CN111712966A - Apparatus, system, and method for suppressing dendrites and roughness in electrochemical structures - Google Patents

Abstract

A method involving the induction of an electric and/or magnetic field (field induced current) across an electrode of an electrochemical cell, such as the anode of a battery, and associated batteries and battery charging units. The field and current across the electrodes may be referred to herein as a lateral current, as this current is generally transverse to the ionic charging current that may be applied when charging the battery. The field and current may be induced by connecting AC energy, such as AC current, across the electrodes or at one or more discrete points of the electrodes. Among other advantages, the induced field and current may inhibit dendrite growth experienced in conventional batteries without AC energy.

Description

Apparatus, system, and method for suppressing dendrites and roughness in electrochemical structures

Cross Reference to Related Applications

The present Patent Cooperation Treaty (PCT) application is related to and claims priority from U.S. patent application No. 62/617,103 entitled "APPATUS, SYSTEM METHOD FOR DENDRITE AND ROUGHNESS SUPPRESSION" filed on 12.1.2018, the entire contents of which are incorporated herein by reference FOR all purposes.

This application is also a continuation-in-part application, No. 15/649,633, of U.S. non-provisional patent application No. entitled "electroche METHODS, device AND COMPOSITIONS," filed on 13.7/2017, which claims priority from U.S. patent application No. 62/361,650, filed on 13.7/2016, entitled "electroche METHODS, device AND COMPOSITIONS," in accordance with 35 u.s.c. § 119, both of which are hereby incorporated by reference in their entirety for all purposes.

Technical Field

The present application relates to electrochemistry and, in particular, to electrochemical structures, such as batteries, and methods and apparatus for inhibiting growth of dendrites and the like in the electrochemical structures.

Background

Batteries typically include an electrochemical cell of one or more sources of counter charge and a first electrode layer separated by an ionically conductive barrier, typically a liquid or polymer membrane filled with an electrolyte. These layers are made thin so that multiple cells can occupy the volume of the cell, thereby increasing the available power of the cell with each stacked cell. As these components become thinner, they also become more fragile. Further, as the electrodes become thinner, a greater ohmic drop occurs across the surface, resulting in a decrease in charge density uniformity during charge/discharge cycles. Still further, the battery electrodes may acquire growth (or dendrites) during the charging cycle of the battery, which may further damage or degrade the battery performance.

For example, lithium ion batteries typically have a metal oxide electrode (M is typically iron, cobalt, manganese) and a carbon electrode coated on a metal current collector. The metal oxide serves to attract and stabilize lithium ions during discharge of the battery and generally determines the operating potential of the battery. The metal oxide electrode is initially in an oxidized state and the carbon is graphite infused with lithium ions. During discharge (that is, normal use of the battery to provide power to the device), Li⁺Ions diffuse between graphene layers to the edge sites of graphite and then pass through the Solid Electrolyte Interphase (SEI). SEI is a layer formed when lithium initially reacts with components of an organic electrolyte, including inorganic and organic by-products. Compared to graphite and electrolyte, respectively, SEI is less conductive to both electrons and ions, and therefore the nature and quality of SEI tends to determine the overall performance of the battery. Continued diffusion of lithium ions from the SEI through the ionA sub-transport layer and diffusing towards the metal oxide, which is reduced to LiM_xO_y. During charging, Li⁺The ions follow the opposite path and instead eventually diffuse back through the SEI and intercalate back into the carbon. Under ideal charging conditions, lithium ions can enter the graphite at the edge regions without creating excessive polarization that could lead to plating (rate limiting step). Plating problems can occur if the cell voltage becomes too high, the electrodes are too hyperpolarized, or the SEI is porous, non-uniform, or too thick or too thin. In the extreme case, Li in dendritic form⁰The aggregates may create an explosion hazard within the cell. In particular if Li⁰Reach the opposite electrode, the cell may short and Li is present⁰Dendrites formed during deposition can damage the membrane that divides the cell into two parts.

In the case of lithium metal electrodes or in the event of electroplating on graphite electrodes, the deposits become increasingly rough with subsequent charge/discharge cycles. Both lithium metal batteries (lithium foil anodes) and lithium ion batteries (lithium ions intercalated into graphite/foil anodes, where the current collector is typically copper) undergo growth of lithium dendrites during the charging cycle of the battery. Although lithium ion anodes can be stable for hundreds of cycles, dendrites are immediately generated in lithium metal. Once formed, dendrites reduce the coulombic efficiency of the cell, damage the ionic membrane, and can short the cell if the dendrites contact the anode. Dendrite punctures are commonly formed or irreversibly damages the electrolyte membrane. If dendrite growth reaches the opposite electrode, the cell will be permanently short circuited and cannot be recovered.

In addition to addressing these issues, features of the present disclosure are also contemplated.

Disclosure of Invention

The following embodiments and features thereof are described and illustrated by systems, tools and methods which are meant to be exemplary and illustrative, but not limiting in scope. In various embodiments, one or more of the problems described above have been reduced or eliminated, while other embodiments are directed to other improvements.

Methods for optimally maintaining an electrode in an electrochemical cell, such as a battery (whether charged, discharged, or dormant), are provided herein. The method inhibits and reverses dendrite growth and controls the quality and healing of the SEI, both of which are common causes of most battery performance degradation and eventual failure.

In particular, provided herein is a method comprising inducing an electric and/or magnetic field (field induced current) across an electrode of an electrochemical cell, such as an anode of a battery. The field and current across the electrodes may be referred to herein as a lateral current, as this current is generally transverse to the ionic charging current that may be applied when charging the battery. The field and current may be induced by connecting AC energy, such as AC current, across the electrodes or at one or more discrete points of the electrodes.

In the presence of a chemical potential between the electrolyte and the surface of the electrode, an electrical potential is induced across the surface of the electrode. The induced electrical potential propagates across and charges the surface of the electrode. In any of the methods or devices described herein, this electrode can be a first electrode.

Another embodiment relates to a charging method, comprising: in a battery including a first electrode and a second electrode, a Direct Current (DC) charging current is applied to one of the first electrode and the second electrode. Applying Alternating Current (AC) energy to at least one of the first electrode and the second electrode in conjunction with applying the DC charging current. In addition to the advantages discussed herein, the presence of AC energy may also inhibit dendrite growth.

Features of the present disclosure may further relate to a battery charger, the battery charger including: a power supply comprising a first conductor and a second conductor, wherein the power supply is configured to apply a Direct Current (DC) charging current through the first conductor to one of a first electrode and a second electrode of a battery operatively coupled with the battery charger. The power supply may be further configured to apply Alternating Current (AC) energy to at least one of the first electrode and the second electrode of the operatively coupled battery through the second conductor.

Yet another feature may relate to various possible cell designs incorporating patterned layers (affecting resonance, and more particularly, may affect resonance of the anode); and the AC signal affects the anode; and the overall effect of suppressing dendrite growth, among other advantages. In one example, a battery may include: a first electrode (e.g., an anode); and an ion transport layer comprising a first side and a second side, the first side operably coupled with the first electrode. The battery may further include: a second electrode operatively coupled with the second side of the ion transport layer; and a patterned layer operatively coupled with the first electrode, wherein the patterned layer is configured to receive AC energy different from charging energy or discharging energy.

Additional embodiments and features are set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by practice of the embodiments discussed herein. A further understanding of certain embodiments may be realized by reference to the remaining portions of the specification and the drawings, which form a part of this disclosure.

Drawings

Example embodiments are illustrated in referenced figures of the drawings. The disclosed embodiments and figures are intended to be illustrative rather than restrictive.

Fig. 1 depicts a cross-sectional view of the layers of a typical battery cell.

Fig. 2A depicts a cross-sectional view of the layers of a typical battery cell, demonstrating the common problems of lithium metal batteries.

Fig. 2B depicts dendrite growth in a battery cell during charging.

Fig. 2C depicts damage to the solid electrolyte interphase layer of the battery during discharge of the battery.

Fig. 3 depicts the introduction of an electrical waveform across the surface of the first electrode of the battery cell.

Fig. 4 is a flow chart of the described method.

Fig. 5 depicts electroplating on a copper electrode with and without lateral current flow, showing the suppression of dendrite growth by applying the method of fig. 4.

