Method for fast charging of an electrical energy storage cell

Abstract

The invention relates to a method for rapid charging of an electrical energy storage cell, in particular a vehicle energy storage cell of a vehicle, wherein the current charging current is set in accordance with the reversible volume change of the active electrode material occurring during the charging process.

Description

Technical Field

[0001] This invention relates to a method for rapidly charging energy storage cells, particularly vehicle energy storage cells for battery-powered vehicles. Background Technology

[0002] Fast charging is a crucial factor in user acceptance of battery-electric vehicles. The goal here is to achieve exceptionally short charging times without compromising battery cell safety or lifespan.

[0003] In energy storage cells configured as lithium-ion or sodium-ion storage cells, ion transport between the anode and cathode is achieved through an electrolyte comprising a lithium conductive salt or a sodium conductive salt and at least one solvent. This electrolyte is present in the pores of the anode and cathode, as well as in the pores of the membrane located between the anode and cathode. When filling the energy storage cell with the electrolyte, an excess volume of electrolyte is added relative to the usable pore volume in the energy storage cell to obtain an energy storage cell with high capacity and long service life. As known mechanisms of aging for energy storage cells, lithium deposition at the anode (so-called "lithium-plating" in the case of lithium-ion storage cells) or sodium deposition at the anode (so-called "sodium-plating" in the case of sodium-ion storage cells) is known. This metal deposition at the anode leads to a rapid loss of capacity in the energy storage cell.

[0004] As is known from existing technology, deposition may occur when the anode potential of a storage cell drops below the anode potential threshold during charging. To address deposition under practical conditions, the charging current is typically reduced; however, this adversely leads to an increase in charging time.

[0005] From the research on known fast charging methods in "Optimum fast charging of lithium-ion pouch cells based on local volume expansion criteria," Spingler et al., Journal of Power Sources, Vol. 393, 2018, pp. 152-160, which considers the volume change of the active material, excessive expansion of the storage element size is associated with the occurrence of lithium plating during fast charging. As a result, a matching fast charging profile is proposed, which also prevents excessive volume expansion of the storage element by reducing the charging current.

[0006] What existing technologies have in common is that they do not analyze or recognize the actual causes of precipitation (hereinafter referred to as the "primary effect"). They merely clarify the possibilities for identifying precipitation (hereinafter referred to as the "secondary effect") and propose a hypothesized optimized charging curve to limit the secondary effect. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide a fast charging method that avoids one or more of the aforementioned disadvantages. In particular, the object of the present invention is to identify the primary mechanisms leading to undesirable deposition on the electrodes and to provide corresponding possibilities for avoiding primary effects, thereby completely eliminating the preconditions for deposition from the outset. Furthermore, the object of the present invention is to propose a fast charging method in which an efficient charging process is possible while simultaneously reducing the probability of premature aging of the storage cells.

[0008] One or more of the tasks described above are achieved in the case of the fast charging method according to the present invention. In the method for fast charging of electric energy storage cells, particularly vehicle energy storage cells for vehicles, the current charging current is set based on the reversible volume change of the active electrode material during the charging process.

[0009] The state of charge (SOC) of a battery cell indicates the capacity present in the cell, defined by reference to a fully charged state (100% SOC) and an uncharged state (0% SOC). Specifically, a 0% SOC exists at a defined lower cutoff voltage, while a 100% SOC exists at a defined upper cutoff voltage. In lithium-ion battery cells, for example, the lower cutoff voltage can be 2.8V, and the upper cutoff voltage can be 4.2V. The lower and upper cutoff voltages of the battery cell can be preset, in particular, by the battery management system.

[0010] The pore volume in the anode, cathode, and separator can particularly relate to the formed storage cell, in which the cell has been charged and discharged after its manufacture, thereby forming a boundary layer, particularly on the anode and cathode. On the anode, this boundary layer is specifically referred to as an SEI film (“solid electrolyte interface”), while on the cathode, this interface layer is specifically referred to as a CEI (“cathode electrolyte interface”).

[0011] The pore volume of the electrode can vary during charging and discharging due to volume changes in the electrochemically active materials in the anode and cathode. Based on these pore volume changes, electrolyte is either squeezed out of or drawn into the electrode. The pore volume of the anode decreases, particularly during charging of the storage cell, according to the state of charge, and increases again during discharging. This can be attributed in particular to the increase in the volume of the electrochemically active anode material during charging of the storage cell. Furthermore, a conductive salt gradient forms 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 conductive salt concentration in the anode decreases. If, in this state, the electrolyte in the anode is squeezed out by the volume change of the active material, an accumulation of electrolyte with a low conductive salt concentration occurs outside the electrode. In the subsequent discharging phase, the conductive salt gradient is reversed compared to the charging phase, and an increase in the conductive salt concentration occurs at the anode. Due to the increase in pore volume based on the decrease in the volume of the active material, electrolyte is now drawn into the anode. This results in the accumulation of electrolyte with a high conductive salt concentration at the center of the anode, while simultaneously, electrolyte with a low conductive salt concentration that had accumulated outside the anode is drawn back into the anode. This effect establishes a conductive salt gradient from the center of the electrode to its edge. An excessive conductive salt gradient affects the cell's electrochemical limit potential and may lead to premature aging of the storage cell. In the case of lithium-ion storage cells, this may result in lithium deposition on the electrodes, and in the case of sodium-ion storage cells, it may lead to increased sodium deposition on the electrodes.

[0012] The volume change of the active electrode material is, in principle, reversible. The active electrode material expands during charging of the storage cell and decreases in volume during discharging. However, this volume change is not constant throughout the entire charging or discharging process, but is particularly significant at the beginning and end of the process. Generally, the reversible volume change of the electrode's active material occurs according to the energy storage cell's state of charge (SOC).

[0013] Metal-ion battery cells typically include an anode and a cathode. Furthermore, a metal-ion battery cell includes: a porous membrane that electrically separates the electrodes; and a metal-ion electrolyte that ionically connects the anode and cathode. The battery cell is charged by a current source that supplies energy.

[0014] Energy storage cells may include electrode windings or electrode stacks. The electrode windings or electrode stacks may be housed within a housing, wherein the electrode windings and electrode stacks include the anode, cathode, and separator described above. The electrode windings or electrode stacks may extend within the housing along the longitudinal axis of the energy storage cell. In the electrode windings, 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 may, in particular, be wound in layers around the winding core together with a second strip-shaped separator. In the electrode stacks, individual anodes, cathodes, and separators located therebetween may be stacked as plate-like elements.

[0015] These types of energy storage cells can achieve exceptionally high capacities.

[0016] Preferably, the electrode winding or electrode stack has a length of at least 3 cm along the longitudinal axis of the energy storage cell. Energy storage cells with this length have particularly high capacity along their longitudinal axis based on the size of the energy storage cell. Due to the large length of at least 3 cm along the main axis of the energy storage cell, the varying concentrations of conductive salts along this axis generally cannot be balanced by diffusion within a short time during the operation of the energy storage cell, and may therefore lead to premature aging of the energy storage cell.

[0017] Energy storage cells having a length of at least 3 cm along their longitudinal axis are, for example, the 18650 type cylindrical cell with a length of 6.5 cm along its longitudinal axis. Other examples of energy storage cells with this length are the 4680 type cell with a length of 8 cm, the 4695 type cell with a length of 9.5 cm along its longitudinal axis, and the 46120 type cell with a length of 12 cm along its longitudinal axis. Such energy storage cells are particularly suitable for use in battery-electric vehicles.

