Lithium ion battery and anode active material thereof

Abstract

The invention relates to a lithium ion battery anode active material with a structural formula of LiaCo1-b-cAbBcO2-dCd, wherein A is at least one element of Mg, Al, Ga, and B; B is at least one element of Ti, Zr, and Hf; C is F or P; 0.95<=a<=1.05; 0.001<=b<=0.02; 0.001<=c<=0.02; 0.003<=b+c<=0.03; 0<d<=0.01; the element A is uniformly distributed on the body phase of the anode active material; the element B is mostly distributed on the surface of the anode active material; and the element C is distributed on the surface of the anode active material. When the anode active material charged to above 4.4V, on an X-ray diffraction spectrum of Cu-Kalpha, a 003 peak maintains complete, and is not split.

Description

technical field [0001] The invention relates to a positive electrode active material for a lithium ion battery and a lithium ion battery using the material Background technique [0002] With the miniaturization and thinning of mobile devices such as mobile phones, digital cameras, notebook computers and portable DVDs, the market demand for mobile energy is increasing. attention. [0003] Lithium-ion batteries generally include: a positive electrode sheet, a negative electrode sheet, a separator spaced between the positive and negative electrode sheets, and an electrolyte, wherein the positive electrode sheet includes a positive electrode current collector and a positive active material distributed on the positive electrode current collector, and the negative electrode sheet It includes a negative electrode collector and a negative electrode active material distributed on the negative electrode collector. At present, the commonly used cathode active materials for lithium-io...

AI Technical Summary

Problems solved by technology

The above positive electrode active materials have their own disadvantages: LiCoO 2 The charging voltage cannot exceed 4.2V, LiNiO 2 The structure is unstable and the storage performance is poor, LiMn 2 o 4 The high temperature performance is not good, the energy density is low, LiNiCoMnO 2 The low energy density of high-end products cannot meet the requirements of high-end products for energy density and safety performance. Therefore, a new way of increasing energy density is urgently needed

Although the coating can improve the cycle performance, the surface coating layer is an electronic insulator. In practical applications, the content of conductive carbon in the cathode is not enough to compensate for the increase in the polarization of the coating layer to the cathode during the charging and discharging process, which will inevitably lead to a voltage plateau. The reduction and the deterioration of the rate performance, which will reduce the energy density

US Patent 7018741 discloses a doped LiCoO 2 , distribute the doping elements on the surface of the material, and form a solid solution with Co, thus solving the problems of low voltage platform and poor rate performance in US Patent 7135251, but there is a problem of high temperature storage, and the coating elements and LiCoO 2 After the combination, the contact between Co and the electrolyte cannot be completely prevented, and there will inevitably be more side reactions released during the storage process, so the high-temperature storage performance will be slightly worse

[0006] These published documents or patents can more or less solve some problems under high voltage (>4.2V), but they only focus on LiCoO 2 Surface problems, but insufficient attention to bulk phase changes, so it can only be applied at 4.3V, 4.4V and other voltages

It is well known that LiCoO 2 During the detachment process, the crystal lattice first expands and then decreases, and the turning point is when the voltage is 4.45-4.5V. A large number of literatures have reported that coating can inhibit the lattice expansion to a certain extent, so the coated LiCoO 2 It has good cycle performance below 4.45V. Once the voltage exceeds 4.45V, the cycle performance will drop sharply. This is because the coating cannot prevent the internal shrinkage and the internal structure is unstable. Therefore, an effective means is needed to stabilize the internal crystal. Lattice structure, improved cycle performance at >4.45V

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