How to break through the bottleneck of lithium battery energy density?

Solid-state battery technology is one of the key technologies to break through the energy density bottleneck of lithium batteries, and it is also a research hotspot in the field of electrochemical energy storage. Compared with traditional lithium batteries, solid batteries are safer because they do not contain liquid organic solvents, and there are no problems such as liquid leakage and gas burning. In addition, it is now assumed that the solid electrolyte has good mechanical strength and can prevent dendritic growth problems when using metal lithium cathodes. An important problem with solid-state batteries is diversity, that is, slower charging and discharging speeds. In order to solve this problem, a solid electrolyte with high ionic conductivity is required. In recent years, various metal borides (Li2B12H12, LiCB11H12, etc.) have been found to have high ionic conductivity and are expected to become excellent solid electrolytes. However, their thermodynamic stability, suitability between positive and negative electrodes, and ability to inhibit dendrite growth are still in doubt. (Effect analysis) Recently, Francesco Ciucci's team at the Hong Kong University of Science and Technology (hkust) used a quantum chemistry accounting system to study the thermodynamic properties of metal borohydrides (Li, Na, Ca, Mg) and their compatibility with electrodes. Adoption is based on research. The discussion in [4] shows that metal borohydrides are potentially unsafe in high oxidation thermodynamics, but their differentiated products have a higher electrochemical window, so they can limit the further differentiation of electrolyte membranes. Based on the results, a world one is proposed. The interface stabilization mechanism and Li Chai, the mechanical function of the sodium hydride boron microelectrochemical window can be enlarged to 5v. Metal borohydride is also discussed and found that its shear modulus is low, so it has poor mechanical adaptability to pure metal electrodes and difficult to rise dendrites. restraint. Based on the related anion giant wave energy barrier and the observed ion superconducting phase transition temperature (superion phase transition temperature), a method for the ion conductivity of doped anions with different radii is proposed and verified by experiments. Except for Ca, it is not strong against pure metal electrodes, so only the borohydride of Ca is easier to distinguish under the recovery potential. See the electrochemical window in Figure 3. Under oxidizing conditions, Li2B12H12 and Li2B12H12 differentiate into Li2B12H12 for a short time. Li2B12H12 is relatively stable and will not continue to be oxidized, protecting LiBH4 and other solid electrolytes (see Figure 4). Previously, Monroe et al. [5] proposed a theory of twice the shear modulus to predict whether the electrolyte can inhibit the growth of dendrites: when the shear modulus of the electrolyte is greater than that of lithium metal, the interface can be stable. Compared with Li and Naborohydrodes, the shear modulus is relatively small. Therefore, unlike previously widely believed, this solid electrolyte may not be able to inhibit the growth of dendrites. Therefore, a long-term high-current charge-discharge test is required. Figure 6 Quantum chemical calculation of the relationship between the negative ion tumbling energy barrier and the phase transition temperature; the cationic defects of various metal borohydrides usually have two phases. At low temperatures, the metal borohydride anion does not roll, but the cation slowly loosens. Therefore, when the critical temperature is lowered to room temperature, the conductivity of travel ions can be used. The author found that the critical temperature is highly correlated with the energy barrier of anion rollover (Figure 6), and proposed that anion doping with no radius can lower the temperature. Recent experimental discussions by YanYigang et al. verified this. The kinetic simulation results show that magnesium and calcium borohydride have low solubility and are not suitable for use as electrolytes in solid-state batteries at room temperature. (Figure 7) [Abstract] Metal borohydride is an ideal solid electrolyte. Due to the interface stabilization mechanism, they have good electrochemical oxidation resistance. However, the requirements of metal electrodes for long-period dendrite growth have been studied. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete.