the fast-charging characteristic map, a maximum permissible charging current is determined depending on the state of charge, and the maximum permissible charging current is determined based on the electrochemical limit potential of the electrical energy storage device. When determining the electrochemical limit potential, a state-of-charge-dependent conducting salt concentration of the electrolyte at the anode of the power storage cell is taken into account.

[0043] The term "fast charging" as used herein refers to charging methods that use charging rates of more than 1C. With such charging methods, a power storage cell can be charged from SOC = 0% to a charge level of SGC = 100% within one hour.

[0044] The term "volume work of the active electrode material" as used herein refers to volume changes of the active electrode material that occur during the charging process. Due to the "volume work of the active electrode material," the porosity of the active electrode material changes, resulting in the displacement of electrolyte from the pores of the electrode material.

[0045] In the following, the invention will be explained in more detail using exemplary embodiments.

[0046] Fig. 1 shows a correlation between state of charge dependent volume work and a conventional and an inventive charging profile, and

[0047] Fig. 2 additional details of a conventional and a modified loading profile according to the invention.

[0048] Fig. 1 shows two diagrams in which, on the one hand, the volume change of the active material of the electrodes (Fig. 1 above) and, on the other hand, the applied charging current (Fig. 1 below) are plotted against the charge state of an electrical power storage cell.

[0049] To determine the charging current profiles shown in Figures 1 and 2, type 4695 lithium-ion storage cells with a diameter of 4.6 cm and a length (along the longitudinal axis) of 9.5 cm and a cylindrical housing were used. The electrochemically active anode material consisted of a mixture of graphite and silicon, with the weight fraction of silicon in the anode active material being less than 10 weight percent. The electrochemically active cathode material consisted of a typical nickel-cobalt-manganese layered oxide with a nickel content of greater than 85 atomic percent. A copper foil was used as the current collector foil for the anode, with the thickness of the coating with the electrochemically active anode material being 70 μm. An aluminum foil was used as the current collector foil for the cathode, with the thickness of the coating for the cathode being 50 μm.Both the anode current collector foil and the cathode current collector foil were coated on one side. The separator is made of a polymer and contains a ceramic coating. The porosity of the anode at a 0% state of charge was 25%, and the porosity of the cathode at a 0% state of charge for the already formed power storage cell was 23%. The electrolyte solution consisted of ethylene carbonate with a lithium conducting salt LiPFe at a concentration of 1.2 mol / l. Both power storage cells have lower cutoff voltages of 2.8 V (0% state of charge) and upper cutoff voltages of 4.2 V (100% state of charge).

[0050] The charging current profile 10 in the lower diagram of Fig. 1 corresponds to a conventional charging profile. In this charging current profile 10, the charging current is determined according to the determined electrochemical limit potential of the power storage cell. When designing such a conventional fast charging profile, the initial state of charge (SOCj) is taken into account in addition to the dimensions and materials of the power storage cell. n j) and the charging stroke (ASOC). In addition, the temperature or temperature spread in the power storage cell, i.e. the coldest temperature T mjn and the hottest temperature T maxand their difference AT. From these parameters, a fast-charging profile is conventionally determined in which the charging current is maximized "along the electrochemical limit potential." Electrochemical-thermal cell models are typically used to design the fast-charging process, which can be used to describe a limit potential—the so-called anode potential E / N.

[0051] The charging current profile 10 in the lower diagram of Fig. 1 corresponds to such a conventionally determined charging profile. In this charging profile, a maximum charging current Imax(conv) is applied at the beginning of the charging process, when the state of charge is still relatively low. The maximum charging current Imax(conv) w ' rc * soused until the electrochemical limiting potential of the storage cell approaches the anode potential threshold. In the charging current profile 10 of Fig. 1, this is approximately reached at a state of charge of SOG = 30%. From this moment on, the charging current is continuously reduced, with the resulting electrochemical limiting potential of the storage cell always being kept just above the anode potential threshold. The result is the curve shown in Fig. 1, in which a constant, high charging current Imax(conv) is initially set, and this charging current then takes an exponentially decreasing course from a certain state of charge.

[0052] The upper graph of Fig. 1 plots the volume work of the active electrode material against the state of charge. According to this well-known relationship, a volume change of the active electrode material occurs at the beginning and end of the charging process, i.e., at low and high SOG. In the first region, the state of charge region 20, a constant volume change of the active electrode material occurs. In the second region, the state of charge region 22, no significant volume change of the active electrode material occurs. In the third region, the state of charge region 24, a constant volume change of the active electrode material again occurs.