[0018] The housing of the energy storage cell can be arranged along the longitudinal axis around the circumference of the electrode winding or electrode stack. The housing can circumferentially contact the main surface of the anode. In particular, for electrical isolation, a diaphragm layer can also exist between the housing and the individual electrodes. Such a housing (in which the electrodes or diaphragms of the electrode winding or electrode stack are contacted by the housing) allows for a particularly compact structure of the energy storage cell.

[0019] The housing may, in particular, be a metal casing or a casing made of plastic. The housing may, in particular, be cylindrical, with poles at opposite ends of the cylinder for connecting the electrical contacts of the energy storage cell. The housing may also further comprise a flexible foil, for example made of aluminum, in which electrode stacks are securely clamped. Such housings are used, for example, in pouch cells.

[0020] The energy storage device of the present invention can be a metal-ion battery. The energy storage device of the present invention can be a lithium-ion battery. The energy storage device of the present invention can be a sodium-ion battery.

[0021] The pore volume of the anode in an energy storage cell can decrease, in particular, according to the state of charge, during the charging process. The anode can, in particular, comprise an electrochemically active anode material. An electrochemically active anode material is specifically understood to be a material capable of receiving and re-releasing lithium ions, in the case of a lithium-ion energy storage device. The pore volume of the anode in an energy storage cell can, in particular, decrease, according to the state of charge, during the charging process. This can be attributed in particular to the increase in volume of the electrochemically active anode material during charging through the intercalation of lithium into the material, such as graphite or silicon oxide, silicon, or mixtures thereof. Specifically, the electrochemically active anode material can be selected from the group consisting of: synthetic graphite, natural graphite, graphene, mesophase carbon, 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 the group consisting of: graphite, silicon oxide, and silicon, or mixtures thereof. Such electrochemically active anode materials are particularly suitable for providing high-capacity lithium-ion storage cells.

[0022] In sodium-ion energy storage cells, the anode may include an electrochemically active anode material. The electrochemically active anode material in a sodium-ion energy storage cell can be designed to receive and re-release sodium ions during charging and discharging. In particular, the electrochemically active anode material in a sodium-ion energy storage cell may include hard carbon, carbon (e.g., in the form of graphite), which, similar to lithium-ion energy storage cells, can receive and re-release sodium ions through intercalation. Here, similar to lithium-ion energy storage cells, a change in the pore volume of the anode can occur in the sodium-ion energy storage cell.

[0023] In the energy storage cell, the pore volume of the cathode can be increased according to the state of charge during the charging process. The cathode may in particular include an electrochemically active cathode material. In lithium-ion energy storage cells, an electrochemically active cathode material is particularly understood to be a cathode material capable of releasing and re-accepting lithium ions during charging or discharging. In lithium-ion energy storage cells, the electrochemically active cathode material may be selected from the group consisting of: lithium transition metal oxides, such as lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese compounds (known by the abbreviations NCM or NMC), such as LiCoO2, LiNi 0.33 Co 0.33 Mn 0.33O2, lithium nickel cobalt aluminum oxide (NCA), lithium olivine such as lithium iron phosphate (LFP), lithium spinel such as lithium manganese oxide spinel (LMO), or combinations thereof, more preferably, the electrochemically active cathode material is selected from the group consisting of lithium nickel cobalt manganese compounds.

[0024] As a cathode material, sodium-containing materials, such as phosphates and diphosphates, such as sodium iron phosphate or sodium hydroxide, can be used in sodium-ion energy storage cells. 2 / 3 Fe 1 / 2 Mn 1 / 2 Compounds of O2.

[0025] The electrolyte used in energy storage cells may include lithium salt as a conductive salt and at least one organic solvent.

[0026] The electrolyte used in energy storage cells may include sodium salt as a conductive salt and at least one organic solvent.

[0027] In lithium-ion energy storage cells, lithium salts can preferably be selected from the group consisting of: LiPF6, LiAsF6, LiClO4, LiCF3SO3, lithium bis(trifluoromethanesulfonyl)imide or combinations thereof.