Fig. 6 depicts a control sample and an experimental sample comparing dendrite growth by applying the method of fig. 4 on a copper electrode.

Fig. 7 depicts comparison of dendrite peak heights of a control sample and peak heights of various experimental samples having different frequencies of transverse current after applying the method of fig. 4 on a copper electrode.

Fig. 8 depicts comparing the average height of dendrites on a control sample with the average height of experimental samples with transverse currents of different frequencies after applying the method of fig. 4 on the electrodes of a battery.

Fig. 9 depicts dead lithium and SEI damage of the battery anode due to dendrite growth at the surface of the electrode.

Fig. 10A-10C depict a common cell configuration.

Fig. 11 depicts the propagation of an Electromagnetic (EM) pulse on the electrodes of a coin-type cell.

Fig. 12 depicts component layers of a modified coin cell battery cell.

Fig. 13 depicts simulation results of applying electrical waveforms along the electrodes of a battery.

The disclosure may be understood by reference to the drawings, as described above, and to the following detailed description. It should be noted that for illustrative purposes, certain elements in the various figures may not be drawn to scale, may be represented schematically or conceptually, or may not otherwise correspond exactly to some physical configuration of the embodiments.

Detailed Description

Provided herein are methods, devices, and compositions that electrochemically bond or rearrange metals on a surface, particularly on an electrode of a battery. Generally, the methods and devices operate by delivering Alternating Current (AC) energy at the electrodes (e.g., inducing an AC current across the electrode surfaces of the battery cell) that is approximately transverse to an electrochemical current, such as a DC charging current, that is carried by ions diffusing between the anode and cathode of the battery. Typically, the electrolyte is adjacent to the surface of the electrode, forming an electrode-electrolyte interface, wherein metal from the electrolyte contacts the surface of the electrode and causes charge to traverse the interface to generate current during the electrochemical process. Electrons at the surface undergo forward contraction and backward expansion of their electric field by inducing an AC current transverse to the electrochemical current across (or otherwise delivering AC energy to) the surface of the electrode. This contraction and expansion produces relativistic charges that propagate outward from the electron center at the speed of light. The relativistic charges then bend the field lines of the electrochemical current (e.g., DC charging current), thereby directing the metal or partially adsorbed atoms or particles on the surface from the ions in the electrolyte to diffuse and form more uniformly along the electrode surface. More specifically, metal ions or surface particles are guided into cracks and crevices, pits and voids, and high aspect surface features on the electrode. As discussed in more detail below, this flattening effect on the electrode during charge-discharge cycles of the battery can reduce the growth potential and/or growth size and/or dendrite ratio along the battery electrode and otherwise inhibit surface irregularities and roughness that would otherwise form in conventional battery electrodes, thereby effectively extending battery life, improving performance, and avoiding exothermic events from overheating, ignition, and explosion.

The methods and devices described herein may operate to induce an electrical potential across the surface of a battery electrode. The induced electrical potential bends the field lines near the surface, so that metal from the electrolyte follows the path of the bending field lines to deposit the metal onto the surface. In one particular example, the induced electrical potential affects field lines. These bending field lines eventually intersect the surface (including irregularities in the surface) at 90 degrees to the intersecting surface portion. Viewed another way, the curved field lines of the first current change the trajectory when metal from the electrolyte is deposited onto and bonded to the surface, so that the metal is less likely to reach the entire surface at 90 ° to the macroscopic surface of the electrode when approaching, but conforms to the microscopic horizontal profile and irregularities of the surface and exhibits a leveling behavior on the surface. Thus, metal from the electrolyte may be directed away from dendrite growth or other irregularities in which dendrites tend to grow. By directing the metal to this "flattening" effect, the electrodes of the battery can resist dendrite growth, thereby preventing the battery from being damaged or inoperable.

The induced potential of the current (and more generally the energy) applied at or along the surface of the electrode can be controlled by tuning the AC waveform (including its voltage or amperage and frequency). Multiple waveforms may be combined to tune to different features or substances including the workpiece surface. In some cases, the extent of dendrite growth or other electrode surface irregularities can be monitored in real time, and thus the lateral current can be modulated to direct the electrochemical process on the electrode. The processes described herein can improve the formation of an interphase (referred to herein as a Solid Electrolyte Interphase (SEI)) between the electrolyte and the electrode by forming a horizontal or uniform SEI layer along the surface of the electrode.

Fig. 1 depicts a representative cross-sectional view of the layers of a typical battery (also referred to herein as a cell). Generally, batteries convert chemical energy into electrical energy. As shown in fig. 1, the battery 100 may include: a first current collector layer 102 (sometimes referred to as a cathode current collector); a cathode layer 104, which may be referred to as a cathode alone or in combination with an adjacent current collector layer; an ion-transporting dielectric layer 106, which may be an electrolyte; an anode layer 108; and a second current collector 110 (sometimes referred to as an anode current collector) adjacent the anode layer, which may be referred to as the anode alone or in combination with the adjacent current collector layer. During operation, the anode 108 releases ions to the electrolyte 106, which are collected at the cathode 104. The first current collector 102 and the second current collector 110 are typically conductive metals that provide charge transport to and from the adjacent anode or cathode. There are many different types of battery configurations (including batteries having different electrolyte materials for the anode 108 side of the battery and the cathode 104 side of the battery), but the general operations described herein apply.

Generally according to the constitution of a batteryThe material of the anode or ion transport layer 106 of 100 classifies the cell. For example, a lithium battery having a lithium-based anode 108 and an ion transport layer 106, such as a lithium metal battery (containing Li)⁺Or similarly having a lithium foil anode) and lithium ion batteries (containing Li)⁺Or similarly with an electrolyte containing Li⁺Graphite anode of (1). Other types of batteries are relevant, including zinc batteries and lead acid batteries known to those of ordinary skill in the art. Although this discussion illustrates lithium ion batteries (lithium intercalated into graphite), the methods disclosed herein are also applicable to other types of batteries, including lithium metal batteries, lithium silicon batteries, zinc batteries, and lead acid batteries.

When an organic electrolyte is used, both types of lithium batteries (other than batteries comprising lithium silicon) form a solid electrolyte interphase at the interface of anode 108 and electrolyte 106 due to the chemical reaction of lithium with the electrolyte. The mesophase is a layer comprising insoluble inorganic and partially soluble organic reaction products collected at the interface. As discussed above, this layer may be referred to herein as an SEI layer. Generally, lithium ions pass from the anode 108 through the interphase or SEI. Because the interphase generally has a higher impedance, non-uniformity of the solid electrolyte interphase across the anode 108 may cause non-uniform current distribution across the anode. This inhomogeneity promotes channel formation through mesophases where the lithium concentration is high. These channels lead to dendrite formation. In other cases, irregularities along the surface of the anode 108 may also promote dendrite growth.

More specifically, as lithium is plated/deposited on the anode surface 108, the dendrites generally grow during the charging cycle of the battery. Electrodeposition proceeds across the interface of two phases by a charge exchange mechanism between a polarized surface and oppositely charged ions dissolved or suspended in an electrolyte. The mechanism typically involves multiple steps in which ions may undergo partial or complete charge exchange and may diffuse across a partially absorbed surface prior to settling. The growth mechanism can be distinguished as 2D (layer-by-layer type) or 3D (nucleation coalescence). The generality of either mechanism depends on the initial conditions of the electrochemically active surface, the overpotential of the driving voltage with respect to each thermodynamic energy barrier, and the nature of the electrolyte.

Although no two metals exhibit the same material properties and growth behavior during electrodeposition, most electrodeposits tend to exhibit a rough structure and morphology with increasing thickness. Apart from the effects of electrolyte chemistry, low surface energy facets tend to grow faster over time. As one crystal plane begins to dominate, the grain structure of the deposited layer may change from small to randomly columnar in nature. This is true for both copper and lithium deposition, although the elastic and reactive properties of the two are significantly different, which affect their relative morphology in the cell.

