Fluoropolymer membrane for electrochemical devices

Abstract

The present invention pertains to a membrane for an electrochemical device, to a process for manufacturing said membrane and to use of said membrane in a process for manufacturing an electrochemical device.

Claims

1. A membrane for an electrochemical device, said membrane consisting of: at least one polymer (F), wherein polymer (F) is a fluoropolymer, and a liquid medium (L), wherein medium (L) comprises at least one organic carbonate and, optionally, at least one ionic liquid, said membrane being free from one or more metal salts and, optionally, one or more additives.

2. The membrane according to claim 1, wherein polymer (F) is a fluoropolymer hybrid organic/inorganic composite.

3. The membrane according to claim 1, wherein the amount of medium (L) is at least 40% by weight, based on the total weight of said medium (L) and the at least one polymer (F).

4. The membrane according to claim 3, wherein the amount of medium (L) is at least 50% by weight, based on the total weight of said medium (L) and the at least one polymer (F).

5. The membrane according to claim 3, wherein the amount of medium (L) is at least 60% by weight, based on the total weight of said medium (L) and the at least one polymer (F).

6. The membrane according to claim 1, wherein medium (L) consists of at least one organic carbonate and, optionally, at least one ionic liquid.

7. An electrochemical device comprising the membrane according to claim 1.

8. An electrochemical device comprising at least one membrane according to claim 1 between a positive electrode (E) and a negative electrode (E), wherein at least one of the positive electrode (E) and the negative electrode (E) comprises: a current collector, and adhered to said current collector, at least one fluoropolymer layer comprising: at least one polymer (F), wherein polymer (F) is a fluoropolymer, at least one electro-active compound (EA), a liquid medium (L), at least one metal salt (M), optionally, at least one conductive compound (C), and optionally, one or more additives.

9. The electrochemical device according to claim 8, wherein polymer (F) in any of the positive electrode (E) and the negative electrode (E) is a functional polymer (F) comprising recurring units derived from at least one fluorinated monomer, at least one functional hydrogenated monomer comprising at least one carboxylic acid end group and, optionally, at least one hydrogenated monomer different from said functional hydrogenated monomer comprising at least one carboxylic acid end group.

10. The electrochemical device according to claim 9, wherein the functional hydrogenated monomer comprising at least one carboxylic acid end group is selected from the group consisting of (meth)acrylic monomers of formula (V): ##STR00020## wherein each of R.sub.1, R.sub.2 and R.sub.3, equal to or different from each other, is independently a hydrogen atom or a C.sub.1-C.sub.3 hydrocarbon group.

11. The electrochemical device according to claim 8, wherein any of the positive electrode (E) and the negative electrode (E) is a flexible electrode (E), wherein the current collector comprises a polymer substrate and, adhered to said polymer substrate, an electrically conductive layer.

Description

EXAMPLES

Example 1: Manufacture of a Lithium-Ion Battery

(1) A coin cell was manufactured by assembling the membrane prepared according to the general procedure as detailed hereinabove using the liquid medium (L-A) between the negative electrode prepared according to the general procedure as detailed hereinabove using the liquid medium (L-A) (4.9 mAh/cm.sup.2) and the positive electrode prepared according to the general procedure as detailed hereinabove using the electrolyte medium (E-A) containing 2.4 M LiPF.sub.6 (3.3 mAh/cm.sup.2).

(2) The coin cell so obtained was cycled between 2.8 V and 4.15 V. After a step of 2 cycles at C/20-D/20, the test protocol was carried out according to successive series of 5 cycles at C/10-D/10, C/5-D/5, C/2-D/2, C/2-D, C/2-2D.

(3) The discharge capacity values of the coin cell under different discharge rates are set forth in Table 1 here below.

