Composite negative electrode for thermal battery and preparation method thereof

Abstract

The invention provides a composite negative electrode for a thermal battery and a preparation method thereof. The composite negative electrode is mainly formed by physical pressing of a flake LiB alloy and a powdered LiSi alloy, and the LiSi alloy powder is 10% to 25% of the weight of the LiB alloy; LiSi The surface of the alloy powder is coated with molten salt electrolyte, and after forming a single battery, it is in direct contact with the isolation layer. During the activation process of the thermal battery, the electrolyte coating on the surface of the composite negative electrode quickly enters the activated state, and establishes ion migration channels with the negative electrode, which effectively improves the activation speed of the thermal battery. In the composite negative electrode of the present invention, the interface polarization internal resistance between the separator and the coated LiSi layer is significantly reduced, which is conducive to the rapid and stable pressure building of the thermal battery, and improves the LiB negative electrode caused by insufficient ion activity in the initial stage of work. The problem of "voltage pit" is especially suitable for the design of power type thermal battery.

Description

technical field [0001] The invention relates to a composite negative electrode for a thermal battery and a preparation method thereof. Background technique [0002] Thermal battery is a storage battery whose electrolyte is a non-conductive solid. When in use, an electric ignition head or a firing pin mechanism is used to ignite the heating agent inside, so that the electrolyte melts into a high-conductivity ion conductor and is activated as a reserve battery. The negative electrode material of the thermal battery is usually made of lithium-based metals with low electrode potential, but since the melting point of elemental lithium is lower than the operating temperature of the thermal battery, direct use may cause short circuit or corrosion inside the battery, so the actual production usually uses safer Lithium alloys such as LiSi, LiX (X=Fe, Al). [0003] Recently, LiB alloy has received extensive attention due to its advantages of negative potential, high capacity, and eas...

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Problems solved by technology

LiB alloy is composed of a sponge-like porous Li7B6 skeleton and metallic lithium embedded in the pores. Free lithium directly participates in the electrode reaction, and the lithium content directly determines the battery capacity. At the same time, its actual utilization rate can reach more than 90%, which is much higher than that of LiSi. The utilization rate of the alloy (~75%); but in addition to the above advantages, due to the existence of the dense framework of the LiB alloy, there is a large interface resistance between the negative electrode layer and the isolation layer, which leads to the fact that the thermal battery cannot be quickly established after receiving the activation signal. Stable plateau voltage, long activation time and poor discharge rate characteristics

[0004] At present, the method to improve the initial performance of activation is mainly to increase the content of free lithium in LiB alloy (Applied Chemical Industry, 2015.44(5):947), but this method is prone to lithium overflow, which leads to safety problems of thermal batteries

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