Fig. 2A and 2B illustrate a common problem that may occur on the surface of the electrodes of the battery 200. The cell of fig. 2A includes the same layers as the cell described above with respect to fig. 1, such as a first current collector layer 102, a cathode layer 104, an ion-transporting medium layer 106 or electrolyte, an anode layer 108, and a second current collector 110. The figure also shows a solid electrolyte interphase 112. As graph 200 shows, dendrites 214 have grown from anode 108 of cell 200 over multiple charge cycles of the cell. Fig. 2B illustrates the problem of the effectiveness of the battery 200 due to the growth of dendrites 214. Specifically, during battery charging, dendritic growth occurs on the anode 108. These dendrites begin to block lithium ions from reaching other regions on the surface of the electrode, thereby preventing the lithium ions from participating in the reaction. These ions may also form other dendrites, further increasing the inefficiency of the battery. Thus, limiting dendrite growth on the electrodes of the battery 200 may improve the operation and life of the battery.

Another problem that arises in batteries through charge cycling is the creation of irregularities in the SEI 112, thereby causing weak spots 218 in the SEI layer 12 between the electrolyte 106 and anode layer 108, which is also shown in fig. 2C. During discharge of the battery, dendrites that have formed on the electrode 108 may partially dissolve back into the electrolyte layer 106. However, the dendrites do not dissolve uniformly and the connection to the anode substrate 108 may be weakened. Partially dissolved lithium residues may lose electrical contact with the surface and no longer participate in the reaction. This may leave weak areas in the SEI layer 112 and/or the anode surface. The SEI 112 can immediately reform in the damaged area, causing irregularities 218 in the surface.

Returning to fig. 2A, another common problem that arises through charge-discharge cycling of the battery 200 is a non-conductive metal deposit 216 (sometimes referred to as dead lithium 216 or other inert metal collection) in the electrolyte 106. In some cases, fragile roughness features such as moss and crushed lithium may form along the surface of the electrode 108. These growths may eventually break free of the surface 108 and lose electrical contact. Thus, the energy potential of this metal block is no longer available for power storage and battery capacity is permanently lost. Each of these problems can be addressed by applying an AC energy signal at or along the electrodes 108.

Conventional techniques for preventing rough deposits have included chemical additives (known as brighteners and levelers) that are commonly used in the surface processing industry for electrodeposition and electroplating. Pulse plating and signal modulation techniques provide improvements and control over electrodeposition that are theoretically better predicted and easier to transport from one metal chemistry to another. However, the benefits of these approaches are not yet clearly defined for lithium systems where the reaction rate and diffusion layer thickness are strongly dependent on the SEI layer. For example, the pulse may cause the electrode to temporarily reverse its polarity (reverse pulse plating) to periodically re-dissolve rough edges that may have formed before it has significantly grown. However, when applied to a battery, the pulses may destroy the output power of the battery.

In certain types of batteries, these problems may be more prevalent than in other types of batteries. For example, pure lithium metal batteries have a higher energy capacity (about 5-10 times) than lithium ions, but it is less well known in the art how to control dendrite growth. The main obstacle preventing the commercial use of lithium metal batteries is the inability to routinely electrodeposit lithium onto the anode without destructive and dangerous dendrite growth, which also results in electrolyte consumption, low coulombic efficiency and eventual cell failure. Identifying potential solutions that do not compromise the capacity or operating voltage of the battery and that are suitable for the entire range of form factors currently needed across industries and across products is particularly challenging. Currently, these batteries typically last only ten charge-discharge cycles. Failures are typically transient and severe compared to common lithium ion batteries.

In addition, as batteries become smaller and smaller with increasing power capacity, these problems have been magnified and pose significant design constraints. The life and performance of lithium or any other chemical based battery can be greatly extended by increasing the smoothness and uniformity of the electrode surface using the techniques and apparatus of the present disclosure. This may also allow for an increase in the charge rate without compromising battery life, as with conventional batteries.

Methods and devices for controlling dendritic growth on electrodes and reabsorbing growth into the electrolyte in a battery to improve the performance and life of the battery are described herein. In some embodiments, the methods and apparatus may operate during DC charging of a battery to impede or reduce formation of dendrites on electrodes of the battery. Additionally, the method may be performed during other operating conditions of the battery to provide additional benefits to the life and performance of the battery, such as leveling the mesophase layer of the battery or dissolving growth into the electrolyte layer. Controlling or reducing dendrite growth in the cell may also result in a cell that is relatively more durable. In general, a uniform time-averaged current distribution can be maintained across the entire surface by applying an AC signal at or across an electrode of a battery, without the need for such alternating energy to be formed on the electrode (e.g., anode), in comparison to conventional techniques, to more evenly distribute the concentration of lithium ions or other charge transfer species throughout the solid electrolyte interphase to maintain an anode/electrolyte interface with uniform electrical behavior.

Method of producing a composite material

In view of the foregoing description, as well as problems and limitations with respect to conventional processes, provided herein are electrochemical devices and methods for controlling a deposition process on an electrode of a cell through electrical mitigation or other electrokinetic effects of surface features (e.g., dendrites) of the electrode. Fig. 3A and 3B illustrate example apparatus for practicing the methods discussed herein, and fig. 4 illustrates an example method according to the present disclosure. In particular, the method 400 of fig. 4 may be performed during a charge cycle of a battery to inhibit or reduce dendrite growth on a surface of an electrode of the battery. Referring to fig. 3A, 3B, and 4, the system 300 may determine when the battery is in a charging operating state (410). When a battery charger is connected, the battery may or may not be charged, and the amount of charge may be more or less depending on the state of charge or other factors. For example, during the subsequent phase of charging, the state of charge is close to 100%, and the charging current may decrease. Similarly, the current drawn from the battery may be more or less dependent on the load on the battery. During a charging cycle of the battery, a current (420) may be induced across the anode, which may be an alternating or non-DC current across the surface of the electrode. During a period when the charge amount is small or the discharge amount is small, relatively large AC energy may be applied, and thus the induced AC energy may depend on the charge (or discharge state). As discussed herein, the AC energy level may further be a function of the physical and material properties of the particular battery system. If the charging cycle process is incomplete (430), the lateral current along the electrodes may be modulated (440) to adjust the AC energy applied to the anode. Thus, for example, AC energy application may be adjusted based on state of charge, temperature, impedance measurements, and other feedback mechanisms. If the charging cycle process is complete, the process terminates (450). In some cases, the AC energy may continue as the lithium orphan (orphan lithium) reabsorbs or other materials are reabsorbed into the anode (or cathode), as the case may be.

Referring in more detail to fig. 3A and 3B, a battery environment 300 is shown. Specifically, environment 300 includes a cathode 320 electrode, an anode 310 electrode, and an electrolyte 340 adjacent to the cathode and the anode. During charging of the battery, ions 324 contained in the electrolyte 340 are collected at the anode 310. Further, by the described methods, the power source 360 can be in electrical communication 363 to at least a single contact point on the anode 310 (fig. 3A) or more than one point of the electrode of fig. 3B. Thus, the power source 360 may provide an AC energy signal or wave 350 at and/or across the surface 311 of the anode 310 through one or more contact points on the anode. A single contact point may generate a wave across the surface, particularly when the current has a path as absorbed by the electrolyte. This applied AC energy may be an AC current 350 induced across the first electrode 310, which makes it transverse to the first (charging) current 330 between the cathode and anode. The second current 350 induces a relativistic charge 312 in and/or across the surface 311 of the first electrode 310. In some embodiments, the device includes a power source 161 in electrical communication 161 with the counter charge source 120 and in electrical communication 162, 163 with the first electrode 110. The first current 130 and the second current 150 may be provided and controlled depending on the embodiment of the power supply involving more than one device.

More specifically, a lateral current 350 may be applied at, through and/or across the surface 311 of the first electrode 310 to affect surface electrons and induce favorable properties in the deposit without changing the design parameters of the electrolyte 340. In the presence of AC energy at the electrodes, the electrons at surface 311 undergo forward contraction and backward expansion of their electric field. This contraction and expansion produces relativistic charges 312 that propagate outward from the center of the electron at the speed of light. The relativistic charges then bend the field lines of the electro/chemical reaction (which typically do not bend during charging) so as to direct the formation of metal from the electrolyte on the electrodes in a controlled manner, wherein surface roughness is suppressed. Viewed another way, the induced electrical potential bends the field lines near the surface, so that metal from the electrolyte follows the path of the bending field lines to deposit the metal onto the surface. The bending field lines eventually intersect the surface (including irregularities in the surface) at 90 degrees in close proximity to the intersecting surface. The difference between the deposition point at induced potential and the deposition point without induced potential is the displacement of the field lines towards the crevice and the area of surface roughness not normally filled. AC energy to the anode can enhance many features of the electrodeposition process that occurs in the cell during charge/discharge cycles, including but not limited to two-dimensional growth (smoothness and uniformity); grain properties, such as crystallinity and morphology; inductive nucleation on energy-difficult surfaces; a decrease in porosity in the metal; adhering to a substrate; and controlled linear crystal growth.

