Lithium Bis(oxalate)borate Research Articles

Study on γ-butyrolactone for LiBOB-based electrolytes

To solve the problems of LiBOB-based electrolytes, small salt solubility and low conductivity, a sort of cyclic carboxylate, γ-butyrolactone (GBL) was applied in the lithium-ion battery electrolyte as the main solvent of lithium bis(oxalate)borate (LiBOB). LiBOB–GBL electrolyte exhibits good electrochemical stability, which is suitable to be the candidate of the lithium-ion battery electrolyte. Using GBL as the solvent of the LiBOB salt can increase the solubility and conductivity dramatically. At room temperature, LiFePO 4/LiBOB–GBL/Li half cell shows satisfying cycle performance with no capacity fading in the first 50 cycles and promising capacity performance with stable discharge capacity of about 125 mAh g −1. EA is mixed with GBL to get lower viscosity solvent. In LiFePO 4/Li half cell with 0.5 C discharge rate, 0.2 M LiBOB–GBL/EA (1:1, wt) electrolyte exhibits best at room temperature and 0.7 M LiBOB–GBL/EA (1:1, wt) electrolyte exhibits best at elevated temperature.

A high energy Li-ion battery based on nanosized LiNi 0.5Mn 1.5O 4 cathode material

The electrochemical performance of a Li-ion battery made from nanometric, highly crystalline LiNi 0.5Mn 1.5O 4 as positive electrode and mesoporous carbon microbeads (MCMBs) as negative electrode was assessed. The best performance was obtained by using a slight excess of spinel (a cathode/anode mole ratio of 1.3) and lithium bis-oxalate borate (LiBOB) instead of LiPF 6 as an electrolyte salt. Higher spinel contents caused the formation of metallic Li in the carbon and the rapid degradation of battery performance as a result. The calculated output energy was 322 Wh kg −1 which is higher than the value reported for the LiMn 2O 4/C cell (250 Wh kg −1).

An advanced electrolyte for improving surface characteristics of LiMn 2O 4 electrode

To apply widely the cathode material lithium manganese oxide (LiMn 2O 4) with spinel structure, temperature characteristics of LiMn 2O 4 electrode were studied to decrease the expansion extent by applying different additives in the electrolytes. Different addition contents of 1,3-propane sultone (1,3-PS) and propylene carbonate (PC) in the electrolytes were studied. The results showed PC and 1,3-PS could decrease the thickness variation of cells stored at elevated temperature. Lithium bis(oxalate) borate (LiBOB) additive was investigated to improve the storage characteristics at elevated temperature and cycling performance (25 °C) of the cell with LiMn 2O 4 cathode. The results showed that LiBOB improved remarkably the storage characteristics and cycling performance of the cells. And an advanced electrolyte was developed.

Effect of electrolyte additives in improving the cycle and calendar life of graphite/Li 1.1[Ni 1/3Co 1/3Mn 1/3] 0.9O 2 Li-ion cells

Lithium-rich layered metal oxide Li 1.1[Ni 1/3Co 1/3Mn 1/3] 0.9O 2 was investigated as a potential positive electrode material for high-power batteries for hybrid electric vehicle (HEV) applications. In order to evaluate the power and life characteristics of the graphite/Li 1.1[Ni 1/3Co 1/3Mn 1/3] 0.9O 2 cell chemistry, hybrid pulse power characterization (HPPC) and accelerated calendar life tests were conducted on several pouch cells containing electrolytes with and without additives. The data show that the cells containing 0.5 wt% lithium bis(oxalate)borate (LiBOB) or vinyl ethyl carbonate (VEC) additives, or the novel lithium difluoro(oxalato)borate (LiDFOB) additive, have much improved cycle and calendar life performance.

Enhanced performance of Li-ion cell with LiBF 4-PC based electrolyte by addition of small amount of LiBOB

LiBF 4-PC based electrolytes have superior potentials in enhancing cycling performance of Li-ion cells at low temperature and at high current rate, respectively. However, their application is prevented because of the poor capability in enabling graphite to form a solid electrolyte interface (SEI). In this work, we found that addition of small amount of lithium bis(oxalate)borate (LiBOB) into the LiBF 4-based electrolytes could significantly promote SEI formation on the surface of graphite even in solutions with a high content of PC. This is attributed to the fact that LiBOB participates in the formation chemistry of the SEI. Results showed that 1–5 mol% LiBOB is sufficient to promote graphite cycling reversibly in 1.0 m LiBF 4 1:1:3 PC/EC/EMC and 1.0 m LiBF 4 1:1 PC/EC, respectively, while the excellent cycling performance of LiBF 4-PC based electrolytes at low temperatures was maintained.

LiBOB-based gel electrolyte Li-ion battery for high temperature operation

In this work, we evaluated the chemical compatibility of 1.0m (molality) lithium bis(oxalate)borate (LiBOB) 1:1 (w/w) propylene carbonate (PC)/ethylene carbonate (EC) liquid electrolyte with lithium metal and spinel LiMn 2O 4 cathode using storage and cycling tests at high temperatures. Impedance analyses show that LiBOB and lithium are very compatible due to the formation of a stable passivation layer on the surface of lithium. Cycling tests of Li/Cu and Li/LiMn 2O 4 cells, respectively, show that lithium can be plated and stripped in LiBOB-based electrolyte with more than 80% cycling efficiency, and that this electrolyte can support LiMn 2O 4 cycling reversibly up to 60 °C without visible capacity loss. Using LiBOB-based liquid electrolyte and porous Kynar ® membrane, microporous gel electrolyte (MGE) Li-ion cells were assembled and evaluated. Results show that the MGE cell presents an improved cycling performance compared with a liquid cell, especially at elevated temperatures. It is confirmed that the LiBOB-based gel electrolyte Li-ion batteries can be operated at 60 °C with good capacity retention.

Profiling of Anode Surface Cycled in LiBOB-based Electrolyte of Li Ion Batteries

AbstractAs the youngest battery chemistry, Li ion technology was made possible by the formation of stable electrode/electrolyte interfaces. The correlation between the electrochemistry and the surface profile of the graphitic anode was studied in this work with a new salt lithium bis (oxalate) borate (LiBOB).In an attempt to depict a dynamic picture of the formation of graphite/electrolyte interface during the initial forming cycle, we employed X-ray photoelectron spectroscopy in combination with the “pre-formation” technique to establish the dependence of the surface chemistry on the forming potential of the anode. A progressive transition in the 1s electron binding energies of the major elements was observed as the lithiation proceeds; however, the surface chemical species as well as their abundances seemed to stabilize around 0.55 V and remained constant during the subsequent delithiation process, indicating that a stable solid electrolyte interface (SEI) exists thereafter. Integrating the information revealed by different analyses, we believe that the reductive decomposition of BOB−-anion starts at ca. 1.00 V, while the effective protection of graphene surface by SEI is available after the anode is lithiated below the potential of 0.55 V.