Lithium ion secondary battery with high energy density

Abstract

The invention provides a lithium ion secondary battery with high energy density. The lithium ion secondary battery mainly comprises an anode, a cathode and electrolyte. The anode active substance comprises a LiNixCoyM1-x-yO2 material, wherein 0.7<=x<=1.0, 0<=y<=0.3, and M is Co or Mn. Also, the anode active substance is coated with MeaOb on the surface, wherein Me is Al or Ti. The electrolyte comprises lithium salt, a non-aqueous organic solvent, and a nitrile compound additive containing fluoroethylene carbonate (FEC) and chain-shaped saturated hydrocarbon. The operation method of the lithium ion secondary battery comprises steps that: the battery is charged to a charge cutoff voltage of 4.5V or higher, such that the application requirement of the lithium ion battery of high energy density is satisfied.

Description

Technical field: [0001] The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion secondary battery with high energy density. Background technique: [0002] The lithium-ion battery with aluminum-plastic composite film as the outer packaging has the characteristics of high energy density, excellent safety performance, large-capacity monomer and environmental protection; and because of its advantages of thinness, lightness and arbitrary shape, it can be tailored to achieve Miniaturization, light weight, and space maximization, so there is an increasing demand for it as a power source for portable devices such as mobile phones, notebook computers, wireless headsets, Bluetooth devices, MPx, and watches. In addition, this lithium-ion battery is also attracting attention as a power source for Scooter, xEV, etc. [0003] Cathode material is one of the key factors restricting the cost performance of lithium-ion batteries. At present, the...

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Problems solved by technology

Of course, the material itself also has certain defects: it has strong water absorption, and it is easy to gel during the preparation of the slurry, which is difficult to prepare; it is particularly noteworthy that: Li in the structure + and Ni 2+ It is easy to mix and discharge, which leads to the release of active oxygen and makes high-valent nickel ions easily dissolve into the electrolyte, catalyzing the decomposition of the electrolyte, so that the high-nickel (Ni≥0.7mol) Ni-Co-Mn / Al ternary material is made Lithium-ion secondary batteries produce a large amount of gas when stored at high temperature, which deteriorates battery performance. Especially for lithium-ion batteries that use aluminum-plastic composite film or iron-plastic composite film as the outer packaging, the outer shell is relatively soft, and the generation of gas will lead to rapid battery life. Expansion and deformation, bringing serious safety hazards, thus limiting its use

However, when the charging cut-off voltage is greater than or equal to 4.25V, the side reaction between the high-nickel (Ni≥0.7mol) Ni-Co-Mn / Al ternary material and the electrolyte will be accelerated, so that while the electrolyte is decomposed, the metal Ions are eluted from the positive electrode and deposited on the surface of the negative electrode, which drastically deteriorates the high-temperature storage performance, cycle performance and safety performance of lithium-ion secondary batteries, which limits the use of high-nickel (Ni≥0.7mol) Ni-Co-Mn / Al ternary materials Applications under high voltage (≥4.25V)

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