WO2014186455A1

WO2014186455A1 - Negative electrode for lead-acid battery

Info

Publication number: WO2014186455A1
Application number: PCT/US2014/037987
Authority: WO
Inventors: Enders Dickinson; Michael Romeo
Original assignee: Axion Power International Inc.
Priority date: 2013-05-14
Filing date: 2014-05-14
Publication date: 2014-11-20
Also published as: WO2014186455A9

Abstract

A negative electrode comprising lead oxide and a naphthalene sulfonate polymer dispersant or a derivative or a structural analog thereof.

Description

NEGATIVE ELECTRODE FOR LEAD-ACID BATTERY

This PCT international application claims priority to U.S. provisional application 61/823, 1 12, filed on 14 May 2013, and to U.S. provisional application 61/823,991 , filed on 16 May 2013, both filed in the U.S. Patent and Trademark Office.

I. TECHNICAL FIELD

The present invention is directed to a negative electrode and to a battery manufactured with particular classes and loadings of negative electrode additives (e.g., glass frit, carbon additive, and synthetic dispersant).

II. BACKGROUND OF INVENTION

Various batteries exist for use in automobiles, such as lead-acid batteries. With regard to conventional automobiles (e.g., combustion engine automobiles), related conventional lead-acid batteries generally do not exhibit good charge characteristics (also referred to as charge acceptance). More specifically, lead-acid batteries in conventional automobiles are used to start the automobile at an origination point (starting point), after which time the lead-acid batteries serve only to stabilize voltage of the power net in the vehicle until the vehicle arrives at a destination point. As a result, conventional lead-acid batteries generally perform only one single charge/discharge cycle per trip in conventional (e.g., combustion engine) automobiles.

Electric vehicles, such as hybrid electric vehicles (HEVs), micro hybrid electric vehicles

(μΗΕΝ/ε), and plug-in hybrid electric vehicles (PHEVs) continue to increase in popularity as an alternative to conventional internal combustion engine vehicles. Electric vehicle technology is heavily reliant on related battery technology and battery performance.

With regard to battery performance and electric vehicles, batteries for micro-hybrid vehicles require significantly higher charge characteristics when compared with conventional automobiles. Micro-hybrid vehicles are generally designed such that the engine is shut off when the vehicle comes to a stop, regardless of whether that stop is a stop at the final destination point, or the stop is one of several intermittent stop(s) between the origination and final destination (e.g., stop at a traffic light, stop at a pedestrian crossing). The engine is then restarted immediately before the micro-hybrid vehicle begins moving again. Therefore, during a trip where there are, for example, 2, 3, 4, 5...or "x" number of traffic stops between the origination and destination point, micro-hybrid vehicle engines will have to stop and re-start at least "x" number of times more than a conventional automobile. For each start/stop operation during a trip, the lead-acid battery for micro-hybrid vehicles is forced to discharge for the length of time that the engine is off to provide support for electrical loads in the vehicle, and then charge again at a high rate to re-start the engine. As referenced above, this discharge-charge process can often be repeated numerous times during a single trip in a hybrid electric vehicle, as opposed to only once in a conventional vehicle.

In view of the foregoing, lead-acid batteries capable of withstanding prolonged and repeated charge-discharge processes are desirable, particularly with regard to the high battery demands of hybrid and especially micro-hybrid vehicles.

III. SUMMARY OF INVENTION

A negative electrode is described herein. Negative electrodes of the present invention include lead oxide and a naphthalene sulfonate polymer dispersant or a derivative thereof. A method of making a negative electrode is also provided herein. The method includes mixing lead oxide, a naphthalene sulfonate polymer dispersant or derivative thereof, water, and an acid to form a paste. The paste can be placed onto a grid to form a negative electrode.

IV. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of a DCA (Dynamic Charge Acceptance) cycle test.

FIG. 2 illustrates cycling voltage/current/time profiles using the Dynamic Overcharge PSOC algorithm for a standard VARTA® VRLA battery manufactured by VARTA AG, owned by Johnson Controls Hybrid and Recycling GmbH Corporation (RIGHT) versus the enhanced negative electrode formulation battery of the present invention (LEFT) at 80% SOC.

FIG. 3 illustrates fractured negative electrode paste pellets from batteries cycled on the dynamic overcharge algorithm (5,000 cycles). FIG. 4 illustrates fractured negative electrode paste pellets from batteries cycled on the dynamic overcharge algorithm (20,000 cycles).

FIG. 5 illustrates a typical 12 hour charge curve for a negative electrode formulation battery according to one embodiment of the present invention versus a carbon additive battery.

FIG. 6 illustrates results of water loss testing for a negative electrode formulation battery according to one embodiment of the present invention versus a carbon additive battery. FIG. 7 illustrates an example of a current profile for a 900A EN-CCA test algorithm.

FIG. 8 illustrates 725A Cold Crank data for a negative electrode formulation battery according to one embodiment of the present invention (thick line trace) versus carbon additive battery (thin line trace).

FIG. 9 illustrates dynamic cycling results for an enhanced negative electrode formulation battery according to one embodiment of the present invention (TOP) versus a traditional dispersant battery (BOTTOM).

FIG. 10 illustrates dynamic cycling results for a battery with no glass additive (LEFT) and with glass additive (RIGHT).

