Battery module, electronic device using the same, and assembly method of battery module
A battery module includes n batteries, n≥3. The n batteries are stacked in a sequence along a thickness direction of the battery, and m is defined as a round number of n/2, and the first battery and the m-th battery satisfy at least one of the following conditions: a1: a capacity of the m-th battery is greater than that of the first battery; b1: under a same state of charge, an open circuit voltage of the m-th battery is less than that of the first battery; and c1: under a same state of charge, an AC impedance of the m-th battery is less than that of the first battery.
1 . A battery module, comprising n batteries, n≥3, the n batteries being stacked in a sequence along a thickness direction of the battery from a first battery to an n-th battery, wherein
m is defined as a round number of n/2, and the first battery and the m-th battery satisfy at least one of the following conditions:
a1: a capacity of the m-th battery is greater than that of the first battery and the n-th battery;
b1: under a same state of charge, an open circuit voltage of the m-th battery is less than that of the first battery and the n-th battery; and
c1: under a same state of charge, an AC impedance of the m-th battery is less than that of the first battery and the n-th battery.
2 . The battery module according to claim 1 , wherein under the same state of charge, the open circuit voltage of the m-th battery is less than that of the first battery.
3 . The battery module according to claim 2 , wherein the capacity of the m-th battery is greater than that of the first battery.
4 . The battery module according to claim 1 , wherein p is defined as a round number of m/2, n≥5, and the first battery, the p-th battery and the m-th battery satisfy at least one of the following conditions:
a2: a capacity of the p-th battery is greater than that of the first battery, and less than that of the m-th battery;
b2: under a same state of charge, an open circuit voltage of the p-th battery is less than that of the first battery, and greater than that of the m-th battery; and
c2: under a same state of charge, an AC impedance of the p-th battery is less than that of the first battery, and greater than that of the m-th battery.
5 . The battery module according to claim 1 , wherein the first battery to the m-th battery satisfy at least one of the following conditions:
a3: a capacity of the first battery is greater than that of a second battery, the first battery being closer to the m-th battery than the second battery;
b3: under a same state of charge, an open circuit voltage of a battery closer to the m-th battery is less than that of a battery farther away from the m-th battery; and
c3: under a same state of charge, an AC impedance of a battery closer to the m-th battery is less than that of a battery farther away from the m-th battery.
6 . The battery module according to claim 1 , wherein in the first battery to a s-th battery, a maximum capacity is C max , a minimum capacity is C min , (C max −C min )/C max ≤6%,
when s=2, n≥3; or
when s=3, n≥7; or
when s=4, n≥9.
7 . The battery module according to claim 1 , wherein under a same state of charge, in the first battery to a s-th battery, a maximum open circuit voltage is V max , a minimum open circuit voltage is V min , V max −V min ≤10 mV,
when s=2, n≥3; or
when s=3, n≥7; or
when s=4, n≥9.
8 . The battery module according to claim 1 , wherein under a same state of charge, in the first battery to a s-th battery, a maximum AC impedance is R max , a minimum AC impedance is R min , (R max −R min )/R max ≤25%,
when s=2, n≥3; or
when s=3, n≥7; or
when s=4, n≥9.
9 . The battery module according to claim 1 , wherein the state of charge is 25% to 80%.
10 . The battery module according to claim 1 , wherein the AC impedance of each battery is less than or equal to 20 mΩ.
11 . The battery module according to claim 1 , wherein each battery includes a housing, and the housing is a soft package or a hard shell.
12 . An electronic device, comprising a battery module, the battery module comprises n batteries, n≥3, the n batteries being stacked in a sequence along a thickness direction of the battery from a first battery to an n-th battery, wherein
m is defined as a round number of n/2, and the first battery and the m-th battery satisfy at least one of the following conditions:
a1: a capacity of the m-th battery is greater than that of the first battery and the n-th battery;
b1: under a same state of charge, an open circuit voltage of the m-th battery is less than that of the first battery and the n-th battery; and
c1: under a same state of charge, an AC impedance of the m-th battery is less than that of the first battery and the n-th battery.
13 . The electronic device according to claim 12 , wherein the electronic device comprises a plurality of battery modules arranged in a direction perpendicular to a thickness direction of the battery, and the plurality of battery modules are connected in series or in parallel.
14 . The electronic device according to claim 12 , wherein under the same state of charge, the open circuit voltage of the m-th battery is less than that of the first battery.
15 . The electronic device according to claim 12 , wherein the capacity of the m-th battery is greater than that of the first battery.
16 . The electronic device according to claim 12 , wherein p is defined as a round number of m/2, n≥5, and the first battery, the p-th battery and the m-th battery satisfy at least one of the following conditions:
a2: a capacity of the p-th battery is greater than that of the first battery, and less than that of the m-th battery;
b2: under a same state of charge, an open circuit voltage of the p-th battery is less than that of the first battery, and greater than that of the m-th battery; and
c2: under a same state of charge, an AC impedance of the p-th battery is less than that of the first battery, and greater than that of the m-th battery.
17 . The electronic device according to claim 12 , wherein the state of charge is 25% to 80%.
18 . The electronic device according to claim 12 , wherein the AC impedance of each battery is less than or equal to 20 mΩ.
19 . The electronic device according to claim 12 , wherein each battery includes a housing, and the housing is a soft package or a hard shell.
20 . An assembly method of a battery module, comprising the following steps:
step S 1 : detecting n batteries, n≥3, and recording at least one of the following three parameters of the n batteries: capacities of the batteries; open circuit voltages of the batteries under a same state of charge; and AC impedances of the batteries under a same state of charge; and
step S 2 : stacking the n batteries along a thickness direction of the battery from a first battery to an n-th battery to form a battery module, defining m as a round number of n/2, wherein the first battery and the m-th battery satisfy at least one of the following conditions:
a1: a capacity of the m-th battery is greater than that of the first battery and the n-th battery;
b1: under a same state of charge, an open circuit voltage of the m-th battery is less than that of the first battery and the n-th battery; and
c1: under a same state of charge, an AC impedance of the m-th battery is less than that of the first battery and the n-th battery.