Methods and systems for silicon-dominated lithium-ion batteries with controlled silicon usage

Abstract

Systems and methods for a silicon-dominated lithium-ion battery with controlled silicon use may include a cathode, an electrolyte, and an anode, wherein the anode has an active material comprising greater than 50% silicon. The battery can be charged by lithiating the silicon without lithiating the carbon. The active material may comprise greater than 70% silicon. During discharge of the battery, the voltage of the anode may remain above a minimum voltage at which silicon can be lithiated. The anode may have a specific capacity greater than 3000 mAh / g. The battery may have a specific capacity greater than 1000 mAh / g. The anode may have an initial coulombic efficiency greater than 90% and may be free of a polymer binder. The battery may be charged at a 10C rate or higher. The battery may be charged at temperatures below freezing without lithium precipitation. The electrolyte may include a liquid, a solid, or a gel.

Description

[0001] Cross-reference / incorporation by reference to related applications

[0002] This application claims priority to and the benefit of U.S. Patent Application No. 16 / 594,508, filed on October 7, 2019, which is incorporated herein by reference in its entirety. Technical Field

[0003] Aspects of the present disclosure relate to energy generation and storage. More specifically, certain embodiments of the present disclosure relate to methods and systems for silicon-dominated lithium-ion batteries with controlled silicon usage. Background Art

[0004] Conventional methods for battery anodes can be expensive, cumbersome, and / or inefficient, e.g., they can be complex and / or time-consuming to implement, and can limit battery life.

[0005] Other limitations and disadvantages of conventional and traditional approaches will become apparent to those skilled in the art by comparing such a system with certain aspects of the present disclosure as set forth in the remainder of this application with reference to the accompanying figures. Summary of the Invention

[0006] A system and / or method for a silicon-dominated lithium-ion battery with controlled silicon usage, substantially as shown in and / or as described with respect to at least one of the figures, as more fully set forth in the claims.

[0007] These and other advantages, aspects and novel features of the present disclosure, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a diagram of a lithium ion battery according to an exemplary embodiment of the present disclosure.

[0009] Figure 2 Illustrated are anode, cathode, and battery voltages during charging of a lithium-ion battery according to an exemplary embodiment of the present disclosure.

[0010] Figure 3 A lithium ion battery having lithium precipitation and dendrites according to an exemplary embodiment of the present disclosure is illustrated.

[0011] Figure 4 Illustrated are voltage levels during charging of a silicon-added graphite anode according to an exemplary embodiment of the present disclosure.

[0012] 5A and 5B illustrate mechanical processes during lithiation and delithiation of a silicon-added anode and a silicon-film anode according to exemplary embodiments of the present disclosure.

[0013] Figure 6 Illustrated are voltage levels during charging of a silicon membrane anode according to an exemplary embodiment of the present disclosure.

[0014] Figure 7 Illustrated is the anode half-cell first cycle voltage profile for a silicon-dominated anode according to an exemplary embodiment of the present disclosure.

[0015] Figure 8 Illustrated are the electrodes and cell voltage of a cell having a silicon-dominated anode according to an exemplary embodiment of the present disclosure.

[0016] Figure 9 The charge rates of a graphite battery and a silicon-dominated battery are illustrated according to exemplary embodiments of the present disclosure.

[0017] Figure 10 The charging duration of a silicon-dominated battery at low temperatures is illustrated according to an exemplary embodiment of the present disclosure.

[0018] Figure 11 Capacity retention rates of silicon-dominated batteries according to exemplary embodiments of the present disclosure for different charging temperatures are illustrated.

[0019] Figure 12 Exemplary lithiation and delithiation processes for silicon-dominated anodes according to exemplary embodiments of the present disclosure are illustrated.

[0020] Figure 13 Illustrated is a voltage profile of a lithium-ion battery having a silicon-dominated anode according to an exemplary embodiment of the present disclosure.

[0021] Figure 14 A silicon-dominant anode cell process is illustrated according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] Figure 1 is a diagram of a lithium ion battery according to an exemplary embodiment of the present disclosure. Figure 1 , shows a battery 100 including a separator 103 sandwiched between an anode 101 and a cathode 105, and current collectors 107A and 107B. Also shown is a load 109 coupled to the battery 100, illustrating the situation when the battery 100 is in a discharge mode. In this disclosure, the term "battery" may be used to refer to a single electrochemical cell, a plurality of electrochemical cells formed into a module, and / or a plurality of modules formed into an assembly.

