WO2012137188A1

WO2012137188A1 - Batteries having coiled electrode plate group

Info

Publication number: WO2012137188A1
Application number: PCT/IB2012/051739
Authority: WO
Inventors: Pui Tsang Peter Ling; Sung-On Andrew Ng
Original assignee: Pui Tsang Peter Ling; Sung-On Andrew Ng
Priority date: 2011-04-07
Filing date: 2012-04-10
Publication date: 2012-10-11
Also published as: CN103493251A

Abstract

A battery (100) comprises a coiled electrode plate group which comprises a positive electrode plate (120), a negative electrode (130) plate and an insulating separator sheet (140). The separator sheet (140) provides electrical insulation between the positive and negative plates (120, 130). The insulating separator sheet (140) comprises a first longitudinal portion, a second longitudinal portion and a intermediate perforated portion (148) between the first and second longitudinal portions.

Description

BATTERIES HAVING COILED ELECTRODE PLATE GROUP

Field

The present disclosure relates to batteries and more particularly to batteries having a coiled electrode plate group and insulating separator sheets.

Background

Batteries are a convenient stored energy source which are useful in many applications. For example, batteries are commonly used as a power source to operate portable or wireless telecommunications devices, toys such as toy trains, musical mobiles and toy dolls, consumer electronic products such as digital cameras, torch, and music players; and many other portable or non-portable electrical appliances. Batteries typically come in many different sized packages and are readily available as a stable part at competitive prices. For example, batteries are available in AAA, AA, A, C, D and other standard or non-standard sizes. Such batteries are packaged in a cylindrical or prismatic casing in which a coiled electrode plate group is housed, and are commonly referred to as cylindrical or prismatic batteries.

A typical battery comprises a battery housing which houses an electrode plate group and electrolyte. Each electrode plate group comprises positive and negative electrodes which are separated by an insulating separator and packed together within the battery housing. The energy content of a battery is largely determined by the total effective or active surface area of the electrode plates soaked in electrolyte, which is the overlapping area the between the positive and negative electrode plates. For a standard sized metal can battery, the dimensions of the battery are determined by the battery housing which is a standard sized can or pouch or casing.

As there is a need to squeeze more energy capacity into a sized battery, it is highly desirable to provide an improved electroplate group design.

Summary

There is provided a battery comprising a coiled electrode plate group, wherein the coiled electrode plate group comprises a positive electrode plate, a negative electrode plate and an insulating separator sheet which provides electrical insulation between the positive and negative electrode plates; and wherein the insulating separator sheet comprises a first longitudinal portion, a second longitudinal portion and a perforated portion which is intermediate the first and second longitudinal portions.

A perforated region reduces the volume occupied by the portion of the insulating separator sheet which is not intermediate the positive and negative electrode plates.

The active surfaces of the positive and negative electrode plates may be oppositely facing to form an overlapping active region comprising corresponding active surfaces of the positive and negative electrode plates, and the first longitudinal portion of the insulating separator sheet is intermediate the positive and negative electrode plates; and wherein the perforated portion of the insulating separator sheet is outside the overlapping active region.

The perforated portion of the insulating separator may form a looped portion outside the overlapping active region. The looped portion of the perforated portion of the insulating separator may be used to engage with a spindle shaft for winding the electrode plate group from a 1 planar electrode plate group into a coiled electrode plate group.

The dimensions of the looped portion of the insulating separator sheet may be equal to or comparable to that of the central bore.

In one example, the coiled electrode plate group defines a central bore, and the perforated portion of the insulating separator sheet is exposed to the central bore.

The central bore may be formed after a spindle shaft for winding the planar electrode plate group into a coiled electrode plate group has been removed.

The perforated region of the insulating separator sheet may have a length equal to or greater than the perimeter of the central bore, the length being in a direction orthogonal to the axis of the central bore.

Perforations on the perforated region of the insulating separating sheet may be distributed axially and lengthwise in the looped portion of the separator sheet.

Perforations on the perforated region of the insulating separating sheet may include dots or slots, the slots extending along a lengthwise direction which is transverse to the axis of central the core.

The volume defined by perforations of the perforated region of the insulating separator sheet may be more than 5% of the volume defined by the periphery dimensions of the wrap around portion. The insulating separator sheet may include a positioning flap, the position flap defining a receptacle for receiving one end of one of the positive or the negative electrode plates.

The entire active surface of the positive electroplate may rest on and is covered by the insulating separator sheet, and a longitudinal end portion of the negative electrode plate is exposed and in contact with a metallic battery housing to form a negative electrode of the battery.

There is also provided a battery insulating separator sheet for providing insulation between a first electrode plate and a second electrode plate of opposite polarity of a coiled electrode plate group, wherein the insulating separator sheet comprises a first longitudinal portion, a second longitudinal portion and a perforated portion which is intermediate the first and second longitudinal portions.

Perforations on the perforated portion may be distributed at uniform spacing across the width of the separator sheet.

The separator sheet may be elongate with the first and second longitudinal portions located at longitudinal ends, and wherein the perforations are distributed between the first and second longitudinal portions.

The perforations may be distributed at uniform spacing along the length of the perforated portion.

The perforations may include dots or slots, the slots extending along the length of the perforated portion. The volume defined by the perforation may be more than 5% of the volume defined by the periphery dimensions of the intermediate separator portion.

The area of each perforation may be equal to or larger than 1 mm² in case of dots, and equal to or larger than 10 mm² in case of slots.

The separator sheet may comprise a transversely extending positioning flap to limit the longitudinal position of an electrode plate on the separator sheet, the positioning flap being intermediate the perforated portion and the longer one of the first and second longitudinal portions. According to another aspect of the present invention, there is provided a method of making a battery comprising a coiled electrode plate group, the electrode plate group may comprise a first electrode plate and a second electrode plate of opposite polarity separated by a separator sheet; wherein each electroplate may comprise upper and lower active electrode plate surfaces, and the separator sheet may comprise upper and lower separator surfaces, first and second separator portions for covering active surfaces of the electrode plates, and a perforated intermediate separator portion interconnecting the first and second separator portions; wherein the method may comprise the steps of: placing a first electrode plate on the upper surface of a separator sheet such that one active surface is in physical contact with one surface of the separator sheet; placing a second electrode plate underneath the lower surface of the separator sheet; wrapping the separator sheet around a spindle such that the first and second active surfaces of the second electrode plate are sandwiched by the lower surface of the separator sheet, with the perforated intermediate separator portion projects outside of the second electrode plate; rolling the electrode plate stack about the spindle to form a coiled electrode plate group, and inserting the coiled electrode plate group into a casing, completing electrode connections, and filling the casing with electrolyte.

Description of Drawings

The disclosure will be explained below by way of example and with reference to the accompanying drawings or figures, in which:-

Figure 1 is a longitudinal cross sectional view taken along part of a coiled electrode plate group according to an example of the present disclosure,

Figure 2 is a top perspective view of an insulating separator sheet of the present disclosure in a fully spread form,

Figure 3 shows the insulating separator sheet of Figure 2 with a spindle shaft 160 placed underneath the perforated region 148,

Figure 4 shows the insulating separator sheet of Figure 3 with the second longitudinal portion 146 underneath the first longitudinal portion 144 after wrapping about the spindle shaft 160 with the longitudinal edges aligned,

Figure 5 shows the insulating separator sheet of Figure 4 with a positive electrode plate 120 placed on the upper surface of the first longitudinal portion 144 of the separator sheet and a positive current collector attached to the positive electrode plate,

Figure 6 shows the insulating separator sheet of Figure 5 with a negative electrode plate 130 placed intermediate the first longitudinal portion 144 and the second longitudinal portion 144 of the separator sheet to form an electrode plate stack assembly,

Figure 7 is an enlarged perspective view showing a spindle shaft engaging with a bore formed by the perforated portion 148 of the separator sheet and beginning to wind the electrode plate stack assembly into a coiled electrode plate group,

Figure 8A is a perspective view showing the winding of the electrode plate stack assembly into a partially coiled electrode plate group,

Figure 8B shows the partially coiled electrode plate group of Figure 8B without showing the spindle shaft,

Figure 9 is a perspective view of a coiled electrode plate group formed by winding of the electrode plate stack,

Figures 10,1 1 ,12,13 are perspective views showing steps to wind an electrode plate stack assembly of Figure 6 using an open-type spindle, and

Figure 14A and 14B are schematic views of further examples of insulating separator sheets having a perforated region.