(4) TABLE-US-00001 TABLE 1 Average Discharge C-Rate [mAh/g] 0.05 Discharge D/20 125 0.1 Discharge D/10 118 0.2 Discharge D/5 111 0.5 Discharge D/2 94 1 Discharge D 74 2 Discharge 2D 42 0.05 Discharge D/20 117

Example 2: Manufacture of a Li-Ion Battery

(5) A coin cell was manufactured by assembling the membrane prepared according to the general procedure as detailed hereinabove using the liquid medium (L-A) between the negative electrode prepared according to the general procedure as detailed hereinabove using the electrolyte medium (E-A) containing 2.4 M LiPF.sub.6 (1.8 mAh/cm.sup.2) and the positive electrode prepared according to the general procedure as detailed hereinabove using the liquid medium (L-A) (1.6 mAh/cm.sup.2).

(6) The coin cell so obtained was cycled between 2.6 V and 3.7 V.

(7) After a step of 2 cycles at C/20-D/20, the test protocol was carried out according to successive series of 5 cycles at C/10-D/10, C/5-D/5, C/2-D/2, C/2-D, C/2-2D.

(8) The discharge capacity values of the coin cell under different discharge rates are set forth in Table 2 here below.

(9) TABLE-US-00002 TABLE 2 Average Discharge C-Rate [mAh/g] 0.05 Discharge D/20 114 0.1 Discharge D/10 108 0.2 Discharge D/5 103 0.5 Discharge D/2 94 1 Discharge D 83 2 Discharge 2D 36 0.05 Discharge D/20 102

Example 3: Manufacture of a Li-Ion Battery

(10) A coin cell was manufactured by assembling the membrane prepared according to the general procedure as detailed hereinabove using the liquid medium (L-B) between the negative electrode prepared according to the general procedure as detailed hereinabove using the liquid medium (L-B) and the positive electrode prepared according to the general procedure as detailed hereinabove using the electrolyte medium (E-B) containing 2.4 M LiTFSI (1.6 mAh/cm.sup.2).

(11) The coin cell so obtained was cycled between 2.6 V and 3.7 V.

(12) After a step of 2 cycles at C/20-D/20, the test protocol was carried out according to successive series of 5 cycles at C/10-D/10, C/5-D/5, C/2-D/2, C/2-D, C/2-2D.

(13) The discharge capacity values of the coin cell under different discharge rates are set forth in Table 3 here below.

(14) TABLE-US-00003 TABLE 3 Average Discharge C-Rate [mAh/g] 0.05 Discharge D/20 88 0.1 Discharge D/10 85 0.2 Discharge D/5 83 0.5 Discharge D/2 79 1 Discharge D 76 2 Discharge 2D 56 0.05 Discharge D/20 79

Example 4: Manufacture of a Li-Ion Battery

(15) A coin cell was manufactured by assembling the membrane prepared according to the general procedure as detailed hereinabove using the liquid medium (L-B) between the negative electrode prepared according to the general procedure as detailed hereinabove using the electrolyte medium (E-C) containing 1.2 M LiTDI (1.6 mAh/cm.sup.2) and the positive electrode prepared according to the general procedure as detailed hereinabove using the electrolyte medium (E-C) containing 1.2 M LiTDI (1.6 mAh/cm.sup.2).

(16) The coin cell so obtained was cycled between 2.8 V and 4.15 V.

(17) After a step of 2 cycles at C/20-D/20, the test protocol was carried out according to successive series of 5 cycles at C/10-D/10, C/5-D/5, C/2-D/2, C/2-D, C/2-2D.

(18) The discharge capacity values of the coin cell under different discharge rates are set forth in Table 4 here below.

(19) TABLE-US-00004 TABLE 4 Average Discharge C-Rate [mAh/g] 0.05 Discharge D/20 133 0.1 Discharge D/10 131 0.2 Discharge D/5 126 0.5 Discharge D/2 107 1 Discharge D 96 2 Discharge 2D 53 0.05 Discharge D/20 130

(20) In view of the above, it has been found that the electrochemical device of the invention advantageously exhibits outstanding electrochemical performances due to migration of at least one metal salt contained in at least one of the electrodes towards the membrane of the invention, in spite of the absence of any metal salt and, optionally, one or more additives in said membrane.