[0053] Due to these volume changes of the active electrode materials that occur during the charging process, the pore volume of the electrodes, especially the anode, also changes. The change in the pore volume of the electrodes results in the displacement of electrolyte solution with a lower conducting salt concentration than the originally used conducting salt concentration from the electrodes. This results in areas with different conducting salt concentrations in the electrolyte solution forming, particularly near the electrodes. The different conducting salt concentrations influence the electrochemical limiting potential. In particular, the electrochemical limiting potential at the anode decreases due to the lower conducting salt concentration. The reduction in the electrochemical limiting potential can result in plating.Such plating can occur even at charging currents at which plating should not occur based on conventional electrochemical-thermal cell models.

[0054] In order to account for the local change in the conducting salt gradient caused by the volume work of the active electrode material or the reduction in the local conducting salt concentration, a modified charging current profile 12 is proposed according to the invention. This modified charging current profile 12 is plotted for direct comparison in the lower graph of Fig. 1. According to the charging current profile 12, the initial charging current lj n j is still high, but significantly lower than the maximum charging current Imax(conv) ' m conventional charging current profile 10. This charging current lj nj is used throughout the first state of charge range 20. As soon as the state of charge reaches a value of 20%, no significant volume change of the electrode material takes place, as can be seen from the upper graph of Fig. 1. For this reason, in the second state of charge range 22, the charging current can be set to a value Imax(req) 9 emaccording to the charging current profile 12 according to the invention. The charging current Imax(erf) can even be significantly higher than the conventionally used maximum charging current Imax(conv)'. In fact, it has been found that in this second state of charge range 22, no or hardly any buffer distance needs to be maintained, so that the maximum possible charging current due to the chemical limit potential can be almost fully utilized. This is also due to the fact that in this second state of charge range 22, no appreciable volume work occurs, so that the maximum charging current determined using conventional electrochemical-thermal cell models can be used. For this reason, a higher charging current is shown in the charging current profile 12 according to the invention in this range than in the conventional charging current profile 10.

[0055] As can be seen from the upper graph in Fig. 1, volumetric work of the active electrode material begins again at a state of charge of SOG = 80%. As a result, the local conducting salt concentration changes again in the third state of charge range 24. The electrochemical limit potential also shifts in this state of charge range 24. Therefore, the charging current is reduced again according to the invention in order to reduce the probability of plating in this state of charge range 24 as well.

[0056] Fig. 2 also compares a conventional charging current profile 10 and a charging current profile 12 according to the invention. The conventional charging current profile 10 was again determined using a conventional electrochemical-thermal cell model, and the charging current profile 12 according to the invention was determined using the method according to the invention.

[0057] The conventional charging current profile 10 essentially corresponds to the conventional charging current profile from Fig. 1 , in which a relatively high charging current Imax(conv) is used at the beginning of the charging process, which then decreases exponentially from a certain state of charge, in Fig. 2 at a state of charge SOG = 30%.

[0058] According to the charging current profile 12 according to the invention, the initial charging current lj is shown in Fig. 2 n j as high as the conventional charging current Imax(conv)- l m However, in the first state of charge range 20, as discussed above, a reversible volume change of the active electrode material occurs. This also results in a change in the conducting salt concentration at the anode. Since this concentration change does not occur instantly, but takes a certain amount of time to settle, a high charging current lj can be achieved up to a state of charge SOG = 15%. nj can be used. After a certain period of time, however, the conducting salt concentration in the anode area has changed, which also changes the electrochemical limit potential and increases the risk of plating. For this reason, in the charging current profile 12 according to the invention in Fig. 2, the charging current is reduced from a charge level SOG = 15%.

[0059] As soon as the state of charge is in the second state of charge range 22, no more volume work occurs on the active electrode material, so that from this moment on, the charging current can be set again to the maximum applicable charging current Imax(erf). The charging current then follows the exponentially decreasing curve already described in Fig. 1 in this second state of charge range 22. From a state of charge of SOG = 80%, volume work occurs again on the active electrode material, so that the electrochemical limit potential also changes again. This is taken into account by a further reduction in the charging current in the third state of charge range 24.