FIG. 11 illustrates results from four batteries cycled on a DCA test.

FIG. 12 illustrates results from four batteries tested on an EN-CCA crank algorithm. V. DETAILED DESCRIPTION OF INVENTION

As used herein "substantially", "relatively", "generally", "about", and "approximately" are relative modifiers intended to indicate permissible variation from the characteristic so modified. They are not intended to be limited to the absolute value or characteristic which it modifies but rather approaching or approximating such a physical or functional characteristic.

In the following detailed description, references to "one embodiment", "an embodiment", or "in embodiments" mean that the feature being referred to is included in at least one embodiment of the invention. Moreover, separate references to "one embodiment", "an embodiment", or "embodiments" do not necessarily refer to the same embodiment; however, neither are such embodiments mutually exclusive, unless so stated, and except as will be readily apparent to those skilled in the art. Thus, the invention can include any variety of combinations and/or integrations of the embodiments described herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms, "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the root terms "include" and/or "have", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of at least one other feature, integer, step, operation, element, component, and/or groups thereof. It will be appreciated that as used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus.

It will also be appreciated that as used herein, and unless expressly stated to the contrary, "or" refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Micro-hybrid vehicles generally require significantly higher charging characteristics compared to conventional automobiles, as described above. As a result, lead-acid batteries capable of withstanding prolonged and repeated charge-discharge processes would be beneficial, particularly with regard to the significantly increased demands of charge/discharge relating to micro-hybrid vehicles.

The objective of a battery is to store and release energy at a desired time and in a controlled manner. Batteries contain a positive electrode, a negative electrode, and an electrically insulating and ion conductive electrolyte in between. The positive electrode carries a higher potential than the negative electrode. While the battery is charging, the positive electrode operates as an anode carrying out a reduction reaction; and the negative electrode operates as a cathode carrying out an oxidation reaction. During battery discharge, the reactions are reversed and the positive and negative electrodes operate as the cathode and anode, respectively.

In the case of lead-acid batteries, one significant limiting factor with regard to partial state-of- charge cycle life can be attributed to a steady increase in negative electrode lead sulfate crystal size, which in turn lowers its solubility and impedes recharge. When charging begins, Pb⁺² (lead) ions are reduced (via reduction reaction) to form lead on the negative electrode. As charging continues, the amount of available Pb⁺² ions is depleted and needs to be replenished by the dissolution of PbSCU (lead sulfate). The rate of this process is heavily dependent on the size (e.g., solubility) of the lead sulfate crystals.

If the charge rate is high and/or prolonged, the negative electrode becomes highly polarized (insufficient Pb²⁺ ion available), and the voltage of the negative electrode decreases dramatically, which in turn increase the overall battery voltage. This rise in voltage then leads to a decreasing charge acceptance and increasing charge time that becomes exponentially worse as the lead sulfate crystals continue to grow during PSOC (partial state of charge) cycling. This limiting process reduces the overall effectiveness of the battery in PSOC applications as the efficiency of such systems degrade over time.

For example, a micro-hybrid vehicle with a lead-acid battery will not be capable of sustaining the initial miles per gallon (MPG) performance obtainable when the battery is new compared to just a few months later when the lead sulfate crystals are larger and less soluble. The reduced charge acceptance requires that the battery be charged longer and therefore the battery will spend more time charging and less time supporting the loads while the engine is off.

One traditional approach for increased PSOC (partial stage of charge) performance using a negative plate additive involves simply adding a carbon material to the existing negative paste formulation (said existing negative paste formulation typically including lead oxide,

lignosulfonate, and barium sulfate).

Although the addition of carbon remains a widely used method of negative electrode additive modification, the presence of carbon in the negative electrode can result in significant performance degradation with respect to many aspects of battery performance, and with only a very minor improvement in charge acceptance. Because carbon materials have a low density, their addition to the negative active material (NAM) via weight percent displaces critical amounts of lead by volume, resulting in a severe reduction in cranking capacity. Carbon additive batteries have also been shown to exhibit magnified gassing rates due to carbon's lowering effect on the cell's hydrogen over-potential. In comparison, as described below, the present invention functions more similarly to an unmodified lead-acid battery than does the state-of-the- art carbon additive battery.

To overcome this rapid shortage of lead ion and other deficiencies in conventional lead-acid batteries, the inventors have unexpectedly discovered two paste additives that can act as a replacement for or in some instances, in addition to, traditional additives. The two paste additives: (1 ) a synthetic dispersant derived from naphthalene sulfonate polymer; and (2) glass frit, can work together to drastically modify the rate of lead sulfate crystal growth and dissolution. Accordingly, the present invention involves the addition of a synthetic dispersant derived from naphthalene sulfonate polymer to the lead oxide of the negative electrode paste mix. In certain embodiments, a glass frit can also be added to the lead oxide of the negative electrode paste mix with the synthetic dispersant derived from naphthalene sulfonate polymer. Moreover, it will be appreciated that in cases where it is desired, it is possible to retain the use of carbon additives in place of the glass frit and still realize the benefit of the naphthalene sulfonate polymer (or derivative or structural analog thereof) despite potential performance loss in other areas (cranking, end-of-charge current - as described below). This combination represents a variation of the primary embodiment, as well as combinations of the dispersant with other similar materials that provide a charge acceptance improvement. Suitable carbon additives include, but are not limited to, carbon black, graphite, and activated carbon.

As with many additive formulation-based batteries, certain performance characteristics in addition to charge acceptance are often affected. The glass additive displaces a portion of NAM resulting in less NAM per plate and it introduces a very small amount of impurities due to the chemical composition of the glass— thus weakening certain VRLA performance characteristics such as cold cranking power and end-of-charge current. However, these changes are much less severe when compared to the current state-of-the-art additive approach for increased PSOC performance via a negative plate additive, which is simply adding a carbon material to the existing negative paste formulation (typically lead oxide, lignosulfonate, and barium sulfate).

Accordingly, embodiments of the present invention are directed to a negative electrode manufactured with particular classes and loadings of negative electrode additives and batteries including said negative electrode. The inventors have unexpectedly discovered that certain particular classes of loadings of negative electrode additives, as described herein, inter alia, enhance lead sulfate solubility of said negative electrode.

As a result, the useful life cycle and useful product life cycle of negative electrodes according to present invention, and batteries including said negative electrodes are unexpectedly and significantly extended, while maintaining sufficient cranking performance and adequate water loss when cycled in Partial State-of-Charge (PSOC or PsOC) applications, such as with regard to micro-hybrid vehicles. More specifically, negative electrode formulations according to the present invention include lead oxide and a synthetic dispersant comprising a naphthalene sulfonate polymer or a derivative or a structural analog thereof. Negative electrode formulations according to the present invention can also include a carbon additive or glass frit. The quantity of carbon additive or the quantity of glass frit can range from 1.0 wt. % to 5.0 wt. % (wt. % = weight percent), relative to the weight amount of lead oxide present in the negative electrode. The quantity of synthetic dispersant in embodiments of the present invention can range from 0.05 wt. % to 1.0 wt. %, relative to the weight amount of lead oxide present in the negative electrode. With regard to the quantity of glass frit, or the quantity of carbon additive, in terms of ranges, the quantity of glass frit, or the quantity of carbon, relative to the weight amount of lead oxide present can range from 1.0 to 5.0 wt. %, such as from 1.1 to 5.0 wt. %, from 1.2 to 5.0 wt. %, from.3 to 5.0 wt. %, from 1.4 to 5.0 wt. %, from 1.5 to 5.0 wt. %, from 1.6 to 5.0 wt. %. from 1.7 to 5.0 wt. %, from 1.8 to 5.0 wt. %, from 1.9 to 5.0 wt. %, from 2.0 to 5.0 wt. %, from 2.1 to 5.0 wt. %, from 2.2 to 5.0 wt. %, from 2.3 to 5.0 wt. %, from 2.4 to 5.0 wt. %, from 2.5 to 5.0 wt. %, from 2.6 to 5.0 wt. %, from 2.7 to 5.0 wt. %, from 2.8 to 5.0 wt. %, from 2.9 to 5.0 wt. %, from 1.0 to 4.9 wt. %, from 1.0 to 4.8 wt. %, from 1.0 to 4.7 wt. %, from 1.0 to 4.6 wt. %, from 1.0 to 4.5 wt. %, from 1.0 to 4.4 wt. %, from 1.0 to 4.3 wt. %, from 1.0 to 4.2 wt. %, from 1.0 to 4.1 wt. %, from 1.0 to 4.0 wt. %, from 1.0 to 3.9 wt. %, from 1.0 to 3.8 wt. %, from 1.0 to 3.7 wt. %, from 1.0 to 3.6 wt. %, from 1.0 to 3.5 wt. %, from 1.0 to 3.4 wt. %, from 1.0 to 3.3 wt. %, from 1.0 to 3.2 wt. %, from 1.0 to 3.1 wt. %, from 1.0 to 3.0 wt. %, from 1.0 to 2.9 wt. %, from 1.0 to 2.8 wt. %, from 1.0 to 2.7 wt. %, from 1.0 to 2.6 wt. %, from 1.0 to 2.5 wt. %, from 1.0 to 2.4 wt. %, 1.0 to 2.3 wt. %, from 1.0 to 2.2 wt. %, from 1.0 to 2.1 wt. %, from 1.0 to 2.0 wt. %, from 1.1 to 4.8 wt. %, from 1.2 to 4.7 wt. %, from 1.3 to 4.6 wt. %, from 1.4 to 4.5 wt. %, from 1.5 to 4.5 wt. %, from 1.6 to 4.5 wt. %, from 1.7 to 4.5 wt. %, from 1.8 to 4.5 wt. %, from 1.9 to 4.5 wt. %, from 2.0 to 4.5 wt. %, from 2.1 to 4.5 wt. %, from 2.2 to 4.5 wt. %, from 2.3 to 4.5 wt. %, from 2.4 to 4.5 wt. %, from 2.4 to 4.5 wt. %, from 2.5 to 4.5 wt. %, from 1.5 to 2.0 wt. %, from 1.5 to 2.1 wt. %, from 1.5 to 2.2 wt. %, from 1.5 to 2.3 wt. %, from 1.5 to 2.4 , from 1.5 to 2.5 wt. %, from 1.5 to 2.7 wt. %, from 1.5 to 3.0 wt. %, from 2.0 to 5.0 wt. %, from 2.1 to 5.0 wt. %, from 2.2. to 5.0 wt. %, from 2.3 to 5.0 wt. %, from 2.4 to 5.0 wt. %, 2.5 to 5.0 wt. %, from 2.5 to 4.9 wt. %, from 2.5 to 4.8 wt. %, from 2.5 to 4.7 wt. %, from 2.5 to 4.6 wt. %, from 2.5 to 4.5 wt. %, from 2.4 to 4.5 wt. %, from 2.4 to 4.5 wt. %, from 2.3 to 4.5 wt. %, from 2.2 to 4.5 wt. %, from 2.1 to 4.5 wt. %, from 2.4 to 4 wt. %. from 3.0 to 5.0 wt. %, from 3.0 to 4.9 wt. %, from 3.0 to 4.8 wt. %, from 3.0 to 4.7 wt. %, from 3.0 to 4.6 wt. %, from 3.0 to 4.5 wt. %, from 3.1 to 4.9 wt. %, or from 3.2 to 4.9 wt. %, relative to the weight amount of lead oxide present.