Description of Exemplary Embodiments

Figure 1 is a longitudinal cross sectional view taken along part of a coiled electrode plate group of a standard size AAA rechargeable battery 100. The rechargeable battery 100 is a non-limiting example of a rechargeable battery and comprises a Nickel Metal Hydride (NiMH) electrode plate group which is wound into a coiled electrode plate group. The coiled electrode plate group is housed within an AAA sized cylindrical metal can which is filled with electrolyte. The top end portion of the metal can is sealed to preserve the electrolyte after the electrode plate group has been fitted inside the metal can, the metal can filled with electrolyte, and the positive terminal formed.

The electrode plate group (or 'electroplate group' in short) is an assembly comprising a positive electrode plate 120, a negative electrode plate 130, and an insulating separator sheet 140. The assembly is initially formed into a stack of electrode plates with the insulating separator sheet 140 intermediate the positive 120 and negative 130 electrode plates so that there is electrical insulation between electrode plates of opposite polarity. The electrode plate stack is then wound into a coiled electrode plate group for fitting into a metal can as an example of a battery housing.

In general, each electrode plate comprises an active region and an inactive region. The active region of each electrode plate is coated with active substances, and the electrode plates are arranged such that the active regions of the positive and negative electrodes are aligned in an oppositely facing manner separated by the insulating separator sheet. During battery charging or discharging, electrochemical reactions will take place on the corresponding active regions of the electrode plates in the presence of the electrolyte. The inactive region of each electrode plate is primarily a lead portion which is for current collection when discharging and for current distribution when charging.

For a NiMH rechargeable battery, the electrode plate typically comprises a Nickel foamed substrate. The active region of a positive electrode plate is typically coated with Nickel hydroxide as the main active substance. The active region of the negative electrode plate is typically coated with a hydrogen absorbing alloy as the active substance. The separator is usually a polymer sheet such as a polypropylene sheet.

The active region of the positive electrode plate of the battery 100 comprises a nickel-foamed metal sheet coated or mixed with nickel hydroxide. The active region of the negative electrode plate comprises a nickel or nickel-plated punched metal sheet coated with negative electrode constituting materials which are typically a hydrogen-absorbing alloy. The electrode plates are typically very thin sheets to reduce material costs and weight, since the electro-chemical reactions involved in battery charging and/or discharging is primarily surface in nature. Usually, only the active areas are coated with active substances to maximize cost benefits. The active areas of an electrode plate are primarily the regions on the electrode plate which overlap or substantially overlap with adjacent electrode plates of the opposite polarity.

The lead portions of the positive and negative electrode plates are connected respectively to the positive and negative current collectors. Each of the current collectors is made of a good electrical conductor, and is usually made of nickel, nickel-plated copper, or steel for good thermal and electrical conductivity. The positive and negative current collectors are in turn connected to the positive and negative battery terminals.

The insulating separator sheet 140 depicted in Figure 2 comprises a rectangular or substantially rectangular polypropylene sheet having an upper surface and a lower surface. The total length of the insulating separator sheet is more than the cumulative length of the positive and negative electrode plates. The width of the separator sheet is the same as, or larger than, the width of the electrode plates to mitigate the risks of short-circuiting between adjacent positive and negative electrode plates. The insulator sheet is made of an insulating material suitable for prolonged immersion in electrolyte. Plastic materials such as polypropylene are commonly used. As shown in Figure 2, the insulating separator sheet 140 comprises a first longitudinal portion 144, a second longitudinal portion 146 and a perforated portion 148 interconnecting the first and second longitudinal portions. The first 144 and second 146 longitudinal portions are at longitudinal ends of the elongate insulating separator sheet and the perforated portion is located adjacent the longitudinal centre line of the insulating separator sheet.