This change in electron distribution then changes the behavior of the metal atoms close to the surface. Conventionally, the charge density around the irregularities of the workpiece is greater, which then promotes the metal layer to build up irregularities even more. In contrast, in the disclosed method, atoms are encouraged to follow paths to produce a smooth surface because in the absence of lateral current, the charge density of regions with large charge density is less than the typical charge density, and in the absence of lateral current, the charge density of regions with small charge density is greater than the typical charge density. The waveform frequency of the transverse current can be swept through several values, thus modulating irregularities of many sizes. In one particular embodiment, the frequency range of the transverse current waveform may be 100Hz to 300 GHz.

Device for measuring the position of a moving object

The present disclosure also provides an apparatus for performing the methods described herein. In particular, an apparatus may be used to provide an AC signal to an anode of a battery cell. The signal may be applied through a single contact point with electrode 310 or through two contact points. The apparatus may include a current generating source, such as a power supply 360, to induce a current 350 along the electrode surface as described in the example methods contained herein. In some embodiments, a Master Control Unit (MCU)363 may be included to control the current sources.

The power supply may include or otherwise be associated with an MCU, and the MCU may include a processor or other computing component in communication with a memory or other tangible storage medium including: software that forms executable instructions or control sequences to perform the various methods discussed herein; a computer controlled power modulator; and auxiliary electronics. In the main control unit, a processor is configured to execute instructions stored on a computer-readable medium. The power modulator and the power supply may be controlled by the MCU. The MCU may contain one or more additional electronic components for providing any signals to the battery electrodes. In some embodiments, the charging current and AC energy connection points to the electrodes may be shared.

In still other embodiments, the system may utilize existing charging circuitry in electrical communication to provide the AC energy signal to the electrodes of the battery. For example, the power supply (charging power supply) of a personal computing device (such as a cell phone, laptop computer, or other mobile computing device that may be depleted of batteries) may be modified to provide an AC energy signal to the anode of the battery contained in the device. In another example, a Battery Management System (BMS) of a vehicle may be modified to transmit electrical current to the electrodes of a larger packaged battery or discrete battery to implement the methods described herein. In the embodiments discussed herein, a conventional charging device may be modified with an appropriate control scheme to provide conventional DC charging by adding an AC signal applied at the anode. For example, the conductor may provide a path between the anode and a power supply portion of the charger, in addition to conventional charging electronics, plugs, conductors, etc., and the power supply is configured to provide an AC signal to the anode under control of the MCU.

Dendrite mitigation

The methods described herein control various possible forms of non-uniform, rough, and/or non-optimal surface effects including dendrite growth and dendrite precursor growth on one or more electrodes in many types of electrochemical structures (such as batteries, including but not limited to lithium metal batteries, lithium ion batteries, silicone lithium, zinc batteries, lead acid batteries, and the like). The methods may be performed on an electrode of a battery to provide a variety of electrokinetic effects, including inhibiting growth of dendrites on the electrode of the battery.

In particular embodiments, the method involves generating tailored waveforms and applying these waveforms to the electrodes, which may be combined with a charging current to excite in the surface at a frequency related to a particular resonance of the electrode or a desired mode of induced current density. A real world conductive surface is susceptible to a particular charge distribution based on geometry and intrinsic properties, independent of its application environment. Resistive losses attenuate power across the surface. The current density is greater at curved or sharp points and the electric field potential lines are eventually orthogonal to the surface. For these reasons, the polarizing electrode experiences a non-uniform charge distribution independent of the electrolyte in the absence of the techniques set forth herein.

For example, during conventional electrodeposition, which occurs during battery charging, electrons are uniformly dispersed tangentially to the electrode surface due to mutual repulsion of their electric fields. The tangent points may not be parallel and the curved nature appears to allow the population of electrons to group together. Such regions may attract more metal ions and develop dendrites. By using AC energy to shift these charges from a high energy region to a neighboring region for a statistically significant period of time, the intrinsic charge distribution of the electrode, as well as the overall deposition pattern, can be altered.

With the wavelength (lambda) of the AC_AC) The size decreases and the energy changes essentially from capacitive to inductive, approaching the length scale of the electrode or the length scale of a certain feature on the electrode. That is, in the electrode length dimension<<λ_ACThere will be a potential gradient across the surface from one end to the other. When each electrode tip is aligned with the maximum and minimum values (. lamda.) of the waveform_AC) The gradient magnitude is greatest when spatially matched. When electrode length scale>>λ_ACThere will be many points of maxima and minima, resulting in higher inductive energy at the surface. This phenomenon can affect absorption, surface and bulk diffusion, and nucleation processes even at frequencies much faster than the characteristic times of those processes.

In contrast to conventional pulsing or modulation techniques at lower frequencies, high frequency AC will experience a continuous superposition of incident and reflected energy throughout the system, which will interact constructively or destructively at different points along the surface. For this reason, it is not necessary to take into account the applied transient waveform, but rather the resulting standing wave pattern. Frequencies above about 200MHz saturate and exceed the relaxation time of most electrolytes, although the contribution of ions moving without an ion cloud is negligible (known as the wien effect). The lack of high frequency ionic conductivity through the electrolyte causes the anode and cathode to be considered independently and possibly modified.

The electrolyte will modify the inherent electrical behavior of the electrode at the interface in a predictable manner. The electrolyte will absorb a portion of the AC energy due to its conductivity, thereby attenuating the signal with distance. This can be overcome by selecting a waveform and frequency for which the incident energy is constructively combined with the reflected energy at a distance from the point of signal application on the electrode. For example, incident energy may combine constructively with reflected energy to provide a region along the electrode surface where a high energy signal is present. Further, the dielectric constant of the electrolyte will determine the degree of dielectric shrinkage of the waveform.

The amplitude of the waveform presents a possible control parameter for the effect of the AC energy on the electrodes. For example, control of the frequency or amplitude of the AC energy may be used to tune the AC energy waveform applied to the electrodes. The resulting standing wave can be used to keep rough regions of the electrode below or smooth regions beyond thermodynamic potential boundaries. Similarly, the current density may be focused away from particularly rough regions to prevent additional dendrite growth in the regions. By analyzing the condition of the electrode surface, the peaks and troughs of the applied AC energy wave can be determined to select which portions of the electrode surface have higher or lower current densities. Under conditions where the frequency and amplitude are sufficiently large, the potential difference between adjacent regions of the surface of the electrode can induce local electrical chain reactions with or without a counter electrode. This phenomenon is well understood for dissolving dendrites and homogenizing the SEI layer in lithium based cells.

Low frequency AC power supplies exhibit DC-like behavior with respect to the electrodes. As the AC frequency increases, the power is more closely focused to the surface according to the skin effect. In an ideal conductor, the expected skin depth is 2mm at 1kHz, 2pm at 1GHz, and so on. That is, most of the AC power is focused at a higher frequency into a very thin sub-portion of the anode surface. When the interface is more complex, such as when the roughness thickness and skin depth are similar, then it can be said that most of the AC power resides at the interface. Thus, the efficiency of AC power is related to the applied frequency, and less power may be required at higher frequencies.