In terms of lower limits, the quantity of glass frit, or the quantity of carbon additive, relative to the weight amount of lead oxide can be in an amount of at least 1.0 wt. % relative to the amount of lead oxide present, such as at least 1.1 wt. %, at least 1.2 wt. %, at least 1.3 wt. %, at least 1.4 wt. %, at least 1.5 wt. %, at least 1.6 wt. %, at least 1.7 wt. %, at least 1.8 wt. %, at least 1.9 wt. %, at least 2.0 wt. %, at least 2.1 wt. %, at least 2.2 wt. %, at least 2.3 wt. %, at least 2.4 wt. %, at least 2.5 wt. %, at least 2.6 wt. %, at least 2.7 wt. %, at least 2.8 wt. %, at least 2.9 wt. %, or at least 3.0 wt. %, relative to the weight amount of lead oxide present.

In terms of upper limits, the quantity of glass frit, or the quantity of carbon additive, relative to the weight amount of lead oxide present in the negative electrode can be in an amount of no greater than 5.0 wt. %, such as no greater than 4.9 wt. %, no greater than 4.8 wt. %, no greater than 4.7 wt. %, no greater than 4.6 wt. %, no greater than 4.5 wt. %, no greater than 4.4 wt. %, no greater than 4.3 wt. %, no greater than 4.2 wt. %, no greater than 4.1 wt. %, or no greater than 4.0 wt. %, relative to the weight amount of lead oxide present. With regard to the quantity of synthetic dispersant, the amount of synthetic dispersant can range from 0.05 wt. % to 1.0 wt. %, relative to the weight amount of lead oxide present in the negative electrode, such as from 0.05 wt. % to 0.9 wt. %, from 0.05 wt. % to 0.8 wt. %, from 0.05 wt. % to 0.7 wt. %, from 0.05 wt. % to 0.6 wt. %, from 0.05 wt. % to 0.5 wt. %, from 0.05 wt. % to 0.4 wt. %, from 0.05 wt. % to 0.3 wt. %, from 0.05 wt. % to 0.2 wt. %, from 0.05 wt. % to 0.10 wt. %, from 0.05 wt. % to 0.09 wt. %, from 0.05 wt. % to 0.08 wt. %, from 0.06 to 1.0 wt.5, from 0.07 to 1.0 wt. %, from 0.08 to 1.0 wt. %, from 0.09 to 1.0 wt. %, from 0.10 to 1.0 wt. %, from 0.11 to 1.0 wt. %, from 0.12 to 1.0 wt. %, from 0.13 to 1.0 wt. %, from 0.14 to 1.0 wt. %, from 0.15 to 1.0 wt. %, from 0.16 to 1.0 wt. %, from 0.17 to 1.0 wt. %, from 0.18 to 1.0 wt. %, from 0.19 to 1.0 wt. %, or from 0.20 to 1.0 wt. %, relative to the weight amount of lead oxide present in the negative electrode.

In terms of lower limits, the quantity of synthetic dispersant, relative to the weight amount of lead oxide can be at least 0.05 wt. %, such as at least 0.06 wt. %, at least 0.07 wt. %, at least 0.08 wt. %, at least 0.09 wt. %, at least 0.10 wt. %, at least 0.1 1 wt. %, at least 0.12 wt. %, at least 0.13 wt. %, at least 0.14 wt. %, at least 0.15 wt. %, at least 0.16 wt. %, at least 0.17 wt. %, at least 0.18 wt. %, at least 0.19 wt. %, at least 0.20 wt. %, at least 0.21 wt. %, at least 0.22 wt. %, at least 0.23 wt. %, at least 0.24 wt. %, at least 0.25 wt. %, at least 0.26 wt. %, at least 0.27 wt. %, at least 0.28 wt. %, at least 0.29 wt. %, at least 0.30 wt. %, or at least 0.31 wt. %, relative to the weight amount of lead oxide present in the negative electrode.

In terms of upper limits, the quantity of synthetic dispersant, relative to the weight amount of lead oxide can be no greater than 1.0 wt. %, such as no greater than 0.90 wt. %, no greater than 0.80 wt. %, no greater than 0.70 wt. %, no greater than 0.60 wt. %, no greater than 0.50 wt. %, and no greater than 0.40 wt. %, relative to the weight amount of lead oxide present in the negative electrode.

