MOLTEN SALT BATTERIES

Abstract: A secondary battery employing an aluminium anode and a variety of cathodes, such as carbon, and a low temperature molten electrolyte composition comprising mixtures of a metal halide, such as an aluminium halide or a gallium halide, and an organic onium salt, such as diphenylethylsulfonium tetrafluoroborate, with or without an inorganic salt. Lewis acidity of molten salts containing aluminium chloride can be buffered by adding inorganic salts containing either Al3<+> or C1<-> ions. The buffered salts are molten at ambient temperature.

Description: Molten Salt Batteries The present invention relates to molten salt batteries and in particular secondary, i.e. rechargable batteries. Conventional batter/ systems are typically based on lead-acid, nickel-cadmium and mercury and are associated with toxic heavy metal waste in both manufacture and subsequent disposal. In addition, lead acid secondary baπeries are bulkv and heaw. whilst nickel cadmium secondarv batteries are of relatively low specific energy, comparatively high self-discharge characteristics and suffer undesirable "memory ' ' effects that reduce recharging efficiency. More recently developed primary batteries use lithium and sodium electrodes. These tend to have relatively good performances but they are not re-chargeable. Lithium and sodium also suffer from being expensive and difficult to work with. This makes manufacturing time consuming and costly. In addition. lithium and sodium are highly reactive metals, which limits their potential use in transport applications, where safety in the event of an accident is important. Furthermore, these primary batteries have a fairl short shelf life as a result of their self-discharge characteristics. As an alternative to lithium and sodium, it is known that aluminium can be used as an anode in an electrolytic cell. Aluminium has a volumetric energy density of 8.050 Ah/dn which is about 4 times as large as that of lithium, and a gravimetric charge density of 2980 Ah/kg, which is second only to lithium (3860 Ah/kg). It is lightweight, inexpensive, non-toxic, easy to fabricate and readily available. In addition, it is anticipated that aluminium will be capable of recycling from battery components at the end of their useful life. Whilst conventional batteries use acid as the electrolyte, some batteries use molten salts. Of particular interest in the field of electrochemical cells are fused salt compositions that are molten at low temperature. Such molten salt compounds are ionic and liquid at temperatures below the individual melting points of the component compounds. These melts can form liquids simultaneously upon mixing the components together. One known group of low temperature molten salts comprises an admixture of a metal halide (a compound consisting of a metal and a halogen, generally covalently bonded together) and an organic salt. Examples of such molten salts are mixtures of aluminium trichloride and organic onium compounds such as N- (n-butyl) pyridinium chloride (BPC) and l-methyl-3-ethylimidazolium chloride (MEIC). These salts are, however, toxic, expensive and sensitive to the presence of oxygen and moisture, with which they react and decompose readily. This is disadvantageous. An object of the invention is to provide a batten that is less harmful to the environment than those available at present. In particular, it is an object of the present invention to provide a secondary, re-chargeable battery that avoids the heavy metal pollution that is associated with conventional primary batteries. According to one aspect of the invention, there is provided a banery having an anode, a cathode and a molten electrolyte that comprises a mixture of a metal halide and a tetraalkyl/tetraphenyl ammonium salt that has the form R 4 N.X-. wherein R- 4 N includes four identical alkyls of from 1 to 12 carbon atoms or four identical phenyl groups, and X- is a halide or complex halogen-containing ion. A suitable mole ratio of tetraalkyl/tetraphenyl ammonium salt to metal halide may range from about 2: 1 to about 1 :2. The composition may have a mole ratio of tetraalkyl/tetraphenyl ammonium salt to metal halide of about 1 : 1 to about 1 :2. According to another aspect of the invention, there is provided a battery having an anode, a cathode and a molten