Enhancing The Performance Of Hard Carbon Anode By Blending For Lithium Ion Batteries

The lithium-ion batteries have become one kind of promising candidates for renewable energy due to its low weight,high energy density,excellent cycle stability.With the rapid development of electric automobiles and intellectualization,lithium-ion batteries are expected higher performance to meet the requirements of growing market and extensive applications.However,the graphite anode,which is the most successfully adopted commercial anode material for lithium-ion batteries,can’t meet the market requirements in terms of energy density and power density.To overcome these bottlenecks,the hard carbon（HC）with higher capacity,remarkable rate performance,and decent safety is explored as the alternative anode for lithium-ion batteries.Nevertheless,its poor initial coulombic efficiency（≤85%）,and inferior capacity compared to alloy-based anode materials hamper its further implementation of commercialization.Herein,the strategy of blended modification is exploited to improve the comprehensive performance of hard carbon.To be specific,Ge P₅incorporated into HC is proposed to enhance the energy density and coulombic efficiency of hard carbon;subsequently,the capacity of full cells which integrate hard carbon anode with a cathode containing lithium oxalate is enhanced,where the irreversible loss of lithium-ion in the first charging process is compensated with the assistance of lithium oxalate.The details are as follows:（1）A hard-carbon-based blending material exhibiting high capacity and remarkable rate performance is synthesized.Blending the HC material with Ge P₅ which possesses high specific capacity,fascinating coulombic efficiency,and excellent conductivity yields drawback compensation and performance optimization for hard carbon anode.It is worth noting that the specific capacity up to 898 m Ah g^-1(from 580 m Ah g^-1)is achieved when Ge P₅ is added an amount of 20%.Moreover,at a high current density of 8C(1C=372 m Ah g^-1),it still exhibits a high capacity of 540 m Ah g^-1 as well as excellent cycle performance.The mechanism of enhanced rate performance,which is attributed to the Ge P₅-induced excellent electrical conductivity and the promoted interfacial storage mechanism stemming from the ball milling process,is also validated in this paper.（2）Furthermore,the performance of full cell which possesses hard carbon anode and lithium-oxalate-involved cathode is improved.Firstly,we study the electrochemical properties of lithium oxalate and its high de-lithium potential is unraveled.To match it with commercial cathode materials,temperature control and catalyst are carried out to decrease the de-lithium potential to 4.5 V.Next,we adopt optimum technology to blend Li Fe PO₄ with lithium oxalate,whose capacity in the first charging process exhibits 26 m Ah g^-1 higher than the pure Li Fe PO₄when it is charged at 35℃.Based on the above research,we assemble this blended cathode material with hard carbon anode into a full battery,there is a 17%increase of capacity and cathode utilization rate,which overcome the disadvantage of low energy density coming from HC’s low initial coulombic efficiency（ICE）.