Several experiments were completed using copper electrodeposits as an analog of lithium metal on the battery electrodes. Tests demonstrated the initial feasibility of significantly inhibiting dendrite formation in an aggressive testing environment designed to produce moss-like dendrites. A control test for dendrite formation was performed on copper electrode 500 using a fully saturated electrolyte solution of copper sulfate in deionized water. Additives or other methods for reducing dendrite or roughness are intentionally excluded. The charging current density for the control was about 65mA/cm 2. In more detail, fig. 5 shows a snapshot of a control sample 500 having a surface coverage of moss dendrites greater than 60% compared to the same test condition with an AC signal applied across the electrodes. As shown, the samples were run in the following manner: at the noted charge current density and in the absence of AC energy (end view of sample 504 and side view of sample 506); and operating at the noted charge current density and in the presence of AC energy (end view 508 and side view 510); with aggressive electrolyte (low purity, reagent grade, saturated copper sulfate), oxygen-containing copper counter electrode, excessive current density (65mA/cm 2), asymmetric cell (surface area of counter electrode > surface area of working electrode) and longer deposition time (8 hours) (process 502). The method as shown in views 508 and 510 eliminates a significant amount of moss dendrite surface coverage as compared to the method without AC energy (views 504 and 506).

In particular, fig. 5 and 6 (and fig. 7 and 8) show the results of applying an AC signal having a frequency of 75kHz and a power of 23dBm to electrode 500.

To perform the experiments relating to fig. 5 and 6, a DC power supply and an AC power generator were employed. The signals from the AC generator and the DC negative polarized power source are both independently connected to the T-junction. From which the lead wires are fed into the test cell. The DC positive polarization is directly connected to the counter electrode of the test cell. The AC generator line contains an inline DC filter and upstream of T to block DC current from flowing into the signal generator. Similarly, the DC power supply contains an inline AC filter and upstream of T to block AC energy from flowing into the power supply and perturb the DC current and voltage measurements. Generally, this configuration may be employed in a battery charger. The results show that moss dendrite surface coverage is significantly reduced relative to the control results while achieving the desired performance on the deposited mass. As shown in fig. 7 and 8, in addition to the substantial elimination of moss dendrite surface area, the peak and average surface height of the deposited region were also reduced by > 50%, respectively. In fig. 7 and 8, each box (relative to the respective control) illustrates variability within the respective data set represented by the respective box, wherein each graph illustrates a respective trend of a reduction in dendrite height of each data set relative to the respective control of each graph.

Fig. 13 depicts simulation results of applying electrical waveforms along the electrodes of a battery. Specifically, the simulation results of fig. 13 show that the sections (a) to (i) are obtained by performing the simulation under aqueous conditions (ρ ═ 1.68E-8 Ω m, σ ═ c)_soln5S/m, ═ 80) or lithium battery/organic electrolyte conditions (ρ ═ 80)_Li＝9.28E-8Ωm，σ_soln1S/m, 45) simulating a conductive electrode. An AC energy signal is applied along the surface of the electrode in a manner similar to the methods described herein. The conductive electrode was a foil conductor 6mm wide, 35pm thick, triangular roughness w/w/o 1 mm. A cross-sectional view of the conductor is best shown in section (d), which shows the triangular roughness of the foil conductor surface.

Sections (a) - (c) show various AC energy signals applied to the conductor during simulation. Specifically, section (a) shows an AC energy signal of 9.9 GHz; section (b) shows an AC energy signal of 10 GHz; and (c) exhibits an AC energy signal of 100 GHz. Further, the electric field (arrows), the magnetic field (contour line), and the current density are also shown for each signal showing the skin depth () in the aqueous condition.

Section (d) shows the current density profile (grey scale) due to the DC signal (approximating the charging current on the electrodes) and the surface roughness. Thus, section (d) shows the case where no AC signal is applied along the surface of the electrode. Instead, only a DC charging current is applied to the electrodes. As can be seen, the current density in this case is collected around the point of the triangular roughness of the electrode. Dendrite growth is likely to continue at this point. In other words, there are three regions at the tip of each triangle roughness where the current density is higher, causing more current to flow at these regions and therefore faster growth at these regions.

In contrast, section (e) shows the current density profile (grey scale) resulting from the application of an AC signal along the surface of a smooth conductor. As can be seen, the electric field and current density can be manipulated manually by applying an AC energy signal to the electrodes. Thus, for example, using the systems and methods discussed herein, the high density points (e.g., (d)) of conventional systems can be distributed away from the peak, thereby reducing or eliminating dendrite growth. Further manipulation of the characteristic parameters of the AC signal allows tuning of the current density as desired. In section (e) (AC power), there is no triangular roughness (e.g., similar to that in (d)), but the surface is flat. Nonetheless, the system and method uses AC energy to induce three different regions of higher current density from the flat surface, indicated by the U-shaped lines, which show magnetic field behavior. By manipulating the frequency and power of the AC energy, the system can change the spatial position of these lines and the higher current density (and faster deposition rate) across the electrodes.

Sections (f) - (h) show time-averaged behavior, with an applied AC signal of 100 GHz. Although the high frequencies are much faster (cross section (f)) than the characteristic time of charge transfer and convection processes (about 0.1 ms-10 s), significant transient electric and magnetic field effects can still be induced. The high conductivity and dielectric constant (cross section (g)) of aqueous conditions increases the difficulty of making the current distribution uniform using a fixed frequency. In (f) - (h), in the presence of an AC signal, the arrows represent the vector of the electric field, and the contours represent the strength of the magnetic field. The more realistic conditions for lithium batteries (lithium metal or lithium ions) (h) allow a more uniform energy distribution and thus a reduction of the required AC power. These conditions are promising indicators: even at high RF, the AC energy should be primarily confined to the electrode and electrolyte interfaces, imparting a homogenizing effect across the SEI, disrupting the dominant ion channels, and helping it evolve more quickly and uniformly in response to stresses generated by interfacial expansion or contraction. Regardless of the operational state of the battery, high frequencies that affect capacitive and inductive coupling of surfaces with conductive objects that are not in direct contact will provide a means to dissolve and recover dead lithium.

In the absence of AC energy, (f) would look exactly the same as (d), (f) shows the higher current density at the rough tip and at the electric field arrows, which are directed mainly straight down towards the electrode, except near the rough triangle that causes the field lines to bend. In (f), the AC energy causes sharp bending of the electric field arrows and irregular distribution of current density in the electrolyte above the roughness. In this case, the roughest areas no longer grow faster than the flat areas of the electrodes. In (g) and (h) using AC energy, everything else is the same except that the electrode and electrolyte in (g) have the dielectric properties of water-based chemicals, while (h) has the dielectric properties of lithium ion batteries (with organic electrolytes). In (g), the pattern and coloration across the surface was much less uniform than in (h), indicating that the AC energy will be more evenly distributed across the lithium battery electrode compared to the water-based copper experiment.

Section (i) shows the magnification of the current skin depth and the lateral current distribution at a fixed frequency. The regions of different grey scale show how the current density is spatially distributed according to frequency. As can be seen in the cross section, the current density, represented by the light and dark grey variations along the electrode surface, can be varied by applying an AC energy signal.

Lithium ion intercalation

In addition to controlling and mitigating dendrites, applying lateral AC energy/current at the electrode surface may also bring additional benefits to the operation and maintenance of the cell. For example, lithium intercalation/diffusion within graphite is a rate-fixing step during charging of lithium ion batteries. Rapid charging at the voltage limits of the battery cell results in potential over concentration polarization. Continuous operation under such conditions may cause the SEI layer to thicken, resulting in an increase in system resistance. Continuous operation may also cause lithium to begin to plate onto the graphite. Starting from the formation of lithium dendrites, this quickly leads to the same problems encountered in lithium metal batteries.

AC energy and lateral current (either by transport or conductively applied directly to the anode) can be used to excite lithium ions and increase the rate of intercalation without increasing the cell DC voltage across the electrolyte. The conductivity along the graphene plane (σ -2.5E 5S/m) is three orders of magnitude greater than the conductivity between the planes. This promotes energy to propagate primarily along the lithium ion diffusion plane between the graphite edges which serve as the lithium ion entry and presence points. At slower frequencies (less than about 1000Hz), the AC energy may directly enhance the diffusion of ions, while at higher frequencies the AC energy may be used to further excite the embedded ions to diffuse across the surface and the embedded energy barrier, with less potential across the cell. As during the pretreatment step (discussed later), application of AC energy to the electrodes avoids the adverse effects of concentration polarization, including SEI thickening and cathode damage. Increasing the intercalation rate may also enable the battery to be run more densely, with a reduced risk of lithium plating.

Electrolyte-electrode interface and SEI

As explained above, the SEI is a layer containing by-products formed as lithium reacts with components of the organic electrolyte. It is present in all Li-ion, Li-Si and Li metal batteries, except batteries that use inorganic films instead of organic films or electrolytes. The ionic conductivity and viscosity of the layer are typically lower and higher than the bulk electrolyte, and therefore dominate the diffusion and charge transfer processes in the cell. The lower conductivity and generally higher dielectric constant also allow the AC/RF signal to propagate more uniformly across the electrode surface, resulting in reduced power for the AC/RF signal.

Ideally, the SEI is uniform across the entire electrode. When the electrode surface expands and contracts or creates rough features as the battery cycles, the SEI may not adapt quickly enough and may become thinner in some areas than others. This can present a problem in lithium silicon batteries because the electrodes undergo unusually large deformations between charge-discharge cycles. Since the SEI is a resistive barrier to migration of dissolved lithium in the electrolyte to the electrode, more lithium can diffuse through the thinner regions of the SEI and be deposited unevenly. The dominant ion transport channel may also be formed by the SEI and become the basis for dendrites.

One method for suppressing SEI thinning on an electrode of a battery is to apply AC energy to the electrode. This energy can be applied during the charge cycle or when the battery is dormant to recover the weakened section or flatten the SEI layer. Typically, the applied AC energy is partially absorbed by the SEI as it traverses the electrode surface. This can induce charge transfer reactions and facilitate SEI adaptation to changing electrode surface geometries. AC may add a degree of mixing to the charge transfer activity that prevents the initiation of the dominant ion transport channel. It also increases the local current density and causes the deposit to become dense and less fragile, reducing moss or fragmented dendrites that may detach from the electrode surface, losing electrical contact and becoming "dead lithium".

Some lithium batteries may not use an organic liquid electrolyte, but rather tend to have a conductive glass or polymer ion transport layer (typically, but not always, a membrane). In the absence of any electrolyte reaction with lithium, SEI may not be present. Dendrites are less problematic in this scenario because the surface is less prone to dendrite formation or the solid ion transport layer physically blocks its continued growth toward the cathode. However, the electrode surface will continue to age and degrade. In these cases, the glass or polymer layer still provides a dielectric medium with low conductivity, and thus still promotes efficient propagation of AC energy for charge redistribution and generally prevents surface non-uniformities.

Depending on conditions and waveform parameters to account for many irregularities in the SEI layer, the effect of the applied AC energy may be to thin or thicken the SEI. When the battery cells are neither charged nor discharged, but are in a resting state, control of one or the other may be most effective when AC energy is applied.

Pretreatment of New electrodes for initial SEI formation

The optimally evolving SEI layer on the anode is generally critical to the performance of a lithium ion battery. Prior to distribution, manufacturers will subject the unencapsulated electrode material and subsequently encapsulated electrodes to various time and energy intensive pre-treatment steps that typically last for weeks. The pretreatment step will typically involve circulation and heating and be an energy and time intensive pretreatment step.

Typically, the graphite of the electrodes is porous and must be fully wetted by the electrolyte during the initialization phase to access the full capacity of the cell. However, in many applications, the surface tension of the electrolyte makes this difficult and slow for small scale porosities of 200nm or less. This porosity accounts for a significant portion of the total surface area of the graphite. Wetting is usually accomplished under vacuum and heating for several days to weeks, making the wetting the slowest part of the pretreatment process. However, it is crucial for forming an optimal SEI layer later.

Later, the encapsulated electrode undergoes a series of slow charge-discharge cycles under a temperature control program to properly step up an initial SEI layer that is dense, thin, electrically insulating and contains non-reactive, insoluble inorganic lithium species. This is called forming a loop. These cycles are typically 1/10 at the normal cycle (0.05 to 0.1C) rate^thTo 1/20^thIs done slowly. This contributes to a process that lasts several weeks and involves a large amount of energy usage. These steps involve two electrodes in the cell, and the conditions required to optimize the SEI at the anode are not ideal for the cathode. The forming cycle consumes a portion of the lithium content of the cathode before the cell reaches its final application, thereby shortening the overall battery life.

The use of AC energy to excite the anode described in the above methods, either through transmission or conductive application, provides a way to improve both the electrode wetting step and the SEI formation step in the battery manufacturing process. AC energy, particularly at higher frequencies, has the remarkable behavior of inducing strong local electric field gradients and much higher local current densities. This type of local energy density can be used to overcome capillary forces that oppose complete electrolyte wetting of the graphite, thereby requiring less or no time under vacuum and heat when energy is applied directly to the graphite. Local electrical and magnetic energy build-up can also stimulate the charge transfer process at only one electrode, thereby gradually forming an optimal solid electrolyte interphase at the anode without polarizing, depleting, or otherwise relating the cathode.

Because the conductivity of graphite parallel to the graphene plane is much greater, the energy density at the edges will be relatively high at most frequencies of interest. Because most chemical reactions occur at the edges and act as entry and presence points for Li-ion insertion, the current density is along the edge where the mass of the SEI most affects the process. Thus, from an energy efficiency and propagation perspective, the application of AC energy may provide the greatest benefit targeting a particular region, which is useful. In particular, AC energy can be applied as a single electrode process to quickly generate the initial SEI at the edges without worrying about generation elsewhere.

Energy coupling to dead lithium

As described above, more fragile roughness features such as bryoid and fragmented lithium may be formed on the electrode surface. The roughness features may eventually break away from the surface and lose electrical contact. Fig. 9 demonstrates this dead lithium in the electrolyte layer 108 of the cell due to the growth of fragile dendrites on the anode 108. The stored energy potential of this lithium block is no longer available for power storage and battery capacity is permanently lost when such a block is formed.

The method used to provide AC energy to the anode 108 may help dissolve these dead lithium pieces back into the electrolyte 106 and restore the energy potential of the battery 100. Specifically, the AC energy may non-conductively induce charge into the dead lithium, which begins to dissolve into the electrolyte 106. Capacitive or inductive coupling may occur close to the surface depending on the frequency. The electrical or magnetic energy closest to the surface will dominate and a significant part of the energy will be reactive. If the dead material is further from the surface, the energy transfer mechanism will be dominated by the more coherent radiant energy. These two mechanisms correspond approximately to the near field region and the far field region of the radiator, respectively. Even in the case of radiant energy, the dead matter will have its own near surface coupling phenomena, generating reactive energy. By inducing an electrical current into the dead mass, the local current density can be increased sufficiently to carry out the charge transfer process and dissolution. In the dissolved state, the substance can be used again for energy storage.

Reabsorption can be monitored in various ways. For example, in various charge and discharge cycles, the storage capacity may be monitored in each successive cycle during charging and/or when AC energy is applied explicitly. In some cases, the capacity may be compared to a storage capacity value that is initially set or measured when the battery is put into use, or may be compared to a measured trend over time (e.g., a decrease in capacity or a significant decrease in capacity over time as compared to an increase in capacity after a reabsorption process). The reabsorption may also be determined based on the cell resistance, where the resistance is reduced relative to a previously measured value, indicating that there is reabsorption of dead material at the previously measured value.

Single point of contact

Traditionally, the battery has only one electrical contact point with the electrode. For example, fig. 10A-10C illustrate three common battery cell or battery formats and externally accessible electrical contacts. Specifically, fig. 10A shows a top view of a pouch cell 1002 containing electrode tabs and an ion transport layer that are cut to specific dimensions. The electrode cutouts contain tabs 1004 that can be accessed to provide electrical contact. In some cases, additional tabs may be added at different points to enable multiple contact points, if desired. However, there is typically only a single electrical contact 1004 per electrode. In the example shown, a first tab 1004(A) is connected to a counter electrode and a second tab 1004(B) is connected to a working electrode (e.g., an anode). AC energy may be coupled at tab 1004(b) or a separate tab 1004(C) may provide a connection point to the working electrode. Alternatively, AC energy may be applied across or between tabs on the same electrode, such that an AC (+) connection is made at one tab and an AC (-) connection is made at the other tab.

