Non-aqueous electrolyte secondary cell and method for manufacturing same
A non-aqueous electrolyte secondary cell has reduced degradation of the electrolytic solution or the anode active material and high cycle durability. The non-aqueous electrolyte secondary cell includes: a cathode capable of doping and de-doping lithium ions; an anode capable of occluding and releasing lithium ions, lithium or a lithium alloy; and an electrolytic solution containing an organic solvent, a lithium salt electrolyte and an additive. The cathode active material of the cathode contains a layered lithium-containing transition metal oxide of formula Li 1.5 [Ni a Co b Mn c [Li] d ]O 3 , where a, b, c, and d satisfy 0<a<1.4, 0≦b<1.4, 0<c<1.4, 0<d≦0.5, a+b+c+d=1.5, and 1.0≦a+b+c<1.5. The anode active material contains a carbon-based material with the surface fully or partly covered with a coating derived from the additive.
1. A method for manufacturing a non-aqueous electrolyte secondary cell, comprising:
(A) preparing a pre-cell comprising:
a cathode comprising a layered lithium-containing transition metal oxide of the following composition formula as a cathode active material Li 1.5 [Ni a Co b Mn c [Li] d ]O 3 where a, b, c and d satisfy 0<a<1.4, 0≦b<1.4, 0<c<1.4, 0<d≦0.5, a+b+c+d=1.5, and 1.0≦a+b+c<1.5;
an anode comprising a carbon-based material as an anode active material; and
an electrolytic solution containing an organic solvent, a lithium salt electrolyte and an additive;
(B) carrying out an anode aging treatment that is a charge-discharge cycle treatment of applying a voltage between the cathode and the anode of the prepared pre-cell;
(C) subsequently carrying out a cathode activating treatment that is a charge-discharge cycle treatment of applying a voltage between the cathode and the anode, the cathode activating treatment carried out by applying a voltage lower than a potential plateau region of the cathode active material; and
(D) subsequently applying a voltage within a range of 4.5 V to 4.8 V that is a voltage within or over the potential plateau region of the cathode active material.
2. The method for manufacturing the non-aqueous electrolyte secondary cell according to claim 1 , wherein the anode aging treatment is carried out such that charge level of the non-aqueous electrolyte secondary cell is maintained at 10% to 30% of a full charge (SOC).
3. The method for manufacturing the non-aqueous electrolyte secondary cell according to claim 1 , wherein the voltage applied in the anode aging treatment is lower than the voltage applied in the cathode activating treatment.
4. The method for manufacturing the non-aqueous electrolyte secondary cell according to claim 1 , wherein the anode aging treatment is carried out at the voltage of 3.5 V or less.
5. The method for manufacturing the non-aqueous electrolyte secondary cell according to claim 1 , wherein in the cathode activating treatment, a charge-discharge cycle treatment of applying the voltage lower than the potential plateau region is controlled such that a charging rate is equal to or slower than a discharging rate.
6. The method for manufacturing the non-aqueous electrolyte secondary cell according to claim 1 , further comprising: after the anode aging treatment and the cathode activating treatment, carrying out a charge-discharge cycle treatment in which charge level of the non-aqueous electrolyte secondary cell is maintained at 60% or more to less than 100% of a full charge (SOC).
7. The method for manufacturing the non-aqueous electrolyte secondary cell according to claim 1 , further comprising: after the anode aging treatment and the cathode activating treatment, carrying out a charge-discharge cycle treatment in which charge level of the non-aqueous electrolyte secondary cell is maintained at 80% or more to less than 100% of a full charge (SOC).
8. The method for manufacturing the non-aqueous electrolyte secondary cell according to claim 1 , wherein the potential plateau region of the cathode active material corresponds to a range from 4.3 to 4.65 V in applied voltage.