US007261970B2 (12) United States Patent (10) Patent N0.: US 7,261,970 B2 Young et a]. (45) Date of Patent: Aug. 28, 2007 (54) NICKEL METAL HYDRIDE BATTERY 4,049,027 A 9/1977 Seiger DESIGN 4,609,599 A 9/1986 Percheron et a1. 4,847,174 A * 7/1989 Palmer et al. ..... .. 429/218.2 X (75) Inventors: KWo Young, Troy, MI (US); Cristian 4,935,318 A 6/1990 IkOIIl? et a1~ Fierro, Northville, MI (US); Benjamin 5,032,475 A 7/1991 Hasebe et a1~ Reichman’ West Bloom?eld’ MI (US); 5,131,920 A * 7/1992 Moriwaki et a1. ...... .. 429/60 X Michael A. Fetcenko, Rochester, Ml 5,344,728 A 9/1994 Ovshinsky et 31' (Us); John Koch’ West Bloom?eld, MI 5,348,822 A 9/1994 Ovshinsky et al. (US); Avram Zallen, West Bloom?eld, 5’498’403 A 3/1996 Shln _ MI (Us) 5,523,182 A 6/1996 Ovshinsky et a1. 5,536,591 A * 7/1996 Fetcenko et al. ........... .. 429/59 (73) Assignee: Ovonic Battery Company Inc., i glfzrifzflél Rochester Hills, MI (US) ’ ’ ' ( * ) Notice: Subject to any disclaimer, the term of this (Continued) patent is extended or adjusted under 35 U_S_C_ 154(1)) by 103 days_ Primary ExamineriStephen J. Kalafut (74) Attorney, Agent, or F irmiRobert J. Svoboda; Marvin (21) Appl. No.: 10/887,434 S. Siskind (22) Filed: Jul. 8, 2004 (57) ABSTRACT (65) Pnor Pubhcatlon Data The present invention relates to rechargeable nickel metal US 2005/0238959 A1 Oct. 27, 2005 hydride batteries and methods for making the same. More particularly, the present invention relates to rechargeable Related U-S- Application Data nickel metal hydride batteries having a precharge in the (60) Provisional application NO‘ 60/565 170 ?led on Apr‘ negative electrode su?icient for oxidation prevention in the 23 2004' ’ ’ negative electrode. The present invention discloses a nickel ’ metal hydride battery, Wherein the precharge of the negative (51) Int_ CL electrode may be supplied by a variety of sources. The H01M 4/58 (200601) positive active material of the positive electrode may have H01M 4/62 (200601) positive active particles, such as nickel hydroxide, having a (52) us. Cl. ................... .. 429/60' 429/217- 429/218.2- Precursor Coating that incorporates Cobalt material Capable ’ ’ 429/223’ of forming a condulctive 1rlietvvork. Soilirces Ether tlhain iobialt (58) Fleld. of Classl?catlon. 39/5293’ gencontalmn gas Erovided materia directlys 1nt e Iioos1t1ve the negative e ectro eactive me u magerial,e ro See application ?le for Complete Search ilistolly’ nickel aluminum mixed With the negative active material, ' the etching of the negative active material With an alkaline (56) References Cited solution and borohydride chemically charging the negative active material. Preferably, a majority of the precharge of the U.S. PATENT DOCUMENTS negative electrode is supplied by sources other than cobalt 3,951,686 A 4/1976 Ness et a1. containing materials in the positive electrode. 3,959,018 A 5/1976 Dunlop et a1. 4,004,943 A 1/1977 Boter 23 Claims, 5 Drawing Sheets Mix Cobalt Form Mixture of Hydroxide Powder Cobalt Hydroxide and Combine Mixture with Nickel Nickel Hydroxide with Oxygen Hydroxide Powder 40 42 44 Apply Heat while Form Eneapsulam Mixing Caustic into Layer of Cobalt Mixture Hydroxide on Nickel Hydroxide Particles 46 48 US 7,261,970 B2 Page 2 US. PATENT DOCUMENTS 6,444,349 B1 * 9/2002 Berlureau et a1. .......... .. 429/60 _ 6,593,024 B2* 7/2003 Fetcenko et a1. .. .. 429/60 6,042,753 A 3/2000 IZuIm er 31- 2003/0031923 Al* 2/2003 Aoshima et a1. ...... .. 429/223 X 6,268,083 B1 7/2001 Iida et a1. 6,399,247 B1 * 6/2002 Kitayama et a1. 429/2182 X * cited by examiner U S. Patent Aug. 28, 2007 Sheet 1 0f 5 US 7,261,970 B2 .n. FIG. 1A U S. Patent Aug. 28, 2007 Sheet 2 0f 5 US 7,261,970 B2 FM}. 1 U.S. Patent Aug. 28, 2007 Sheet 3 0f 5 US 7,261,970 B2 PCT @ 30 C for Type B AB5 10000 1000 00.1 atm H2 (Torr)Pressure 100 1 , 0 0.5 1 1.5 About 0.21% precharge Hydrogen wLo/o H/(mM) The precharge was done by maintaining the hydrogen pressure at 0.1 atm. The total precharge amount is about 56 mAh/g. US 7,261,970 B2 1 2 NICKEL METAL HYDRIDE BATTERY at least nickel hydroxide and the encapsulant layer prefer DESIGN ably includes cobalt hydroxide or cobalt oxyhydroxide. TWo primary forms of positive electrodes exist at present CROSS-REFERENCE TO RELATED and include sintered and pasted type electrodes. Sintered APPLICATION electrodes are produced by depositing the active material in the interstices of a porous metal matrix folloWed by sintering The present invention relates to, and is entitled to the the metal. Pasted electrodes are made With nickel hydroxide bene?t of the earlier ?ling date and priority of, US. Provi particles in contact With a conductive netWork or substrate, sional Patent Application No. 60/565,170, ?led