Fig. 10B shows a representative cross-sectional view of a coin or button cell 1006 containing standard layers inside the 'can'. The top and bottom of the can are electrically isolated from each other by spacers 1008. A single electrical contact 1010 is formed through the bottom of the can anywhere within the contact area. The can is in direct electrical contact with the current collector layer (usually aluminum at the cathode and copper at the anode). Fig. 10C shows a "jelly-roll" battery 1012 based on rolled up multiple layers most similar to the pouch cell 1002. However, as with coin-type cells, packaging is typically limited to a single electrical contact 1014(A) and 1014(B) per electrode.

Although the battery provides a single point of contact for the anode, the AC energy discussed herein can still be applied to achieve the performance results of the battery. For example, fig. 11 shows a single contact point for supplying AC energy to the anode 1106 of a coin or button cell 1008. The 3D view shows EM pulses (1108 and 1110) propagating across the anode surface at different times and from different single contact points (a-centered 1102, B-offset 1104). Generally, when wavelength > > anode diameter, the location of the contact point is less important. When the wavelength is ≦ the anode diameter, reflections along the boundaries of the electrodes will contribute to more complex patterns and standing waves across the surface. Therefore, because the cell is typically limited to a single contact point, the effect of the generated standing AC wave is considered based on the location of the single contact point on the anode.

Transmitting RF signals

In contrast to conduction by a source in direct electrical contact, AC/RF may be transmitted over a distance to the electrode to cause benefits similar to those described herein. In this case, the directionality of the emitter and the orientation of the electrodes within the radiation field are the main considerations. In some embodiments, such as large batteries, the anode access may be limited or challenging. In such cases, strategically placed transmitters may be positioned throughout the battery pack to radiate AC signals to the electrodes of the battery cells in the battery pack. In some cases, a shield antenna or directional antenna may be deployed to shield the cathode or otherwise direct energy to the anode only if the anode is the only target.

Anode and cathode independent modulation

In some cases, the AC signal may not necessarily be applied proportionally or inversely proportionally at both the anode and cathode of the cell. Conversely, an input signal at the cathode may affect the anode by conductance, coupling or transmission (depending on frequency), and vice versa. In such cases, AC energy may be used to cause cell repair (homogenization of the electrode/electrolyte interface) whether the cell is active or dormant. Homogenization can occur at the electrodes whether the cell is charging, discharging or dormant if the AC signal is sufficient to cause local diffusion and charge transfer processes.

The frequency and power of the AC energy should be selected to achieve the desired effect (dendrite prevention, SEI thinning or thickening, ion intercalation, etc.) in as energy efficient a manner as possible. Overall process efficiency is important for battery charging, and in most applications, a small reduction in efficiency has a significant impact on the application. Calculating the total efficiency requires combining the energy input between the two electrodes (DC, standard) with the energy input for AC energy as a ratio compared to the storage capacity, lifetime (total cycle) or similar measure of the battery. In one case, AC can increase ion intercalation, thereby reducing the required galvanic potential. In another case, AC energy may improve the repair rate of the SEI after structural change of the electrode, thereby increasing the battery life. The benefits of the additional energy for the AC signal must be weighed against these results on a case-by-case basis.

Situations involving fast charging (particularly for large systems such as EV battery packs or stationary applications) may be more tolerant of additional energy for the AC input, since the energy requirement of the DC input is already high (the relative additional burden on the system may be lower). When charging, the AC input can target prevention of dendrite formation and generation of uneven porosity in the SEI (containing ion channels), and increase Li diffusion without (or even if) increasing the cell potential. It can also regulate SEI growth and prevent the layer from becoming too thick. The diffusion of the stimulating ions out of the graphite when the cell is discharged is still of value.

The AC energy applied during discharge or when the cell is dormant can also provide a quieter environment for the SEI to be repaired (reformed at the deformed regions of the electrode or densified under conditions that have caused the SEI to become porous) and restore uniformity after aggressive charging cycles or operating conditions. Further, the dead lithium and existing dendrites may be dissolved at any of these stages.

Electrokinetic flow and diffusion effects

As AC energy propagates across the electrodes, electrokinetic behavior can produce electrokinetic effects at the electrode | electrolyte, electrode | SEI, and SEI | electrolyte interfaces. The nature of these effects depends on the material properties of one layer relative to the other at the interface. For example, high frequencies far outside of conventional considerations (e.g., 100GHz) can alter the steady state diffusion pattern in the electrolyte near the surface when applied at the electrodes. The exact pattern depends on the frequency.

As previously discussed, the local charge density, electron path, and magnitude of the local electric field gradient all depend on frequency and generally increase proportionally. Exceptions may occur under certain resonant (energy is capacitive or inductive in nature) or ambient absorption conditions. When the applied frequency is slower than the charge relaxation time of the layers, the conduction mechanism will dominate the round-trip transfer of charge between the interfaces. If conduction is dominant in one layer and not in the other, the interface will become polarized. If the applied frequency is faster than the charge relaxation time of the layers, the interfacial polarization will be proportional to the difference in the dielectric constants of the two layers.

The basic behavior of any interface in response to AC energy can be estimated based on the above general guidelines and the relative properties of all layers. This may be the simplest basis for starting to determine the appropriate waveform to achieve a particular effect:

electrode (lithium): high electric conductivity and low dielectric constant

SEI: low conductivity, medium dielectric constant

Organic electrolyte: medium conductivity, medium and high dielectric constant.

Regardless of which interface is considered, at frequencies that reach or exceed resonance across an interface size or feature, the effects are mixed and spatially correlated-i.e., localized. The correct frequency and power can induce dielectrophoretic forces that produce a diffusion pattern at or near the surface. In other words, the frequency and power of a given AC energy application may be based on the difference in electrical and dielectric properties of the materials inside the battery.

Reforming battery cell

In the case discussed so far, the nature of the applied energy and its mechanism of influence on the diffusion and charge transfer processes may depend on the relationship of the applied wavelength versus the electrode size. In particular, the electrodes or features on the electrodes are resonant to a degree at the applied frequency. This is a suitable focus of the battery system whose electrochemical behavior should be modified by the process without changing the geometry or design of the battery.

Where the cell can be re-engineered, a tailored (patterned) resonant layer can be added near the electrodes to direct or shape the energy applied to the electrode surface. For example, fig. 12 shows the component layers of a button cell format 1200. In the cell fabricated herein, the anode 1202 is modified with a dielectric 1204 and a conductive/patterned layer 1206 to electrically couple with the primary conductive layer. Example patterned layers a-C1218-. As shown, in example a, the geometry of patterned layer 1208 matches the primary layer. In example B, the patterned layer 1210 contains rings for more robust coupling with magnetic energy. In example C, patterned layer 1212 contains a complex geometry to control the resonant frequency and induce a specific pattern of current density at the primary electrode. In general, patterned layer 1206 may take any shape and size to form or generate an AC wave that is applied to the anode of the battery cell.

In the case of a modified battery cell, DC energy may be applied to the primary conductive layer 1202 in contact with the electrolyte, while AC is applied to the patterned layer 1206. Patterned layer 1206 is designed to have a unique conductive via with a desired resonant behavior that may or may not be similar to the primary conductive layer. A given cell layer (and specifically the electrode of the cell) will resonate based on the size and material properties of the layer. The patterned layer may be tailored to resonate and interact with the target cell layer to produce an overall resonance in the presence of an AC signal. In one example, computer simulation can be used to develop a particular pattern for any given application, and tune or otherwise adjust the pattern for overall expected impact on dendrite suppression, etc. The AC energy applied to a carefully patterned conductive layer can be made to flow in a unique direction that does not necessarily match the pattern. If the patterned layer is separated from the electrodes by a thin dielectric layer, the electric and magnetic fields generated by the AC energy on the patterned layer will travel through the dielectric layer and affect the electric and magnetic fields on the disk electrodes.

In various cases, the primary conductive layer 1202 may be connected to the patterned conductive layer 1206 by one or more conductive vias through or around the dielectric layer, such that DC and AC may be applied at a single point and to both layers. In this case, by coupling with patterned layer 1206, the resonant behavior of primary conductive layer 1202 is modified and may be dominated. The patterned layer 1206 may also affect the electrochemical process on the primary conductive layer 1202 when only the primary conductive layer receives DC and/or AC conductive inputs.

