Cost analysis of Sodium-ion battery cathode

Analysis of negative electrode materials for sodium batteries

Since the Atomic radius of sodium ion is larger than that of lithium ion, sodium ion can not be effectively de embedded at the graphite anode material, so it is crucial to find a suitable sodium storage anode material. The negative electrode materials of Sodium-ion battery mainly include Amorphous carbon, alloy, Transition metal oxides, etc. Among them, alloys have higher capacity but poor cycling and rate performance; The capacity of Transition metal oxides is low; Amorphous carbon has good reversible capacity and cycling performance, and is expected to be commercialized after cost control. Amorphous carbon materials are mainly divided into hard carbon and soft carbon. Hard carbon materials have high capacity but high cost; The soft carbon material has low gram capacity, but can be used as the precursor of Anthracite, which has cost performance advantages. Anthracite can reach 150-300Ah/yuan, higher than other precursors.

Hard carbon is a type of carbon that is difficult to graphitize even at high temperatures above 2500 ℃, named after its high mechanical hardness. For Sodium-ion battery, hard carbon is an ideal material. In the state of high-temperature carbonization, the graphite domain in hard carbon presents many nano pores, which provides more space for sodium ions to be embedded in hard carbon. The precursors of hard carbon are diverse, including biomass (lignin, wood, fruit shell, starch), fossil fuels (asphalt, coal), and high polymers (phenolic resin). The cost of resin based hard carbon is high, and the biomass hard carbon production rate is only 20% -30%. In addition, the low first week Coulomb efficiency of hard carbon materials is also one of the important obstacles to industrialization.

Soft carbon is a kind of Amorphous carbon that can be easily graphitized at a high temperature above 2500 ℃. Its structure contains a pore structure formed by the irregular stacking structure of graphite microcrystals, which has the function of containing sodium ions, so it can be used as the anode material of Sodium-ion battery. Compared to hard carbon materials, soft carbon materials have higher electronic conductivity and rate performance, as well as lower costs. The defect of soft carbon materials is that they are prone to graphitization at high temperatures, and the interlayer spacing gradually decreases with the increase of carbonization temperature, causing the pore structure to collapse and significantly reducing the sodium storage performance. However, the lower carbonization temperature cannot fully utilize its electronic conductivity advantage, and its structure is unstable with large irreversible capacity.
The Institute of Physics of the Chinese Academy of Sciences uses Anthracite as the precursor to obtain a carbon anode material with excellent sodium storage performance through simple crushing and one-step carbonization. The soft carbon material obtained by cracking Anthracite still has a high degree of disorder below 1600 ° C, with a carbon production rate of 90%, a sodium storage capacity of 220mAh/g, excellent cycle stability, and better performance than the soft carbon material from asphalt.
In addition, according to Xu Bin of Beijing University of Chemical Technology in the Structural Regulation of Hard Carbon Anode Materials for Sodium-ion battery, Anthracite is oxidized by concentrated sulfuric acid to introduce more oxygen-containing functional groups on the molecular surface of Anthracite, improve the cross-linking activity with sucrose, and build a heterostructure. Its electrochemical performance can reach 325 mAH/g, and the first effect is 84.5%.
In addition to Zhongke Haina, at present, the domestic enterprises that have arranged the negative electrode of Sodium-ion battery are mainly lithium battery negative electrode enterprises, and the Technology roadmap is basically hard carbon negative electrode.

Soft carbon is a kind of Amorphous carbon that can be easily graphitized at a high temperature above 2500 ℃. Its structure contains a pore structure formed by the irregular stacking structure of graphite microcrystals, which has the function of containing sodium ions, so it can be used as the anode material of Sodium-ion battery. Compared to hard carbon materials, soft carbon materials have higher electronic conductivity and rate performance, as well as lower costs. The defect of soft carbon materials is that they are prone to graphitization at high temperatures, and the interlayer spacing gradually decreases with the increase of carbonization temperature, causing the pore structure to collapse and significantly reducing the sodium storage performance. However, the lower carbonization temperature cannot fully utilize its electronic conductivity advantage, and its structure is unstable with large irreversible capacity.
The Institute of Physics of the Chinese Academy of Sciences uses Anthracite as the precursor to obtain a carbon anode material with excellent sodium storage performance through simple crushing and one-step carbonization. The soft carbon material obtained by cracking Anthracite still has a high degree of disorder below 1600 ° C, with a carbon production rate of 90%, a sodium storage capacity of 220mAh/g, excellent cycle stability, and better performance than the soft carbon material from asphalt.
In addition, according to Xu Bin of Beijing University of Chemical Technology in the Structural Regulation of Hard Carbon Anode Materials for Sodium-ion battery, Anthracite is oxidized by concentrated sulfuric acid to introduce more oxygen-containing functional groups on the molecular surface of Anthracite, improve the cross-linking activity with sucrose, and build a heterostructure. Its electrochemical performance can reach 325 mAH/g, and the first effect is 84.5%.
In addition to Zhongke Haina, at present, the domestic enterprises that have arranged the negative electrode of Sodium-ion battery are mainly lithium battery negative electrode enterprises, and the Technology roadmap is basically hard carbon negative electrode.

The first charge discharge curve of hard carbon material to metal sodium in the electrolyte environment with a) Ethylene carbonate (EC), b) propylene carbonate (PC), c) butyl carbonate (BC) as solvent; Note: When Ethylene carbonate is the solvent, the working temperature is 60 ℃.

Cost overview of Sodium-ion battery

According to the data on the official website of Zhongke Haina, if the price of Lithium carbonate is 150000 yuan/ton and the price of sodium carbonate is 2000 yuan/ton, the material cost of Sodium-ion battery is 30% -40% lower than that of lithium ion battery. The cost distribution of sodium battery materials is more dispersed, with the cost proportion of positive electrode materials decreasing from 43% to 26% of lithium batteries.
The positive electrode materials, negative electrode materials, and electrolyte system of sodium batteries are significantly different from those of lithium batteries, while the demand for aluminum foil in the current collection process of sodium batteries is greatly driven. Previously, only aluminum foil was used for the positive electrode of lithium batteries, while aluminum foil can be used for both positive and negative electrodes of sodium batteries.

References

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[2]StevensDA，DahnJR．J．Electrochem．Soc．，2000，147:4428．

[3]KomabaS，MurataW，IshikawaT，YabuuchiN，OzekiT，NakayamaT，OgataA，GotohK，FujiwaraK．Adv．Funct．Mater．，2011，21:3859．