阅读说明：本技术 燃料电池堆 (Fuel cell stack ) 是由 裴普成 王明凯 袁星 任棚 陈东方 王鹤 宋鑫 于 2021-07-06 设计创作，主要内容包括：本发明公开了一种燃料电池堆,所述燃料电池堆包括：基座,所述基座上具有原料氢气入口、第一空气入口,所述基座内具有与所述原料氢气入口、所述第一空气入口分别连通的处理腔；CO消除模块,所述CO消除模块的至少一部分设于所述处理腔内；发电模块,所述发电模块的至少一部分设于所述处理腔内,在原料氢气的流动方向上,所述CO消除模块位于所述发电模块的上游。根据本发明实施例的燃料电池堆具有容忍一定浓度CO的能力、CO消除模块和发电模块易于集成、降低燃料电池堆用氢成本等优点。(The invention discloses a fuel cell stack, comprising: the hydrogen treatment device comprises a base, a hydrogen gas inlet, a first air inlet, a second air inlet, a hydrogen gas outlet and a hydrogen gas inlet, wherein a treatment cavity communicated with the hydrogen gas inlet and the first air inlet is formed in the base; a CO elimination module, at least a portion of which is disposed within the processing chamber; and at least one part of the power generation module is arranged in the processing cavity, and the CO elimination module is positioned at the upstream of the power generation module in the flowing direction of the raw material hydrogen. The fuel cell stack disclosed by the embodiment of the invention has the advantages of capability of tolerating CO with a certain concentration, easiness in integration of the CO elimination module and the power generation module, reduction of the cost of hydrogen used by the fuel cell stack and the like.)

1. A fuel cell stack, comprising:

the hydrogen treatment device comprises a base, a hydrogen gas inlet, a first air inlet, a second air inlet, a hydrogen gas outlet and a hydrogen gas inlet, wherein a treatment cavity communicated with the hydrogen gas inlet and the first air inlet is formed in the base;

a CO elimination module, at least a portion of which is disposed within the processing chamber;

and at least one part of the power generation module is arranged in the processing cavity, and the CO elimination module is positioned at the upstream of the power generation module in the flowing direction of the raw material hydrogen.

2. The fuel cell stack of claim 1 wherein the CO elimination module comprises a CO elimination membrane electrode, the anode side of which is coated with a catalyst that oxidizes CO.

3. The fuel cell stack of claim 2 wherein the CO oxidation catalyst is at least one of a PtRu/C, Ru/C, Pt/C, PtM/C binary alloy catalyst, a PtMN/C ternary alloy catalyst.

4. The fuel cell stack according to claim 2, wherein at least one CO elimination membrane electrode is provided, and the number of the CO elimination membrane electrodes is positively correlated with the concentration of CO in the raw material hydrogen.

5. The fuel cell stack of claim 1 wherein the base further comprises a second air inlet, and wherein the raw hydrogen entering the raw hydrogen inlet mixes with air entering the second air inlet and flows to the inlet of the CO elimination module.

6. The fuel cell stack according to claim 5, wherein the intake amount of air in the second air inlet is positively correlated with the concentration of CO in the raw material hydrogen gas, and the ratio of the intake amount of air in the second air inlet to the intake amount of raw material hydrogen gas in the raw material hydrogen gas inlet is greater than 0.5% and less than 5%.

7. The fuel cell stack according to claim 1, wherein the power generation module includes at least one power generation membrane electrode, an anode side of the power generation membrane electrode communicates with an outlet of the CO elimination module, and a cathode side of the power generation membrane electrode communicates with the first air inlet.

8. The fuel cell stack of claim 1, wherein the operating temperature of the CO elimination module is lower than the operating temperature of the power generation module.

9. The fuel cell stack of claim 1, wherein the base further has a coolant inlet and a coolant outlet, and wherein the base has a coolant flow path therein in communication with the coolant inlet and the coolant outlet, the coolant flow path passing through the CO elimination module before passing through the power generation module.