electrolyte that comprises a mixture of a metal halide and an alkylary ammonium salt that has the form R 1 R 2 R 4 N+ .X-, wherein R h R 2 and R 3 are alkyl groups of from 1 to 12 carbon atoms, at least one of Ri. R 2 and R 3 having from 5 to 12 carbon atoms. R. is a benzyl or phenyl group and X- is a halide or complex halogen-containing ion. A suitable mole ratio of alkylaryiammonium salt to metal halide can range from about 2: 1 to about 1 :2. The composition may have a mole ratio of about 1 : 1 to about 1 :2. According to another aspect of the invention, there is provided a battery having an anode, a cathode and a molten electrolyte that comprises a mixture of a metal halide and an alkyltriphenylphosphonium salt that has the form .X-, wherein Ri is an alkyl group of from 1 to 12 carbon atoms, and R 2 . R : , and R 4 are phenyl groups, and X- is a halide or complex halogen-containing ion. 0/16415 A suitable mole ratio of alkyltriphenylphosphonium salt to metal halide can be in the range from about 2: 1 to about 1 :2. The composition may have a mole ratio of alkyltriphenylphosphonium salts to metal halide of about 1 : 1 to about 1 :2. According to another aspect of the invention, there is provided a battery having an anode, a cathode and a molten electrolyte that comprises a mixture of a metal halide and a alkyltriphenylphosphonium salt that has the form XR 1 R 2 R R P+ .X-. wherein XRi is a haloalkyl group of from 1 to 12 carbon atoms, and R 2 , R 3 and R 4 are phenyl groups, and X- is a halide or complex halogen-containing ion. A suitable mole ratio of haloalkyltriphenylphosphonium salt to metal halide can range from about 2: 1 to about 1 :2. The composition may have a mole ratio of haloalkyltriphenylphosphonium salts to metal halide of about 1 : 1 to about 1 :2. According to yet another aspect of the invention, there is provided a battery having an anode, a cathode and a molten electrolyte that comprises a mixture of a metal halide and an alkylarylsulfonium salt that has the form R 1 R 2 R 3 S- .X-. wherein R is an alkyl group having from 1 to 12 carbon atoms, and R 2 and R 3 are alkyl or phenyl groups and X- is a halide or complex halogen-containing ion. A suitable mole ratio of alkylarylsulfonium salt to metal halide can range from about 2: 1 to about 1 :2. Preferably, the composition comprises a mole ratio of alkylarylsulfonium salt to metal halide of about 1 : 1 to about 1 :2. 00/16415 The halide may be an aluminium halide. The complex halogen-containing ion may be one of the BF - or PF 6 - methylsulfonate group. The anode may be aluminium. The cathode may be glassy carbon. The molten electrolyte composition may have three or more components. According to a yet further aspect of the present invention, there is provided an electrochemical cell comprising an anode, a cathode and a molten electrolyte composition comprising a mixture of a first metal halide, a second metal halide and an organic onium salt. Preferably, the molten electrolyte composition is a low temperature molten electrolyte composition. By "low temperature" what is meant is that the molten compositions are in liquid form below about 100 ~ C. including ambient temperature of between 20 to 35 °C at standard pressure. The melt may have four or more components. Preferably, the anode is aluminium. An advantage of this is that a high energy. lightweight, economic and environmentally friendly secondary battery can be implemented. The cathode may be glassy carbon. The first metal halide may be an aluminium halide, for example aluminium chloride or aluminium bromide or a gallium halide. 00/16415 The second metal halide is preferably a halide of a metal other than aluminium such as iron, nickel or copper halides, for example iron, nickel or copper chloride. The second metal halide or halogen containing ion may be selected from one of the following: • Inorganic aluminium salts, such as aluminium phosphate, aluminium tungstate. • Alkali metal halides, such as, LiCl, KC1. NaCl. RuCl. CsCl. • Heavy metal halides or transit metal halides. such as. CuCl. CuCk FeCI 2 . FeCl 3 , SnC • Alkali metal complex halogen-containing salts, such as. PF 6 , K_BF 4 . The organic onium salt may be an organic ammonium, phosphonium or sulphonium salt, such as trimethylphenylammonium chloride (TMPAC). trimethylsulponium chloride (TMSC) and benzyltrimethylammonium (BTMAX), with or without an inorganic salt. The organic onium salt may be selected from the following: • R 4 N.X. where iN includes four identical alky Is of 1 to 12 carbons or four identical phenyl groups and X- is a halide or a complex halogen containing ion. • where R { , R 2 and R 3 are alkyl groups of 1 to 12 carbons, R. is a benzyl or phenyl group and X- is a halide or a complex halogen containing ion. 0/16415 7 R^R^P+.X-, where R, is an alkyl group of 1 to 12 carbons, and R 2 , R 3 and R« are phenyl groups and X- is a halide or a complex halogen containing ion. XR|R 2 R 3 R4P + .X-, where XR, is a haloalkyl group of 1 to 12 carbons, and R 2 , R 3 and ^ are phenyl groups and X- is a halide or a complex halogen containing ion. RιR 2 R 3 S+.X-, where Rj is an alkyl group of 1 to 12 carbons, and R 2 and R 3 are alkyl or phenyl groups and X- is a halide or a complex halogen containing ion. The electrochemical cells described above may be primary or secondary cells. Various electrochemical cells in which the invention is embodied will now be described by way of example only. The electrochemical cells in which the invention is embodied have electrolytes that include at least two separate components that are mixed together to form a melt. Examples of low temperature molten electrolytes that comprise two components, i.e. binary melts, are mixtures of aluminium halide or gallium halide and an organic onium salt. These mixtures have one of the following formulas: ( 1 ) tetraalkyl/tetraphenyl ammonium salts: R 4 N-.X-. where 4 are four identical alkyls that have from 1 to 12 carbon atoms or four identical phenyl groups, and X- is a halide or a complex halogen-containing ion. such as BF 4 - and PF 6 -. 0/16415 8 A suitable mole ratio of tetraalkyl/tetraphenyl ammonium salts to metal halide can range from about 2: 1 to about 1 :2. The composition may have a mole ratio of tetraalkyl/tetraphenyl ammonium salts to metal halide of about 1 : 1 to about 1 :2. As used herein, "alkyl" means saturated hydrocarbyl groups. (2) alkylaryiammonium salts: R 1 R 2 R 3 R 4 N+ .X-, where R,. R 2 and R 3 are alkyl groups of from 1 to 12 carbon atoms, R 4 is a benzyl or phenyl group, and X- is independently a halide or a complex halogen-containing ion, such as BF - and PF 6 -methylsulfonate group. A suitable mole ratio of alkylaryiammonium salts to metal halide can range from about 2: 1 to about 1 :2. The composition may have a mole ratio of alkylaryiammonium salts to metal halide of about 1 : 1 to about 1 :2. (3) alkyltriphenylphosphonium salts: R 1 R 2 R 3 1P+ .X-. where R, is alkyl group of from 1 to 12 carbon atoms, and R 2 , R 3 and i are phenyl groups, and X- is a halide or a complex halogen-containing ion such as BF 4 - and PF 6 - A suitable mole ratio of alkyltriphenylphosphonium salts to metal halide can range from about 2: 1 to about 1 :2. The composition have a mole ratio of alkyltriphenylphosphonium salt to metal halide of about 1 : 1 to about 1 :2. (4) haloalkyltriphenylphosphonium salts: XR 1 R 2 R 3 R P- t - .X-. where XRl is haloalkyl group of from 1 to 12 carbon atoms, R 2 . R 3 and R 4 are phenyl groups, and X- is a halide or a complex halogen-containing ion such as BF 4 - and PF 6 - ΛΛ n ,„ B PCT/GB99/03058 00/16415 A suitable mole ratio of haloalkyltriphenylphosphonium salts to metal halide can range from about 2: 1 to about 1 :2. Preferably, the composition has a mole ratio of haloalkyltriphenylphosphonium salt to metal halide of about 1 : 1 to about 1 :2. (5) alkylarylsulfonium salts: R,R 2 R 3 S+ .X-, where K is an independent alkyl group of 1 to 12 carbons, and R 2 and R 3 are alkyl or phenyl groups, and X- is an independent halide or a complex halogen-containing ion. such as BF 4 - and PF 6 -. A suitable mole ratio of alkylarylsulfonium salt to metal halide can range from about 2: 1 to about 1:2. The composition has a mole ratio of alkylarylsulfonium salt to metal halide of about 1 :1 to about 1 :2. The melts described above can be synthesized by a simple process in a glove box filled with nitrogen. For example, when the metal halide is aluminium trichloride, an appropriate onium salt is weighed and the correct stoichiometric amount of aluminium trichloride is slowly added to the onium salt to form a 2: 1 molar ratio fused salt composition