Spinel-type cathodes are considered an optimal substitute for conventional layered oxide cathodes owing to their use of inexpensive and earth-abundant manganese as the redox-active element.Moreover,the introduction of...Spinel-type cathodes are considered an optimal substitute for conventional layered oxide cathodes owing to their use of inexpensive and earth-abundant manganese as the redox-active element.Moreover,the introduction of cation disorder can effectively suppress the detrimental two-phase reaction to realize high capacities in a wide voltage range.However,the continuous capacity decay during cycles has hindered the widespread application of these cathode materials.Inorganic fluorides exhibit excellent electrochemical stability at high voltage;therefore,in this study,the direct F2 gas reaction with a partially disordered spinel cathode(Li_(1.6)Mn_(1.6)O_(3.7)F_(0.3,)LMOF1.6)was initially applied to investigate the impacts of fluorination on the surface structure and electrochemical performances.The inorganic fluorinated layer,mainly containing LiF,was distributed uniformly on the surface of LMOF1.6nanoparticles after fluorination for an appropriate time without the turbulence caused by the valency of manganese cation,which improved the capacity retention and rate capability by the suppression of structural damage,parasitic reaction,and cation dissolution.The LMOF1.6cathode fluorinated for 0.5 h exhibited a capacity of283.6 mAh·g^(-1)at 50 mA·g^(-1)and an enhanced capacity retention of 29.6%after 50 cycles in the voltage range of1.5-4.8 V,as compared to the pristine LMOF1.6 with only27.9%capacity retention.展开更多
This paper aims at achieving a simultaneously sparse and low-rank estimator from the semidefinite population covariance matrices.We first benefit from a convex optimization which develops l1-norm penalty to encourage ...This paper aims at achieving a simultaneously sparse and low-rank estimator from the semidefinite population covariance matrices.We first benefit from a convex optimization which develops l1-norm penalty to encourage the sparsity and nuclear norm to favor the low-rank property.For the proposed estimator,we then prove that with high probability,the Frobenius norm of the estimation rate can be of order O(√((slgg p)/n))under a mild case,where s and p denote the number of nonzero entries and the dimension of the population covariance,respectively and n notes the sample capacity.Finally,an efficient alternating direction method of multipliers with global convergence is proposed to tackle this problem,and merits of the approach are also illustrated by practicing numerical simulations.展开更多
基金financially supported by the National Key R and D Program of China(No.2022YFB3805702)State Key Program of the National Natural Science Foundation of China(No.52130303)+1 种基金National Natural Science Foundation of China(Nos.51973152,51973119,5210309352173078)。
文摘Spinel-type cathodes are considered an optimal substitute for conventional layered oxide cathodes owing to their use of inexpensive and earth-abundant manganese as the redox-active element.Moreover,the introduction of cation disorder can effectively suppress the detrimental two-phase reaction to realize high capacities in a wide voltage range.However,the continuous capacity decay during cycles has hindered the widespread application of these cathode materials.Inorganic fluorides exhibit excellent electrochemical stability at high voltage;therefore,in this study,the direct F2 gas reaction with a partially disordered spinel cathode(Li_(1.6)Mn_(1.6)O_(3.7)F_(0.3,)LMOF1.6)was initially applied to investigate the impacts of fluorination on the surface structure and electrochemical performances.The inorganic fluorinated layer,mainly containing LiF,was distributed uniformly on the surface of LMOF1.6nanoparticles after fluorination for an appropriate time without the turbulence caused by the valency of manganese cation,which improved the capacity retention and rate capability by the suppression of structural damage,parasitic reaction,and cation dissolution.The LMOF1.6cathode fluorinated for 0.5 h exhibited a capacity of283.6 mAh·g^(-1)at 50 mA·g^(-1)and an enhanced capacity retention of 29.6%after 50 cycles in the voltage range of1.5-4.8 V,as compared to the pristine LMOF1.6 with only27.9%capacity retention.
基金The work was supported in part by the National Natural Science Foundation of China(Nos.11431002,11171018,71271021,11301022).
文摘This paper aims at achieving a simultaneously sparse and low-rank estimator from the semidefinite population covariance matrices.We first benefit from a convex optimization which develops l1-norm penalty to encourage the sparsity and nuclear norm to favor the low-rank property.For the proposed estimator,we then prove that with high probability,the Frobenius norm of the estimation rate can be of order O(√((slgg p)/n))under a mild case,where s and p denote the number of nonzero entries and the dimension of the population covariance,respectively and n notes the sample capacity.Finally,an efficient alternating direction method of multipliers with global convergence is proposed to tackle this problem,and merits of the approach are also illustrated by practicing numerical simulations.