Suitable carbon additives for the present invention include, but are not limited to, carbon black, graphite, and activated carbon. Suitable glass frit according to the present invention can be in fiber or powder form.

The addition of the above-described additive materials (synthetic dispersant, glass frit, and/or carbon additive) according to the present invention allow for improved charge acceptance and cycle life by, for example: (1 ) creating acid reservoirs/pathways in the negative active material (NAM) which minimize the need for excessive ion migration, thereby maximizing NAM utilization; and (2) managing lead sulfate growth to maintain small, highly soluble lead sulfate crystals which are more readily dissolved compared to the crystals formed in a standard negative electrode during PSOC operation.

Embodiments of the present invention also demonstrate, inter alia: (1 ) increased solubility; (2) improved charge acceptance; (3) a significant decrease in charge time; (4) substantially increased NAM (negative active material) utilization; (5) lower end of charge currents; (6) decreased rate of water loss; (7) improved cold crank performance; and (8) improved acid penetration and reduced lead sulfate size.

Embodiments of the present invention will now be described below with reference to the drawings. For convenience, the following abbreviations are contained herein: EODV: End of Discharge Voltage

PDRV: Post Discharge Rest Voltage

TOCV: Top of Charge Voltage

TOC: Top of Charge

PCRV: Post Charge Rest Voltage

SP: Set Point

EN-CCA: European testing algorithm for cold cranking amps

VRLA: Valve Regulated Lead Acid

DCA: Dynamic Charge Acceptance

PSOC or PsOC: Partial State-of-Charge

Ah: ampere-hour

NAM: negative active material

CCA: cold cranking amps or cold cranking amperes

VDA: German Association of the Automotive Industry (German: Verband der

Automobilindustrie e. V.)

AGM: absorbent glass mat

FIG. 1 illustrates a schematic diagram of a Dynamic Charge Acceptance ("DCA") cycle test. The Dynamic Charge Acceptance (DCA) test of FIG. 1 is performed on lead-acid batteries using battery testing equipment and circuits, such as those available from Arbin Instruments. In the Dynamic Charge Acceptance (DCA) test, a programmable logic controller-based algorithm, herein a "dynamic overcharge" algorithm, is used to evaluate the Partial State-of-Charge (PSOC or PsOC) cycling performance for a variety of lead-acid batteries. Per the dynamic overcharge algorithm, the amount of overcharge is determined for each cycle based on a specific post discharge rest voltage (PDRV) prior to the charge during each cycle. If the State-Of-Charge (SOC) of the battery is decreasing based on the rest voltage, the ampere- hour (Ah) input is increased for the subsequent charge step. If the opposite is true, the Ah input is decreased. For the DCA test of FIG. 1 , the crank is accomplished by discharging at 200A for 1.5 seconds (equivalent to 300 A s).

FIG. 2 illustrates cycling results using the above-described dynamic overcharge algorithm for two Valve Regulated Lead-Acid (VRLA) batteries. VLRA batteries can have several features, including but not limited to: (1 ) gases generated during charging (by, for example, electrolysis of water) are recombined internally; (2) the sulfuric acid electrolyte is immobilized (e.g., per a separator or a gel); and (3) each cell (a cell being a single unit having a voltage which is characteristic of the battery system, whereby a battery can have one or more cells, generally connected in a series) has a re-sealable valve capable of venting gases to the atmosphere if the internal pressure exceeds a certain level.

The two VRLA batteries subjected to the tests corresponding to FIG. 2 are:

1. A standard premium 12V VARTA® L5 Value Regulated Lead-Acid (VRLA) battery

manufactured by VARTA AG, owned by Johnson Controls Hybrid and Recycling GmbH

Corporation; and

2. A 12V AXION® L5 VRLA battery with an enhanced negative electrode formulation, according to the present invention.

a. The enhanced negative electrode formulation according to the present invention, as tested with regard to FIG. 2, includes a carbon additive in an amount ranging from 1.0 to 5.0 wt. % based on the weight amount of lead oxide present in the electrode. Glass frit is not present in this formulation.

Results for the standard VRLA battery results are illustrated on the RIGHT in FIG. 2, whereas the results for the VRLA battery according to the present invention are illustrated on the LEFT in FIG. 2.

As can be observed in FIG. 2, the battery according to the present invention clearly

demonstrates an enhanced negative electrode formulation, resulting, inter alia, in a superior and distinct improvement in terms of charge acceptance.

More specifically, the enhanced negative electrode of the present invention demonstrates an increase of about 630% charge acceptance after about 22,000 cycles, or approximately two years of equivalent micro-hybrid vehicle operation. The enhanced negative electrode of the present invention also demonstrates a decrease of about 60% of charge time after the same number of cycles/equivalent micro-hybrid vehicle operation. As illustrated in FIG. 2, the negative electrode formulation of the present invention also results in a VRLA battery that provides: (1 ) significantly higher charge acceptance (current at end of charge step: 30A vs. 4A); (2) a faster charge time (70 seconds vs. 180 seconds); and (3) a longer useful cycle life (greater than 21 ,000 cycles vs. about 600 cycles, whereas "useful" is defined herein as a charge time less than 2x the initial charge time at the start of cycling) when compared to the standard VARTA® VRLA battery.