[0028] In sodium-ion energy storage cells, the sodium salt may preferably be selected from the group consisting of: NaPF6, NaClO4, sodium bis(trifluoromethane)sulfonylimide, sodium bis(fluorosulfonylimide), sodium difluoro(oxalate)borate, sodium bis(oxalate)borate, or combinations thereof.

[0029] The organic solvent may in particular include organic polar solvents. The organic solvent may be selected from the group consisting of: C2 to C4 cyclic carbonates, such as propylene carbonate, ethylene carbonate, lactones, such as γ-, δ- and ε-lactones or combinations thereof.

[0030] According to one aspect of the invention, the metal ion energy storage cell is charged with a reduced charging current in a first state of charge range, i.e., in a state of charge range with a low state of charge. Thus, the charging current is matched to the reduced conductive salt concentration of the electrolyte in the environment surrounding the anode, based on the volume work of the active material of the electrode.

[0031] During the charging of a metal-ion energy storage cell, a conductive salt gradient is formed in the electrolyte. The significance of this conductive salt gradient depends particularly on the magnitude of the charging current. It has also been confirmed that this conductive salt gradient can be enhanced by the volume work of the active material of the electrode. More precisely, it has been confirmed that, especially during rapid charging in the first state of charge range, there is an enhanced volume work of the active material of the electrode, and consequently, an additionally reduced conductive salt concentration in the electrolyte surrounding the anode in this first state of charge range. Furthermore, it has been confirmed that, based on the reduced conductive salt concentration, the electrochemical limit potential also decreases. This, in turn, increases the probability of deposition, thereby leading to avoidable and premature aging of the energy storage cell. To address this effect, according to the present invention, a smaller charging current is proposed, particularly in this first state of charge range.

[0032] The precise boundaries of the first state of charge (SOC) range depend on the design of the energy storage cell and the materials used. Generally, the SOC range, where enhanced volumetric work is achieved through active electrode materials, can extend between SOC = 0% and SOC = 30%. The SOC range can also extend between SOC = 0% and SOC = 20%. Furthermore, the SOC range can extend between SOC = 0% and SOC = 15%.

[0033] The extent to which the charging current should be reduced within this first state of charge range to decrease the probability of deposition can also depend on the design of the energy storage cell and the materials used. According to the present invention, a metal-ion energy storage cell is charged within the first state of charge range with a charging current reduced by up to 70% of the maximum applicable charging current for a given energy storage cell. Furthermore, it is proposed that a metal-ion energy storage cell be charged within the first state of charge range with a charging current reduced by up to 80% of the maximum applicable charging current for a given energy storage cell. Finally, it is proposed that a metal-ion battery be charged within the first state of charge range with a charging current reduced by up to 90% of the maximum applicable charging current for a given energy storage cell.

[0034] In the design of conventional fast charging curves, in addition to considering the size and materials of the energy storage cell, the initial state of charge (SOCini) and charge boost (ΔSOC) are also taken into account. Furthermore, the temperature or temperature distribution within the energy storage cell is also considered, i.e., the coldest temperature Tmin and the hottest temperature Tmax, and their temperature difference ΔT. The fast charging curve is conventionally derived from these parameters, in which the charging current is maximized "along the electrochemical threshold potential". For the design of fast charging methods, an electrochemical-thermodynamic cell model is typically applied, which can describe the threshold potential, i.e., the so-called anodic potential E. AN .

[0035] By reducing the charging current to below the maximum possible charging current value in this conventional electrochemical-thermodynamic cell model, the additional effect of the change in conductive salt concentration caused by the volume work of the active electrode material in the first state of charge range is taken into account. Therefore, the probability of deposition is significantly reduced by decreasing the charging current. While the selective reduction of the charging current in the first state of charge range temporarily prolongs the charging time of the energy storage cell, it significantly delays premature aging of the cell in terms of its lifespan. In summary, by using the fast charging method according to the invention, a significant power increase in the energy storage cell can be achieved over its entire lifespan.