[0023] The development of portable electronic devices and the electrification of transportation are driving the demand for high-performance electrochemical energy storage. Small-scale (<100Wh) to large-scale (>10KWh) devices primarily use lithium-ion (Li-ion) batteries due to their high performance compared to other rechargeable battery chemistries.

[0024] Anode 101 and cathode 105, along with current collectors 107A and 107B, can comprise electrodes that can comprise plates or membranes within or containing an electrolyte material, wherein the plates can provide a physical barrier for containing the electrolyte and conductive contact with external structures. In other embodiments, the anode / cathode plates are immersed in the electrolyte, while the housing provides electrolyte containment. Anode 101 and cathode are electrically coupled to current collectors 107A and 107B, which comprise metal or other conductive materials for providing electrical contact with the electrodes and physical support for the active materials when forming the electrodes.

[0025] Figure 1 The configuration shown in the example illustrates the battery 100 in discharge mode, while in the charging configuration, the load 107 can be replaced by a charger to reverse the process. In one type of battery, the separator 103 is typically a membrane material made of, for example, an electrically insulating polymer, which prevents electrons from flowing from the anode 101 to the cathode 105, or vice versa, while being porous enough to allow ions to pass through the separator 103. Typically, the materials of the separator 103, cathode 105, and anode 101 are formed into sheets, films, or foils coated with active materials, respectively. The sheets of cathode, separator, and anode are stacked or rolled in sequence so that the separator 103 separates the cathode 105 from the anode 101 to form the battery 100. In some embodiments, the separator 103 is a sheet and a winding method and stacking are typically used in its manufacture. In these methods, the anode, cathode, and current collector (e.g., electrode) may include a membrane.

[0026] In an exemplary embodiment, the battery 100 may include a solid, liquid, or gel electrolyte. The separator 103 is preferably insoluble in typical battery electrolytes and may, for example, include a combination of ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dissolved LiBF4, LiAsF6, LiPF6, and LiClO4. The separator 103 may be wetted or soaked with a liquid or gel electrolyte. In addition, in an exemplary embodiment, the separator 103 does not melt below approximately 100°C to 120°C and exhibits sufficient mechanical properties for battery applications. During operation, the battery may experience expansion and contraction of the anode and / or cathode. In an exemplary embodiment, the separator 103 can expand and contract by at least approximately 5% to 10% without failure and may also be flexible.

[0027] Separator 103 can be sufficiently porous so that once wetted with, for example, a liquid or gel electrolyte, ions can pass through the separator. Alternatively (or additionally), even without significant porosity, the separator can absorb the electrolyte by gelation or other methods. The porosity of separator 103 is generally not too porous to allow anode 101 and cathode 105 to transfer electrons through separator 103.

[0028] Anode 101 and cathode 105 comprise electrodes for battery 100, providing electrical connections to the device used to transfer charge during charge and discharge. For example, anode 101 may comprise silicon, carbon, or a combination of these materials. Typical anode electrodes comprise carbon materials, including a current collector such as a copper sheet. Carbon is commonly used because it has excellent electrochemical properties and is also conductive. Anodes currently used in rechargeable lithium-ion batteries typically have a specific capacity of approximately 200 milliampere-hours per gram. Graphite, the active material used in most lithium-ion battery anodes, has a theoretical energy density of 372 milliampere-hours per gram (mAh / g). In comparison, silicon has a high theoretical capacity of 4200 mAh / g. To increase the volumetric and gravimetric energy densities of lithium-ion batteries, silicon may be used as the active material in either the cathode or anode. Silicon anodes may be formed, for example, from a silicon composite containing more than 50% silicon. In another example, the anode may comprise more than 70% silicon and may comprise a free-standing, monolithic, single-particle film without any binder material.

