Lithium ion secondary battery with the large current discharging capability

Abstract

The invention relates to a lithium ion secondary cell which uses LiFePO4 with low conductivity as the anode active material and possesses big current. A lithium ion secondary cell includes LiFePO4 as the main composition of the anode active material. Aiming at the lithium ion secondary cell possesses big current (the electricity capacity can bigger than 80% of the 1C discharging rate at 10C discharging rate), the invention designs the coat which is at the base and includes anode active material to the ratio(A / t) between the area of the coat and thickness is bigger than 1.2*106(mm), so the coat possesses a decreased ion impedance; And more than one conducting handles are set on the base of the anode to decrease the electron impedance, so the anode possesses a decreased impedance. The invention also can be used in other anode material with low conductivity.

Description

technical field [0001] The present invention relates to a lithium-ion secondary battery with large current discharge capacity, especially to a lithium-ion secondary battery using low-conductivity LiFePO 4 A lithium-ion secondary battery with high current discharge capability as the main component of the positive electrode active material. Background technique [0002] Lithium iron phosphate (LiFePO 4 ) has an olivine (olive) crystal structure and is one of the positive active materials for lithium-ion secondary batteries that have been studied in recent years. with LiFePO 4 The biggest disadvantage of the positive electrode active material as lithium ion secondary battery is its very low electrical conductivity (being 10 -9 S / cm order of magnitude), much lower than the commonly used cathode active material LiMn 2 o 4 or LiCoO 2 Those (10 -3 ~10 -4 S / cm), causing lithium ions to encounter obstacles when moving into / out of the positive electrode, making LiFePO 4 As th...

AI Technical Summary

Problems solved by technology

[0009] The present invention, through the design of the lithium-ion secondary battery, respectively discusses the impact of the electronic impedance and ionic impedance of the coating material on the positive plate and the positive plate on the discharge capacity of the battery, so as to overcome the current LiFePO 4 Due to the shortcomings of poor electrical conductivity that cannot discharge large currents, lithium-ion secondary batteries with high current discharge capabilities have been prepared, such as the capacitance ratio (hereinafter referred to as 10C) of the 10C discharge rate relative to the 1C discharge rate (hereinafter referred to as 10C rate). capacity) greater than 80%, which is suitable for applications in high power products

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