Non-aqueous electrolyte secondary battery

Abstract

The invention relates to a non-aqueous electrolyte secondary battery cathod of which adopts a negative electrode active material capable of alloying with lithium. The non-aqueous electrolyte used by the non-aqueous electrolyte secondary battery is improved; the charge and discharge cycle characteristic and the storage characteristic at the charge state are improved. The non-aqueous electrolyte secondary battery comprises a positive electrode (1), a negative electrode (2), a separator (3) interposed between the positive electrode and the negative electrode, and non-aqueous electrolyte solution in which a solute is dissolved in a non-aqueous solvent. The negative electrode uses a negative electrode active material capable of alloying with lithium and uses fluorinated cyclic carbonates and a carboxylic ester as the non-aqueous solvent of the non-aqueous electrolyte solution. In addition, the non-aqueous electrolyte solution contains a nitrile compound having a chain saturated hydrocarbon group with two or more carbon atoms.

Description

Technical field [0001] The present invention relates to a non-aqueous electrolyte secondary battery, which includes a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution in which a solute is dissolved in a non-aqueous solvent. In particular, the non-aqueous electrolyte secondary battery using the negative electrode active material alloyed with lithium in the negative electrode in order to increase the charge and discharge capacity has the following characteristics: it can improve the non-aqueous electrolyte and the charge and discharge cycle characteristics while improving Storage characteristics under charge. Background technique [0002] In recent years, non-aqueous electrolyte secondary batteries that use a non-aqueous electrolyte solution and allow lithium ions to move between a positive electrode and a negative electrode to perform charging and discharging have been used as po...

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Problems solved by technology

[0006] However, when graphite material is used as the negative electrode active material, there is a problem that the capacity in the graphite material is not necessarily sufficient, and the above requirements cannot be fully met.

[0008] However, these materials that form an alloy with lithium have a large volume change as lithium is absorbed and released, and when charge and discharge are performed, an electrode body formed by interposing a separator between the positive electrode and the negative electrode, especially a separator interposed between the positive electrode In the electrode body wound between the negative electrode and the non-aqueous electrolyte, there are problems in that the non-aqueous electrolyte held inside flows out to cause liquid depletion, the internal resistance of the battery increases significantly, and battery characteristics such as charge-discharge cycle characteristics decrease significantly.

[0010] However, if a non-aqueous solvent composed of fluorocarbonate is used in the non-aqueous electrolytic solution, there are problems as follows: the viscosity of the non-aqueous electrolytic solution increases, the liquid operation of the non-aqueous electrolytic solution in the battery deteriorates, and the internal Resistance increases, battery characteristics such as charge-discharge cycle characteristics decrease

[0012] However, chain carboxylic acid esters such as methyl acetate generally have lower electrochemical stability than chain carbonates such as dimethyl carbonate, and for example, when such a nonaqueous electrolyte secondary battery is charged, it is placed in the In a high temperature environment, there is a problem that the non-aqueous electrolyte is decomposed and the discharge characteristics are significantly reduced.

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