[0029] For example, the anode 101 and the cathode 105 store ions such as lithium for separating charges. In this example, the electrolyte carries positively charged lithium ions from the anode 101 to the cathode 105 in a discharge mode, such as Figure 1 As shown in FIG, , and vice versa, in charge mode, through separator 103. The movement of lithium ions creates free electrons in anode 101, which creates a charge at positive current collector 107B. Current then flows from the current collector through load 109 to negative current collector 107A. Separator 103 blocks the flow of electrons within battery 100.

[0030] When the battery 100 is discharged and current is supplied, the anode 101 releases lithium ions through the separator 103 to the cathode 105, thereby generating a flow of electrons from one side to the other side through the connected load 109. When the battery is charged, the opposite occurs, with lithium ions being released by the cathode 105 and received by the anode 101.

[0031] The materials selected for the anode 101 and cathode 105 are important for the reliability and energy density possible for the battery 100. The energy, power, cost and safety of current lithium-ion batteries need to be improved in order to compete with internal combustion engine (ICE) technology and allow the widespread adoption of electric vehicles (EVs). With the development of high-capacity and high-voltage cathodes, high-capacity anodes and functional non-flammable electrolytes with high voltage stability and interfacial compatibility with electrodes, lithium-ion batteries with high energy density, high power density and improved safety have been achieved. In addition, using materials with low toxicity as battery materials is beneficial to reducing process costs and promoting consumer safety.

[0032] Current state-of-the-art lithium-ion batteries typically use graphite-dominated anodes as the lithium intercalation material. However, silicon-dominated anodes offer improvements over graphite-dominated lithium-ion batteries. Silicon exhibits higher gravimetric capacity (3579 mAh / g versus 372 mAh / g for graphite) and volumetric capacity (2194 mAh / L versus 890 mAh / L for graphite). In addition, silicon-based anodes offer a higher capacity than Li / Li + It has a low lithiation / delithiation voltage plateau at about 0.3V to 0.4V, which keeps it at open circuit potential and avoids Figure 3 Undesirable Li precipitation and dendrite formation are exemplified in .

[0033] While silicon exhibits excellent electrochemical activity, achieving stable cycling life for silicon-based anodes is challenging due to the large volume changes of silicon during lithiation and delithiation. Silicon regions can lose electrical contact with the anode because the large volume change combined with its low electrical conductivity separates the silicon from the surrounding material in the anode.

[0034] In addition, large silicon volume changes exacerbate the formation of solid electrolyte interphase (SEI), which can further lead to electrical insulation and thus capacity loss. The expansion and contraction of silicon particles during charge-discharge cycles causes the silicon particles to pulverize, which increases their specific surface area. As the silicon surface area changes and increases between cycles, the SEI repeatedly disintegrates and reorganizes. As a result, the SEI continuously accumulates around the pulverized silicon areas during cycling, becoming a thick electronic and ionic insulating layer. This accumulated SEI increases the impedance of the electrode and reduces the electrode electrochemical reactivity, which is detrimental to the cycle life.

[0035] Figure 2 The anode, cathode, and battery voltages during charging of a lithium-ion battery according to an exemplary embodiment of the present disclosure are illustrated. Figure 2 , shows the voltage versus time in a lithium-ion battery during charging. As the battery is charged, the cathode voltage increases as it donates lithium to the anode, and the anode voltage decreases as it lithiates, causing the battery voltage to increase.

[0036] In conventional graphite anodes, lithium precipitation can also occur any time the anode voltage drops to a level where the graphite becomes lithiated, reducing the capacity of the battery and causing safety issues with the formation of dendrites over time, which can catastrophically short the battery, e.g. Figure 3 As shown in .

[0037] Figure 3 A lithium ion battery with lithium precipitation and dendrites according to an exemplary embodiment of the present disclosure is illustrated. Figure 3 , shows a battery 300 having an anode 301, a separator 303, and a cathode 305. In this example, the anode comprises a graphite active material, where low anode voltages cause lithium precipitation and the formation of dendrites over time. Dendrites extending through the separator 303 cause catastrophic failure of lithium-ion batteries and can lead to fires. This effect can be eliminated with a silicon-dominated anode with little or no graphite in the active material, and by configuring the discharge voltage to only drop to a level where the silicon is lithiated, thereby never reaching a sufficiently low voltage for any graphite in the battery to be lithiated.