that is fluid at ambient temperature. This causes a spontaneous exothermic reaction, resulting in a clear viscous colored solution. If a melt does not form spontaneously, the solids can be heated until a substantially homogeneous liquid forms. The reaction t pically takes place in a closed vessel and the evolved heat can be controlled by periodically cooling the reaction vessel. After complete addition of A1C1 3 the room temperature melt is heated to up to 70 °C to expedite dissolution of any remaining solid. After cooling down, the melt remains a liquid at temperatures below 70 °C. Most of 0/16415 10 the A 1C 1 and onium salt melts, in fact, remain liquid at 50 °C, and some of them below about 20 °C. As a specific example, a 2: 1 molar ratio of AlCl 3 :diphenylethylsulfonium tetrafluoroborate (DPES+ BF 4 -) melt was prepared as follows. Ten grams of aluminium trichloride was slowly added to 11.32 g of DPES+ BF - in a 100 ml flask. This caused a spontaneous exothermic reaction to occurr, resulting in a clear brown solution having a 2:1 molar ratio fused salt composition that was fluid at 50 °C. After twenty four hours of heating at 75 °C. all solids were dissolved and the melt was cooled down to ambient temperature. This method can also be used in the preparation of 2: 1 molar ratio of GaCl 3 :trimethylpheny ammonium methylsulfonate (TMPA- CH 3 SO 3 -) and 2: 1 molar ratio of AlCh.xhloromethyl triphenylphosphonium chloride (CMTPP+ Cl). In addition, to using binary melts as an electrolyte for a battery, ternary or quarternary melts could be used. The composition of ternary low temperature molten electrolytes comprises a mixture of an onium salt and a metal halide. such as. although not exclusively, used for the binar melts described above, plus one of the following inorganic salts: 1. Inorganic aluminium salts, such as aluminium phosphate, aluminium tungstate. 2. Alkali metal halides, such as, LiCl, C1. NaCl. RuCl. CsCl. 3. Heavy metal halides or transit metal halides. such as. CuCl. CuCl 2 . FeCl 2 . FeCl 3 , SnCl 2 . 4. Alkali metal complex halogen-containing salts, such as. PF 6 , KBF 4 . Other examples of onium salts that can be used in ternary melts include trimethylphenylammonium chloride (TMPAC), trimethylsulponium chloride 5 (TMSC) and benzyltrimethylammonium (BTMAX). Generally, the salts listed in (1) above have the same cations AI 3 + as the binary melts described previously. The salts listed in (2) have the same halide anions X- as the previously described. When not involved in battery reactions, these 10 salts play a role to buffer the Lewis acidity of the binary melts, and to lower the freezing points. The salts listed in (3) are cathodic activating materials. As supporting electrolytes, salts (4) are useful for increasing the conductivities of the melts. 15 Each of the melts described above can be used in a battery . For example, an AlC -trimethylphenylammonium chloride melt was used by the inventors to form an Al/Fe secondary battery. The AI/Fe battery consists of a 2mm diameter aluminium rod anode and a 4mm 20 diameter glassy carbon rod cathode, introduced through the side ports of a 20 ml H-shaped cell comprising of two tubes that are separated by a glass frit. One tube contains approximately 8 ml of the molar ratio of 2: 1 AlCl 3 :trimethylphenylammonium chloride and contacts the Al anode. The other tube contains approximately 8 ml of the molar ratio of 2: 1 :0.2 "> S AlCl 3 :trimethylphenylammonium chloride:FeCl 2 . This is in contact with the glassy carbon cathode. Both electrodes extended approximately 5 cm into the electrolyte. 00/16415 12 The H cell described above is typically constructed in an argon-filled Schlenk line and all experiments are carried out with the Schlenk line under argon atmosphere at or near 20 °C. This cell initially shows an open-circuit voltage of 1.7 V. The cell is charged at room temperature by increasing the applied voltage in 0.05 V steps from about 1.0 V to 2.5 V. The open-circuit voltage after charging is, typically, 2.05 V. The cell is then discharged in 0.1 N steps down from about 2.0 V to 0.8 V. A gradually sloped cell voltage is obsen'ed on discharge, having an average voltage of 1.87 V. Following the eight cycles described above, the cell can be repeatedly charged for 1 hour at 2.5 V and discharged for 1 hour