Apr. 23, most commonly foam nickel or perforated stainless steel 2004, the disclosure of Which is herein incorporated by coated With nickel. Several variants of these electrodes exist reference. and include plastic-bonded nickel electrodes, Which may utiliZe graphite as a micro-conductor, and pasted nickel ?ber FIELD OF THE INVENTION electrodes, Which utiliZe nickel hydroxide particles loaded onto a high porosity, conductive nickel ?ber or nickel foam. The disclosure relates to rechargeable nickel metal The current trend has been aWay from using sintered elec hydride batteries and methods for making the same. More trodes in favor of pasted electrodes because of cost and particularly, the disclosure relates to rechargeable nickel because pasted electrodes can provide signi?cantly higher metal hydride batteries having a precharge in the negative loading. electrode to prevent oxidation of the negative electrode and Several processes for making positive electrodes are also maintain long cycle life. 20 generally knoWn, see for example US. Pat. No. 5,344,728 issued to Ovshinsky et al., the disclosure of Which is herein BACKGROUND OF THE INVENTION incorporated by reference, Where electrodes having a capac ity in excess of 560 mAh/cc are reported. The particular Rechargeable batteries With high energy density, high process used for making electrodes can have a signi?cant capacity and long cycle life are highly desirable. TWo types 25 impact on the electrode’s performance. For example, con of alkaline rechargeable batteries commonly used are the ventional sintered electrodes may noW be obtained With an Ni4Cd (nickel cadmium) type and the NiiMH (nickel energy density of 480-500 mAh/cc. Sintered positive sub metal hydride) type. In both types of batteries the positive strates are constructed by applying a nickel poWder slurry to electrodes are made With an active nickel hydroxide material a nickel-plated, steel base folloWed by sintering at high While the negative electrodes are di?ferent. 30 temperature. This process causes the individual particles of NiiMH cells operate by a different mechanism than nickel to Weld at their points of contact, resulting in a porous Ni4Cd cells. NiiMH cells utiliZe a negative electrode that material that is approximately 80% open volume and 20% is capable of reversible electrochemical storage of hydrogen, solid metal. The sintered material is then impregnated With hence the term hydrogen storage battery. The negative and active material by soaking it in an acidic solution of nickel positive electrodes are spaced apart in an alkaline electro 35 nitrate, folloWed by conversion to nickel hydroxide in a lyte. Upon application of an electrical potential across a reaction With alkali metal hydroxide. After impregnation, the NiiMH cell, the active material of the negative electrode is material is subjected to electrochemical formation. Pasted charged by the electrochemical absorption of hydrogen and electrodes may be made by mixing various poWders, such as the electrochemical discharge of a hydroxyl ion, as shoWn in nickel hydroxide particles, binders and other additives into equation 1. 40 a slurry and applying the mixture to a conductive grid. Production methods for making nickel hydroxide poWder are generally knoWn and such poWder may be made using a The negative electrode half-cell reactions are reversible. precipitation reaction, such as the one described in US. Pat. Upon discharge, the stored hydrogen is released to form a No. 5,348,822, issued to Ovshinsky et al., the disclosure of Water molecule and release an electron through the conduc 45 Which is herein incorporated by reference. In US. Pat. No. tion netWork into the battery terminal. 5,348,822, Ovshinsky et al describes producing nickel The reactions that take place at the positive electrode of hydroxide material by combining a nickel salt With a the NiiMH cell are shoWn in equation 2. hydroxide to precipitate nickel hydroxide. Like electrode formation, the method for making the nickel active material 50 can have a signi?cant impact on properties and performance The use of nickel hydroxide as a positive active material of the electrode. for NiiMH batteries is generally knoWn. See for example, Nickel hydroxide material should have high capacity and US. Pat. No. 5,523,182, issued Jun. 4, 1996 to Ovshinsky et long cycle life. Excellent results have been found by forming al., entitled “Enhanced Nickel Hydroxide Positive Electrode nickel hydroxide With an apparent density of 1.4-1.7 g/cm3, Materials For Alkaline Rechargeable Electrochemical 55 a tap density of about 1.8-2.3 g/cm3, and an average siZe Cells”, the disclosure of Which is herein incorporated by range of about 5-50 um.