[0036] According to another aspect of the invention, the energy storage cell can be charged with a maximum charging current in a second state of charge, i.e., an intermediate state of charge. The second state of charge range is a range in which there is little or no volumetric work of the active electrode material.

[0037] The second state of charge (SOC) range can extend above 30% SOC. The second SOC range can extend above 20% SOC. The second SOC range can extend above 15% SOC. Since the second SOC range typically extends over more than 50% of the entire SOC range of the energy storage cell, the overall charging time depends particularly on the magnitude of the charging current within this second SOC range. In conventional charging profiles, a charging current buffer is often set. This means that only about 90-95% of the maximum charging current is used throughout the charging process. This invention has confirmed that this buffer is not mandatory within the second SOC range. Based on this invention, it is not only possible to forgo a reduction in charging current within the second SOC range. This invention enables a solid understanding of the fast charging process and now even allows for the foregoing of unnecessary charging current buffers within the second SOC range.

[0038] According to another aspect of the invention, the metal-ion energy storage cell is charged with a reduced charging current in a third state of charge range, i.e., in a state of charge range with a high state of charge. Thus, the charging current is also matched to the reduced conductive salt concentration of the electrolyte in the anode's surrounding environment based on the volume work of the electrode's active material.

[0039] The third state of charge (SOC) range can extend above 70% SOC. The third SOC range can extend above 80% SOC. The third SOC range can extend above 90% SOC. The same applies to the reduced charging current described above regarding the first SOC range for the charging current applicable in the third SOC range. Specifically, in the third SOC range, metal-ion batteries can also be charged with a reduced charging current of up to 70% of the maximum applicable charging current for a given energy storage cell in that SOC range. Alternatively, they can also be charged with a reduced charging current of up to 80% or up to 90% of the maximum applicable charging current for a given energy storage cell in that SOC range.

[0040] This invention discloses new insights into primary effects that contribute to undesirable deposition in energy storage cells. Specifically, it has been recognized that the volume work performed on the active electrode material within a specific state of charge range during charging leads to additional changes in the conductive salt gradient. Furthermore, it has been recognized that this results in a shift in the electrochemical limit potential. Accurate understanding of the electrochemical limit potential of the energy storage cell is crucial for designing optimized fast-charging profiles, which in turn provide the possibility of utilizing the electrochemical limit potential of the energy storage cell during fast charging while simultaneously avoiding secondary effects, such as aging due to deposition.

[0041] In another aspect, the present invention relates to a method for designing a fast-charging characteristic profile for fast charging of electric energy storage cells, particularly vehicle energy storage cells. In designing the fast-charging characteristic profile, a maximum permissible charging current is determined based on the state of charge (SOC), and said maximum permissible charging current is determined according to the electrochemical limit potential of the energy storage device. Here, in determining the electrochemical limit potential, the SOC-related conductive salt concentration of the electrolyte at the anode of the energy storage cell is taken into consideration.

[0042] As used in this article, fast charging is understood to be a charging method that applies a charging rate exceeding 1C. In such a charging method, the energy storage cell can be charged from SOC = 0% to SOC = 100% within one hour.

[0043] The term "volume work of the active electrode material," as used in this paper, refers to the volume change of the active electrode material during the charging process. Based on the "volume work of the active electrode material," the porosity of the active electrode material changes, thereby causing the electrolyte to be squeezed out of the pores of the electrode material. Attached Figure Description

[0044] The invention will be further illustrated below with the aid of examples.

[0045] Figure 1 The correlation between volumetric work related to the state of charge and conventional and according to the invention's charging curves is shown, and

[0046] Figure 2 Additional details are shown for the conventional and modified charging curves according to the invention. Detailed Implementation

[0047] Figure 1 Two figures are shown, in which the volume change of the active material of the electrode is presented ( Figure 1 (above) and on the other hand, the applied charging current ( Figure 1 (Below) The state of charge relative to the energy storage cell is drawn.

