Zhonghua Lu

Structure and Electrochemistry of Li[Ni[sub x]Co[sub 1−2x]Mn[sub x]]O[sub 2] (0≤x≤1/2)

In a recent paper, Lu et al. showed that Li[Ni 0.25 Co 0.5 Mn 0.25 ]O 2 and Li[Ni 0.375 Co 0.25 Mn 0.375 ]O 2 are attractive electrode materials for Li-ion cells. Most interesting, they appear to be much less reactive with electrolyte at high temperatures than LiCoO 2 . Since these two materials are part of the solid-solution series Li[Ni x C 1-2x Mn x ]O 2 with 0 ≤ x ≤ 1/2, which also contains LiCoO 2 when x = 0, it is possible to study the reasons for the safety advantage by a careful study of electrochemical, structural, and thermal properties as a function of x. This paper reports the structural and electrochemical properties of Li[Ni x Co 1-2x Mn x ]O 2 for 0 ≤ x ≤ 1/2. The materials all show good specific capacity (between 110 and 130 mAh/g between 3.0 and 4.2 V vs. Li at 40 mA/g) and very little capacity loss over 50 cycles. Careful consideration of differential capacity measurements proves that Ni 2+ and Mn 4+ do, indeed, substitute for Co 3+ , at least for x < 0.15, as was hypothesized by Lu et al. The thermal stability of the charged cathode materials improves rapidly compared to LiCoO 2 , then saturates as x in Li[Ni a Co 1-2x Mn x ]O 2 increases. Materials with x ≥ 0.075 show approximately equal thermal stability. The reason for the variation of the thermal stability with x is the subject of a companion paper.

Structure and Electrochemistry of Li [ Ni x Co1 − 2x Mn x ] O 2 ( 0 ⩽ x ⩽ 1 / 2 )

In a recent paper, Lu et al. showed that Li[Ni 0.25 Co 0.5 Mn 0.25 ]O 2 and Li[Ni 0.375 Co 0.25 Mn 0.375 ]O 2 are attractive electrode materials for Li-ion cells. Most interesting, they appear to be much less reactive with electrolyte at high temperatures than LiCoO 2 . Since these two materials are part of the solid-solution series Li[Ni x C 1-2x Mn x ]O 2 with 0 ≤ x ≤ 1/2, which also contains LiCoO 2 when x = 0, it is possible to study the reasons for the safety advantage by a careful study of electrochemical, structural, and thermal properties as a function of x. This paper reports the structural and electrochemical properties of Li[Ni x Co 1-2x Mn x ]O 2 for 0 ≤ x ≤ 1/2. The materials all show good specific capacity (between 110 and 130 mAh/g between 3.0 and 4.2 V vs. Li at 40 mA/g) and very little capacity loss over 50 cycles. Careful consideration of differential capacity measurements proves that Ni 2+ and Mn 4+ do, indeed, substitute for Co 3+ , at least for x < 0.15, as was hypothesized by Lu et al. The thermal stability of the charged cathode materials improves rapidly compared to LiCoO 2 , then saturates as x in Li[Ni a Co 1-2x Mn x ]O 2 increases. Materials with x ≥ 0.075 show approximately equal thermal stability. The reason for the variation of the thermal stability with x is the subject of a companion paper.

The Effect of Al Substitution on the Reactivity of Delithiated LiNi ( 0.5 − z ) Mn ( 0.5 − z ) A12z O2 with Nonaqueous Electrolyte

The high-temperature reactions between 1 M LiPF 6 ethylene carbonate:diethyl carbonate and Al-doped LiNi (0.5-z) Mn (0.5-z) Al 2z O 2 charged to 4.3 V are studied by accelerating rate calorimetry and compared with those of charged LiNi 1/3 Mn 1/3 Co 1/3 O 2 and spinel LiMn 2 O 4 . Simultaneous Al substitution for Ni and Mn in LiNi 0.5 Mn 0.5 O 2 improves the thermal stability. The maximum self-heating rate attained and the specific capacity decrease as the Al content increases. Materials with z > 0.03 are less reactive with electrolyte than spinel LiMn 2 O 4 at all temperatures studied. There is a range of compositions near z = 0.05 that show excellent promise as materials which are both safer and more energy dense than spinel LiMn 2 O 4 .

Structure and electrochemistry of LiNixCo1-2xMnx]O2 (0 'le x 'le 1/2)

In a recent paper, Lu et al. showed that Li[Ni 0.25 Co 0.5 Mn 0.25 ]O 2 and Li[Ni 0.375 Co 0.25 Mn 0.375 ]O 2 are attractive electrode materials for Li-ion cells. Most interesting, they appear to be much less reactive with electrolyte at high temperatures than LiCoO 2 . Since these two materials are part of the solid-solution series Li[Ni x C 1-2x Mn x ]O 2 with 0 ≤ x ≤ 1/2, which also contains LiCoO 2 when x = 0, it is possible to study the reasons for the safety advantage by a careful study of electrochemical, structural, and thermal properties as a function of x. This paper reports the structural and electrochemical properties of Li[Ni x Co 1-2x Mn x ]O 2 for 0 ≤ x ≤ 1/2. The materials all show good specific capacity (between 110 and 130 mAh/g between 3.0 and 4.2 V vs. Li at 40 mA/g) and very little capacity loss over 50 cycles. Careful consideration of differential capacity measurements proves that Ni 2+ and Mn 4+ do, indeed, substitute for Co 3+ , at least for x < 0.15, as was hypothesized by Lu et al. The thermal stability of the charged cathode materials improves rapidly compared to LiCoO 2 , then saturates as x in Li[Ni a Co 1-2x Mn x ]O 2 increases. Materials with x ≥ 0.075 show approximately equal thermal stability. The reason for the variation of the thermal stability with x is the subject of a companion paper.