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IMPROVED ANTI-STATIC PROPERTIES OF LITHIUM ION BATTERY SEPARATORS

IP.com Disclosure Number: IPCOM000180891D
Publication Date: 2009-Mar-19
Document File: 3 page(s) / 32K

Publishing Venue

The IP.com Prior Art Database

Abstract

This paper relates to the improvement of the anti-static properties of separators used in the secondary lithium ion battery (LIB) field. The static dissipation properties of the separator were improved by the addition of LITFSI (an imide salt: Lithium (Bis) Trifluoromethane sulfon imide) to the separator. LITFSI is known to exhibit anti-static properties and has been used as an anti-static additive. In the fabrication of batteries, the modified separator will solve many of the process issues associated with static charge effects.

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IMPROVED ANTI-STATIC PROPERTIES OF LITHIUM ION

BATTERY

SEPARATORS

Abstract

This paper relates to the improvement of the anti-static properties of separators used in the secondary lithium ion battery (LIB) field. The static dissipation properties of the separator were improved by the addition of LITFSI (an imide salt: Lithium (Bis) Trifluoromethane sulfon imide) to the separator.  LITFSI is known to exhibit anti-static properties and has been used as an anti-static additive.  In the fabrication of batteries, the modified separator will solve many of the process issues associated with static charge effects.

Key words: LiTFSI, Static, Separator

Background

During the fabrication of lithium ion batteries, electrostatic charge on the separator can cause a variety of problems including adherence of the separator to various surfaces, adsorption of dust or other undesirable particles to the separator surface and can make the separator difficult to divide. This paper focuses on improving the anti-static properties of the separator. Generally speaking, the separator is made from polyethylene (PE), Polypropylene (PP) or PP/PE/PP materials. It is insulator, so the static charge can be high.  This static charge may adversely effect the battery assembly process including causing separator handling issues and may lead to short-circuits or micro short-circuits of the battery if inappropriate contaminants adhere to the separator surface and transfer to the battery during assembly.

LiTFSI is a salt additive and/or an ionic liquid component used in the lithium ion battery field.  It has also recently been used in anti-static applications.  In the lithium ion battery field, LiTFSI is mainly used for electrolytes.  Many patents disclosed that LITFSI salt or additives in the electrolyte will greatly improve battery solid electrolyte interphase (SEI) film formation of the anode and cathode surfaces. Furthermore, good SEI film formation will improve the battery’s high performance, prolong cycle life and reduce gas swelling. Relative to the antistatic field, LiTFSI has been used as additives in rubbers and plastics.  The fact that LiTFSI is already used within the Li ion battery industry, combined with its anti-static properties, make it a good choice as an additive for the separator.

This paper describes the use of LiTFSI as an anti-static additive to modify a separator used in lithium ion batteries.  Use of LiTFSI has three main advantages. First, the modified separator with reduced static charge improves the assembly process for battery makers through improved ease of handling, e.g. can divide the separator more easily.  Second, the modified separator can reduce the probability of battery short-circuit or micro short-circuit by reducing contaminants within the battery.  As described above, static charge can cause contam...