at 0.5 V. The cell repeatedly displays a charging voltage of 2.1 V and gave an average discharge voltage of 1.8 N. In another example, the cathode used is a 2mm diameter tungsten rod and the anode is again Al. The Al and tungsten rods are introduced through the side ports of a 15ml tube cell. The cell contains approximately 10 ml of electrolyte. which is AlCktrimethylphenylammonium chloride:FeCl 2 having a molar ratio of 2: 1 :0.2. Both the Al anode and tungsten cathode extended approximately 5 cm into the electrolyte. The cell is constructed in an argon filled Schlenk line and all experiments are carried out with the Schlenk line under argon atmosphere at or near 20 °C. The tube cell described above initially shows an open-circuit voltage of 1.4 V. The cell is charged at room temperature by increasing the applied voltage in 0.05 V steps from about 1.0 V to 2.5 V. The cell is then discharged in 0.1 N steps down from about 2.0 V to 0.8 N. The open-circuit voltage after charging was 1.65 V. A gradually sloped cell voltage is obsen'ed on discharge, having 00/16415 13 an average voltage of 1.55V. Following ten of the cycles described above, the cell was repeatedly charged for 1 hour at 2.0 V and discharged for 1 hour at 0.5 V. After this, the cell displays a charging voltage of 1.55 V and gives an average discharge voltage of 1.46 V. In another example, a battery consists of a 5 x 10cm aluminium foil anode and a 20mm diameter graphite rod. The Al foil and graphite rod are introduced into a tube containing approximately 8 ml of 2: 1 :0.1 (mole/mole/mole) A1C1 3 : TMPAC:SnCl 2 and each extend approximately 5 cm into the electrolyte. The cell is constructed under argon atmosphere and all experiments are carried out at or near 20 °C. The open-circuit voltage of this cell before charging is 1.2 V. The cell is charged at room temperature by increasing the applied voltage in 0.05 V steps from about 1.0 V to 2.5 N. The cell is then discharged in 0.1 V steps down from about 2.0 V to 0.8 V. The open-circuit voltage after charging is 1.65 V. With low temperature especially ambient temperature molten electrolytes, a secondary battery using an aluminium or an aluminium alloy anode in combination with an appropriate cathode material and operating at low temperature, particularly at room temperature, is provided.

Claims: 00/16415 14 Claims 1. A battery having an anode, a cathode and a molten electrolyte that comprises a mixture of a metal halide and a tetraalky 1 tetraphenyl ammonium salt that has the form R 4 N.X- wherein RjN includes four identical alkyls of from 1 to 12 carbon atoms or four identical phenyl groups, and X- is a halide or complex halogen-containing ion. 2. A battery as claimed in claim 1, wherein the mole ratio of R 4 N.X to metal halide ranges from about 2:1 to about 1:2. 3. A battery as claimed in claim 1, wherein the mole ratio of R N.X to metal halide is in the range of substantially 1 :1 to about 1 :2. 4. A battery having an anode, a cathode and a molten electrolyte that comprises a mixture of a metal halide and an alkylaryiammonium salt that has the form RιR R N+ .X. wherein R,. R and R, are alkyl groups of from I to 12 carbon atoms, at least one of R,. R : and R ; . having from 5 to 12 carbon atoms. j is a benzyl or phenyl group and X- is a halide or complex halogen-containing ion. A battery as claimed in claim 4. wherein the mole ratio of R|R 2 R 3 4 N r - ; -.X to metal halide ranges from about 2:1 to about 1 :2. 6. A battery as claimed in claim 4. wherein the mole ratio of R 1 R 2 R 3 R N-.X to metal halide ranges from about 1 :1 to about 1 :2. 7. A battery having an anode, a cathode and a molten electrolyte that comprises a mixture of a metal halide and an alkyltriphenylphosphonium salt that has the form R 1 R 2 R 3 R P+ .X-, wherein Ri is an alkyl group of from 1 to 12 carbon atoms, and R 2 , R 3 and are phenyl groups, and X- is a halide or complex halogen-containing ion. 8. A batter as claimed in claim 7, wherein the mole ratio of alkyltriphenylphosphonium salt to metal halide is in the range of from about 2: 1 to about 1 :2. 9. A battery as claimed in claim 7, wherein the mole ratio of the alkyltriphenylphosphonium salt to metal halide is in the range of from about 1: 1 to about 1 :2. 