Without wishing to be bound by theory, it is believed that the significant improvement and superior findings are a result of the particular negative paste formulation containing lead oxide, glass frit, and a synthetic dispersant derived from naphthalene sulfonate polymer.

FIG. 3 illustrates fractured negative electrode paste pellets from batteries cycled for 5,000 cycles on the dynamic overcharge algorithm. As referenced above, embodiments of the present invention allow for improved charge acceptance and cycle life by: (1 ) creating acid

reservoirs/pathways in the negative active material (NAM) which minimize the need for excessive ion migration, thereby maximizing NAM utilization; and (2) managing lead sulfate growth to maintain small, highly soluble lead sulfate crystals which are more readily dissolved compared to the crystals formed in a standard negative electrode during PSOC operation.

As such, the discolored edges of the paste in FIG. 3 represent NAM utilization. The image on the LEFT represents results for an enhanced negative electrode of the present invention; and the image on the RIGHT represents results for a standard lead-acid battery. The enhanced negative electrode of the present invention includes a carbon additive in an amount ranging from 1 .0 to 5.0 wt. % based on the weight amount of lead oxide present in the electrode. Glass frit is not present in this formulation. The negative electrode of the present invention

demonstrates approximately 80% NAM utilization, whereas the standard lead-acid battery demonstrates a remarkably lower 25% NAM utilization.

FIG. 4 illustrates fractured negative electrode paste pellets from batteries cycled on the dynamic overcharge algorithm (20,000 cycles). The image on the LEFT represents an enhanced negative electrode of the present invention, whereas the image on the RIGHT represents a standard lead-acid battery. The enhanced negative electrode of the present invention includes a carbon additive in an amount ranging from 1 .0 to 5.0 wt. % based on the weight amount of lead oxide present in the electrode. Glass frit is not present in this formulation. The negative electrode of the present invention contains significantly smaller lead sulfate crystals and, thus, much greater solubility than the standard lead-acid battery on the RIGHT.

FIG. 5 illustrates a typical 12 (twelve) hour charge curve for an enhanced negative electrode formulation battery of the present invention, versus a carbon additive battery. The enhanced negative electrode formulation of FIG. 5 includes glass frit in an amount ranging from 1.0 to 5.0 wt. % based on the weight amount of lead oxide present in the electrode. A carbon additive is not present in this formulation. As illustrated in FIG. 5, the carbon additive battery end-of- charge current is more than 4x (four times) higher than the end-of-charge current for the enhanced negative electrode formulation battery of the present invention.

It will be appreciated that a low end-of-charge current can be imperative for extended battery life. During normal micro-hybrid vehicle operation (e.g., engine on) the alternator system provides constant current to the battery to maintain a high state-of-charge in anticipation for the next stop event (and subsequent crank). As such, the battery must self-regulate the current input to a minimal value to avoid excess gassing and eventual dry-out. Carbon additive VRLA batteries have significantly higher end-of-charge currents compared to the enhanced negative electrode formulation batteries due to a lower hydrogen over-potential caused by the carbon, as illustrated in FIG. 5 and referenced above.

With regard to water loss, a standard method for assessing end-of-charge currents and their effect on water loss is outlined and can be found in the VDA AGM test manual AK4.14.AG6 under the sub-heading of "Water Consumption Test at 60 °C". A modified version of this test (six weeks at 14.0V in 60 °C water bath) has been used to compare the water loss performance of the enhanced negative electrode formulation battery of the present invention against the performance of the carbon additive battery, as illustrated in FIG. 6. The enhanced negative electrode formulation of FIG. 6 includes glass frit in an amount ranging from 1.0 to 5.0 wt. % based on the weight amount of lead oxide present in the electrode. A carbon additive is not present in this formulation.

With reference to FIG. 6, there is a significant decrease in the rate of water loss for the enhanced negative electrode formulation battery of the present invention compared to the carbon additive battery. As mentioned previously, carbon acts to lower the hydrogen over- potential of the battery, thereby causing it to electrolyze water at a lower voltage compared to non-carbon modified lead-acid batteries. By avoiding the addition of carbon to realize an improvement in charge acceptance, the enhanced negative electrode formulation battery of the present invention does not show the rapid and catastrophic rate of water loss seen with carbon additive batteries. Cold cranking performance is critical to today's single battery micro-hybrid vehicle architectures. Generally, battery performance decreases with cold temperature and increases with heat to a certain level. CCA (cold cranking amps or cold cranking amperes) specifies the ability to draw high load current at -18°C (0°F) on starter batteries. Different norms specify dissimilar load durations and end voltages.

Cold cranking performance is evaluated with the EN-CCA test algorithm illustrated in FIG. 7 (cited in VDA AGM test manual AK4.14 AG6), which requires that the battery be cooled to -18°C and discharged with a current specific to that battery size (900A for L5 AGM) followed by a successive discharge at 60% of the original current (540A for L5 AGM). The battery must remain above 7.5V during the first step, and voltage should remain above 9V for 20sec during the second step. FIG. 7 illustrates an example of a current profile for 900A En-CCA test algorithm.