[0048] In seeking Figure 1 and 2 The charging current curves were based on a 4695-type lithium-ion energy storage cell with a cylindrical shell, a diameter of 4.6 cm, and a length of 9.5 cm (along the longitudinal axis). The electrochemically active anode material consisted of a mixture of graphite and silicon, with silicon comprising less than 10% by weight. The electrochemically active cathode material consisted of a typical nickel-cobalt-manganese layered oxide having a nickel content greater than 85 atomic percent. Copper foil was used as the current collector foil for the anode, with a coating thickness of 70 μm for the electrochemically active anode material. Aluminum foil was used as the current collector foil for the cathode, with a coating thickness of 50 μm. Both the anode and cathode current collector foils were coated on one side. The separator was composed of a polymer and contained a ceramic coating. The porosity of the anode was 25% at 0% state of charge, and the porosity of the cathode was 23% at 0% state of charge for the formed energy storage cell. The electrolyte consists of ethylene carbonate containing 1.2 mol / L of lithium conductive salt LiPF6. Both energy storage cells have a lower cutoff voltage of 2.8 V (0% state of charge) and an upper cutoff voltage of 4.2 V (100% state of charge).

[0049] exist Figure 1 The charging current curve 10 in the figure below corresponds to a conventional charging curve. In this charging current curve 10, the charging current is specified according to the determined electrochemical limit potential of the energy storage cell. In the design of this conventional fast charging curve, in addition to the size and material of the energy storage cell, the initial state of charge (SOCini) and charge boost (ΔSOC) are also considered. Furthermore, the temperature or temperature distribution within the energy storage cell, i.e., the coldest temperature T, is also considered. minand the hottest temperature T max And its difference ΔT. From these parameters, a fast-charging curve is conventionally derived, in which the charging current is maximized "along the electrochemical limit potential". For the design of fast-charging methods, an electrochemical-thermodynamic cell model is typically applied, which describes the limit potential, i.e., the so-called anodic potential E. AN .

[0050] exist Figure 1 The charging current curve 10 in the figure below corresponds to this conventionally derived charging curve. In this charging curve, at the beginning of the charging process, when the state of charge is still relatively low, the maximum charging current I is used. max（conv） The maximum charging current I is always applied. max（conv） This continues until the electrochemical limit potential of the storage cell approaches the anode potential threshold. Figure 1 In the charging current curve 10, this is reached at approximately a state of charge (SOC) of 30%. From this point onward, the charging current continuously decreases, during which the electrochemical limit potential generated by the storage cell remains just above the anode potential threshold. As a result, it is concluded that... Figure 1 The curve shown in the figure first sets a constant high charging current I. max（conv） Furthermore, the charging current then decreases exponentially from a specific state of charge.

[0051] exist Figure 1 In the diagram above, the volumetric work of the active electrode material is plotted relative to the state of charge. Based on this known correlation, volume changes in the active electrode material occur at the beginning and end of the charging process, i.e., at low and high SOCs. In the first range, i.e., state of charge range 20, a constant volume change in the active electrode material occurs. In the second range, i.e., state of charge range 22, no noteworthy volume change in the active electrode material occurs. In the third range, i.e., state of charge range 24, a constant volume change in the active electrode material again occurs.

[0052] Based on these volume changes in the active electrode material during the charging process, the pore volume of the electrode, particularly the anode, also changes. This change in pore volume causes the electrolyte, with a lower concentration of conductive salt relative to the original concentration, to be squeezed out of the electrode. Consequently, regions with varying concentrations of conductive salt in the electrolyte are formed, particularly near the electrode. These different conductive salt concentrations affect the electrochemical limit potential. Specifically, the lower conductive salt concentration reduces the electrochemical limit potential at the anode. This reduction in the electrochemical limit potential can lead to deposition. And while such deposition may occur in a charging current that should not occur based on a conventional electrochemical-thermodynamic cell model, it is possible.