A transversally extending positioning flap 142 is formed on the upper surface of the separator sheet and extends orthogonally across the entire width of the separator sheet. The positioning flap 142 divides the separator sheet into a first longitudinal region comprising the first longitudinal portion 144, and a second longitudinal region comprising the second longitudinal portion 146 and the perforated region 148. The positioning flap 142 is formed at about the longitudinal middle portion of the separator sheet 140 and sets the longitudinal boundary of the first longitudinal portion 144 of the separator sheet. The positioning flap 142 projects from the upper surface of the insulating separator sheet 140 and extends with an inclination with respect to the upper surface of the first longitudinal portion and forms a receptacle or hood for receiving one longitudinal end of the positive electrode plate 120. The receptacle or hood extends orthogonally to the length of the separator sheet 140 and the intersection between the positioning flap 142 and the first longitudinal portion 144 is also orthogonal to the length of the separator sheet. This intersection defines a stop which limits the longitudinal position of the positive electrode plate 120 relative to the insulator sheet 140.

As shown in Figure 5, the positive electrode plate 120 is to rest on the upper surface of the first longitudinal portion 144 with one free longitudinal end received inside the receptacle defined by the positioning flap 142. The first longitudinal portion has the same length as or is slightly longer than that of the positive electrode plate. A positive current collector 122 is mounted at the other end of the positive electrode plate 120. The positive current collector 122 extends transversely across the entire width of the positive electrode plate 120 and is in permanent electrical contact with the lead portion of the positive electrode plate 120 to facilitate current collection and current distribution.

The perforated region 148 is intermediate the positioning flap 142 and the second longitudinal portion 146, and is for engaging with a winding spindle 160 for winding the electrode plate assembly into a coiled electrode plate group., The perforated portion 148 is outside the active regions of the electrode plate group and the length of the perforated portion 148 is about the same or slightly larger than the perimeter of the spindle for rolling the electrode plates into a coiled electrode plate group as explained below. The perforated portion 148 will remain as a transversally extending tab inside the central empty core of the coiled electrode plate group after removal of the spindle as shown in Figure 1 .

Formation of an example coiled electrode plate group as shown in Figure 1 will be explained below with reference to the Figures.

Referring to Figure 2, the insulating separator sheet 140 is laid flat in its fully expanded state with its upper surface facing upwards. The positioning flap 142 defines a receptacle having an elongate opening which faces the free longitudinal end of the first longitudinal portion 144. The perforated portion 148 is immediately adjacent the positioning flap 142 and is intermediate the positioning flap 142 and the second longitudinal portion 146. The first longitudinal portion 144 is longer than the second longitudinal portion 146 due to the need to expose the negative electrode plate in this specific embodiment in order to form a negative electrode with the metal can by physical contact.

Referring to Figure 3, a spindle adapted for rolling the stacked electrode plate assembly into a coiled electrode plate group is placed underneath the perforated region 148 of the separator sheet 140. The spindle is disposed orthogonal to the length of the separator sheet and is parallel to the transversally extending positioning flap 142.

Referring to Figure 4, the second longitudinal portion 146 of the separator sheet is folded about the spindle shaft, and the perforated portion 148 is wrapped around the spindle shaft such that the perforated portion surrounds the spindle 160. After folding about the spindle shaft, the lower surface of the second longitudinal portion 146 oppositely faces the lower surface of the first longitudinal portion 144.

Referring to Figure 5, a positive electrode plate 120 is placed on the upper surface of the first longitudinal portion 144 of the separator to form a partial electrode plate stack. One longitudinal end of the positive electrode plate 120 is aligned with and stopped by the positioning flap 142. A positive current collector 122 is attached to the other (free) longitudinal end of the first longitudinal portion 144. It will be noted that the perforated portion 148 of the separator sheet projects beyond the positive electrode plate.

Referring to Figure 6, a negative electrode plate is placed directly underneath the positive electrode plate 120 and intermediate the lower surfaces of the first and second longitudinal portions to form an electrode plate stack.

Referring to Figure 7, the spindle engages firmly with the roller collar formed by the perforated portion 148 and begins to roll clockwise towards the free end of first longitudinal portion 144. When the spindle shaft encounters, the electrode plate stack and engage therewith as shown in Figure 7, the electrode plate stack will begin to curl as shown in Figures 8A & 8B, and progressively curled to form the coiled electrode plate group of Figure 9.

As depicted in Figure 7, the positioning flap also provides a shield so that the portion of the positive electrode plate 120 immediately adjacent the perforated portion 148 is not directly exposed to the apertures of the perforated portion 148, thereby mitigating possible leakage contact between the positive and negative electrode plates via the perforations. In general, the positioning flap defines a receptacle opening and a moveable flap or hood which faces away from the perforated region to provide the shied.