10. A battery having an anode, a cathode and a molten electrolyte that comprises a mixture of a metal halide and a haloalkyltriphenylphosphonium salt that has the form XR,R 2 R 3 R P+ .X-. wherein XR, is a haloalkyl group of from 1 to 12 carbon atoms, and R 2 . R 3 and R 4 are phenyl groups, and X- is a halide or complex halogen- containing ion. 1 1. A battery as claimed in claim 10. wherein the mole ratio of haloalkyltriphenylphosphonium salt to metal halide ranges from about 2: 1 to about 1 :2. 12. A battery as claimed in claim 10. wherein the mole ratio of the haloalkyltriphenylphosphonium salt to metal halide ranges from about 1 : 1 to about 1 :2. 13. A battery having an anode, a cathode and a molten electrolyte that comprises a mixture of a metal halide and an alkylarylsulfonium salt that has the form has the form R^^S-i- .X-, wherein R ! is an alkyl group of from 1 to 12 carbon atoms, and R and R 3 are alkyl or phenyl groups and X- is a halide or complex halogen-containing ion. 14. A battery as claimed in claim 13, wherein the mole ratio of the alkylarylsulfonium salt to metal halide ranges from about 2: 1 to about 1:2. 15. A battery as claimed in claim 13. wherein the mole ratio of the alkylarylsulfonium salt to metal halide of about 1 : 1 to about 1 :2. 16. A battery as claimed in any one of the preceding claims, wherein the halide is an aluminium halide or a gallium halide. 17. A battery as claimed in any one of the preceding claims, wherein the complex halogen-containing ion is one of the BF 4 - or PF 6 - methylsulfonate group. 18. A battery as claimed in any one of the preceding claims, wherein the anode is aluminium. 0/16415 17 19. A battery as claimed in any one of the preceding claims, wherein the cathode is made of glassy carbon. 20. An electrochemical cell comprising an anode, a cathode and a molten electrolyte composition comprising a mixture of a first metal halide, a second metal halide and an organic onium salt. 21. An electrochemical cell as claimed in claim 20, wherein the molten electrolyte composition has four or more components. 22. An electrochemical cell as claimed in claim 20 or claim 21. wherein the first metal halide is an aluminium halide, for example aluminium chloride or aluminium bromide, or a gallium halide. 23. An electrochemical cell as claimed in claim 20 or claim 21 or claim 22. wherein second metal halide is selected from one of the following: • Inorganic aluminium salts, such as aluminium phosphate, aluminium tungstate. • Alkali metal halides. such as. LiCl. KC1. aCl. RuCl. CsCl. • Heavy metal halides or transit metal halides. such as. CuCl. CuCk FeCk FeCk SnCk • Alkali metal complex halogen-containing salts, such as. KPF 6 . KBF . 24. An electrochemical cell as claimed in any one of claims 20 to 23. wherein the organic onium salt is an organic ammonium, phosphonium or sulphonium salt. 00/16415 18 25. An electrochemical cell as claimed in claim 24. wherein the organic onium salt is any one of trimethylphenylammonium chloride (TMPAC), trimethyisulponium chloride (TMSC) and benzyltrimethylammonium (BTMAX), with or without an inorganic salt. 26. An electrochemical cell as claimed in claim 24, wherein the onium salt is selected from the following: • R 4 N.X. where R|N includes four identical alkyls of 1 to 12 carbons or four identical phenyl groups and X- is a halide or a complex halogen containing ion. • R 1 R 2 R 3 R 4 N+.X-, where R ( . R 2 and R are alkyl groups of 1 to 12 carbons. R_, is a benzyl or phenyl group and X- is a halide or a complex halogen containing ion. • where Ri is an alkyl group of 1 to 12 carbons, and R 2 . R 3 and R- 4 are phenyl groups and X- is a halide or a complex halogen containing ion. • where XRi is a haloalkyl group of 1 to 12 carbons, and R . R 3 and R are phenyi groups and X- is a halide or a complex halogen containing ion. • R 1 R 2 R 3 S-.X. where R| is an alkyl group of 1 to 12 carbons, and R 2 and R : , are alkyl or phenyl groups and X- is a halide or a complex halogen containing ion. 27. An electrochemical cell or battery as claimed in any one of the preceding claims that is rechargable.

Inventors: VANDERNOOT THEODORE JOHN, ZHAO YUGUAN, VANDERNOOT, THEODORE, JOHN, ZHAO, YUGUAN
Applicants: LINWOOD TRADING LIMITED, VANDERNOOT THEODORE JOHN, ZHAO YUGUAN, VANDERNOOT, THEODORE, JOHN, ZHAO, YUGUAN
Application year: 1999
Main classification: H01M
IPC codes: H01M6, H01M10