1. A metal foil electrode comprising
i) a reinforcement layer formed from a porous substrate, and
ii) first and second layers of metal foil formed comprising lithium andor sodium, wherein the reinforcement layer is disposed between the first and second metal foil layers and bonded (preferably pressure bonded) together to form a composite structure having a thickness of 100 microns or less.
2. A metal foil electrode as claimed in claim 1, wherein the composite structure has a thickness of 60 microns or less.
3. A metal foil electrode as claimed in claim 1 or 2, wherein the metal foil is formed of lithium metal.
4. A metal foil as claimed in any one of the preceding claims, wherein the porous substrate is formed from a non-conducting material.
5. A metal foil as claimed in any one of the preceding claims, wherein the porous substrate is formed from a fibrous material.
6. A metal foil as claimed in any one of the preceding claims, wherein the fibrous material is a material formed from polymer fibres.
7. A metal foil electrode as claimed in any one of the preceding claims, wherein the porous substrate is formed of a material selected from at least one of non-woven fabric, woven fabric and polymer mesh.
8. A metal foil electrode as claimed in claim 7, wherein the non-woven or woven fabric is free from metal.
9. A metal foil electrode as claimed in claim 7 or 8, wherein the porous substrate is formed from a non-woven polypropylene fabric.
10. A metal foil electrode as claimed in any one of the preceding claims, wherein the reinforcement layer has a density of less than 6 gcm3.
11. An electrochemical cell comprising a metal foil electrode as claimed in any one of the preceding claims.
12. An electrochemical cell as claimed in claim 11, which is a lithium-sulphur cell comprising the metal foil electrode as the anode, a sulphur-containing cathode and an electrolyte.
13. An electrochemical cell as claimed in any one of claims 11 to 12, wherein the cell is a reversible electrochemical cell.
14. A method of forming a metal foil electrode, which comprises:
providing a reinforcement layer formed from a porous substrate,
providing first and second layers of metal foil formed from lithium andor sodium,
placing the reinforcement layer between said first and second layers of metal foil, and
applying pressure to bond the layers together to form a composite structure,
whereby the thickness of the composite structure is at least 25% less than the sum of the initial thicknesses of the reinforcement layer, first layer of metal foil and second layer of metal foil.
15. A method as claimed in claim 14, wherein the metal foil electrode is an electrode as claimed in any one of claims 1 to 10.
16. A method as claimed in claim 14 or 15, which further comprises the step of cutting the composite structure.
17. A method as claimed in any one of claims 14 to 16, wherein the thickness of the composite structure is at least 50% less than the sum of the initial thicknesses of the reinforcement layer, first layer of metal foil and second layer of metal foil.
18. A method as claimed in claim 17, wherein the thickness of the composite structure is at least 75% less than the sum of the initial thicknesses of the reinforcement layer, first layer of metal foil and second layer of metal foil.
19. A method as claimed in any one of claims 14 to 18, wherein the thickness of the composite structure is less than the sum of the initial thicknesses of the first layer of metal foil and second layer of metal foil.
20. A method as claimed in claim 19, wherein the thickness of the composite structure is less than the initial thickness of the first layer of metal foil or the second layer of metal foil.
21. A method as claimed in any one of claims 14 to 20, which further comprises using the electrode as an anode of an electrochemical cell.
22. A method as claimed in any one of claims 14 to 21, wherein the pressure bonding step is achieved by calendaring the layers together to form a composite structure.
The claims below are in addition to those above.
All refrences to claims which appear below refer to the numbering after this setence.
1. A method of detecting an abnormality of a capacitor in a circuit in which two or more capacitors are connected in series, the method comprising:
measuring capacitance of the circuit from both ends of the circuit;
storing the measured capacitance of the circuit and hours of use of the circuit during the measurement in a storage unit;
calculating a decrease rate of the capacitance according to the hours of use of the circuit based on capacitance data of the circuit and data of the hours of use of the circuit stored according to a plurality of times of measurement; and
determining whether an abnormality is generated in at least one capacitor configuring the circuit by comparing the measured capacitance of the circuit and capacitance expected according to the calculated decrease rate.
2. The method of claim 1, wherein the determining includes determining that the abnormality is generated in the capacitor in a case where the measured capacitance of the circuit is beyond a predetermined range from the capacitance expected according to the calculated decrease rate.
3. The method of claim 1, further comprising:
estimating the number of abnormalities by calculating average capacitance of unit capacitors configuring the circuit based on the capacitance expected according to the calculated decrease rate, and estimating the number of capacitors in which the abnormality is generated based on the calculated average capacitance, the number of capacitors configuring the circuit, and the measured capacitance of the circuit.
4. A method of detecting an abnormality of a capacitor in a circuit in which two or more capacitors are connected in series, the method comprising:
measuring capacitance of the circuit from both ends of the circuit;
storing the capacitance of the circuit according to a plurality of times of measurement and hours of use of the circuit during the measurement in a storage unit; and
determining whether the measured capacitance of the circuit is larger than capacitance of the circuit which is measured and stored just before the measurement by a predetermined value, and determining that the abnormality is generated in at least one capacitor configuring the circuit when it is determined that the measured capacitance of the circuit is larger than capacitance of the circuit which is measured and stored just before the measurement by the predetermined value.
5. An apparatus for detecting an abnormality of a capacitor in a circuit in which two or more capacitors are connected in series, the apparatus comprising:
a measuring unit configured to measure capacitance of the circuit from both ends of the circuit;
a storage unit configured to store the measured capacitance of the circuit and hours of use of the circuit during the measurement; and
a determining unit configured to determine whether an abnormality is generated in at least one capacitor configuring the circuit by comparing the measured capacitance of the circuit and predetermined expected capacitance.
6. The apparatus of claim 5, wherein the predetermined expected capacitance is capacitance of the circuit measured and stored just before the measurement of the capacitance, and
the determining unit determines that the abnormality is generated in said at least one capacitor by determining whether the measured capacitance of the circuit is larger than the capacitance of the circuit measured and stored just before the measurement of the capacitance by a predetermined value.
7. The apparatus of claim 5, further comprising:
a calculation unit configured to calculate a decrease rate of the capacitance according to hours of use of the circuit based on capacitance data of the circuit and data of the hours of use of the circuit stored according to a plurality of times of measurement,
wherein the determining unit compares the measured capacitance of the circuit and the expected capacitance.
8. The apparatus of claim 6, further comprising:
a calculation unit configured to calculate a decrease rate of the capacitance according to hours of use of the circuit based on capacitance data of the circuit and data of the hours of use of the circuit stored according to a plurality of times of measurement; and
an abnormality number estimating unit configured to calculate average capacitance of unit capacitors configuring the circuit based on the capacitance expected according to the calculated decrease rate, and estimate the number of capacitors in which the abnormality is generated based on the calculated average capacitance, the number of capacitors configuring the circuit, and the measured capacitance of the circuit.