With reference to FIG. 8, cold crank data for the enhanced negative electrode formulation of the present invention and a carbon additive battery are illustrated therein at 725A. The enhanced negative electrode formulation of FIG. 8 includes glass frit in an amount ranging from 1.0 to 5.0 wt. % based on the weight amount of lead oxide present in the electrode. A carbon additive is not present in this formulation. The thick line trace of FIG. 8 represents the negative electrode formulation of the present invention. The thin line trace of FIG. 8 represents the carbon additive battery, and the dotted line trace indicates areas where both of the lines (negative electrode of the present invention, and carbon additive battery) overlap. As can be observed from FIG. 8, the addition of carbon significantly reduces the battery's cold crank performance compared to the enhanced negative electrode formulation battery of the present invention. Without wishing to be bound by theory, it is believed that the added carbon detrimentally displaces a significant amount of lead by volume in the NAM. Accordingly, the inventors have found and demonstrated that the addition of glass frit to the

NAM (negative active material) of a VRLA battery can increase charge acceptance and prolong PSOC cycle life similar to that of carbon. Moreover, the addition of this inert glass frit further minimizes the aforementioned negative effects associated with carbon additives as the glass frit is able to mimic the role of carbon in NAM without displacing significant quantities of lead and lowering the hydrogen over-potential.

The inventors have also found and demonstrated that addition of glass frit and a synthetic dispersant derived from naphthalene sulfonate polymer results in unexpectedly and superior improved acid penetration and reduced lead sulfate crystal size, thereby overcoming the voltage limitations of PSOC cycling. The quantity of glass frit ranges from 1.0 wt. % to 5.0 wt. %, relative to the weight amount of lead oxide present, and the quantity of synthetic dispersant can range from 0.05 wt. % to 1.0 wt. %, relative to weight amount of lead oxide present, as referenced above.

Furthermore, it will be appreciated that the level of additive addition can be modified by one of ordinary skill to adequately balance the charge acceptance improvement with the decrease in cranking performance (as well as the other related metrics discussed above). This balance requires both additive types and at particular loadings depending on the balance position and magnitude desired (higher charge acceptance, lower crank; lower charge acceptance, higher crank). It has been determined through dynamic cycling that charge acceptance and cycle life are extremely dependent upon the chemical makeup of the dispersant additive, and not simply on the presence of the glass additive.

FIG. 9 illustrates dynamic cycling results for an enhanced negative electrode formulation according to one embodiment of the present invention (TOP) and results for a traditional dispersant battery (BOTTOM). Both of the batteries contain identical loadings (amounts) of glass and respective dispersants: a naphthalene sulfonate polymer dispersant according to the present invention (TOP); and a carbon material dispersant for the traditional battery (BOTTOM).

As can be observed from FIG. 9, the type of dispersant used in the enhanced negative electrode formulation battery according to the present invention is critical for both charge acceptance and charge time improvement in simulated micro-hybrid cycling. The negative electrode formulation of the present invention demonstrated a charge time of 68.3 s, versus 132.3 s for the traditional battery, an approximate almost 50% advantageous decrease in charge time. The negative electrode formulation of the present invention also demonstrated a TOC (top of charge) current of 33.1 A, versus 14.1 A for the traditional battery, an approximate 135% increase in TOC current from the traditional battery, as illustrated in FIG. 9.

FIG. 10 illustrates dynamic cycling results for two batteries which contain identical loadings (amounts) of synthetic naphthalene sulfonate polymer dispersant according to the present invention. There is no glass frit present in the battery on the LEFT in FIG. 10, whereas the battery on the RIGHT in FIG. 10 does have glass frit additive present, in an amount ranging from 1.0 to 5.0 wt. %, relative to the weight amount of lead oxide present.

As illustrated in FIG. 10, the addition of glass frit can be necessary for optimized performance, as both the glass and synthetic dispersant act together for enhanced charge acceptance and charge time. The glass additive battery on the RIGHT demonstrated a charge time of 68.3 seconds, as opposed to 97.5 seconds for the battery with no glass additive, an approximate 30% improved decrease in charge time. The glass additive battery on the RIGHT also demonstrated a top of charge (TOC) current of 33.1 , compared to 16.7 for the battery with no glass additive, an approximate 98% increase in TOC current.

Due to the unique chemistry inherent to all lead-acid battery products, an important and difficult trade-off exists between charge acceptance and cranking power— both of which are essential for optimum micro-hybrid vehicle operation. It has been demonstrated that as VRLA modifications are carried out in an attempt to increase charge acceptance, a subsequent decline in cranking power can be observed.

FIG. 11 illustrates results from four batteries of the present invention cycled on the DCA test, the results labeled as Optimizations 1 to 4. The batteries of FIG. 11 each have a carbon additive present in an amount ranging from 1.0 to 5.0 wt. %, based on the weight amount of lead oxide present. Incremental additions of synthetic naphthalene sulfonate polymer dispersant according to the present invention are added, beginning with Optimization 1 and ending with Optimization 4. As a result, Optimization 1 contains the lowest weight percent of naphthalene sulfonate polymer dispersant, and Optimization 4 contains the highest weight percent. From this, a progressive and somewhat linear decrease in charge acceptance can be observed starting at Optimization 1 , and progressing to Optimization 4. As the synthetic naphthalene sulfonate polymer dispersant loadings are increased, the charge acceptance steadily decreases.