10. The fuel cell stack of claim 9, wherein the base comprises:

the raw material hydrogen inlet and the cooling liquid inlet are arranged on the first end plate, and the first air inlet and the cooling liquid outlet are arranged on the second end plate;

a plurality of bipolar plates disposed between the first end plate and the second end plate, the first end plate, the second end plate, and the plurality of bipolar plates defining the process chamber and the coolant flow path.

11. The fuel cell stack according to claim 10, wherein said CO elimination module comprises a plurality of CO elimination membrane electrodes, and said power generation module comprises a plurality of power generation membrane electrodes, each of said CO elimination membrane electrodes being sandwiched between two adjacent bipolar plates or said bipolar plate and a first end plate, and each of said power generation membrane electrodes being sandwiched between two adjacent bipolar plates or said bipolar plate and a second end plate.

12. The fuel cell stack of claim 10, wherein the base further comprises fasteners that are coupled to the first end plate, the second end plate, and the plurality of bipolar plates, respectively.

13. The fuel cell stack of claim 10 wherein the base further defines a first current collector plate and a second current collector plate.

Technical Field

The invention relates to the technical field of fuel cell manufacturing, in particular to a fuel cell stack.

Background

The rapid development of the fuel cell depends on the construction of hydrogen infrastructure and the convenient acquisition of low-cost hydrogen, and the non-pure hydrogen obtained by the modes of blue hydrogen, ash hydrogen, on-line hydrogen production and the like has low cost, various sources and wide distribution, and is an important hydrogen supply mode in the future. The CO contained in the non-pure hydrogen can cause the poisoning failure of a Pt catalyst used by the fuel cell and reduce the performance output of the fuel cell, and is a technical problem which needs to be solved urgently.

The fuel cell can improve the tolerance capability to CO by using a high-temperature proton exchange membrane fuel cell, injecting anode air, regulating and controlling working conditions, using an improved membrane electrode and the like. These methods all have certain effects but have not yet achieved practical requirements. The high-temperature proton exchange membrane fuel cell works at 180 ℃ of 120 ℃, and CO is compared with H at high temperature₂Adsorption capacity on Pt catalysts is reduced, enabling fuel cells to tolerate higher levels of CO, studies have shown that high temperature proton exchange membrane fuel cells can tolerate up to 5% CO, and the higher the operating temperature, the stronger the tolerance. However, the high temperature proton exchange membrane fuel cell has the problems of low PBI membrane conductivity, poor durability caused by phosphoric acid loss, long cold start time and the like. The industrial control method is to slow down the poisoning of CO by changing the operation conditions of the fuel cell, such as increasing the operation temperature and increasing the back pressure of the cathode, but these methods are only suitable for relieving the poisoning in short-term operation and cannot fundamentally solve the poisoning problem of high-concentration CO. The anode air injection is to mix a certain amount of air into the impure hydrogen and remove CO on the surface of the Pt by using oxygen, so that the poisoning effect of the CO can be quickly eliminated, but Pt dissolution and accelerated aging of the proton exchange membrane can be caused.

The improvement of the membrane electrode is a research hotspot and has more development prospect. The improvement of the membrane electrode mainly has two modes, namely, the change of the anode catalyst component and the change of the membrane electrode configuration. The common binary or multi-element alloy catalyst replaces the traditional carbon-supported platinum (Pt/C) catalyst, the CO tolerance is improved, and meanwhile, the catalyst has high Hydrogen Oxidation (HOR) activity, such as PtRu/C, Ru/C, PtMo/C, PtCo/C and the like, in the aspect of changing the configuration of the membrane electrode, the common method is to use CCM as the basis, add an auxiliary catalyst capable of oxidizing CO, match the auxiliary catalyst and the Pt electrocatalyst on the layer surface of the membrane electrode, and achieve the membrane electrode which eliminates CO and has high power generation performance. The method has three defects that firstly, the auxiliary catalyst and the point catalyst are very close, CO is extremely easy to eliminate and poisons a Pt catalyst layer, the improvement level of the resistance of the pile to CO is limited, secondly, the CO treatment catalyst needs to be distributed on each membrane electrode, the cost is increased, thirdly, the membrane electrode configuration and the catalyst loading capacity greatly influence the mass transfer and the load transfer, and the performance of the obtained membrane electrode cannot be improved necessarily.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides the fuel cell stack which has the advantages of capability of tolerating CO with certain concentration, easiness in integration of the CO elimination module and the power generation module, reduction of the cost of hydrogen used by the fuel cell stack and the like.

To achieve the above object, there is provided a fuel cell stack according to an embodiment of the present invention, including: the hydrogen treatment device comprises a base, a hydrogen gas inlet, a first air inlet, a second air inlet, a hydrogen gas outlet and a hydrogen gas inlet, wherein a treatment cavity communicated with the hydrogen gas inlet and the first air inlet is formed in the base; a CO elimination module, at least a portion of which is disposed within the processing chamber; and at least one part of the power generation module is arranged in the processing cavity, and the CO elimination module is positioned at the upstream of the power generation module in the flowing direction of the raw material hydrogen.

The fuel cell stack disclosed by the embodiment of the invention has the advantages of capability of tolerating CO with a certain concentration, easiness in integration of the CO elimination module and the power generation module, reduction of the cost of hydrogen used by the fuel cell stack and the like.

In addition, the fuel cell stack according to the above embodiment of the present invention may further have the following additional technical features:

according to some embodiments of the invention, the CO elimination module comprises a CO elimination membrane electrode, the anode side of which is coated with a catalyst that oxidizes CO.

According to some embodiments of the invention, the catalyst for oxidizing CO is at least one of a PtRu/C, Ru/C, Pt/C, PtM/C binary alloy catalyst, a PtMN/C ternary alloy catalyst.

According to some embodiments of the present invention, at least one of the CO elimination membrane electrodes is provided, and the number of the CO elimination membrane electrodes is positively correlated with the concentration of CO in the raw material hydrogen.

According to some embodiments of the invention, the base further comprises a second air inlet, and the raw material hydrogen entering from the raw material hydrogen inlet is mixed with the air entering from the second air inlet and flows to the inlet of the CO elimination module.

According to some embodiments of the present invention, the air intake amount in the second air inlet is positively correlated with the CO concentration in the raw material hydrogen, and the ratio of the air intake amount in the second air inlet to the raw material hydrogen intake amount in the raw material hydrogen inlet is greater than 0.5% and less than 5%.

According to some embodiments of the invention, the power generation module comprises at least one power generation membrane electrode, the anode side of which communicates with the outlet of the CO elimination module, and the cathode side of which communicates with the first air inlet.

According to some embodiments of the invention, the operating temperature of the CO elimination module is lower than the operating temperature of the power generation module.

According to some embodiments of the invention, the base further has a coolant inlet and a coolant outlet, and the base has a coolant flow path therein communicating with the coolant inlet and the coolant outlet, the coolant flow path flowing through the CO elimination module before flowing through the power generation module.

According to some embodiments of the invention, the base comprises: the raw material hydrogen inlet, the first air inlet and the cooling liquid inlet are arranged on the first end plate, and the second air inlet and the cooling liquid outlet are arranged on the second end plate; a plurality of bipolar plates disposed between the first end plate and the second end plate, the first end plate, the second end plate, and the plurality of bipolar plates defining the process chamber and the coolant flow path.

According to some embodiments of the invention, the CO elimination module comprises a plurality of CO elimination membrane electrodes, the power generation module comprises a plurality of power generation membrane electrodes, each of the CO elimination membrane electrodes is sandwiched between two adjacent bipolar plates or the bipolar plate and a first end plate, and each of the power generation membrane electrodes is sandwiched between two adjacent bipolar plates or the bipolar plate and a second end plate.

According to some embodiments of the invention, the base further comprises fasteners respectively associated with the first end plate, the second end plate, and the plurality of bipolar plates.

According to some embodiments of the invention, the base is further provided with a first collecting plate and a second collecting plate.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic structural view of a fuel cell stack according to an embodiment of the present invention.

Fig. 2 is a schematic structural view of a fuel cell stack according to an embodiment of the present invention.

Reference numerals: the fuel cell stack 1, a raw material hydrogen inlet 101, a first air inlet 102, a coolant inlet 103, a first end plate 110, a second end plate 120, a bipolar plate 130, a first collecting plate 141, a second collecting plate 142, a CO eliminating membrane electrode 210, and a power generation membrane electrode 310.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

A fuel cell stack 1 according to an embodiment of the present invention is described below with reference to the drawings.

As shown in fig. 1 to 2, a fuel cell stack 1 according to an embodiment of the present invention includes a base, a CO elimination module, and a power generation module.

In some embodiments, the susceptor has a raw material hydrogen inlet 101, a first air inlet 102, and the raw material hydrogen inlet 101 is used for introducing raw material hydrogen, and it is understood that the raw material hydrogen is non-pure hydrogen and the raw material hydrogen at least includes H₂And CO, e.g. feed hydrogen includes H2, CO and CO₂. The first air inlet 102 is used for introducing air, a processing cavity is arranged in the base, and the processing cavity is respectively communicated with the raw material hydrogen inlet 101 and the first air inlet 102. Thus, the raw materials of hydrogen and air can enter the cathode side and the anode side of the power generation module in the base respectively according to requirements to generate power.

At least a part of the CO elimination module is arranged in the processing cavity, at least a part of the power generation module is arranged in the processing cavity, and the CO elimination module is positioned at the upstream of the power generation module in the flowing direction of the raw material hydrogen. That is, the CO elimination module and the power generation module are connected in series in the flow relationship of the impure raw material hydrogen, and the raw material hydrogen firstly flows through the CO elimination module to eliminate CO and then flows through the power generation module to perform reaction power generation. Therefore, CO gas contained in the raw material hydrogen can be reacted and eliminated when flowing through the CO eliminating module, the CO concentration in the non-pure hydrogen is reduced, and then the raw material hydrogen enters the power generation module to carry out normal power generation.

According to the fuel cell stack 1 provided by the embodiment of the invention, the CO eliminating module and the power generation module are arranged, and the CO in the raw material hydrogen is eliminated in a centralized manner by the preposed CO eliminating module, so that the fuel cell stack 1 which is not tolerant to the CO originally has the capability of tolerating the CO with a certain concentration, the requirement on the purity of the raw material hydrogen can be reduced, the problem of CO poisoning is solved, and the popularization of the hydrogen fuel cell is facilitated.

Moreover, the centralized CO treatment helps to reduce the consumption of CO eliminating catalysts, so that the hydrogen cost of the fuel cell stack 1 is reduced, and the operation cost of the fuel cell stack 1 is reduced. In the flowing process of the raw material hydrogen, the raw material hydrogen can be humidified by using water generated on the air side, and a humidifier on the hydrogen side (anode side) of the power generation module can be omitted. Meanwhile, the CO elimination module and the power generation module are easy to integrate, and the structure of the original fuel cell stack 1 is not changed greatly.

Therefore, the fuel cell stack 1 according to the embodiment of the present invention has the advantages of the capability of tolerating a certain concentration of CO, the easy integration of the CO elimination module and the power generation module, the reduction of the cost of hydrogen for the fuel cell stack 1, and the like.

A fuel cell stack 1 according to an embodiment of the present invention is described below with reference to the drawings.

In some specific embodiments of the present invention, as shown in fig. 1 to 2, a fuel cell stack 1 according to an embodiment of the present invention includes a base, a CO elimination module, and a power generation module.

In some embodiments of the invention, as shown in fig. 1 and 2, the CO elimination module includes a CO elimination membrane electrode 210, the anode side of the CO elimination membrane electrode 210 being coated with a catalyst that oxidizes CO. During operation, the raw material hydrogen introduced through the raw material hydrogen inlet 101 may flow to the anode side of the CO elimination membrane electrode 210, and CO in the raw material hydrogen is removed by oxidation reaction at the anode side of the CO elimination membrane electrode 210, thereby reducing the CO concentration in the raw material hydrogen. Meanwhile, water generated by reaction on the air side (cathode side) of the power generation module of the fuel cell stack 1 may be collected to the cathode side of the CO elimination membrane electrode 210, and the raw material hydrogen gas after the CO removal treatment may be humidified by water permeated from the cathode side of the CO elimination membrane electrode 210, so that a humidifier on the hydrogen side may be eliminated.

It is to be understood herein that the power generation module may include the power generation membrane electrode 310, the power generation membrane electrode 310 having a cathode side (positive side) and an anode side (negative side). And introducing hydrogen as a raw material subjected to CO removal treatment on the anode side, wherein the hydrogen is used as the raw material. Air is introduced into the cathode side, and oxygen is used as a raw material. The power generation membrane electrode 310 can generate power while generating water after the reaction.

Also, the CO elimination module includes a CO elimination membrane electrode 210, and the CO elimination membrane electrode 210 has a cathode side (positive side) and an anode side (negative side). The anode side of the CO elimination membrane electrode 210 is fed with hydrogen as a raw material, and the hydrogen as the raw material is reacted to remove CO therefrom. The water generated by the power generation membrane electrode 310 may be collected on the cathode side (positive side) of the CO elimination membrane electrode 210, and the raw material hydrogen gas after the CO removal treatment may be humidified by the water permeated from the cathode side of the CO elimination membrane electrode 210.

In some alternative embodiments, the catalyst for oxidizing CO is at least one of a PtRu/C, Ru/C, Pt/C, PtM/C binary alloy catalyst and a PtMN/C ternary alloy catalyst, wherein M, N is other kinds of metal elements. Thus, the CO can react with the oxygen in the air through the catalytic action of the catalyst, so as to remove the CO in the raw material hydrogen.

Optionally, at least one CO elimination membrane electrode 210 is provided, and the number of the CO elimination membrane electrodes 210 is positively correlated with the concentration of CO in the raw material hydrogen. That is, the number of the CO elimination membrane electrodes 210 is one or more, and the number of the CO elimination membrane electrodes 210 is determined by the concentration of CO in the raw material hydrogen.

In some embodiments of the invention, the base also has a second air inlet therein, the air in the second air inlet originating from the air supply end of the fuel cell stack 1, the second air inlet being disposed adjacent to the raw material hydrogen inlet 101. The raw material hydrogen entering the raw material hydrogen inlet 101 is mixed with the air entering the second air inlet and flows to the inlet of the CO elimination module. Thus, under the action of the catalyst of the CO elimination module, CO can react with oxygen in the air to remove CO in the raw material hydrogen.

In some embodiments, the air intake amount of the second air inlet is positively correlated with the concentration of CO in the raw material hydrogen, that is, the air intake amount of the second air inlet is determined by the concentration of CO in the raw material hydrogen. Further, the ratio of the air intake amount in the second air inlet to the raw material hydrogen intake amount in the raw material hydrogen inlet 101 is more than 0.5% and less than 5%. Here, it is to be understood that the intake air amount refers to the volume flow rate of the gas.

In some embodiments of the present invention, as shown in fig. 1 and 2, the power generation module includes at least one power generation membrane electrode 310, the anode side of the power generation membrane electrode 310 communicates with the outlet of the CO elimination module, and the cathode side of the power generation membrane electrode 310 communicates with the first air inlet 102. The hydrogen gas from which CO has been removed in this way may flow to the power generation membrane electrode 310 and react on the anode side of the power generation membrane electrode 310, and the air taken in from the first air inlet 102 may flow to the cathode side of the power generation membrane electrode 310 and react on the cathode side of the power generation membrane electrode 310, whereby the power generation membrane electrode 310 may generate electricity.

In some alternative embodiments, the operating temperature of the CO elimination module is lower than the operating temperature of the power generation module. Thus, H in the raw material hydrogen can be inhibited when the CO elimination module removes CO₂The reaction takes place.

Alternatively, as shown in fig. 1, the base further has a coolant inlet 103 and a coolant outlet, and a coolant flow path communicating with the coolant inlet 103 and the coolant outlet is provided in the base, and the coolant flow path flows through the CO elimination module and then flows through the power generation module. That is, the coolant flows into the coolant flow path from the coolant inlet 103, then flows to the CO elimination module first, cools and reduces the temperature of the CO elimination module, then flows to the power generation module again, cools and reduces the temperature of the power generation module, and finally flows out from the coolant outlet.