[0038] Figure 4 1 illustrates the voltage levels during charging of a silicon-doped graphite anode according to an exemplary embodiment of the present disclosure. Figure 4 , showing three different voltage stages for silicon and graphite anodes. The upper stage illustrates the anode voltage when the battery is fully discharged and is at its highest level, above the voltage at which silicon or graphite is lithiated. In this stage, the anode is delithiated.

[0039] The second stage illustrates an intermediate voltage where the battery is charging and silicon is lithiated, but graphite has not yet reacted. For silicon to be added to a graphite anode, the graphite needs to be lithiated to achieve full battery capacity, so the battery is further charged to the third stage. In the third stage, the battery continues to charge, and the anode voltage is now low enough for silicon to be fully lithiated and graphite to be lithiated. And because the voltage continues to decrease as graphite is lithiated, it decreases to a level where precipitation can occur and dendrites can form, as described above.

[0040] Figures 5A and 5B illustrate the mechanical processes during lithiation and delithiation of a silicon-doped anode and a silicon film anode according to an exemplary embodiment of the present disclosure. Referring to Figure 5A , a schematic diagram of the expansion and contraction of the anode's active material, comprising silicon-doped graphite, is shown. The first window is before lithiation, the second window is after lithiation, and the third window is after delithiation.

[0041] In such conventional silicon-containing anodes, the graphite and silicon materials are typically held together by a soft polymer binder that allows the materials to expand during lithiation, which is a normal process for silicon during lithiation. The silicon is highly or fully lithiated, allowing the graphite of the anode active material to be fully lithiated, thereby achieving full battery capacity, such as Figure 4 As shown in . In silicon-doped graphite anodes, the expansion of fully lithiated silicon is ~300 to 400%, which leads to significant deformation or failure of the binder. In addition, when the active material delithiates, the silicon shrinks, generating tensile stresses, the polymer holding the electrode together fails, and cracks can form in the material.

[0042] The silicon film anode shown in Figure 5B is held together by a strongly conductive matrix and does not use graphite as the active material. Therefore, compared to silicon-graphite anodes, a larger amount of silicon can be used at a lower fraction during lithiation, resulting in less swelling or expansion of the electrode. Furthermore, the nanocoating on the electrode material prevents side reactions. Therefore, due to the reduced expansion and strong conductive matrix, silicon-dominated anodes do not suffer from the cracking issues associated with silicon-graphite anodes.

[0043] Figure 6 1 illustrates the voltage level during charging of a silicon film anode according to an exemplary embodiment of the present disclosure. Figure 6 , showing two different voltage stages for a silicon-dominated anode. Since there is little to no graphite in the anode's active material, the carbon lithiation voltage is not shown here, as there is no graphite lithiation. The upper stage illustrates the anode voltage when the battery is fully discharged, and the anode voltage is at its highest level, above the voltage at which silicon lithiation occurs. During this stage, the anode is delithiated. When the anode is charged, its voltage decreases as silicon lithiation occurs. Since the anode only uses silicon for lithiation, and not all silicon is lithiated for a full charge, the battery is fully charged when the voltage drops to somewhere within the silicon lithiation voltage range (i.e., the voltage does not drop below the lower voltage edge of the silicon lithiation range). Since the anode voltage never drops to or below the lower silicon lithiation voltage, if any carbon is lithiated, lithium precipitation is essentially eliminated. For example, during normal operation, less than 10% of the carbon may be lithiated. In another example, during normal operation, less than 20% of the carbon is lithiated. Furthermore, since a smaller fraction of silicon is lithiated, expansion is reduced, as described above.

[0044] Figure 7 The first cycle voltage profile of the anode half-cell for an exemplary silicon-dominated anode is shown. In this case, the initial lithiation voltage curve is lower than that seen during normal operation because it is the initial charge. Figure 7, shows the voltage profile of a silicon-dominated anode, showing a first charge capacity of the anode of ~3000 mAh / g and an irreversible capacity of the anode of ~250 mAh / g, resulting in an initial coulombic efficiency of 92%. During this initial charge, the anode was charged at a C / 16 rate and the anode voltage was 0.01 V to 1.2 V.