Conversely, although modifications to increase the amount of naphthalene sulfonate polymer dispersant can be shown to decrease the charge acceptance, the same modifications can be shown to steadily increase cranking performance, as illustrated in FIG. 12.

FIG. 12 illustrates results from four batteries tested on EN-CCA crank algorithm. The batteries of FIG. 12 each have a carbon additive present in an amount ranging from 1.0 to 5.0 wt. %, based on the weight amount of lead oxide present. Similar to the batteries tested in FIG. 11 , incremental additions of synthetic naphthalene sulfonate polymer dispersant according to the present invention are added, beginning with Optimization 1 and ending with Optimization 4. As a result, Optimization 1 contains the lowest weight percent of naphthalene sulfonate polymer dispersant, and Optimization 4 contains the highest weight percent. From this, a progressive and somewhat linear increase in cranking power can be observed starting at Optimization 1 , and progressing to Optimization 4. As the synthetic naphthalene sulfonate polymer dispersant loadings are increased, the cranking power steadily increases. In summary, without wishing to be bound by theory, as negative electrode paste additive modifications are made to a VRLA battery, a direct trade-off can exist between charge acceptance and cranking performance. From these data illustrated in FIGS. 11 and 12, enhanced negative electrode formulation batteries can be designed and manufactured for the required performance levels of both high charge acceptance (optimized: 33A) and high cold cranking power (optimized: 725A).

Methods for making a negative electrode according to the present invention are also described herein. Methods include mixing lead oxide, a naphthalene sulfonate polymer dispersant or derivative or structural analog thereof, water, and acid to form a paste. Methods also include placing the paste onto a grid to form the negative electrode. In certain embodiments, the paste can also include glass frit. In alternate embodiments, the paste can include a carbon additive.

The amount of glass frit, and the amount of carbon additive, which may be present in mixtures correspond to the amounts described above (1.0 to 5.0 wt. %, relative to the weight amount of lead oxide present). The amount of naphthalene sulfonate polymer dispersant or derivative or structural analog thereof which may be present in mixtures also correspond to the amounts described above (0.05 to 1.0 wt. %, relative to the weight amount of lead oxide present). The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

It will be appreciated that not all of the features, components and/or activities described above in the general detailed description in relation to embodiments of the present disclosure or the examples are required, that a portion of a specific feature, component and/or activity may not be required, and that one or more further features, components and/or activities may be required, added or performed in addition to those described. Still further, the orders in which activities are listed are not necessarily the order in which they are performed. Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims.

In the foregoing, reference to specific embodiments and the connections of certain components is illustrative. It will be appreciated that reference to components as being coupled or connected is intended to disclose either direct connection between said components or indirect connection through one or more intervening components as will be appreciated to carry out the methods as discussed herein. As such, the above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true scope of the present invention.

Further, references to values stated in ranges include each and every value within that range, and the endpoints of said ranges. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.

VI. INDUSTRIAL APPLICABILITY

An energy storage device (e.g., a lead-acid battery) is provided having particular classes and loadings of negative electrode additives, which enhance lead sulfate solubility and greatly extend its useful cycle life while maintaining sufficient cranking performance and adequate water loss when cycled in Partial State-of-Charge (PSOC) applications (e.g., Micro-Hybrid Vehicles).

Claims

WHAT IS CLAIMED IS:

1. A negative electrode, comprising:

lead oxide; and

a naphthalene sulfonate polymer dispersant or a derivative thereof.

2. A negative electrode according to Claim 1 further comprising a carbon additive.

3. A negative electrode according to Claim 1 further comprising glass frit.

4. A negative electrode according to Claim 2, characterized in that a quantity of carbon ranges from 1.0 wt. % to 5.0 wt. %, relative to lead oxide, while the quantity of dispersant ranges from 0.05 wt. % to 1.0 wt. %, relative to lead oxide.

5. A negative electrode according to Claim 3, characterized in that a quantity of glass frit ranges from 1.0 wt. % to 5.0 wt. %, relative to lead oxide, while the quantity of dispersant ranges from 0.05 wt. % to 1.0 wt. %, relative to lead oxide

6. A negative electrode according to any one of claims 1 , 3, or 5 comprising no carbon additive.

7. A negative electrode according to any one of claims 1 , 3, or 5 comprising no graphite, carbon black, or activated carbon.

8. A battery comprising at least one negative electrode according to any one of claims 1 , 2, 3, 4, or 5.

9. A lead-acid battery comprising at least one negative electrode according to any one of claims 1 , 2, 3, 4, or 5.

10. A vehicle comprising at least one battery according to Claim 8.

1 1. A hybrid vehicle comprising at least one battery according to Claim 8.

12. A method of making a negative electrode, comprising:

mixing lead oxide, a naphthalene sulfonate polymer dispersant or a derivative thereof, water, and an acid to form a paste; and

placing the paste onto a grid to form the negative electrode.

13. The method of claim 12, further characterized in that the mixing includes glass frit, characterized in that a quantity of glass frit ranges from 1 .0 wt. % to 5.0 wt. %, relative to lead oxide.

14. The method of claim 12, further characterized in that the mixing includes a carbon additive, characterized in that a quantity of carbon ranges from 1 .0 wt. % to 5.0 wt. %, relative to lead oxide.