In some embodiments, as shown in fig. 1, the base includes a first end plate 110, a second end plate 120, and a plurality of bipolar plates 130, a feed hydrogen inlet 101 and a coolant inlet 103 are provided in the first end plate 110, and a first air inlet 102 and a coolant outlet are provided in the second end plate 120. A plurality of bipolar plates 130 are disposed between the first end plate 110 and the second end plate 120, the first end plate 110, the second end plate 120, and the plurality of bipolar plates 130 defining a process chamber and a coolant flow path. Specifically, the plurality of bipolar plates 130 are sandwiched between the first end plate 110 and the second end plate 120, and the first end plate 110, the second end plate 120, and the plurality of bipolar plates 130 are clamped and fixed. This makes it possible to support and fix the CO elimination module and the power generation module by the base, and also facilitates formation of the CO elimination module, the installation space of the power generation module, and the gas flow path and the coolant flow path in the base to facilitate operation of the fuel cell stack 1 for power generation.

Alternatively, the first end plate 110, the second end plate 120, and the plurality of bipolar plates 130 may be respectively formed with through holes penetrating in the thickness direction, and the through holes may form a gas flow passage and a coolant flow passage after the first end plate 110, the second end plate 120, and the plurality of bipolar plates 130 are tightly fitted together.

Specifically, the CO elimination module includes a plurality of CO elimination membrane electrodes 210, and the power generation module includes a plurality of power generation membrane electrodes 310, each CO elimination membrane electrode 210 being sandwiched between two adjacent bipolar plates 130 or bipolar plates 130 and the first end plate 110, and each power generation membrane electrode 310 being sandwiched between two adjacent bipolar plates 130 or bipolar plates 130 and the second end plate 120. This makes it possible to reliably support and fix the CO elimination membrane electrode 210 and the power generation membrane electrode 310, and also facilitates the reaction of the gas at the CO elimination membrane electrode 210 and the power generation membrane electrode 310.

In some embodiments, the base further comprises fasteners that are coupled to the first end plate 110, the second end plate 120, and the plurality of bipolar plates 130, respectively. Alternatively, the fastening member may be a fastening bolt which passes through the first end plate 110, the plurality of bipolar plates 130, and the second end plate 120 in sequence, and the fastening bolt cooperates with a nut to compressively couple the first end plate 110, the plurality of bipolar plates 130, and the second end plate 120.

Optionally, as shown in fig. 1, the susceptor is further provided with a first collecting plate 141 and a second collecting plate 142. Specifically, first collector plate 141 may have a negative electrode tab connected to the external power transmission structure, and second collector plate 142 may have a positive electrode tab connected to the external power transmission structure.

According to the fuel cell stack 1, a plurality of power generation membrane electrodes 310 near a raw material hydrogen inlet 101 are replaced by the CO elimination membrane electrode 210, the gas path structure is changed, non-pure raw material hydrogen passes through the CO elimination membrane electrode 210, CO is converted into gas without toxic action on a fuel cell catalyst, and the purified gas is sent to the following power generation membrane electrode 310 to generate power. The fuel cell stack 1 configuration utilizes a plurality of preposed CO elimination membrane electrodes 210 to intensively eliminate CO, so that the fuel cell stack 1 which is not tolerant to CO originally has the capability of tolerating CO with certain concentration, and has the advantages that a CO elimination module and a power generation module are easy to integrate, the structure of the original fuel cell stack 1 is not greatly changed, and the hydrogen cost for the fuel cell can be reduced.

Other constructions and operations of the fuel cell stack 1 according to the embodiment of the present invention are known to those skilled in the art and will not be described in detail herein.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention. Furthermore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified. In the description of the present invention, the first feature being "on" or "under" the second feature may include the first and second features being in direct contact, and may also include the first and second features being in contact with each other not directly but through another feature therebetween.

In the description of the invention, "above", "over" and "above" a first feature in a second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.