[0045] In exemplary embodiments, silicon film anodes with >70% silicon achieve specific capacities of ~3000 mAh / g (compared to a maximum of 372 mAh / g for graphite) and 1000 to 2000 mAh / g when used in batteries, resulting in volumetric energy densities as high as ~2000 Wh / L and gravimetric energy densities as high as ~350 Wh / kg.

[0046] Figure 8 The electrodes and cell voltage of a battery having a silicon-dominated anode according to an exemplary embodiment of the present disclosure are illustrated. Figure 8 , showing the anode voltage, cathode voltage, and cell voltage versus time for the charge and discharge cycles. The left half of the figure illustrates the charging of the cell, where the cell voltage reaches a maximum of 4.2 V at 45,000 seconds, a C / 10 charge rate for this cell example. The charging process reduces the anode voltage to ~0.1 V. During normal operation of such a cell, due to the high specific capacity of the silicon in the anode, the anode voltage can be maintained within the full range without using the anode, effectively eliminating any lithium precipitation issues while also not completely delithiating the silicon, which would result in greater stress and potential cracking.

[0047] The right half of the graph illustrates a C / 10 discharge of the cell, where the cell voltage drops to ~3.4 V. In this example scenario, the anode cycles between 0.1 V and 0.5 V, the cathode voltage is higher than for the graphite cell, and the cell voltage exhibits a larger slope than for cells containing both silicon and graphite.

[0048] Figure 9 The charge rates of a graphite battery and a silicon-dominated battery according to an exemplary embodiment of the present disclosure are illustrated. Figure 9 , shows a plot of the percentage of full charge versus time for a graphite cell with a silicon-added anode and a cell with a silicon-dominant anode. As shown, when charged at a 10C rate, the graphite cell was still only 50% charged after 30 minutes, while the silicon-dominant anode cell reached 75% charge in just 5 minutes. Even when charged at a 10C rate, the cell still maintained at least 50% of its 1C rate charge retention, reaching 80% of the cell's original capacity.

[0049] These charging curves illustrate the advantages of silicon-dominant anode cells, where a smaller percentage of a larger amount of silicon is lithiated / delithiated during use, compared to a silicon-doped graphite cell where 100% of the smaller amount of silicon is also lithiated in addition to the graphite lithiating. When the material reaches maximum lithiation, the rate at which the material can take on more lithium decreases, which is why silicon-graphite cells must be charged at much lower rates. Because of silicon's much higher specific capacity, and because only a portion of the silicon needs to be lithiated in a silicon-dominant anode, the lithiation rate can remain high until fully charged, greatly increasing the battery's charge rate capability.

[0050] Figure 10 The charge duration of a silicon-dominated battery at low temperatures according to an exemplary embodiment of the present disclosure is illustrated. Figure 10 , shows a plot of the percentage of full charge versus time for a silicon-dominated anode battery at -20°C. As shown in the figure, the battery can achieve a 75% charge in less than 30 minutes, which is slower than room temperature charging but at least still possible without causing lithium precipitation.

[0051] Figure 10 -20°C charging is shown for a silicon-dominant anode battery, not a silicon-graphite battery, because conventional silicon-graphite batteries cannot be charged below 0°C (32°F). If attempted, although the battery pack appears to charge normally, metallic lithium precipitation may occur on the anode during subfreezing charging, which is permanent and cannot be removed by cycling. Advanced chargers will not attempt to charge the battery when the temperature is below freezing because lithium precipitation is dangerous to battery operation.

[0052] Figure 11 The capacity retention of a silicon-dominated battery according to an exemplary embodiment of the present disclosure for different charging temperatures is illustrated. Figure 11 , shows the capacity retention percentage of a silicon-dominant anode cell, where the first bar represents 100% of the initial capacity and the second bar represents the capacity after a charging sequence of 0.3C, 0.7C, 1C, 2C, 3C, 5C, and 7C at 23°C. As can be seen, the cell did not lose any capacity after this sequence. The third bar represents the cell after the same charging sequence but at -20°C. This demonstrates that the disclosed silicon-dominant anode cell can not only be charged below freezing, but also retain its capacity, in contrast to silicon-graphite anode cells that suffer from lithium precipitation when attempted to charge at subfreezing temperatures.