The coiled electrode plate group of Figure 9 will be inserted into a standard sized battery metal can and the spindle shaft will be removed. After that electrodes and battery terminals will be formed, electrolyte is filled and the metal can is sealed to complete making of the battery.

Figures 10-13 shows an alternative method to construct a battery comprising a coiled electrode plate group having an insulating separator sheet with a perforated portion. The method is substantially identical to that described above with reference to Figures 3-8A, except that an open spindle 260 is used to roll the electrode plate stack into a coiled electrode plate group. The description above in relation to the spindle shaft 160 is incorporated herein by reference except that numerals are increased by 100, and the spindle now is an open spindle 260 comprising a first spindle part 262 and a second spindle part 264. An open spindle is similar to the spindle 160 above, except that it is formed from two half-cylindrical spindle parts each comprising a longitudinally extending planar surface and a semi-cylindrical outer surface. Figures 10, 1 1 , 12 & 13, corresponding respectively to the steps depicted in Figures 3, 4, 6 & 8A, are described in further detail below.

Referring to Figure 10, the open spindle 260 is inserted into the separator sheet 241 with the first 262 and second 264 spindle parts respectively above and below the perforated portion 248 such that the planar surfaces of the first and second spindle parts are oppositely facing and the spindle axis is orthogonal to the longitudinal axis or length of the separator sheet. The spindle parts are urged together to maintain engagement with the separator sheet, as depicted in Figures 10 to 12. The subsequent rolling steps are substantially identical to that described above and are incorporated herein.

Figures 14A and 14B are schematic views of variations to the insulating separating sheet of Figure 2. The separator sheets 340 and 440 are for an AA sized battery as a convenient example. The first variation shown in Figure 14A includes a total of 104 dots each having a diameter of 1 .2 mm. In the second variation of Figure 14B, the perforations are elongate and having a length of about 10 mm. The total clearance area provided by the dots and the slots are respectively 1 17.5 mm2 and 196.4 mm2.

While the present invention has been illustrated with examples using NiMH electrode plate group, it would be appreciated that NiMH is only used as a non-limiting example. Other electrode plate materials such as lithium, NiCd, could be used without loss of generality. Moreover, while the second longitudinal portion of the separator sheet is shorter than the negative electrode plate in order to expose the negative electrode plate for making physical contact with the metal can to form the negative electrode, it would be appreciated that an negative current collector could be attached to a longitudinal end of the negative electrode plate for connection with the negative battery terminal, similar to the arrangement of the positive terminal connection described above. Furthermore, while the positive electrode is placed on the first longitudinal portion and the negative electrode is placed intermediate the lower surfaces of the first and second longitudinal portions of the separator sheet, the arrangement could be reversed without loss of generality.

Table of Numerals

100 200 Battery

120 220 Positive electrode plate

130 230 Negative electrode plate

140 240 Separator sheet

142 242 Positioning flap

144 244 First longitudinal portion

146 246 Second longitudinal portion

148 248 Perforated portion

160 260 Spindle

262 First spindle part

264 Second spindle part

Claims

1 . A battery comprising a coiled electrode plate group, wherein the coiled electrode plate group comprises a positive electrode plate, a negative electrode plate and an insulating separator sheet which provides electrical insulation between the positive and negative electrode plates; and wherein the insulating separator sheet comprises a first longitudinal portion, a second longitudinal portion and a perforated portion which is intermediate the first and second longitudinal portions.

2. A battery according to Claim 1 , wherein active surfaces of the positive and negative electrode plates are oppositely facing to form an overlapping active region comprising corresponding active surfaces of the positive and negative electrode plates, and the first longitudinal portion of the insulating separator sheet is intermediate the positive and negative electrode plates; and wherein the perforated portion of the insulating separator sheet is outside the overlapping active region.

3. A battery according to Claim 2, wherein the perforated portion of the insulating separator forms a looped portion outside the overlapping active region.

4. A battery according to Claim 3, wherein the looped portion of the perforated portion of the insulating separator is to engage with a spindle shaft for winding the electrode plate group from a planar electrode plate group into a coiled electrode plate group.