As discussed, the patterned layer may take a variety of forms. The resonant behavior in example a 1208 will be fixed even if the primary layer undergoes changes during cell operation. Coupling will occur through the dielectric layer between the conductive layers. This will also allow the AC signal to propagate more uniformly without being attenuated by the conductive electrolyte. In another case, the patterned layer may be a closed loop that couples more strongly with the applied magnetic energy at the AC frequency, as in example B1210.

In another case, the patterned layer may require complex geometries that shift the strongest capacitance-inductance transformation (e.g., shift the resonance point to lower frequencies). The geometry may also induce uniquely patterned regions of electromagnetic behavior onto the primary conductive layer (example C1212). In a very particular case, the pattern may affect spurious surface plasmons inducing a directional pattern of current displacement. The patterned layer may not be subjected to direct conductive input, but rather affects the electrochemical process at the primary conductive layer entirely by coupling.

Other battery types

The energy capacity of zinc batteries is similar to or better than that of lithium ion batteries (in particular zinc air batteries). Both zinc and lithium are negative electrode metals and, when used in a battery, zinc and lithium also encounter similar dendrite problems. The main difference is that zinc can be used in an aqueous (usually alkaline) environment. Dendrites are also a major obstacle to the ability to cycle Zn electrodes in rechargeable zinc batteries. The dendrites are easily formed and may damage or short-circuit the anode and the cathode. Dendrite suppression can be achieved by using organic additives in the electrolyte that eventually co-deposit into the electrode and deplete. Small concentrations of various metals or metal oxides can also be added directly to the zinc electrode surface to affect the solubility and mobility of the reversible byproducts, thereby maintaining a more uniform surface during cycling. To prevent the need for these types of additives, the processes and methods described herein can be used to inhibit dendrite formation and homogenize the surface of a zinc electrode in a rechargeable zinc cell.

With respect to lead acid batteries, the methods described herein may be modified to illustrate the construction of electrochemical cells and their electrochemistry. Unlike lithium-based batteries, both the anode and cathode plates corrode during charging and discharging. Existing cells have only two ports, so a lateral current is sent in one port, which is calculated to reflect off the far wall of the cell and return to the incoming port. Thus, the waveform of the transverse current is swept through several frequencies to achieve a relatively balanced time-averaged current profile across the anode and cathode surfaces of the lead acid battery.

Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosure. Several well-known processes and elements have not been described in detail in order to avoid unnecessarily obscuring the disclosed embodiments. Therefore, the above description should not be taken as limiting the document.

Those skilled in the art will appreciate that the disclosed embodiments are illustrative and not restrictive. Accordingly, the matter set forth in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. These claims should be construed to cover all generic and specific features described herein, and all statements of the scope of the present methods and systems that, as a matter of language, might be said to fall therebetween.

Claims (39)

1. A method of charging, comprising:

applying a direct DC charging current to one of a first electrode and a second electrode in a battery comprising the first electrode and the second electrode; and

applying alternating AC energy to at least one of the first electrode and the second electrode in conjunction with applying the DC charging current.

2. The charging method according to claim 1, wherein applying alternating-current energy to at least one of the first electrode and the second electrode suppresses a surface irregularity phenomenon.

3. The charging method of claim 1, further comprising applying the alternating current energy to the first electrode, wherein the first electrode is an anode.

4. The charging method of claim 3, further comprising applying the direct charging current to the anode.

5. The charging method of claim 4, wherein the DC charging current is at least one of constant or pulsed.

6. The charging method of claim 3, further comprising applying the alternating energy across the anode, wherein the alternating energy comprises an alternating current.

7. The charging current of claim 6, wherein the frequency of the alternating current is between 100Hz and 300 GHz.

8. The charging method of claim 3, further comprising applying the alternating current energy at a point of the anode.

9. The charging method of claim 1, further comprising applying the alternating current energy based on resonance of the anode.

10. The charging method of claim 3, further comprising:

applying the alternating current energy to the anode at a frequency; and

the frequency is adjusted.

11. A method, comprising:

applying an Alternating Current (AC) waveform to an electrode of a battery cell comprising a plurality of layers, the AC waveform inducing an electrodynamic effect in at least one layer of the plurality of layers of the battery cell.

12. The method of claim 11, wherein the electrokinetic effect comprises an electrokinetic effect.

13. The method of claim 11, further comprising:

applying a charging current to the electrode of the battery cell in the presence of the alternating current waveform, the charging current being different from the alternating current waveform.

14. The method of claim 11, wherein the electrode of the battery cell is an anode.

15. The method of claim 12, wherein the at least one of the plurality of layers of the battery cell comprises a solid electrolyte interphase SEI layer, the solid electrolyte interphase layer being located between the anode and an electrolyte layer.

16. The method of claim 15, wherein the electrokinetic effect on the solid electrolyte interphase layer comprises reducing growth of one or more dendrites within the solid electrolyte interphase layer.

17. The method of claim 11, wherein the electrokinetic effect comprises dissolving metal deposits in an electrolyte layer of the battery cell, the metal deposits not in electrically conductive electrical communication with the electrode of the battery.

18. The method of claim 11, wherein the induced electrodynamic effect comprises displacing a plurality of high current density regions and a plurality of low current density regions on a surface of the electrode.

19. The method of claim 11, wherein the alternating current waveform is applied to the electrode of the battery cell through a single contact point with the electrode.

20. The method of claim 11, wherein the alternating current waveform is applied to the electrode of the battery cell by irradiation of the alternating current waveform.

21. The method of claim 11, wherein the electrode comprises graphite and the electrokinetic effect comprises inducing grinding of the graphite electrode.

22. The method of claim 11, wherein the alternating current waveform comprises one of a continuous wave, a pulsed wave, or a continuous converted wave.

23. The method of claim 11, wherein the electrokinetic effects comprise local current densities and potential gradients across the electrodes of the battery cell.

24. The method of claim 11, wherein the battery cell comprises one of a lithium ion battery, a lithium metal battery, a lithium silicon battery, a zinc battery, a nickel battery, or a lead acid battery.

25. The method of claim 11, wherein the plurality of layers of the battery cell comprise at least one dielectric layer adjacent to the electrode and a modified conductive layer configured to alter an electrical potential and charge distribution at an electrode interface.

26. The method of claim 11, wherein the electrokinetic effect comprises suppression and dissolution of one or more dendrites attached to a surface of the electrode.

27. A battery charger, comprising:

a power supply comprising a first conductor and a second conductor, the power supply configured to apply a direct DC charging current through the first conductor to one of a first electrode and a second electrode of a battery operatively coupled to the battery charger; and is

The power supply is further configured to apply Alternating Current (AC) energy to at least one of the first and second electrodes of the operatively coupled battery through the second conductor.

28. The battery charger of claim 27, wherein the first conductor and the second conductor are operatively coupled to a common connection point through which the dc charging current and the ac energy are applied to one of the first electrode and the second electrode.

29. The battery charger of claim 27, wherein the alternating energy is alternating current.

30. The battery charger of claim 29, wherein the frequency of the alternating current is between 100Hz and 300 GHz.

31. The battery charger of claim 27, wherein the power source is further configured to apply the alternating current energy to the first electrode through the second conductor, the battery further comprising a patterned layer operatively coupled with the first electrode, the patterned layer affecting a resonance of the first electrode in the presence of the alternating current energy.

32. The battery charger of claim 27, wherein the direct charging current is at least one of constant or pulsed.

33. A battery, comprising:

a first electrode;

an ion transport layer comprising a first side and a second side, the first side operatively coupled with the first electrode;

a second electrode operatively coupled with the second side of the ion transport layer; and

a patterned layer operatively coupled with the first electrode, the patterned layer configured to receive alternating energy different from charging energy or discharging energy.

34. The battery of claim 33, further comprising:

a dielectric layer between the first electrode and the patterned layer.

35. The battery of claim 34, wherein the first electrode is an anode.

36. The battery of claim 35, further comprising a solid electrolyte interphase SEI layer, the solid electrolyte interphase layer being located between the anode and the ion transport layer.

37. The battery of claim 33, wherein the patterned layer affects resonance of the first electrode.

38. The battery of claim 33, wherein the ion transport layer is an electrolyte.

39. The battery of claim 33, wherein the alternating energy is alternating current.

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