[0053] Figure 12 An exemplary lithiation and delithiation process for a silicon-dominated anode according to an exemplary embodiment of the present disclosure is illustrated. Figure 12, showing the lithiation levels of the cathode and silicon-dominated anode. The cathode lithiation level shows the amount of Δ that can be transferred to the anode during charging. Li , so that the lithiation level of the anode is increased from x D Raised to x C As can be seen from the width of the anode capacity compared to the cathode, a small percentage of the silicon lithiation capacity is used, which is why the charge rate can be so high as mentioned above.

[0054] The anode lithiation level is shown on a scale of 0 to 3.75, where 3.75 represents the fully lithiated phase of silicon, Li 3.75 Si. Amount Δ Li can be a function of the number of charge carriers in the cathode and the cathode discharge cutoff voltage. Therefore, in this example, the lithiation of the anode is controlled by the cutoff voltage and for optimal cycle life it should be kept above x L . Discharge lithiation level x D is the irreversible charge Q of the anode and cathode irr,阳极 and Q irr,阴极 and the cut-off voltage as a function of the charge lithiation level x C is a function of the number of charge carriers in the material.

[0055] The large lithiation capacity of the silicon anode enables the configuration of the anode voltage during discharge to be well above the precipitation threshold voltage. Figure 12 The example shown in illustrates an anode lithiated solely by the cathode, but pre-lithiation of the anode can also be used to ensure that the lithiation level does not drop below x L , and has nothing to do with the discharge voltage.

[0056] Figure 13 1 illustrates a voltage profile of a lithium-ion battery having a silicon-dominated anode according to an exemplary embodiment of the present disclosure. Figure 13 , the voltage profiles for the anode and cathode are shown, and the vertical line with the arrow represents the full cell voltage, and the resulting cell capacity in ampere-hours is shown on the x-axis for these different full cell voltages.

[0057] In this example, the total charge capacity of the cathode is half the total capacity of the anode. During discharge, the cell voltage can be controlled so that the amount of lithium remaining in the anode is above a critical amount x L , such as about Figure 12For this particular battery, the battery capacity at 2.7V is 5.963mAh, the battery capacity at 3.1V is 4.55mAh, corresponding to 76.4% of the total capacity, the battery capacity at 3.2V is 3.638mAh, corresponding to 61.0% of the total capacity, and the battery capacity at 3.3V is 3.136mAh, corresponding to 52.6% of the total capacity.

[0058] As mentioned above, this silicon-dominated anode configuration allows the anode voltage to be maintained well above the voltage at which lithium deposition occurs in the anode, thereby greatly increasing the battery's service life. Furthermore, because the anode's capacity is very high due to the silicon and the silicon utilization can be kept low, the feasible charge rate is much higher than that of a silicon-graphite anode, and low-temperature charging is also possible, as mentioned above.

[0059] Figure 14 The process of using a silicon-dominated anode cell according to an exemplary embodiment of the present disclosure is illustrated. Figure 14 The process begins at step 1401, where a silicon-dominated anode is combined with a cathode and electrolyte to form a battery (battery / cell). In step 1403, the battery can be charged to lithiate a portion of the silicon in the anode so that the silicon is not fully lithiated, and the anode voltage is configured to remain above a minimum voltage for silicon lithiation. In step 1405, the battery can be discharged, and in step 1407, if the battery voltage is still acceptable, i.e., there is remaining battery life, the process repeats step 1403, if not, the battery ends at step 1409.

[0060] In an exemplary embodiment of the present disclosure, methods and systems are described for silicon-dominated lithium-ion batteries with controlled silicon use. The battery may include a cathode, an electrolyte, and an anode, the anode having an active material comprising greater than 50% silicon. The battery may be charged by lithiating the silicon without lithiating the carbon or without the carbon being lithiated (i.e., the carbon is not lithiated). The active material may comprise greater than 70% silicon. During discharge of the battery, the voltage of the anode may be maintained above the minimum voltage at which the silicon can be lithiated. The anode may have a specific capacity greater than 3000mAh / g. The battery may have a specific capacity greater than 1000mAh / g. The anode may have an initial coulombic efficiency greater than 90%. The anode active material may be free of polymer binders. The battery may be operated to charge at a 10C rate or higher while maintaining a 1C rate charge retention of at least 50% to 80% of the battery's original capacity. The battery may be charged at temperatures below freezing without lithium precipitation. The electrolyte may include a liquid, solid, or gel