5. A battery according to Claim 3, wherein the dimensions of the looped portion of the insulating separator sheet are equal to or comparable to that of the central bore.

6. A battery according to any of the preceding Claims, wherein the coiled electrode plate group defines a central bore, and the perforated portion of the insulating separator sheet is exposed to the central bore.

7. A battery according to Claim 6, wherein the central bore is formed after a spindle shaft for winding the planar electrode plate group into a coiled electrode plate group has been removed.

8. A battery according to any of the preceding Claims, wherein the perforated region of the insulating separator sheet has a length equal to or greater than the perimeter of the central bore, the length being in a direction orthogonal to the axis of the central bore.

9. A battery according to any of the preceding Claims, wherein perforations on the perforated region of the insulating separating sheet are distributed axially and lengthwise in the looped portion of the separator sheet.

10. A battery according to any of the preceding Claims, wherein perforations on the perforated region of the insulating separating sheet include dots or slots, the slots extending along a lengthwise direction which is transverse to the axis of central the core.

1 1 . A battery according to any of the preceding Claims, wherein the volume defined by perforations of the perforated region of the insulating separator sheet is more than 5% of the volume defined by the periphery dimensions of the wrap around portion.

12. A battery according to any of the preceding Claims, wherein the insulating separator sheet includes a positioning flap, the position flap defining a receptacle for receiving one end of one of the positive or the negative electrode plates.

13. A battery according to any of the preceding Claims, wherein the entire active surface of the positive electroplate rests on and is covered by the insulating separator sheet, and a longitudinal end portion of the negative electrode plate is exposed and in contact with a metallic battery housing to form a negative electrode of the battery.

14. A battery insulating separator sheet for providing insulation between a first electrode plate and a second electrode plate of opposite polarity of a coiled electrode plate group, wherein the insulating separator sheet comprises a first longitudinal portion, a second longitudinal portion and a perforated portion which is intermediate the first and second longitudinal portions.

15. A battery separator sheet according to Claim 14, wherein perforations on the perforated portion are distributed at uniform spacing across the width of the separator sheet.

16. A battery separator sheet according to Claims 14 or 15, wherein the separator sheet is elongate with the first and second longitudinal portions located at longitudinal ends, and wherein the perforations are distributed between the first and second longitudinal portions.

17. A battery separator sheet according to any of Claims 14 to 16, wherein the perforations are distributed at uniform spacing along the length of the perforated portion.

18. A battery separator sheet according to any of Claims 14 to 17, wherein the perforations include dots or slots, the slots extending along the length of the perforated portion.

19. A battery separator sheet according to any of Claims 14 to 18, wherein the volume defined by the perforation is more than 5% of the volume defined by the periphery dimensions of the intermediate separator portion.

20. A battery separator sheet according to Claim 19, wherein the area of each perforation is equal to or larger than 1 mm² in case of dots, and equal to or larger than 10 mm² in case of slots.

21 . A battery separator sheet according to any of Claims 14 to 20, wherein the separator sheet comprises a transversely extending positioning flap to limit the longitudinal position of an electrode plate on the separator sheet, the positioning flap being intermediate the perforated portion and the longer one of the first and second longitudinal portions.

22. A method of making a battery comprising a coiled electrode plate group, the electrode plate group comprising a first electrode plate and a second electrode plate of opposite polarity separated by a separator sheet; wherein each electroplate comprises upper and lower active electrode plate surfaces, and the separator sheet comprises upper and lower separator surfaces, first and second separator portions for covering active surfaces of the electrode plates, and a perforated intermediate separator portion interconnecting the first and second separator portions; wherein the method comprises the steps of:

Placing a first electrode plate on the upper surface of a separator sheet such that one active surface is in physical contact with one surface of the separator sheet;

Placing a second electrode plate underneath the lower surface of the separator sheet;

Wrapping the separator sheet around a spindle such that the first and second active surfaces of the second electrode plate are sandwiched by the lower surface of the separator sheet, with the perforated intermediate separator portion projects outside of the second electrode plate;

Rolling the electrode plate stack about the spindle to form a coiled electrode plate group, and

Inserting the coiled electrode plate group into a cylindrical or prismatic casing, completing electrode connections, and filling the can with electrolyte.