Separator paper for electrochemical cells

Patent metadata

Field	Value
Publication number	US-2016197325-A1
Application number	US-201414917112-A
Country	US
Kind code	A1
Filing date	Aug 28, 2014
Priority date	Sep 6, 2013
Publication date	Jul 7, 2016
Grant date	—

Abstract

A paper suitable for use as separator in an electrochemical cell, including at least 60 wt. % of an aramid fibril and at least 1 wt. % of an aramid fiber. The paper has a grammage of 5 to 100 g/m2, and the aramid fibril has a Canadian Standard Freeness (CSF) in a wet phase of less than 300 ml and a specific surface area (SSA) after drying of less than 3 m2/g. It has been found that a paper with this composition combines good electrolyte absorption and ion permeability with high stability during use, leading to a long lifetime for the electrochemical cell.

First claim

1 . A paper suitable for use as a separator in an electrochemical cell, comprising:
at least 60 wt. % of an aramid fibril; and at least 1 wt. % of an aramid fiber, wherein; the paper has a grammage of 5 to 100 g/m2; and the aramid fibril has a Canadian Standard Freeness (CSF) in a wet phase of less than 300 ml and a specific surface area (SSA) after drying of less than 3 m2/g.

2 . The paper according to claim 1 , wherein the paper comprises at most 90 wt. % of the aramid fibril.

3 . The paper according to claim 1 , wherein the CSF of the aramid fibril in the wet phase is less than 200 ml.

4 . The paper according to claim 1 , wherein the aramid fibril has a weight weighted length for particles having a length above 250 micron (WL0.25) of less than 1.2 mm.

5 . The paper according to claim 1 , wherein the paper comprises at least 5 wt % and at most 38 wt. % of the aramid fiber.

6 . The paper according to claim 1 , wherein the aramid fiber has a number-average length in the range of 2-15 mm.

7 . The paper according to claim 1 , wherein the aramid fiber is a meta-para aramid and/or para-aramid fiber, and the paper comprises at least 70 wt. % of a total of the meta-para aramid and para-aramid fiber.

8 . The paper according to claim 1 , wherein the grammage of the paper is 5-50 g/m2.

9 . A method for manufacturing a paper according to claim 1 , comprising:
preparing a suspension comprising the aramid fibril, the aramid fiber, and optional further components; applying the suspension onto a porous screen so as to lay down a mat of randomly interwoven material onto the screen; removing water from the mat; drying the mat to form a paper; and optionally subjecting the paper to a calendaring step.

10 . The method according to claim 9 , further comprising manufacturing the aramid fibril by a process comprising;
polymerizing an aromatic diamine and an aromatic dicarboxylic acid halide to produce an aramid polymer, in a mixture of N-methylpyrrolidone or dimethylacetamide and calcium chloride or lithium chloride, to obtain a dope wherein the polymer is dissolved in the mixture and the polymer concentration is 2 to 6 wt. %; converting the dope to fibrils by using a jet spin nozzle under a gas stream; coagulating the fibrils using a coagulation jet; and optionally subjecting the fibrils to shear forces.

11 - 12 . (canceled)

13 . An electrochemical cell, comprising a cathode, an anode, and an electrolyte between the cathode and the anode, wherein the cathode and the anode are separated by the separator paper according to claim 1 .

14 . The electrochemical cell according to claim 13 , wherein the electrochemical cell is a lithium ion battery, and the electrolyte comprises lithium ions.

15 . The lithium ion battery according to claim 14 , wherein the anode comprises carbon, the cathode comprises a metal oxide or metal phosphate, and the electrolyte comprises a lithium complex in an organic solvent.

16 . The paper according to claim 1 , wherein the aramid fibril is a para-aramid fibril.

17 . The paper according to claim 1 , wherein the aramid fiber is a meta-para-aramid or para-aramid fiber.

18 . The paper according to claim 1 , wherein the SSA after drying of the aramid fibril is less than 1.5 m2/g.

19 . The paper according to claim 1 , wherein the aramid fiber has a linear density of less than 1.6 dtex.

20 . The paper according to claim 1 , wherein the aramid fiber includes a para-aramid fiber, and the paper comprises at least 60 wt. % of the para-aramid fiber.

Assignees

• Teijin Aramid Bv

Inventors

• Alvarado Chacon Fresia
• Van Rooij Ramon
• Visser Richard
• Tiecken Jan David
• Diedering Frank

Classifications

• H01B3/52

  wood; paper; press board · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• D21H13/26 Primary

  Polyamides; Polyimides · CPC title

• H01M50/494

  Tensile strength · CPC title

• H01M50/423

  Polyamide resins · CPC title