A Hig igh Energy Density Full ll Lit ithium Io Ion Battery ry - - PowerPoint PPT Presentation

A Hig igh Energy Density Full ll Lit ithium Io Ion Battery ry Based on Specially Matched Coulombic Efficiency

Nano-spherical Li-rich cathodes and 𝑁𝑜𝑦𝐷𝑝1−𝑦O anodes are synthesized from as-solvothermal 𝑁𝑜𝑦𝐷𝑝1−𝑦C𝑃3 precursors. Such an electrode match-up full cell allows no need for pre-activation of the metal oxide

• anode. It can deliver a high reversible capacity of 205mA h 𝑕−1 and

particularly rather high volumetric energy density. Danqi Qu Mentor: BangK. Zhou Advisor: ChunH.Chen

Introduction

Commercial cathode materials : LiFeP𝑃4 LiM𝑜2𝑃4 (500Wh/Kg) and ternary materials like NMC(Ni Mn Co) NAC(Ni Al Co) 750-800Wh/Kg Anode materials : graphite is the state-of-the-art material for lithium ion battery. Packing density 1.6g/c𝑛3 Specific capacity 350mAh/g Are both insufficient for high capacity power batteries. Transition metal oxides as anode materials for LIB can deliver as high as 700- 900mAh/g

Transition metal oxides are hardly applied in full LIB because their low initial coulombic efficiency(50%-70%) would destroy a big fraction of reversible capacity from the cathode. On the other hand, Li –rich layer-structured cathode materials are found to have much higher reverible capacity(about 250 mAh/g) and energy density(1000Wh/Kg) than the commercial cathodes. But they have drawbacks of low initial coulombic efficiency(about 70%), inferior rate performance and gradual decay of the

• perating voltage.

Herein, a strategy of coulombic efficiency match-up is adopted to overcome the disadvantages of the first-cycle capacity loss for both Li-rich cathodes and TMO anodes in

• rder to achieve high energy density of the cell!

Properties of electrodes LMNO Mn0.8Co0.2O Graphite Charge specific capacity (mAh g-1) 345 757 350 Discharge specific capacity (mAh g-1) 245 1040 372 Initial columbic efficiency 71.0% 72.8% 94.1% Real density (g cm-3) ≈2.50 5.45 2.25

The cycling performance at 0.2C current density and the corresponding coulombic efficiency of LMNO The cycling performance at 0.4A/g current density and the corresponding coulombic efficiency of 𝑁𝑜0.8𝐷𝑝0.2O

Experimental

• 1. Synthesis the Mn-Co carbonate nanospheres as precursors through a solvothermal method.
• 2. Synthesis of Li-rich and 𝑁𝑜𝑦𝐷𝑝1−𝑦O electrode materials.
• 3. Characterization of materials
• 4. Electrochemical measurements

XRD patterns of Li-rich layer-structured cathodes with different compositions XRD patterns of 𝑁𝑜𝑦𝐷𝑝1−𝑦O anodes

Results and Discussion

The comparison of specific capacity and energy density of the full cells between this work and previously reported ones

TEM images of 𝑁𝑜0.8𝐷𝑝0.2C𝑃3(a) 𝑁𝑜0.8𝐷𝑝0.2-Oxide intermediate(b) 𝑁𝑜0.8𝐷𝑝0.2O(c) LMNO(d)

SEM image(a) and enlarge picture(b) of the 𝑁𝑜0.8𝐷𝑝0.2O electrode after 200 cycles at 0.4 A/g current density

Charge&discharge curves and the comparison of energy density of the two cell

Properties of electrodes LMNO Mn0.8Co0.2O Graphite Charge specific capacity (mAh g-1) 345 757 350 Discharge specific capacity (mAh g-1) 245 1040 372 Initial columbic efficiency 71.0% 72.8% 94.1% Real density (g cm-3) ≈2.50 5.45 2.25

Conclusions

In summary, several powders of Li-rich cathode and Mn-Co oxide anode materials with tailored microstructures are synthesized. On the cathode side, 0.5L𝑗2Mn𝑃30.5LiM𝑜0.5N𝑗0.5𝑃2 shows an initial discharge capacity of 247mAh/g with a coulombic efficiency of 71% and the capacity retention is 95.8% after 130 cycles at 0.2C. Binary transition metal oxide 𝑁𝑜0.8𝐷𝑝0.2O offers excellent cycling stability and rate

• performance. The initial reversible capacity is 759mAh/g with a coulombic efficiency of about

72.8% and the capacity retention is 110% after 200 cycles at 0.4Ah/g. The initial charge capacity of the “N-cell” is 363mAh/g, and is approximately equal to the value measured in the LMNO/Li half cell, while the discharge capacity is 205 mAh/g. The capacity retention is as high as 97.5% in the following 20 cycles.

Due to their intrinsic high capacity and the special match-up in coulombic efficiency, such an N-cell demonstrates particularly high volumetric energy density and excellent cycling performance. Further optimization and development of the design and fabrication will lead to new opportunities for higher energy- density batteries. And the next step, we are now doing some work to solve the problem that the operating voltage of Li-rich layer-structured cathode materials will gradually decay with the cycling number increasing.

Thank you for your attention