[0060] In the middle graph of Fig. 2, for the purpose of illustration and better understanding of the invention, the conventionally determined anode potential threshold E^N and the anode potential threshold Eg modified according to the findings of the present invention are plotted against the state of charge. The anode potential threshold E^N calculated using the conventional electrochemical-thermal cell model depends solely on the materials and the currently measured temperatures and is constant for such predetermined values ​​throughout the entire charging process.

[0061] However, based on the findings of the present invention, the actual anode potential threshold Eg is not the same across all charge state ranges 20, 22, 24. In the charge state ranges 20, 24, where volume work of the active electrode material occurs and where, consequently, a local change in the conducting salt concentration occurs, the modified anode potential threshold Eg is increased. With the charging profile according to the invention, in which the charging current is reduced in the charge state ranges 20, 24, the charging current can be adjusted such that the electrochemical cell potential is kept above the anode potential threshold at all times, thus reducing the risk of plating.

[0062] With the conventional charging current profile 10, which uses a constantly high maximum charging current Imax(conv), particularly in the state of charge range 20, there is a significant reduction in the electrochemical limit potential below the actual anode potential threshold. When using such charging profiles, there is a risk that, due to the disregard of the local conducting salt concentration, noticeable plating of the electrodes will occur after just a few charging cycles, which promotes aging of the power storage cell and reduces its capacity and service life.

Claims

Patent claims 1. Method for rapidly charging an electrical power storage cell, in particular a vehicle power storage cell of a vehicle, wherein a current charging current is adjusted as a function of a reversible volume change of the active electrode material occurring during the charging process.

2. A method for rapid charging according to claim 1, wherein the reversible volume change of the active electrode material occurs as a function of the state of charge (SOC) of the power storage cell.

3. A method for rapid charging according to any one of the preceding claims, wherein the electrical power storage cell is a metal-ion battery, for example a lithium-ion battery or sodium-ion battery.

4. A method for rapid charging according to any one of the preceding claims, wherein the metal ion battery comprises an anode, a cathode, a separator, and a metal ion electrolyte ionically connecting the anode and cathode, and wherein the battery is charged by a current source from a power supply.

5. A method for rapid charging according to any one of the preceding claims, wherein the power storage cell is charged at a low state of charge with a reduced charging current, whereby the charging current is adapted to a reduced conducting salt concentration of the electrolyte in the vicinity of the anode due to the volume work of the active electrode material.

6. A method for rapid charging according to claim 5, wherein the power storage cell is charged with a reduced charging current in a first state of charge range extending up to a state of charge of 30%, or up to a state of charge of 20%, or up to a state of charge of 15%.

7. A method for rapid charging according to one of claims 5 or 6, wherein the power storage cell is charged in the first state of charge range with a reduced charging current of a maximum of 70%, of a maximum of 80%, or of a maximum of 90% of the maximum charging current.

8. A method for rapid charging according to one of the preceding claims, wherein the power storage cell is charged with maximum charging current in a second charge state range which extends from a charge state of 30%, or from a charge state of 20%, or from a charge state of 15%.

9. A method for rapid charging according to one of the preceding claims, wherein the power storage cell is charged with a reduced charging current in a third charge state range extending from a charge state of 70%, or from a charge state of 80%, or from a charge state of 95%.

10. Method for designing a rapid charging characteristic map for rapid charging of an electrical power storage cell, in particular a vehicle power storage cell of a vehicle, wherein a maximum permissible charging current is determined as a function of the state of charge when designing the rapid charging characteristic map, and wherein the maximum permissible charging current is determined based on the electrochemical limit potential of the electrical power storage cell, and wherein a state of charge-dependent conducting salt concentration of the electrolyte at the anode is taken into account when determining the electrochemical limit potential.

11. A method for rapidly charging an electrical power storage cell, in particular a vehicle power storage cell of a vehicle, wherein a current charging current is set as a function of a reversible volume change of the active electrode material occurring during the charging process, wherein - the power storage cell is charged at a low charge level with a charging current that is reduced compared to a maximum charging current, whereby the charging current is adapted to a reduced conducting salt concentration of the electrolyte in the vicinity of the anode due to the volume work of the active electrode material, - the power storage cell is charged at a high charge level with a charging current that is reduced compared to the maximum charging current, and - the power storage cell is charged with maximum charging current in a charge state range between the low and high charge state.

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