[0053] To account for the localized changes in the conductive salt gradient caused by the volume work of the active electrode material, or in other words, the decrease in local conductive salt concentration, a modified charging current curve 12 is proposed according to the present invention. This modified charging current curve 12 is designed for direct comparison... Figure 1 The figure below shows the initial charging current I, based on charging current curve 12. ini Although still high, it is significantly lower than the maximum charging current I in the conventional charging current curve 10. max（conv） The charging current I ini It is applied throughout the entire first state of charge range of 20. Once the state of charge reaches 20%, it is as if... Figure 1 As shown in the figure above, the noteworthy volume change of the active electrode material no longer occurs. For this reason, in the second state of charge range 22, the charging current can be increased to a value I according to the charging current curve 12 according to the invention. max（erf Charging current I max（erf） It can even be significantly higher than the maximum charging current I used in the conventional way. max（conv） In fact, it has been confirmed that within this second state of charge range 22, a buffer distance is not necessary, or is rarely necessary, thus allowing for almost complete utilization of the maximum possible charging current based on the chemical limit potential. This is also attributed to the absence of noteworthy volume work within the second state of charge range 22, enabling the application of the maximum charging current derived using conventional electrochemical-thermodynamic cell models. For these reasons, the charging current curve 12 according to the invention shows a higher charging current in this range than in the conventional charging current curve 10.

[0054] As in Figure 1As shown in the figure above, volume work of the active electrode material reappears from the state of charge (SOC) of 80%. Based on this, a change in the localized conductive salt concentration recurs in the third state of charge range 24. Similarly, the electrochemical limit potential shifts accordingly in this state of charge range 24. The charging current is therefore reduced again according to the invention, so as to also reduce the probability of deposition in this state of charge range 24.

[0055] exist Figure 2 In this process, the conventional charging current curve 10 and the charging current curve 12 according to the present invention are also compared with each other. The conventional charging current curve 10 is obtained using a conventional electrochemical-thermodynamic cell model, while the charging current curve 12 according to the present invention is obtained using the method according to the present invention.

[0056] The conventional charging current curve 10 basically corresponds to Figure 1 The conventional charging current curve uses a relatively high charging current I at the beginning of the charging process. max（conv） The charging current then starts from a certain state of charge and... Figure 2 The charge level decreases exponentially at a state of charge (SOC) of 30%.

[0057] According to the charging current curve 12 of the present invention, in Figure 2 In the middle, the initial charging current I ini Compared with the conventional charging current I max（conv） The same applies. However, in the first state of charge range 20, as discussed above, a reversible volume change occurs in the active electrode material. This also leads to a change in the concentration of the conductive salt at the anode. Since this concentration change does not occur instantaneously but requires a certain amount of time until it has occurred, a high charging current I can still be used up to a state of charge of 15% SOC. ini After a certain period of time, the concentration of conductive salt in the anodic region changes, thereby altering the electrochemical limit potential and increasing the risk of precipitation. For this reason, in Figure 2 According to the charging current curve 12 of the present invention, the charging current is reduced from the state of charge (SOC) of 15%.

[0058] Once the state of charge is within the second state of charge range 22, no more volume work occurs on the active electrode material, and the charging current can be set to the maximum applicable charging current I from this moment onward. max（erf） The charging current then follows the current already applied in the second state of charge range 22. Figure 1The exponential decrease described in the text. Starting from the state of charge (SOC) of 80%, volume work reappears on the active electrode material, thus changing the electrochemical limit potential. This is taken into account by the renewed decrease in charging current in the third state of charge range 24.

[0059] exist Figure 2 In the middle figure, for the purpose of illustration and better understanding of the invention, the conventionally determined anode potential threshold E is plotted relative to the state of charge. AN And the modified anode potential threshold E according to the present invention S The anode potential threshold E was calculated using a conventional electrochemical-thermodynamic cell model. AN It depends solely on the material and the temperature measured at the current moment, and for such pre-given values, it is constant throughout the charging process.

[0060] Based on the understanding of this invention, the actual anode potential threshold E S The same applies across all states of charge (20, 22, 24). In states of charge 20 and 24, volume work occurs in the active electrode material, leading to variations in the localized conductive salt concentration, and a modified anodic potential threshold E. S That is, it increases. Using the charging curve according to the invention, the charging current decreases in the state of charge ranges 20 and 24. The charging current can be set so that the electrochemical cell potential is always kept above the anode potential threshold, thereby reducing the risk of precipitation.

[0061] Using a conventional charging current curve 10, a constant high maximum charging current I is applied, particularly within the state of charge range 20. max（conv） If this occurs, the electrochemical limit potential drops significantly below the actual anodic potential threshold. Applying this charging profile carries the risk that, due to neglect of local conductive salt concentration, significant electrode deposition may occur after only a few charging cycles, thus accelerating cell aging and reducing cell capacity and lifespan.

Claims

1. A method for rapidly charging energy storage cells, particularly vehicle energy storage cells, wherein, The current charging current is set based on the reversible volume change of the active electrode material during the charging process.

2. The method for fast charging according to claim 1, wherein, The reversible volume change of the active electrode material occurs according to the state of charge (SOC) of the energy storage cell.

3. The method for fast charging according to any one of the preceding claims, wherein, The energy storage cell is a metal-ion battery, such as a lithium-ion battery or a sodium-ion battery.

4. The method for fast charging according to any one of the preceding claims, wherein, The metal-ion battery includes an anode, a cathode, a separator, and a metal-ion electrolyte, wherein the metal-ion electrolyte connects the anode and cathode ionically, and wherein the battery is charged by a current source that supplies energy.

5. The method for fast charging according to any one of the preceding claims, wherein, The energy storage cell is charged with a reduced charging current in a low-charge state, whereby the charging current is matched to the reduced conductive salt concentration of the electrolyte in the environment surrounding the anode, based on the volume work of the active electrode material.

6. The method for fast charging according to claim 5, wherein, The energy storage cell is charged with a reduced charging current in a first state of charge range, which extends up to 30% state of charge, or up to 20% state of charge, or up to 15% state of charge.

7. The method for fast charging according to any one of claims 5 or 6, wherein, The energy storage cell is charged within the first state of charge range with a reduced charging current of up to 70%, 80%, or 90% of the maximum charging current.

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

9. The method for fast charging according to any one of the preceding claims, wherein, The energy storage cell is charged with a reduced charging current in a third state of charge range, which extends from a 70% state of charge, or from an 80% state of charge, or from a 95% state of charge.

10. A method for designing fast-charging characteristic curves for fast charging of battery cells, particularly vehicle battery cells, wherein, When designing the fast charging characteristic curve, the maximum allowable charging current is determined based on the state of charge, wherein the maximum allowable charging current is determined according to the electrochemical limit potential of the energy storage cell, and wherein the state-of-charge-related conductive salt concentration of the electrolyte at the anode is considered when determining the electrochemical limit potential.

11. A method for rapidly charging energy storage cells, particularly vehicle energy storage cells, wherein, The current charging current is set based on the reversible volume change of the active electrode material during the charging process, wherein... - The energy storage cell is charged at a reduced charging current relative to the maximum charging current in a low-charge state, whereby the charging current is matched to the reduced conductive salt concentration of the electrolyte in the anode environment based on the volume work of the active electrode material. - The energy storage cell is charged at a charging current that is reduced relative to the maximum charging current when in a high-charge state, and - The energy storage cell is charged with the maximum charging current during the state of charge range between the low state of charge and the high state of charge.

Images