[0061] As used herein, the terms "circuits" and "circuitry" refer to physical electronic components (i.e., hardware), as well as any software and / or firmware ("code") that can configure, be executed by, and / or otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may include a first "circuit" when executing one or more lines of code for the first, and may include a second "circuit" when executing one or more lines of code for the second. As used herein, "and / or" means any one or more items in a list connected by "and / or". As an example, "x and / or y" means any element in a three-element set {(x), (y), (x, y)}. In other words, "x and / or y" means "one or both of x and y". As another example, "x, y, and / or z" means any element in a seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, "x, y, and / or z" means "one or more of x, y, and z." As used herein, the term "exemplary" means serving as a non-limiting example, instance, or illustration. As used herein, the terms "e.g.," and "for example," introduce a list of one or more non-limiting examples, instances, or illustrations. As used herein, a circuit or device is "operable" to perform a function whenever it includes the necessary hardware and code (if necessary) to perform the function, regardless of whether performance of the function is disabled or not enabled (e.g., by a user-configurable setting, a factory trim, etc.).

[0062] Although the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt specific situations or materials to the teachings of the present invention without departing from the scope of the invention. Therefore, the present invention is not intended to be limited to the specific embodiments disclosed, but rather the present invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A battery, comprising: a cathode, an electrolyte, and an anode having an active material comprising more than 70% by weight of silicon and free of graphite, wherein the battery is fully charged by lithiating the silicon but not all of the silicon while not lithiating the carbon, wherein the anode is pre-lithiated such that the lithiation level of the anode does not drop below a critical amount that is independent of the discharge voltage, and The anode has an initial coulombic efficiency greater than 90%.

2. The battery of claim 1 , wherein during discharge of the battery, the voltage of the anode remains above the minimum voltage at which silicon can be lithiated.

3. The battery of claim 1, wherein the anode has a specific capacity greater than 3000 mAh / g.

4. The battery of claim 1, wherein the battery has a specific capacity greater than 1000 mAh / g.

5. The battery of claim 1, wherein the anode active material is free of polymer binder.

6. The battery of claim 1, wherein the battery is operable to be charged at a 10C rate or higher while maintaining a 1C rate charge retention of at least 50% to 80% of the original capacity of the battery.

7. The battery of claim 1, wherein the battery can be charged at subfreezing temperatures without lithium precipitation.

8. The battery of claim 1, wherein the electrolyte comprises a liquid, a solid, or a gel.

9. A method of forming a battery, the method comprising: In a battery comprising a cathode, an electrolyte, and an anode, the anode having an active material comprising greater than 70% by weight silicon and free of graphite: The battery is fully charged by lithiating the silicon but not all of the silicon while not lithiating the carbon, wherein the anode is pre-lithiated so that the lithiation level of the anode does not decrease below a critical amount that is independent of the discharge voltage, The anode has an initial coulombic efficiency greater than 90%.

10. The method of claim 9, comprising configuring the voltage of the anode during discharge of the battery to be above a minimum voltage at which silicon can be lithiated.

11. The method of claim 9, wherein the anode has a specific capacity greater than 3000 mAh / g.

12. The method of claim 9, wherein the battery has a specific capacity greater than 1000 mAh / g.

13. The method of claim 9, wherein the anode active material is free of polymer binder.

14. The method of claim 9, comprising charging the battery at a 10C rate or higher.

15. The method of claim 9, comprising charging the battery at subfreezing temperatures without lithium precipitation.

16. An anode for a battery, the anode comprising an active material comprising greater than 70 wt. % silicon and free of graphite, wherein the anode is fully charged when in the battery by lithiating the silicon without lithiating all of the silicon and without lithiating the carbon, wherein the anode is pre-lithiated such that the lithiation level of the anode does not drop below a critical amount that is independent of the discharge voltage, and The anode has an initial coulombic efficiency greater than 90%.

Images